Tech Fete

PSLV-C18

2011-10-11T23:41:00.000-07:00

Reference: http://isro.gov.in/index.aspx

Polar Satellite Launch Vehicle launched Megha-Tropiques satellite along with three auxiliary payloads- Jugnu and SRMSat (from India) and VesselSat-1 (from Luxembourg).Videos also available at the website.

Electronics Quiz

2011-10-07T07:09:00.001-07:00

POOJA GUPTA's Electronics quiz Score Report

Total number of questions:     11

Total number of correct answers:     9

Your QuizMoz Score:     82%

Average Score for this quiz:     54.5%

Number of people taken this quiz:     184

Maximum score for this quiz:     100%

More quizzes

Wireless Terms

2011-09-04T23:35:00.001-07:00

Find wireless industry
terms, acronyms, and definitions instantly:

This industry dictionary is powered by Althos Wireless Dictionary

Integrating ADC

2011-08-09T05:37:00.000-07:00

References:

1. http://en.wikipedia.org/wiki/Integrating_ADC
2.courses.engr.illinois.edu/ece581/int.ppt
3. http://www.maxim-ic.com/app-notes/index.mvp/id/1041
4. http://www.allaboutcircuits.com/vol_4/chpt_13/8.html

1. Longer integration times allow for higher resolutions.

2. Their use is typically limited to digital voltmeters and other instruments requiring highly accurate measurements.

3. One of the slowest ADCs.

4. Block diagram of dual-slope ADC:

5. Integrating analog-to-digital converters (ADCs) provide high resolution analog-to-digital conversions, with good noise rejection.

6. It is possible to avoid using a DAC inside an ADC circuit if we substitute an analog ramping circuit and a digital counter with precise timing. in integrating single slope ADC, instead of using a DAC with a ramped output, we use an op-amp circuit called an integrator to generate a sawtooth waveform which is then compared against the analog input by a comparator.

The time it takes for the sawtooth waveform to exceed the input signal voltage level is measured by means of a digital counter clocked with a precise-frequency square wave (usually from a crystal oscillator).

7. Single-Slope ADC Architecture
The simplest form of an integrating ADC uses a single-slope architecture . Here, an unknown input voltage is integrated and the value compared against a known reference value. The time it takes for the integrator to trip the comparator is proportional to the unknown voltage (T_INT/V_IN). In this case, the known reference voltage must be stable and accurate to guarantee the accuracy of the measurement.

One drawback to this approach is that the accuracy is also dependent on the tolerances of the integrator's R and C values. Thus in a production environment, slight differences in each component's value change the conversion result and make measurement repeatability quite difficult to attain. To overcome this sensitivity to the component values, the dual-slope integrating architecture is used.

Dual-Slope ADC Architecture

A dual-slope ADC (DS-ADC) integrates an unknown input voltage (V_IN) for a fixed amount of time (T_INT), then "de-integrates" (T_DEINT) using a known reference voltage (V_REF) for a variable amount of time (see Figure 2).

Figure 2. Dual-slope integration.

The key advantage of this architecture over the single-slope is that the final conversion result is insensitive to errors in the component values. That is, any error introduced by a component value during the integrate cycle will be cancelled out during the de-integrate phase. In equation form:

Vin × T_INT = V_REF × T_DEINT

or

T_DEINT = T_INT × (V_IN / V_REF)

From this equation, we see that the de-integrate time is proportional to the ratio of V_IN / V_REF. A complete block diagram of a dual-slope converter is shown in Figure 3.

9. In the dual-slope converter, an integrator circuit is driven positive and negative in alternating cycles to ramp down and then up, rather than being reset to 0 volts at the end of every cycle. In one direction of ramping, the integrator is driven by the positive analog input signal (producing a negative, variable rate of output voltage change, or output slope) for a fixed amount of time, as measured by a counter with a precision frequency clock.

Then, in the other direction, with a fixed reference voltage (producing a fixed rate of output voltage change) with time measured by the same counter. The counter stops counting when the integrator's output reaches the same voltage as it was when it started the fixed-time portion of the cycle. The amount of time it takes for the integrator's capacitor to discharge back to its original output voltage, as measured by the magnitude accrued by the counter, becomes the digital output of the ADC circuit.

Question IES 2011:

With a block diagram, explain the function of a dual slope DVM.

A dual slope integrating type of A/D converter has an integrating capacitor of 0.1 uF and a resistance of 100 k ohm. the reference voltage is 2 V and the output of the integrator is not to exceed 10 V. What is the maximum time required for the output voltage to be integrated?

Answer:

check this link:

http://pioneer.netserv.chula.ac.th/~tarporn/311/HandOut/DmmPPT.pdf

DVM is essentially an Analog to digital converter (A/D) with a digital display.

It uses dual slope integrating type A/D converter as explained above.

Maximum time taken by integrator = R * C = .01 sec = 10 ms

relative value corresponding to 10 V = 5 * 10 ms = 50 ms.

Anybody having a different viewpoint for this problem, kindly share the same.

NSN Celebrates 20 years of GSM!

2011-07-29T04:31:00.000-07:00

Reference: http://3g4g.blogspot.com/2011/07/nsn-celebrating-20-years-of-gsm.html?utm_source=feedburner&utm_medium=feed&utm_campaign=Feed%3A+3gAnd4gWirelessBlog+%283G+and+4G+Wireless+Blog%2920 Years of GSM: Past, Present & Future

View more presentations from Nokia Siemens Networks

RS-485

2011-06-25T23:51:00.000-07:00

Reference Links:
http://www.lammertbies.nl/comm/info/RS-485.html
http://www.interworldna.com/accesio/serial/usb-232-422485.html
http://digital.ni.com/public.nsf/allkb/B9A38929D546B796862572C7005F0644
http://www.arcelect.com/485info.htm

RS-232 is the single ended serial protocol and RS-485 and RS-422 are differential serial protocol. The pinout for RS-232, RS-422 and RS-485 is shown below figure.

A loopback test is a test in which a signal in sent from a communications device and returned (looped back) to it as a way to determine whether the device is working right. The figures below will show you what pins you need to connect to perform loopback test on RS-232 and RS-422/RS-485 respectively.
RS-232

RS-422 and RS-485

RS485 will support 32 drivers and 32 receivers (we are talking about bi-directional - half duplex - multi-drop communications over a single or dual twisted pair cable !!). An RS-485 network can be connected in a 2 or 4 wire mode. Maximum cable length can be as much as 4000 feet because of the differential voltage transmission system used. The typical use for RS485 is a single PC connected to several addressable devices that share the same cable. You can think of RS485 as a "party-lined" communications system (the addressing is handled by the Remote Computer unit). The RS232 may be converted to RS485 with a simple interface converter - it can have optical isolation and surge suppression.

RS232 is an interface to connect one DTE, data terminal equipment to one DCE, data communication equipment at a maximum speed of 20 kbps with a maximum cable length of 50 feet. This was sufficient in the old days where almost all computer equipment were connected using modems, but soon after people started to look for interfaces capable of one or more of the following:

Connect DTE's directly without the need of modems
Connect several DTE's in a network structure
Ability to communicate over longer distances
Ability to communicate at faster communication rates

RS485 is the most versatile communication standard in the standard series defined by the EIA, as it performs well on all four points. That is why RS485 is currently a widely used communication interface in data acquisition and control applications where multiple nodes communicate with each other.

RS485 functionality

Default, all the senders on the RS485 bus are in tri-state with high impedance. In most higher level protocols, one of the nodes is defined as a master which sends queries or commands over the RS485 bus. All other nodes receive these data. Depending of the information in the sent data, zero or more nodes on the line respond to the master. In this situation, bandwidth can be used for almost 100%. There are other implementations of RS485 networks where every node can start a data session on its own. This is comparable with the way ethernet networks function. Because there is a chance of data collosion with this implementation, theory tells us that in this case only 37% of the bandwidth will be effectively used. With such an implementation of a RS485 network it is necessary that there is error detection implemented in the higher level protocol to detect the data corruption and resend the information at a later time.

There is no need for the senders to explicity turn the RS485 driver on or off. RS485 drivers automatically return to their high impedance tri-state within a few microseconds after the data has been sent. Therefore it is not needed to have delays between the data packets on the RS485 bus.

Trace your Internet message

2011-06-22T00:31:00.000-07:00

Reference: http://communication.howstuffworks.com/convergence/router10.htm

Tracing a Message

If you're using a Microsoft Windows-based system, you can see just how many routers are involved in your Internet traffic by using a program you have on your computer. The program is called Traceroute, and that describes what it does -- it traces the route that a packet of information takes to get from your computer to another computer connected to the Internet. To run this program, click on the "MS-DOS Prompt" icon on the "Start" menu. Then, at the"C:\WINDOWS>" prompt, type "tracert www.howstuffworks.com". When I did this from my office in Florida, the results looked like this:

The first number shows how many routers are between your computer and the router shown. In this instance, there were a total of 14 routers involved in the process (number 15 is the Howstuffworks.com Web server). The next three numbers show how long it takes a packet of information to move from your computer to the router shown and back again. Next, in this example, starting with step six, comes the "name" of the router or server. This is something that helps people looking at the list but is of no importance to the routers and computers as they move traffic along the Internet. Finally, you see the Internet Protocol (IP) address of each computer or router. The final picture of this trace route shows that there were 14 routers between the Web server and me and that it took, on average, a little more than 2.5 seconds for information to get from my computer to the server and back again.

You can use Traceroute to see how many routers are between you and any other computer you can name or know the IP address for. It can be interesting to see how many steps are required to get to computers outside your nation. Since I live in the United States, I decided to see how many routers were between my computer and the Web server for the British Broadcasting Corporation. At the C:\WINDOWS> prompt, I typed tracert www.bbc.com. The result was this:

You can see that it took only one more step to reach a Web server on the other side of the Atlantic Ocean than it did to reach a server two states away!

It surely works, when tried from a place in North India;

C:\>cd windows

C:\WINDOWS>tracert www.howstuffworks.com

Tracing route to a462.g.akamai.net [96.17.182.8]

over a maximum of 30 hops:

1 <1 ms <1 ms <1 ms 192.168.1.1

2 30 ms 31 ms 33 ms ABTS-North-Static-157.130.160.122.airtelbroadband.in [122.160.130.157]

3 29 ms 31 ms 29 ms ABTS-North-Static-153.130.160.122.airtelbroadband.in [122.160.130.153]

4 30 ms 31 ms 29 ms 125.19.22.145

5 30 ms 30 ms 31 ms 59.145.7.230

6 30 ms 34 ms 34 ms a96-17-182-8.deploy.akamaitechnologies.com [96.17.182.8]

Trace complete.

C:\WINDOWS>

C:\WINDOWS>tracert www.yahoo.com

Tracing route to any-fp.wa1.b.yahoo.com [69.147.125.65]

over a maximum of 30 hops:

1 <1 ms <1 ms <1 ms 192.168.1.1

2 35 ms 47 ms 31 ms ABTS-North-Static-157.130.160.122.airtelbroadband.in [122.160.130.157]

3 31 ms 29 ms 29 ms ABTS-North-Static-149.130.160.122.airtelbroadband.in [122.160.130.149]

4 29 ms 29 ms 29 ms 203.101.83.197

5 50 ms 50 ms 49 ms 203.101.100.22

6 195 ms 195 ms 195 ms so-4-0-3-zcr2.lnt.cw.net [166.63.223.69]

7 195 ms 195 ms 195 ms so-5-2-0-dcr2.tsd.cw.net [195.2.10.134]

8 205 ms 195 ms 195 ms xe-0-3-0-xcr1.lnd.cw.net [195.2.25.1]

9 306 ms 325 ms 306 ms ge-11-0-0-xcr1.nyk.cw.net [195.2.25.18]

10 359 ms 276 ms 277 ms pat1.nyc.yahoo.com [198.32.118.24]

11 279 ms 279 ms 279 ms ae-8.pat1.dcp.yahoo.com [216.115.101.157]

12 277 ms 294 ms 294 ms ae-2-d170.msr2.re1.yahoo.com [216.115.108.69]

13 305 ms 280 ms 278 ms te-9-4.bas-a2.re1.yahoo.com [66.196.112.203]

14 277 ms 276 ms 280 ms ir1.fp.vip.re1.yahoo.com [69.147.125.65]

Trace complete.

How XM Radio Works

2011-06-21T04:36:00.000-07:00

Reference:

http://www.tech-faq.com/how-xm-radio-works.html

XM Radio is a satellite radio service. Satellite radio is a technology that for the most part has been around for many years. For instance, many television studios have been using satellites to beam TV signals from far away locations to viewers for decades, however satellite radio has been in operation in America since 2001.

Satellite radio is pretty easy to describe. The programs for satellite radio include music, talk shows, live sporting events and sport analysis shows. These shows are usually sent from one central location, where they are sent from the ground to satellites rotating in space that then broadcast the signal to those listeners with the hardware such as special antennas and receivers to pick up the signal. Here is some more information

Satellite Radio Starts from the Broadcaster

It is important to note that XM satellite radio initially starts from the studio, where the programming is put together. Programming such as music, talk shows, sports analysis shows, etc are created and then transmitted usually from a main source to two satellites over head. (It is also possible that live events such as news or sporting events are sent individually directly from the location where they are happening to the two satellites overhead). Usually programming is digitized and then compressed to fit lots of data into a small bandwidth of radio frequency which XM satellite is allowed to operate on.

The Satellites

XM Radio has two satellites that are in geostationary orbit located above the equator. Geostationary orbit means that the satellites are moving at the same speed as the earth turns, making it able to be in the same position as the earth at all times. This way, XM satellite radio can always be pointing to their satellites and feeding them programming and the satellites can easily broadcast their signal to the millions of listeners that have antennas and receivers pointed towards the geostationary satellite.

Antenna

A special antenna is necessary to receive XM satellite radio. Usually these antennas are very small in size, smaller than a normal tennis ball and can be placed on top of car roofs, in an office or at home. They are not that expensive and cost usually less than $50. These antennas make it possible to catch the specific digital radio signal that is broadcasted and send it to the special XM Satellite Receiver.

Satellite Repeaters

Because satellites that are in geostationary orbit, their antennas must have a clear line of sight to the southern sky to pick up signals clearly. Obviously not everyone will have a clear line of sight (especially if you live in an urban location) so a technique used to increase the likelihood of anyone using this technology to have good reception are repeaters. A repeater is a large antenna located in key positions around the country, where a satellite signal can be received and then repeated or rebroadcasted to antennas facing any direction, south, north, east, west and in between.

Satellite Receivers

Satellite receivers enable listeners to receive the digital audio broadcasts being relayed off of the satellites in geostationary orbit. These satellite receivers come in many different styles and some have different functions. They all include a chipset that can decode the encrypted signal sent from the satellite. The satellite sends its programming signal encrypted so that people that do not have a receiver or do not pay the monthly subscription fee can not have access to it.

Receivers can come in the form of auto car stereos, add on receivers that hook up to your already installed car stereo, boom boxes, home audio receivers with satellite receiver capability and portable devices that allow you to pick up the satellite signal no matter where you go. These portable devices have their own energy source and are similar to size and shape as iPod's. These receivers usually cost from about $30 to over $300.

Linkedin Poll on Nokia's Strategy

2011-04-01T05:31:00.000-07:00

Schmitt Trigger

2011-01-05T05:52:00.000-08:00

References:
http://www.play-hookey.com/digital/experiments/rtl_schmitt.html

Sometimes an input signal to a digital circuit doesn't directly fit the description of a digital signal. For various reasons it may have slow rise and/or fall times, or may have acquired some noise that could be sensed by further circuitry. It may even be an analog signal whose frequency we want to measure. All of these conditions, and many others, require a specialized circuit that will "clean up" a signal and force it to true digital shape.

The required circuit is called a Schmitt Trigger. It has two possible states just like other multivibrators. However, the trigger for this circuit to change states is the input voltage level, rather than a digital pulse. That is, the output state depends on the input level, and will change only as the input crosses a pre-defined threshold.

The Schmitt Trigger makes its feedback connection through the emitters of the transistors as shown in the schematic diagram. To understand how this circuit works, assume that the input starts at ground, or 0 volts. Transistor Q1 is necessarily turned off, and has no effect on this circuit.

Therefore, RC1, R1, and R2 form a voltage divider across the 5 volt power supply to set the base voltage of Q2 to a value of (5 × R2)/(RC1 + R1 + R2). If we assume that the two transistors are essentially identical, then as long as the input voltage remains significantly less than the base voltage of Q2, Q1 will remain off and the circuit operation will not change.

While Q1 is off, Q2 is on. Its emitter and collector current are essentially the same, and are set by the value of RE and the emitter voltage, which will be less than the Q2 base voltage by V_BE. If Q2 is in saturation under these circumstances, the output voltage will be within a fraction of the threshold voltage set by RC1, R1, and R2. It is important to note that the output voltage of this circuit cannot drop to zero volts, and generally not to a valid logic 0. We can deal with that, but we must recognize this fact.

Now, suppose that the input voltage rises, and continues to rise until it approaches the threshold voltage on Q2's base. At this point, Q1 begins to conduct. Since it now carries some collector current, the current through RC1 increases and the voltage at the collector of Q1 decreases. But this also affects our voltage divider, reducing the base voltage on Q2. But since Q1 is now conducting it carries some of the current flowing through RE, and the voltage across RE doesn't change as rapidly. Therefore, Q2 turns off and the output voltage rises to +5 volts. The circuit has just changed states.

If the input voltage rises further, it will simply keep Q1 turned on and Q2 turned off. However, if the input voltage starts to fall back towards zero, there must clearly be a point at which this circuit will reset itself. The question is, What is the falling threshold voltage? It will be the voltage at which Q1's base becomes more negative than Q2's base, so that Q2 will begin conducting again. However, it isn't the same as the rising threshold voltage, since Q1 is currently affecting the behavior of the voltage divider.

As V_IN approaches this value, Q2 begins to conduct, taking emitter current away from Q1. This reduces the current through RC1 which raises Q2's base voltage further, increasing Q2's forward bias and decreasing Q1's forward bias. This in turn will turn off Q1, and the circuit will switch back to its original state.

Three factors must be recognized in the Schmitt Trigger. First, the circuit will change states as V_INapproaches V_B2, not when the two voltages are equal. Therefore V_B2 is very close to the threshold voltage, but is not precisely equal to it. For example, for the component values shown above, V_B2 will be 2.54 volts when Q1 is held off, and 2.06 volts as V_IN is falling towards this value.

Second, since the common emitter connection is part of the feedback system in this circuit, RE must be large enough to provide the requisite amount of feedback, without becoming so large as to starve the circuit of needed current. If RE is out of range, the circuit will not operate properly, and may not operate as anything more than a high-gain amplifier over a narrow input voltage range, instead of switching states.

The third factor is the fact that the output voltage cannot switch over logic levels, because the transistor emitters are not grounded. If a logic-level output is required, which is usually the case, we can use a circuit such as the one shown here to correct this problem. This circuit is basically two RTL inverters, except that one uses a PNP transistor. This works because when Q2 above is turned off, it will hold a PNP inverter off, but when it is on, its output will turn the PNP transistor on. The NPN transistor here is a second inverter to re-invert the signal and to restore it to active pull-down in common with all of our other logic circuits.

Quiz Time:

Answer 3 questions on the link:
http://www.wisc-online.com/objects/ViewObject.aspx?ID=SSE8507

Fundamental Loop Matrix

2011-01-04T02:52:00.000-08:00

Sources:

http://www.transtutors.com/homework-help/Networks+%26+Systems/Network+Graph+Theories/loop-matrix-question.aspx

http://books.google.com/books?id=9c38IdqCbusC&pg=PA1119&lpg=PA1119&dq=define+fundamental+loop+matrix&source=bl&ots=63Jwqa6QEH&sig=Rqp4AG4sbnI5_eeyaVdgp_DK6AE&hl=en&ei=lfoiTaGdNo3KrAft56D-Cw&sa=X&oi=book_result&ct=result&resnum=5&ved=0CCEQ6AEwBA#v=onepage&q=define%20fundamental%20loop%20matrix&f=false

http://www.transtutors.com/homework-help/Networks+%26+Systems/Network+Graph+Theories/loop-matrix-question.aspx

Definition:

Consider a connected graph G with b branches and n_t nodes. Select any arbitrary tree. The tree will contain n = n_t - 1 tree branches (twigs) and l = (b - n) link branches. Every link defines a fundamental loop of the network. Let us take the example of the graph shown in Fig. a.

Fig.

Let T be a tree of G as shown in Fig. b. The number of fundamental loops of this graph will be (b - n) = 3. the three f-loop l₁, l₂ and l₃ are shown in Fig. c. In order to apply KVL to each fundamental loop, we take reference direction of the loop which coincides with the reference direction of the link defining the loop.

l₁ : v₁ + v₂ + v₅ + = 0

l₂ : v₂ + v₃ + v₄ = 0

l_{3 :}v_{1 +}v_{3 +}v₆ = 0

In matrix form, we can write

B_f v_b = 0 (KVL)

Where is an matrix called the fundamental loop matrix or tie-set matrix

B_f = [b_kj]

Where b_kj are the elements of b_f the (k,j) element of the matrix is defined as follows:

b_kj= 1 when branch b_j is in the f-loop l_k and their reference directions (orientations) coincide

b_kj = -1 when branch b_j is in the f-loop l_k and has opposite orientation

b_kj = 0 when branch is not in the f-loop

Example:

In the graph shown in Fig. a tree consisting of branches 4, 5, 6, 7, 8 is chosen, as shown by heavy lines. Write the fundamental loop matrix of the graph.

SOLUTION

The fundamental loops defined by links {1, 2, 3} and their orientations are shown in Figs, c and d. Consider loop l₁. It contains branches {1, 6, 8, 5}. The orientation of loop l₁ is given the same orientation as its defining link 1. Therefore the element b₁₁ is written 1. The directions of branches 6, 8 and 5 in l₁ are the same as l₁. therefore the entries

FIG.

b₁₆,b₁₈ and b₁₅ are each equal to 1. Since branches 2, 3, 4 and 7 are not in loop b₁₃ = 0,b₁₄ = 0,b₁₇ = 0.

Loop l₂ contains branches {2, 6, 7}. The orientation of l₂ is given the same orientation as its defining link. 2. Therefore the element b₂₂ = 1. The orientations of branches 6 and 7 are opposite to the orientation of l₂ consequently, b₁₂₆ = -1 and b₂₇ = -1 Since branches {1, 3, 4, 5, 8} are not contained in l₂, b₂₁ = 0,b₂₃ = 0,b₂₄ = 0,b₂₅ = 0,b₂₈ = 0.

Loop l₃has branches (3, 4, 8, 7). The orientation of l₃ is the same as that of its defining link 3.Therefore the element b₃₃ = 1 The directions of branches 4 and 7 coincide with the orientation of l₃ Hence b₃₄ = 1, b₃₇ = 1. The orientation of branch 8 does not coincide with the orientation of l₃. Hence b₃₈ = -1. Since branches {1, 2, 5, 6} are not contained in l₃,b₃₁ = 0, b₃₂ = 0, b₃₅ = 0, b₃₆ = 0. Thus, we obtain the following matrix:

Network Graphs

2011-01-04T00:46:00.000-08:00

Reference:
http://venus.ece.ndsu.nodak.edu/ece/academics/courses/ee206/notes/cirtop.htm

Graph: a representation of a circuit where each branch is denoted by a line segment.

Tree (of a graph): a set of branches (each denoted by a line segment) that connects every node to every other node via some path without forming a loop.

Tree branch: a branch of a graph that is part of a particular tree.

Cotree: those branches of a graph which are not part of a particular tree. This is also known as the complement of the tree.

Link: a branch of a cotree.

Cut set: a minimum set of branches that, when cut, will divide a graph into two separate parts.

Fundamental cut set: a cut set containing only a single tree branch.

Fundamental loop: A loop that results when a link is put into the tree.

A cut set divides a graph into two independent parts. In terms of the original circuit, a KCL equation can be written for either part of the circuit divided by the cut; such a KCL equation is called a cut-set equation.

The dual of a fundamental cut set is a fundamental loop. Each time a link is inserted into a tree as a potential tree branch, a loop is formed in the tree (thus the resulting object is no longer a tree). Such a loop is called a fundamental loop.

Tree-branch analysis uses KCL (Kirchhoff's Current Law) but no reference node is selected like is done in nodal analysis; all KCL equations are written in terms of tree branch voltages instead of node voltages.

Loop analysis uses KVL (Kirchhoff's Voltage Law) but the loops chosen may not necessarily be meshes. Instead, each loop needs to be a fundamental loopobtained by inserting a link into a tree.

There is only one graph for a circuit (although there may be many ways to draw it).

Usually, there are several trees for a graph, and each tree has a corresponding cotree.

Spherical Co-ordinate System

2011-01-03T01:12:00.000-08:00

http://mathworld.wolfram.com/SphericalCoordinates.html

1. Curvilinear co-ordinates

2. Used for describing positions on a sphere or spheroid

3. Denoted as set (r, (azimuthal angle), (polar angle) )

4.

In spherical coordinates, the polar angle is the angle measured from the -axis, denoted in this work, and also variously known as the zenith angle and colatitude. ,

( where is the latitude) from the positive z-axis with

5. It is a logical extension of the usual polar coordinates notation, with remaining the angle in the -plane and becoming the angle out of that plane.

6. The symbol is sometimes also used in place of , and and instead of .

7. The spherical coordinates are related to the Cartesian coordinates by

			(1)
			(2)

where , , and , and the inverse tangent must be suitably defined to take the correct quadrant of into account.

8. In terms of Cartesian coordinates,

			(4)
			(5)

9. The line element is

(13)

the area element

(14)

and the volume element

http://en.wikipedia.org/wiki/Spherical_coordinate_system

10. In geography and astronomy, the elevation and azimuth (or quantities very close to them) are called the latitude and longitude, respectively; and the radial distance is usually replaced by an altitude (measured from a central point or from a sea level surface).
11. Spherical coordinates are useful in analyzing systems that have some degree of symmetry about a point, such as volume integrals inside a sphere, the potential energy field surrounding a concentrated mass or charge, or global weather simulation in a planet's atmosphere. A sphere that has the Cartesian equation x² + y² + z² = c² has the simple equation r = c in spherical coordinates.
12.

Traitorware

2010-12-28T21:59:00.000-08:00

https://www.eff.org/deeplinks/2010/12/what-traitorware

What is Traitorware?

Commentary by Eva Galperin

Your digital camera may embed metadata into photographs with the camera's serial number oryour location. Your printer may be incorporating a secret code on every page it prints which could be used to identify the printer and potentially the person who used it. If Apple puts a particularly creepy patent it has recently applied for into use, you can look forward to a day when your iPhone may record your voice, take a picture of your location, record your heartbeat, and send that information back to the mothership.
This is traitorware: devices that act behind your back to betray your privacy.

Perhaps the most notable example of traitorware was the Sony rootkit. In 2005 Sony BMG produced CD's which clandestinely installed a rootkit onto PC's that provided administrative-level access to the users' computer. The copy-protected music CD’s would surreptitiously install itsDRM technology onto PC’s. Ostensibly, Sony was trying prevent consumers from making multiple copies of their CD’s, but the software also rendered the CD incompatible with many CD-ROM players in PC’s, CD players in cars, and DVD players. Additionally, the software left a back door open on all infected PC’s which would give Sony, or any hacker familiar with the rootkit, control over the PC. And if a consumer should have the temerity to find the rootkit and try to remove the offending drivers, the software would execute code designed to disable the CD drive and trash the PC.

Traitorware is sometimes included in products with less obviously malicious intent. Printer dots were added to certain color laser printers as a forensics tool for law enforcement, where it could help authenticate documents or identify forgeries. Apple’s scary-sounding patent for the iPhone is meant to help locate and disable the phone if it is lost of stolen. Don’t let these good intentions fool you—software that hides itself from you while it gives your personal data away to a third party is dangerous and dishonest. As the Sony BMG rootkit demonstrates, it may even leave your device wide open to attacks from third parties.

Traitorware is not some science-fiction vision of the future. It is the present. Indeed, the Sony rootkit dates back to 2005. Apple’s patent application indicates that we are likely to see more traitorware on the horizon. When that happens, EFF will be there to fight it. We believe that your software and devices should not be a tool for gathering your personal data without your explicit consent.

Decibel Usage

2010-12-15T01:41:00.000-08:00

http://www.animations.physics.unsw.edu.au/jw/dB.htm

Why do we use decibels?

1. The decibel ( dB) is used to measure sound level, but it is also widely used in electronics, signals and communication.

2. The dB is a logarithmic unit used to describe a ratio. The ratio may be power, sound pressure, voltage or intensity or several other things.

3. For instance, suppose we have two loudspeakers, the first playing a sound with power P₁, and another playing a louder version of the same sound with power P₂, but everything else (how far away, frequency) kept the same.
The difference in decibels between the two is defined to be

10 log (P₂/P₁) dB where the log is to base 10.

If the second produces twice as much power than the first, the difference in dB is

10 log (P₂/P₁) = 10 log 2 = 3 dB.

To continue the example, if the second had 10 times the power of the first, the difference in dB would be

10 log (P₂/P₁) = 10 log 10 = 10 dB.

If the second had a million times the power of the first, the difference in dB would be

10 log (P₂/P₁) = 10 log 1,000,000 = 60 dB.

Using this as a base, next step is to understand the channel capacity formula:

http://www.dip.ee.uct.ac.za/~nicolls/lectures/eee482f/04_chancap_2up.pdf

http://www.electronics.dit.ie/staff/amoloney/dt008_2/dig-comms-ii-lecture-11-12.pdf

Channel capacity is concerned with the information handling capacity of a given channel. It is aﬀected by:

– The attenuation of a channel which varies with frequency as well as channel length.

– The noise induced into the channel which increases

with distance.

– Non-linear eﬀects such as clipping on the signal.

Some of the eﬀects may change with time e.g. the frequency response of a copper cable changes with temper

ature and age. Obviously we need a way to model a channel in order to estimate how much information can

be passed through it. Although we can compensate for non linear eﬀects and attenuation it is extremely diﬃcult to remove noise.

The highest rate of information that can be transmitted through a channel is called the channel capacity,

Shannon’s Channel Coding Theorem

• Shannon’s Channel Coding Theorem states that if the information rate, R (rH bits/s) is equal to or less than

the channel capacity, C, (i.e. R < C) then there is, in principle, a coding technique which enables transmission

over the noisy channel with no errors.

• The inverse of this is that if R > C, then the probability of error is close to 1 for every symbol.

• The channel capacity is deﬁned as:

the maximum rate of reliable (error-free) information transmission through the channel.

Shannon’s Channel Capacity Theorem

• Shannon’s Channel Capacity Theorem(or the ShannonHartley Theorem) states that:

C = B log2 ( 1 + S/N) bits/s

where C is the channel capacity, B is the channel bandwidth in hertz, S is the signal power and N is the noise

power (N0B with N0/2 being the two sided noise PSD).

as the bandwidth goes to inﬁnity the capacity goes to 1.44S/N0, i.e., it goes to a ﬁnite value and is not inﬁnite!

Note: S/N is the ratio watt/watt not dB.

http://en.wikipedia.org/wiki/Channel_capacity

Since figures are often cited in dB, a conversion may be needed. For example, 30 dB is a power ratio of $10 30 / 10 = 10 3 = 1000$ .

IC Fabrication Process -1

2010-11-18T04:32:00.000-08:00

http://personal.cityu.edu.hk/~appkchu/AP4120/2v.pdf

The first step comprises of preparing Si or Ge wafer with desired purity level.

The processing characteristics and some material properties of silicon wafers depend on its orientation.The <111> planes have the highest density of atoms on the surface, so crystals grow most easily on these planes and oxidation occurs at a higher pace when compared to other crystal planes.Traditionally, bipolar devices are fabricated in <111> oriented crystals whereas <100> materials are preferred for MOS devices.

Electronic-grade silicon (EGS), a polycrystalline material of high purity, is the starting material for the preparation of single crystal silicon. EGS is made from metallurgical-grade silicon (MGS) which in turn is made from quartzite, which is a relatively pure form of sand.

CzochralskiCrystal Growth

The Czochralski(CZ) process, which accounts for 80% to 90% of worldwide silicon consumption, consists of dipping a small single-crystal seed into molten silicon and slowly withdrawing the seed while rotating it simultaneously.Impurities, both intentional and unintentional, are introduced into the silicon ingot. Intentional dopantsare mixed into the melt during crystal growth, while unintentional impurities originate from the crucible, ambient, etc.

Float-Zone Process
The float-zone process has some advantages over the Czochralski process for the growth of certain types of silicon crystals.The molten silicon in the float-zone apparatus is not contained in a crucible, and is thus not subject to the oxygen contamination present in CZ-Sicrystals.The float-zone process is also necessary to obtain crystals with a high resistivity(>> 25 W-cm)

Silicon, albeit brittle, is a hard material. The most suitable material for shaping and cutting silicon is industrial-grade diamond. Conversion of silicon ingots into polished wafers requires several machining, chemical, and polishing operations.

The wafer as cut varies enough in thickness to warrant an additional lapping operation that is performed under pressure using a mixture of Al2O3and glycerine. Subsequent chemical etching removes any remaining damaged and contaminated regions.Polishing is the final step. Its purpose is to provide a smooth, specular surface on which device features can be photo engraved.

Sinc Function

2010-11-18T03:04:00.000-08:00

http://en.wikipedia.org/wiki/Sinc_function

In mathematics, the sinc function, denoted by sinc(x) and sometimes as Sa(x), has two nearly equivalent definitions. In digital signal processing and information theory, the normalized sinc function is commonly defined by

It is qualified as normalized because its integral over all x is one. The Fourier transform of the normalized sinc function is the rectangular function with no scaling. This function is fundamental in the concept of reconstructing the original continuous bandlimited signal from uniformly spaced samples of that signal.

In mathematics, the historical unnormalized sinc function is defined by

The only difference between the two definitions is in the scaling of the independent variable (the x-axis) by a factor of π.

The normalized sinc function can be used as a nascent delta function, meaning that the following weak limit holds:

This is not an ordinary limit, since the left side does not converge.

Important Time Zones

2010-11-16T06:58:00.000-08:00

http://www.timeanddate.com/worldclock/city.html?n=176

1. New Delhi
Standard time zone:UTC/GMT +5:30 hours
No daylight saving time in 2010
Time zone abbreviation:IST - India Standard Time

2. Berlin
Standard time zone:UTC/GMT +1 hour
No daylight saving time at the moment
Time zone abbreviation:CET - Central European Time

3. Tashkent
Standard time zone:UTC/GMT +5 hours
No daylight saving time in 2010
Time zone abbreviation:UZT - Uzbekistan Time

4. Bangkok
Standard time zone:UTC/GMT +7 hours
No daylight saving time in 2010
Time zone abbreviation:ICT - Indochina Time

5. Rio De Janeiro
Standard time zone:UTC/GMT -3 hours
Daylight saving time:+1 hour
Current time zone offset:UTC/GMT -2 hours
Time zone abbreviation:BRST - Brasilia Summer Time

6. Asunción
Standard time zone:UTC/GMT -4 hours
Daylight saving time:+1 hour
Current time zone offset:UTC/GMT -3 hours
Time zone abbreviation:PYST - Paraguay Summer Time

7. Tokyo
Standard time zone:UTC/GMT +9 hours
No daylight saving time in 2010
Time zone abbreviation:JST - Japan Standard Time

8. Nairobi
Standard time zone:UTC/GMT +3 hours
No daylight saving time in 2010
Time zone abbreviation:EAT - Eastern Africa Time

9. Caracas
Standard time zone:UTC/GMT -4:30 hours
No daylight saving time in 2010
Time zone abbreviation:VET - Venezuelan Standard Time

10. New York
Standard time zone:UTC/GMT -5 hours
No daylight saving time at the moment
Time zone abbreviation:EST - Eastern Standard Time

11. Seattle
Standard time zone:UTC/GMT -8 hours
No daylight saving time at the moment
Time zone abbreviation:PST - Pacific Standard Time

Thermocouple

2010-11-13T06:32:00.000-08:00

http://en.wikipedia.org/wiki/Thermocouple
http://www.picotech.com/applications/thermocouple.html
http://www.efunda.com/designstandards/sensors/thermocouples/thmcple_intro.cfm

A thermocouple is a junction between two different metals that produces a voltage related to atemperature difference. Thermocouples are a widely used type of temperature sensor for measurement and control^[1] and can also be used to convert heat into electric power. They are inexpensive^[2] and interchangeable, are supplied fitted with standard connectors, and can measure a wide range of temperatures. The main limitation is accuracy: system errors of less than one degree Celsius (C) can be difficult to achieve.^[3]

^{Thermocouples for practical measurement of temperature are junctions of specific alloys which have a predictable and repeatable relationship between temperature and voltage. Different alloys are used for different temperature ranges. Properties such as resistance to corrosion may also be important when choosing a type of thermocouple.}

Thermocouples are suitable for measuring over a large temperature range, up to 2300 °C.Thermocouples are widely used in science and industry; applications include temperature measurement for kilns, gas turbine exhaust, diesel engines, and other industrial processes.

Pros and Cons

•	Pros:
	-	Low cost.
	-	No moving parts, less likely to be broken.
	-	Wide temperature range.
	-	Reasonably short response time.
	-	Reasonable repeatability and accuracy.

•	Cons:
	-	Sensitivity is low, usually 50 µV/°C (28 µV/°F) or less. Its low voltage output may be masked by noise. This problem can be improved, but not eliminated, by better signal filtering, shielding, and analog-to-digital (A/V) conversion.
	-	Accuracy, usually no better than 0.5 °C (0.9°F), may not be high enough for some applications.
	-	Requires a known temperature reference, usually 0°C (32°F) ice water. Modern thermocouples, on the other hand, rely on an electrically generated reference.
	-	Nonlinearity could be bothersome. Fortunately, detail calibration curves for each wire material can usually be obtained from vendors.

Wheatstone Bridge

2010-11-13T05:36:00.000-08:00

http://en.wikipedia.org/wiki/Wheatstone_bridge

A Wheatstone bridge is an electrical circuit invented by Samuel Hunter Christie in 1833 and improved and popularized by Sir Charles Wheatstone in 1843. ^[1] It is used to measure an unknown electrical resistance by balancing two legs of a bridge circuit, one leg of which includes the unknown component. Its operation is similar to the original potentiometer.

The desired value of

R x

is now known to be given as:

Understanding Cell

2010-11-07T04:10:00.000-08:00

Reference:
http://www.wisegeek.com/what-is-cytology.htm
http://www.britannica.com/EBchecked/topic/148932/cytology

http://ghr.nlm.nih.gov/handbook/basics/chromosome

http://en.wikipedia.org/wiki/Chromatography

Cytology:

Cytology, more commonly known as cell biology, studies cell structure, cell composition, and the interaction of cells with other cells and the larger environment in which they exist.Microscopic examination can help identify different types of cells. In a simple test like a complete blood count, a laboratory can look at white blood cells and identify the presence of an infection, or it may examine a low level of certain types of red blood cells and diagnose anemia.
The biochemical basis of cell differentiation is the synthesis by the cell of a particular set of proteins, carbohydrates, and lipids.The first cells presumably resembled prokaryotic cells in lacking nuclei and functional internal compartments, or organelles. These early cells were also anaerobic (not requiring oxygen), deriving their energy from the fermentation of organic molecules that had previously accumulated on the Earth over long periods of time.

Chromosomes:

In the nucleus of each cell, the DNA molecule is packaged into thread-like structures called chromosomes.

The structure and location of chromosomes is one of the chief differences between the two basic types of cells—prokaryotic cells and eukaryotic cells. Among organisms with prokaryotic cells (i.e., bacteria and blue-green algae), chromosomes consist entirely of deoxyribonucleic acid (DNA). The single chromosome of a prokaryotic cell is not enclosed within a nuclear membrane. Among all other organisms (i.e., the eukaryotes), the chromosomes are contained in a membrane-bound cell nucleus. The chromosomes of a eukaryotic cell consist primarily of DNA attached to a protein core. They also contain ribonucleic acid (RNA). Among both prokaryotes and eukaryotes, the arrangement of components in the DNA molecules determines the genetic information.

Every species has a characteristic number of chromosomes (chromosome number). In species that reproduce asexually, the chromosome number is the same in all the cells of the organism. Among sexually reproducing organisms, the number of chromosomes in the body (somatic) cells is diploid (2n; a pair of each chromosome), twice the haploid (1n) number found in the sex cells, or gametes. The haploid number is produced during meiosis. During fertilization, two gametes combine to produce a zygote, a single cell with a diploid set of chromosomes.

Chromatography:
Chromatography is a physical method of separation in which the components to be separated are distributed between two phases, one of which is stationary (stationary phase) while the other (the mobile phase) moves in a definite direction.Affinity chromatography often utilizes a biomolecule's affinity for a metal. It is often used in biochemistry in the purification of proteins bound to tags.

Ion exchange chromatography uses ion exchange mechanism to separate analytes.Ion exchange chromatography uses a charged stationary phase to separate charged compounds including amino acids,peptides, and proteins.

Facts:

The largest animal that ever lived is also currently living -- the blue whale.
Mitochondrial DNA is only inherited from our mother.
"DNA makes RNA, RNA makes protein, and proteins make us." Francis Crick

General Awareness

2010-11-05T05:09:00.000-07:00

1. Saccharimeter:

A saccharimeter is an instrument for measuring the concentration of sugar solutions.

This is commonly achieved using a measurement of refractive index (refractometer) or the angle of rotation of polarization of optically active sugars (polarimeter).

Saccharimeters are used in food processing industries, brewing, and the distilled alcoholic drinks industry.

http://en.wikipedia.org/wiki/Saccharimeter

2, Ammeters

Zero-center ammeters are used for applications requiring current to be measured with both polarities, common in scientific and industrial equipment. Zero-center ammeters are also commonly placed in series with a battery.

3. Manometer

http://en.wikipedia.org/wiki/Manometer

Static pressure is uniform in all directions, so pressure measurements are independent of direction in an immovable (static) fluid.

4. Barkometer

A barkometer is calibrated to test the strength of tanning liquors used in tanning leather.^[10]

^{5. William Herschel}

^{http://en.wikipedia.org/wiki/William_Herschel}

Herschel became most famous for the discovery of the planetUranus in addition to two of its major moons, Titania and Oberon. He also discovered two moons of Saturn and infrared radiation. Finally, Herschel is less known for the twenty-four symphonies that he composed.

6. Robert koch

He was awarded the Nobel Prize in Physiology or Medicine for his tuberculosis findings in 1905.The crater Koch on the Moon is named after him. The Robert Koch Prize and Medal were created to honour Microbiologists who make groundbreaking discoveries or who contribute to global health in a unique way. The now-defunct Robert Koch Hospital at Koch, Missouri (south of St. Louis, Missouri), was also named in his honor.

7. Alexander Oparin

http://en.wikipedia.org/wiki/Oparin

He was a Soviet biochemist notable for his contributions to the theory of the origin of life, and for his authorship of the book The Origin of Life. Oparin sometimes is called "Charles Darwin|Darwin" of the 20th century.Many of his early papers were on plant enzymes and their role inmetabolism.^[3]He showed that many food-production processes are based on biocatalysis and developed the foundations for industrial biochemistry in the USSR.^[2]

^8.Ole Christensen Rømer

^{http://en.wikipedia.org/wiki/R%C3%B8mer's_determination_of_the_speed_of_light}

^{Rømer starts with an order of magnitude demonstration that the speed of light must be so large that it takes much less than one second to travel a distance equal to Earth's diameter.}

Rømer also invented the Meridian circle, the Altazimuth and the Passage Instrument. Rømer also developed one of the first temperature scales.Fahrenheit visited him in 1708 and improved on the Rømer scale, the result being the familiar Fahrenheit temperature scale still in use today in a few countries.

9. Astrobiology

Astrobiology is the study of the origin, evolution, distribution, and future of life in the universe. Earth is the only known inhabited planet in the universe to date.Nucleic acids may not be the only biomolecules in theUniverse capable of coding for life.^[1]Extremophiles (organisms able to survive in extreme environments) are a core research element for astrobiologists. The NASA Kepler mission, successfully launched in March 2009, searches for extrasolar planets.

10. Philology

Philology is the study of language in written historical sources, as such it is a combination ofliterary studies, history and linguistics.^[1]Another branch of philology, cognitive philology studies written and oral texts, considering them as results of human mental processes. Because of its focus on historical development (diachronic analysis), philology came to be used as a term contrasting with linguistics. Linguistics is the scientific^[1]^[2] study of human language.

Anode and Cathode Electrodes

2010-10-23T06:50:00.000-07:00

Just realised today that anode and cathode need not be always + and -vely charged respectively.

Excerpt from a link:

http://www.av8n.com/physics/anode-cathode.htm
Definition: The anode of a device is the terminal where current flows in from outside. The cathode of a device is the terminal where current flows out. This is illustrated in figure 1.

Figure 1: Anode and Cathode Currents

As always, electrons flowing in is the same as positive current flowing out, and vice versa.

http://en.wikipedia.org/wiki/Anode

http://en.wikipedia.org/wiki/Cathode

A widespread misconception is that anode polarity is always positive (+). This is often incorrectly inferred from the correct fact that in all electrochemical devices negatively charged anions move towards the anode (hence their name) and/or positively charged cations move away from it. In fact anode polarity depends on the device type, and sometimes even in which mode it operates, as per the above electric current direction-based universal definition. Consequently, as can be seen from the following examples, in a device which consumes power the anode is positive, and in a device which provides power the anode is negative:

When the current through the device is reversed, the electrodes switch functions, so anode becomes cathode, while cathode becomes anode, as long as the reversed current is applied, with the exception of diodes where electrode naming is always based on the forward current direction.

Materials and Components

2010-10-20T22:00:00.000-07:00

1. Components incapable of controlling current by means of another electrical signal are called passive devices. Resistors, capacitors, inductors, transformers, and even diodes are all considered passive devices. Active devices include, but are not limited to, vacuum tubes, transistors, silicon-controlled rectifiers (SCRs), and TRIACs.

http://www.allaboutcircuits.com/vol_3/chpt_1/2.html

2. Thyratron is an active device, a type of gas filled tube used as a high energy electrical switch and controlled rectifier.Unlike a vacuum tube, a thyratron cannot be used to amplify signals linearly.A thyratron is basically a "controlled gas rectifier".Gases used include mercuryvapor, xenon, neon, and (in special high-voltage applications or applications requiring very short switching times) hydrogen.

http://en.wikipedia.org/wiki/Thyratron

3. A reflex klystron oscillator is preferred as an ideal source in micro measurements as it provides low power output with multiple frequency components.The interaction between the electron beam and the radio frequency wave in the re-entrant cavity depends upon the average gap transit angle, this is the phase change due to finite time, the electron beam takes to cross the central gap of the re-entrant cavity.

http://www.tpub.com/neets/book11/45d.htm
http://www.worldlingo.com/ma/enwiki/en/Klystron

4. A step recovery diode is also known as snap-off varactor.

5. Schottky diode is a unipolar device because it has electrons as majority carriers on both sides of the junction.It can be used for rectification of signals of frequencies even exceeding 300 MHz. It is also used in clipping and clamping circuits and in computer gating. Its low noise figure finds application in sensitive applications like radars.

-Electronic devices and circuits, by Salivahanan

6. The graded index optical fibre cable can be considered to have smaller
   numerical aperture than step index cable.

7. There are about 25 superconducting metallic elements at low temperatures,
   like tin and aluminium.All superconductors have exactly zero resistivity to low
   applied currents when there is no magnetic field present.Conventional superconductors
   usually have critical temperatures ranging from less than 1K to around 20K.

   When a superconductor is placed in a weak external magnetic field H, the field penetrates for
   only a short distance λ, called the penetration depth, after which it decays rapidly to zero.
   This is called the Meissner effect. For most superconductors, the penetration depth is
   on the order of a hundred nm.
http://fy.chalmers.se/~delsing/LowTemp/LectureSC/Definition%20of%20SC.pdf

8. Porcelain is used as an insulator.Porcelain insulators are made from clay,
   quartz or alumina and feldspar, and are covered with a smooth glaze to shed
   water. Glass has a higher dielectric strength than porcelain.
http://en.wikipedia.org/wiki/Insulator_(electrical)

General Awareness -1

2010-10-16T02:25:00.000-07:00

1. Oral Polio Vaccine (OPV):

http://en.wikipedia.org/wiki/Polio_vaccine
http://india.gov.in/citizen/health/faq_polio.php

Two polio vaccines are used throughout the world to combat poliomyelitis (or polio). The first was developed by Jonas Salk at the University of Pittsburgh and first tested in 1952. Announced to the world by Salk on April 12, 1955, it consists of an injected dose of inactivated (dead) poliovirus. An oral vaccine was developed by Albert Sabin using attenuated poliovirus. Human trials of Sabin's vaccine began in 1957 and it was licensed in 1962.

Every child during the first year of life should receive at least three routine doses of Oral Polio Vaccine (OVP). Interruption of person to person transmission of the virus by vaccination is the critical step in global polio eradication.OPV drops may also be given to newborn children, even if they were born only a few hours ago. Usually, the colour of an Oral Polio Vaccine (OPV) is pink. However, sometimes the colour may also be yellow or white. All the vaccines are the same and this colour difference in no way affects the quality or type of vaccine.

2. Pineal Gland:

http://en.wikipedia.org/wiki/Pineal_gland
http://www.wayfinding.net/pineal.htm

It is a small endocrine gland in the vertebrate brain.It produces a hormone that affects the modulation of wake/sleep patterns and seasonal functions. It is located near the center of the brain between the two hemispheres.Chemical analysis shows that they are composed of calcium phosphate, calcium carbonate, magnesium phosphate, and ammonium phosphate.

The pineal gland was called the "third eye" by ancient people. It was thought to have mystical powers. René Descartes, who dedicated much time to the study of the pineal gland,^[25] called it the "seat of the soul".^[26] He believed that it was the point of connection between the intellect and the body.

FET Concepts

2010-10-03T22:40:00.000-07:00

http://en.wikipedia.org/wiki/Field-effect_transistor

1. The drain and source may be doped of opposite type to the channel, in the case of depletion mode FETs, or doped of similar type to the channel as in enhancement mode FETs.

2. The JFET (Junction Field-Effect Transistor) uses a reverse biased p-n junction to separate the gate from the body.

3. The MOSFET (Metal–Oxide–Semiconductor Field-Effect Transistor) utilizes an insulator (typically SiO₂) between the gate and the body.

4. The most commonly used FET is the MOSFET. The CMOS (complementary-symmetry metal oxide semiconductor) process technology is the basis for modern digital integrated circuits. This process technology uses an arrangement where the (usually "enhancement-mode") p-channel MOSFET and n-channel MOSFET are connected in series such that when one is on, the other is off.

5.

http://www-ferp.ucsd.edu/najmabadi/CLASS/ECE60L/02-S/NOTES/FET.pdf

6. A FET is a "voltage-controlled" device.

7. Complementary MOS technology employs MOS transistors of both polarites PMOS and NMOS, thus many powerful circuits are possible using CMOS.

8. Depletion-type MOSFET has a physically implanted channel. Thus, a n-type depletion-type MOSFET has already a n-type channel between drain and source.

http://www.bcae1.com/tranfet.htm.

9

Schematic symbol for N channel MOSFET

10.

The transistor's "turn on" (a.k.a. threshold) voltage varies from one FET to another but is approximately 3.3 volts with respect to the source.

Complex Variables

2010-10-02T07:13:00.000-07:00

Reference: http://www.math.uiuc.edu/~r-ash/CV/CV1.pdf
http://en.wikipedia.org/wiki/Cauchy%E2%80%93Riemann_equations
http://mathworld.wolfram.com/Cauchy-RiemannEquations.html

1. If z = a + bi, then a is called the real part of z, written a = R ez, and b is called the
imaginary part of z, written b = Imz. The absolute value or magnitude or modulus of z
is defined as (a2 +b2)1/2.

2. A complex number with magnitude 1 is said to be unimodular.

3. An argument of z (written arg z) is defined as the angle which the line segment from (0, 0)
to (a, b) makes with the positive real axis.

4. to a multiple of 2π.
If r is the magnitude of z and θ is an argument of z, we may write
z = r(cos θ + i sin θ)

5. The Cauchy–Riemann equations on a pair of real-valued functions u(x,y) and v(x,y) are the two equations:

(1a)

and

(1b)

Typically u and v are taken to be the real and imaginary parts respectively of a complex-valued function f(x + iy) = u(x,y) + iv(x,y).

6. If , then the Cauchy-Riemann equations become

			(18)

7. If and satisfy the Cauchy-Riemann equations, they also satisfy Laplace's equation in two dimensions, since

(20)

8. An analytic signal is a signal with no negative-frequency components
9. A function is analytic if and only if it is equal to its Taylor series in someneighborhood of every point.
10. Any polynomial (real or complex) is an analytic function. This is because if a polynomial has degree n, any terms of degree larger than nin its Taylor series expansion will vanish, and so this series will be trivially convergent. Furthermore, every polynomial is its own Maclaurin series.
11.

The exponential function is analytic. Any Taylor series for this function converges not only for x close enough to x₀ (as in the definition) but for all values of x (real or complex).

The trigonometric functions, logarithm, and the power functions are analytic on any open set of their domain.

Typical examples of functions that are not analytic are:

The absolute value function when defined on the set of real numbers or complex numbers is not everywhere analytic because it is not differentiable at 0. Piecewise defined functions (functions given by different formulas in different regions) are typically not analytic where the pieces meet.

The complex conjugate function is not complex analytic, although its restriction to the real line is the identity function and therefore real analytic.

12. In mathematics, the Laurent series of a complex function f(z) is a representation of that function as a power series which includes terms of negative degree. It may be used to express complex functions in cases where a Taylor series expansion cannot be applied.

Verbal Analgoies

2010-10-01T23:45:00.001-07:00

Verbal Analogies Practice Test

ZOONOSES

2010-09-24T06:04:00.000-07:00

Diseases which spread from animals to humans are called zoonotic diseases. Some of these are as follows:

1. Bubonic Plague:

Caused by the bacteria Yersinia Pestis. Thus plague is normally a problem when humans live in close proximity to rodents. Historically, this has meant rats. Slum populations, with poor hygiene, were thus at greatest risk.

The typical sign of the most common bubonic form of human plague is a swollen and very tender lymph gland, accompanied by pain. The swollen gland is called a bubo. This is usually accompanied by fevers, chills and extreme exhaustion. Natural plague has not evolved significant resistance to antibiotics, and thus remains treatable in most cases.

http://www.zkea.com/archives/archive02005.html
Since plague is zoonotic, eliminating it from the ecosystem is not possible. The bacteria could always lie latent in its animal reservoir even if somehow eliminated from the human population, thus preserving the possibility of future human infections. This contrasts with other strictly-human diseases, such as smallpox. These non-zoonotic diseases can theoretically be driven extinct by vaccines, since the causative pathogen has no refuge outside of human beings.

2. Avian Influenza:

It is caused by the influenza A viruses most frequently found in birds. Flu viruses are rapidly killed by sunlight and tend to dehydrate to death in the breeze.

Like all contagious intestinal and respiratory infections, avian influenza viruses are density-dependent pathogens with a penchant for darkness, dampness, dirt and weakened immune systems – the perfect conditions in which to mutate and proliferate in birds and humans alike. The poultry and eggs one buys at the store came from birds who lived, day in, day out, in excrement, including the excretory ammonia fumes rising from the decomposing droppings in the chicken and turkey houses.These poisonous gases penetrate egg shells (Carlile, 101). They enter the birds’ airways and immune systems, inviting Salmonella,Campylobacter, and avian influenza viruses to colonize, mutate, and spread.

The droppings themselves contain disease organisms, antibiotic residues, cysts, larvae, and metals such as copper, zinc, and arsenic (UPC [c;d]).

http://www.upc-online.org/poultry_diseases/birdflu.html

Quiz:

1. What is mad cow disease?

2. What are the symptoms of swine flu?

3. Who on an average suffers more from depression, man/woman?

Analog Electronics Ready-Reckoner 1

2010-09-08T05:59:00.000-07:00

1. Forbidden energy gap for insulator diamond is 6 eV.

2. Drift velocity is in the direction opposite to that of the electric field and magnitude is proportional to electric field.

3. Semiconductor has forbidden energy gap of about 1 eV.

4. Silicon is largely preferred to germanium because of its large gap energy, which provide improved device properties at high temperatures.

5. In a capacitor, the dielectric strength is the ability of a dielectric to withstand a potential difference without breakdown. Air/vacuum has dielectric constant 1.

6. Only electrolytic capacitors have polarity. High value capacitors are electrolytic. Electrolytic capacitors need to be connected with the correct polarity. If not, they can explode.

7. The voltage of a capacitor falls by an equal fraction in equal time. V = V0 e^-t/RC

The physics codes are as follows:

V - voltage at any time;
V₀ - the voltage at the start;
t - the time (s);
R - the resistance of the resistor through which the capacitor discharges (W);
C - the capacitance of the capacitance (F);
e - the exponential number, 2.718...

The charge follows the same pattern:

Q = Q0 e^-t/RC

The current follows the same pattern:

I = I0 e^-t/RC

The product between resistance and capacitance (RC) that appears in the formula is called the time constant and is measured in seconds. It may seem strange that ohms × farads = seconds, but it's true. If we multiply the base units of ohms and farads, we end up with seconds.

8. Inductors store energy in the form of magnetic field and delivers it as and when required.

9. A missing electron in the valence band leaves a vacant space there, which is known as the hole.

10. Under thermal equilibrium for any semiconductor, the product of the number of holes and the number of electrons is constant and is independent of the amount of donor and acceptor impurity doping. This relation is known as mass-action law, given by:

n * p = ni²

^{n = number of free electrons per unit volume}

^{p = number of holes per unit volume}

^{ni = intrinsic concentration}

8085 Microprocessor - Reader's Bird View

2010-09-03T06:29:00.000-07:00

In today's fast-paced environment, every thing requires to be clock-driven, from laser printer to semi-automatic washing machine to car stereo to digital timepiece to apple iPhone. Microprocessors are able to perform substantial (similar or non similar) work per clock cycle. The clock speed determines how many instructions per second the microprocessor/CPU can execute.

If required to define, a microprocessor is a digital electronic component with miniaturized transistor (N-MOSFET ) components on a single semiconductor integrated circuit.

Lets start with a basic microprocessor, the beginners in the INTEL series in the late 1970's: 8085

Salient features collected from trustworthy web links are as follow -

An 8-bit processor

16-bit address bus

Program, data and stack memories occupy the same memory space.

Total addressable memory size is 64 KB = 65536 bytes = 2 pow 32

Stack grows downward

Jump, branch and call instructions use 16 bit addresses

5 interrupts with unequal priority

256 input ports

256 output ports

16 bit program counter

Stack pointer is a 16 bit register, always incremented/decremented by 2

Logical instruction set -AND, OR, XOR, ROTATE

Arithmetic instruction set - Add, Subtract, Increment, Decrement

It has single 5 volt power supply

Processor speed - 3 MHz

Multiplexed address and data bus

Manufactured with N-MOS technology

Protocol Analyzers

2010-07-25T04:13:00.000-07:00

After JDSU acquiring Agilent testing unit solutions, the demand for engineers ready to provide telecom measuement equipment support, seems to have risen up in the air!

This post tries to provide insights in varied protocol analyzers' run time usage.

First what is a protocol analyzer?

It is a device analyzing granular details of stream of incoming high speed packets based on the programmed protocol. most commonly used protocol analyzers are ethereal, wireshark, RS-232 analyzers working on windows platform.

Figure below displays network packets captured on ethereal.

Ethereal is a freely available open source program that runs on almost any operating system.It is capable of dissecting 385 protocols including SMTP, ATM, IGRP, PPP, IPX, IP, UDP, TCP, MAC, Etherent. It also supports configurable filters that allow user to drill down on the particular data he is interested in. A snapshot of capturing options provided by ethereal can be seen below:

Wireshark is an enhanced version of ethereal; for details refer link:
http://en.wikipedia.org/wiki/Wireshark

Multi-Dimensional Arrays in C/C++

2010-07-20T22:54:00.000-07:00

Use of multi-dimensional arrays in C/C++ is a little tricky especially after 2+ scale.

I have devised some tips to understand them better:

For a n-scale array, to calculate offset address for a particular element, use the formula:

Base address of array + 2(pow n-1) * (size of data type) (nth index) + 2(pow n-2) * (size of data type) (n-1th index) till n is 1 + (size of data type) * last entryindex.

discussing scale 4:

i     j    k l

0   0    0 0

0   0    0   1

0   0 1    0

0   0   1   1

0 1    0   0

0 1    0   1

0 1 1 0

0 1 1 1

1 0 0 0

1 0 0 1

1 0 1 0

1 0 1 1

1 1 0 0

1 1 0 1

1 1 1 0

1 1 1 1

For example, for second last entry, put values as:

BA + 2 (pow 4-1)* sizeof DT *(1) + 2(pow 2) * sizeof DT *(1) + 2(pow 1) * sizeof DT *(1) + sizeof DT *0

Tip 2:

To completely dereference a data value, total de-reference operators must be equal to the scale of array.

Tip 3:
(arr + index) = &(arr[index) at any level.

Keeping these tips in mind, i have solved a complex code available at:

http://pastie.org/1053208

Output as seen on GNU compiler is pasted below:

Feel free to post multi-dimensional arrays questions in C/C++

C File Splitter

2010-04-11T10:24:00.000-07:00

Simple C Calculator

2010-03-24T17:28:00.000-07:00

Code is compilable for basic integer operations:

x + y

x - y

x * y

x / y

(space reqd between mainline arguments)

Though this code is too simple to share with computer science enthusiasts, but lets build C concepts over a simple snippet:

Code:

#include <stdio.h>
typedef struct {
    int operand1;
    int operand2;
    char inp_operator;   
    
} operation;
void parse_user_input(int arg_index, operation *a, char * mainline_arg);
int string_to_int_conversion(char * string);
int main(int argc, char* argv[])
{
    
    int loop_index;
    operation calc; 
    
    //Extract input digits and end-user's desired operation
    for(loop_index = 1; loop_index <argc; loop_index++)
    {
        //printf(" loop index is %d\n", loop_index);
        //printf("%s\n", argv[loop_index]);
        parse_user_input(loop_index, &calc, argv[loop_index]);
    }
        
    switch (calc.inp_operator)
    {
    case '+':
        printf("%d\n", (calc.operand1 + calc.operand2));
        break;
    case '-':
        printf("%d\n", (calc.operand1 - calc.operand2));
        break;
    case '*':
        printf("%d\n", (calc.operand1 * calc.operand2));
        break;
    case '/':
        printf("%d\n", (calc.operand1 / calc.operand2));
        break;
    default:
        printf("Invalid operands entered as %d, %d, %c, exiting without calculation", calc.operand1, calc.operand2, calc.inp_operator);
    }
    return 0;
}
//Logic for parsing user input storing basic arithmetic operands and operations
void parse_user_input(int arg_index, operation *a, char * mainline_arg)
{
  
  if (arg_index == 1)
  {
     a->operand1 = string_to_int_conversion(mainline_arg); 
     //printf("%d\n", a->operand1);
  }
  
  if (arg_index == 2)
  {
     
     a->inp_operator = mainline_arg[0]; 
     
  }
  if (arg_index == 3)
  {
     a->operand2 = string_to_int_conversion(mainline_arg); 
     //printf("%d\n", a->operand2);
  }
}

//Logic for converting string to decimal if 
//each element entered between 0-9 
int string_to_int_conversion(char * string)
{
    int converted_integer = 0;
    while ((*string != '\0') && (*string >='0') && (*string <='9') )
    {
        converted_integer = (converted_integer * 10) + (*string -'0');
        *string++;
        
    }
 

    return converted_integer;
  
}

Quiz:

1.Use Function polymorphism in above C program
2. Introduce floating point arithmetic in the above code

Multi-Threading

2010-03-15T04:48:00.000-07:00

As user's run-time needs keeps on increasing, it becomes imperative to design effective models where multiple concurrent tasks can be successfully accomplished. One set of possibilities already exists in terms of creating multiple processes running at the same time. Withn 1 process, multiple threads are used to used to devise parallelism. This phenomenon is highly applied in case of network processors. One good link:

http://www.wedevblog.com/posix-threads-threading-with-c.html

As previous posts have already emphasized on these concepts, today's post focusses on testing multithreaded applications.

Reference for this post is:
Object-Oriented Multithreading Using C++ by Cameron Hughes and Tracey Highes
http://www.amazon.com/gp/product/0471180122/ref=cm_li_v_cs_d?tag=linkedin-20

2 important testing guidelines shared by them:
-Don't wait until a software system gets complex before testing it
-Categorize the types of defects to which the software is subject

Unit Testing - Requires that SW be tested one component or unit at a time

Stress Testing - Designed to push a component or a system up to and sometimes beyond its limits

Integration Testing - Used to test the assembly of components. The components are combined into logical groups, and each group is tested as a unit

Regression Testing - Used to retest modules that have changed.Regression tests ensure that the changes to the component do not cause it to lose any functionality

Operational Testing - Used to test the system in its full operation. The operation tests also serve to determine how the component will behave in a totally foreign environment.

Specification Testing - The component is audited against the original specification, used as part of the software verification process.

Acceptance Testing - Used by the end user of the module, component or system to determine performance.

Lets also try to understand several typical categories of software defects that are specific to programs that contain multithreading, concurrency, parallelism or asynchronous process:

Race Condition - Occurs when two or more threads or processes are attempting to modify the same block of shared modifiable data simultaneously.

Deadlock - A thread or process is waiting for an event that will not occur.

Priority Inversion - Occurs when a lower priority thread blocks the execution of a higher priority thread when synchronization variables are being used or when competing for resources.

Performance Degradation - Occurs when a system's performance lowers or degrades in terms of responsiveness, execution time, calculation of results, and so on.

Indefinite Postponement - Occure when a system indefinitely delays the scheduling of processes or threads while other processes or threads receive the attention and the allocation of resources.

Mutex Exhaustion - Occurs when a system has reached its maximum number of mutexes that can be created.

Thread Exhaustion - Occurs when a system has reached its maximum number of threads that can be allocated.

Quiz:
http://testertested.qualityfrog.com/
http://www.informit.com/articles/article.aspx?p=412922&seqNum=4

I scored pretty bad in the first!

Sorting Algorithms

2010-03-06T03:22:00.000-08:00

Today's post talks of various sorting algortihms already in place to sort unsorted sequence of numbers or infact any list where based on some logic the entities can be compared. To name a few that are commonly heard:

Insertion Sort

Bubble Sort

Quick Sort

Selection Sort

Heap Sort

Merge Sort

Bucket Sort

Radix Sort

Wikipedia provides a good insight into various sorting algorithms.

http://en.wikipedia.org/wiki/sorting_algorithm

Another good reference is available in Data Structures and Algorithms book by Bruno R. Preiss.

Inserion sort implies a linear search starting from either left or right direction and inserting the element at a sorted position w.r.t. all the elements from the sorted direction

and it continues as:

4 7 11 13 15 17 35 45 12 19 3 22

4 7 11 12 13 15 17 35 45 19 3 22

4 7 11 12 13 15 17 19 35 45 3 22

3 4 7 11 12 13 15 17 19 35 45 22

3 4 7 11 12 13 15 17 19 22 35 45

While insertion sort looks easy to implement, its disdvantage is large running time for big unsorted arrays.Check out his interesting animation to understand the disadvange more precisely:

http://www.sorting-algorithms.com/insertion-sort

One good thing about insertion sort is that it does not need any scratch space apart from the sequence being sorted

2 . Bubble Sort

Check out the same animation to figure out the difference yourself:

http://www.sorting-algorithms.com/bubble-sort

3. Merge Sort

Merge Sort needs space in which to merge the elements of its sub-lists.

4. Quick Sort

Quick Sort simply swaps elements around to get them on the correct side of the pivot, as a result equal elements may not be in the same relative order as they were when the sort began.

Again check out the same animation for quick sort to figure out the difference yourself:

http://www.sorting-algorithms.com/quick-sort

Quiz:

1. Can recursion algorithm be effectively applied to insertion sort?

2. How do computers sort data internally?

3. Should bubble sort be taught to beginners?

4. Is quick sort a stable sort?

5. http://www.funtrivia.com/playquiz/quiz2710061f06f18.html

Binary Arithmetic

2010-03-01T06:10:00.000-08:00

Boolean variables 0 and 1 form the basis of many complex IC on any of our electronic devices. This post starts with their basics leading to understanding of some basic digital circuits.

Rules of binary addition:

0 + 0 =0

0 + 1 = 1

1+ 0 = 1

1 + 1 = 0 (with a carry of 1)

1+ 1 + 1 = 10 + 1 = 11

Rules of binary subtraction:

0- 0 =0

1 - 0 = 1

1 -1 = 0

0 -1 = 1 (with a borrow of 1)

Rules of binary multiplication:

Repeated addition of one number by times equal to other number

Rules of binary division:

x / y implies count the number of times y can be subtracted from x with positive or zero remainder.

Multiplication of two given floating point numbers is carried out by multiplying their mantissas and adding the exponent values on a common base.

Division of two given floating point numbers is carried out by dividing the dividend mantissa by the divisor mantissa and subtracting their common base exponent values. Normalize the result if required.

Combination of different binary variables gives rise to LOGIC Gates. Each of the basic logic gates is a piece of hardware or an electronic circuit that can be used to implement the most basic logical expressions. 3 basic self explanatory logic gates are AND OR NOT

For Ex-OR gate, output equals 0 for equal inputs and 1 for unequal inputs.

The output of NAND gate is 0 when all the inputs are 1.

The output of NOR gate equals 1 when all its inputs are 0.

NAND and NOR gates have a special property that these gates can individually be used to construct logic circuit for any boolean expression making them universal gates.

Quiz:

1. How many binary digits can be added using a half adder circuit?

2. A logic gate with 4 inputs can give how many possible input combinations?

3. NOT gate can have how many input variables?

4. What is the resultant gate f ormed by shorting all the inputs of a NOR gate?

5. Is 10110001 necessarily a binary number?

Object-Oriented Development

2010-01-17T04:48:00.000-08:00

After spending time in understanding syntax of OOPS languages, it becomes imperative to enter the real world and understand how efficiently problems are mapped to behavior of OOPS objects. At many workstations, this is achieved via a language platform UML.

UML stands for unified modelling language, which via pictorial representations tries to resolve the possible states of the process.To appreciate this language more, lets have a quick recap of some important terms:

1. Abstract Class: No implementation method defined for an operation

2. Actor: Role taken by user while invoking a use case

3. Classifier: A category of UML elements that have some common features

4. Containment by Value: An object contains another object

5. Containment by Reference: An object contains a pointer to another object

6. Join: A point in an activity diagram where several concurrent flows synchronize, waiting until all are complete before continuing with a single flow

7. Namespace : A context in which an identifier exists

8. Package: Grouping of classes with related functionality

9. Template: A class that accepts a compile-time parameter defining the type to be used within the class

Links for reference:

http://en.wikipedia.org/wiki/unified_modeling_language

http://www.modelica.org/

Quiz:

1. Discuss the interacting objects while writing SW for a telephone answering machine.

2. Will this technique be helpful for dynamic or digital models?

Delphi Development Environment

2010-01-16T05:33:00.000-08:00

Delphi, an extension of pascal has proved to be a great object oriented language used for building powerful GUI. Dragging and droping the components automatically adds the appropriate code to the program which makes programming more simple and efficient. The quickest way to select a group of components is to drag a bounding rectangle around them.

Visual Objects can be manipulated at design time. Only visual componens can be seen at design time.The objects placed by designer on the windows form are called components, .dpr (project file), .pas and .dfm file types are needed to build an application in Delphi.

When one component owns another, the memory for the owned component is freed, when its owner's memory is freed. When a form is destroyed, all the components on a form are destroyed.

Delphi vocabulary consists of following terms:

1. Frame Object: It is designed as kind of a template for a part of a form.All windows of a delphi application are based on TForm object.

2. TMenu: To build the menu structure.

3. Pop up Menu: Windows that appear on right clicking

4. Labels: To label items on a form.

5. Edit Boxes: For entering editable user information.

6. Memo Boxes: For displaying single string as multi line wrapped text display.

7. Buttons: For providing user mechanism to choose 1 of the given options. if a button is disabled, its text is grayed out.

8. Check Boxes: For letting user enter a Yes/No choice.

9. List Boxes: To provide selectable names.

10. Scroll Bar: For providing horizontal/vertical scrolling option. If autoscroll is true, the scroll bar appears automatically when necessary.

11. Radio Group Panels: For providing user multiple choice options.Components such as group box, panel and page control can contain other components.

12. Code Reuse: Associating an event with an existing event handler in Delphi is used in purpose of code reuse.

13. Container: The idea of a conainer is that all the components will behave as one at the design time, the child components move with the parent inside a container.

14. DLL: Dynamic linked library called from executable programs leading to effective code reuse.

15. Object Inspector: Located on the left side of the screen for modifying component's properties and events.

16. Event Handler: A section of code invoked in an application in response to an event.

17. Set: A collection of values of one type, e.g. a set of font types.

18: Dynamic Allocation: Memory required for an object is allocated from the heap; heap refers to computer's virtual memory.

19. Self: A pointer to the instance of the class in memory. This pointer should be never modified.

Delhi 5,6,7 editions also provide spell check for 18 languages using 26 dictionaries.

Well, need not say Delphi development interface looks quite different and enriching for OOPS enthusiasts!

Links For Reference:

http://www.delphibasics.co.uk/Article.asp?Name=Standard

http://delphi.about.com/library/howto/htsharehandler.htm

http://101.lv/learn/delphi/ch19.htm

Quiz:

1. In Delphi, every project has atleast how many windows?

2. How can a button and menu item be handled to do the same task?

3. Ignoring the OOPS front, Delhi city is located in which country?

4. Is Delphi case sensitive; what about the case senstivity of its ancestor Pascal?

5. What is the easiest way to place multiple components of the same type on a form?

6. Can three components share the same event handler, what about 10?

7. Can the name and width property of a component be changed at run time? Will it be a good idea to do so?

8. What is a cursor's hot spot?

9. By default class in Delphi is public or private?

Network Processors - C1

2010-01-15T04:14:00.000-08:00

Network Processors seems to have lot of demand and supply these days. After working on 3 processors (Texas DSP TMS320C6416, Atmel ARM AT 91 and Intel NP IXP2350) in my 6 years+ professional experience, it is interesting to understand how network processors differ from the other processors.

The best way to understanding NP is in terms of a router used for processing voics/SMS packets over a digital telecom network in order of nano/micro seconds. The real trick in programming and using the network processor the most efficient way lies in making full benefit of the money paid to the selling entity by tapping its most specific features.

Lets also try to understand how network processors differ form other specialized processors e.g. viterbi coprocessors.Network processors in general work on the logic of efficient parallel processing which inevitably leads to less code space for each sub-module but the amount of data that can be processed is comparatively higher. Again try to visualize the amount of traffic crossing a router of a VOIP based network every second.

Viterbi Coprocessor (VCP) decodes convolutional codes during channel de-coding of voce/data call.VCP also decodes a series of frames in a most efficient manner. Here again VCP related effort is to maximize its processing power, and minimize the wait period for input/output operations.

So this helps in developing an understanding that VCP is specialized for 1 particular operation whereas each sub-module of NP is specialized for a partiular sub-operation. To put in other words, the key feature of a network processor is its parallel processing capacity dealing with huge number of network packets at a very fast pace.

Local memory caching is another concept widely used in NP to reduce the access time of information more frequently required by that particular thread of micro engine running in network processor. Figure below captures main blocks of IXP2400 and IXP1200 processors:

NP vocabulary mainly highlights following terms:

1. MSF: media switch fabric
2. QDR SRAM controller
3. ME: Micro Engine
4. PCI: Peripheral Component Interconnect
5.CAM: Content Addressable Memory
6. XFER: Transfer Register
7. GPR: General Purpose Register

Links for reference:

http://www.embedded.com/story/OEG20010730S0053
www.cs.ucr.edu/~bhuyan/CS260/LECTURE1.ppt

Quiz:

1. What disadvantages do high level languages impose if used on Network processors other than their translation time?

2. What will happen if input packet speed is more than than the data rate supported by NP; also think of scenario where packet speed is less.

3. Buffer management and data compression/decompression pose what kind of challenges to Network processors.

4. Out of TCP and UDP protocol stack, which is more apt to be supported on Motorola C5 NP?