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By: Akshata Sonnad


There has been a dramatic improvement in the technology used for the detection and diagnosis of diseases in the human body, ranging from simple clinical tests to sophisticated imaging technology such as the MRI (Magnetic Resonance Imaging) and radiography. The latest technological breakthrough in the field of medical electronics comes in the form of a tiny prototype robot that functions like a living creature which can be used to pinpoint diseases within the human body.


This micro-bot, called CYBERPLASM, fuses together microelectronics and biomimicry (from bios, meaninglife, and mimesis, meaningto imitate) to detect and diagnose diseases within the body.

Dr.Daniel Frankel of Newcastle University is leading a U.K.-based study on the Cyberplasm with the support of a research team from the National Science Foundation in the United States.


Dr.Daniel Frankel

The aim is for the Cyberplasm to have an electronic nervous system with light and smell sensors derived from mammalian cells, as well as artificial muscles that use glucose as an energy source to propel it forward. The intention of the research team is to engineer and integrate robot components that respond to light and chemicals in the same way as biological systems.




The researchers are hoping to model the Cyberplasm off the sea lamprey, a jawless fish that dwells mainly in the Atlantic Ocean. It has a very simple nervous system, which makes it easier to simulate with electronics. The Cyberplasm prototypes are expected to be less than 1cm long, with future versions being potentially built on a nanometer scale.


Mouth of a Sea Lamprey

The Cyberplasm’s sensors are being developed to respond to external stimuli by converting them into electronic impulses that are sent to an electronic ‘brain’ equipped with sophisticated microchips. This brain will then send the electronic messages to the artificial muscles guiding them as to how to contract and relax, thus enabling the robot to navigate its way safely inside the human body using an undulating motion. The micro-bot is sensitive to its environment and is capable of swimming around inside the body, which enables it to check for tumors or blood clots, for instance, or find chemical signatures of a range of diseases. This data can be collected and stored via these systems for later recovery by the robot’s operators.



Cyberplasm technology also offers insights in the field of advanced prosthetics, where living muscle tissues could possibly be engineered to contract and relax in response to stimulation from light waves or electronic signals.


Other such Biomimetic robots are the Lobster Robots, as shown in the pictures below.

Lobster Robots


Thus, in another 5 years, the Cyberplasm is expected to be fully functional and out in the market, which is most definitely a huge leap not only in the field of robotics, but also in the field of medicine.



References :



By Vrinda Prabhu.

Both Laplace Transforms and Fourier Transforms can be used to solve differential equations, so a natural question is to ask “where to use what?” or “Which one is better?”.

The Fourier Transform is decent enough to be used for functions (or “signals”) that are not having infinite energy and i guess it can be extended to certain finite power, infinite energy functions, like DC or a sinusoid or a periodic function.

But for some functions, like the unit-step function,Weak Dirichlet Condition for the Fourier Transform [integral |f(t)dt| between limits (-infinity,infinity) < infinity] is not satisfied.In simple words function is not absolutely summable so the Fourier Transform doesn’t converge nicely. To counter this there is a change variable of the transformed function from ω or jω to s=σ+jω by adding a little real part to jω which makes some of these integrals converge.

Laplace transform is a more general form of Fourier transform. Laplace transform can be applied to all signals,and all systems. As said before Fourier transform of a system exists only if a system is stable.Because of the negative exponential term in the Laplace Transform integration, convergence is a lot stronger, and polynomial expressions which could not be handled with the Fourier Transform can be considered. The Laplace Transform picks out precisely the solution to a differential equation that obeys certain initial conditions at t=0. Hence it is ideally suited to initial value problems.

However as we are aware  Fourier Transforms tie in beautifully with many areas of applied mathematics, particularly quantum mechanics.Fourier Transform also has many applications beyond the solution of differential equations.The Fourier Transform picks out precisely the solution to a differential equation which decays to zero at large distances. In many applied problems this is exactly the solution we want, since a function which grows at large distances would be considered unphysical.

On the other hand The Fourier transform and the Laplace transform are closely related; in a sense, the Fourier transform can be seen as a special case of the bilateral Laplace transform, where the complex variable ‘s’ in the integral is restricted to be on the imaginary axis. Because of this, Laplace transforms apply to a larger set of functions than Fourier transforms, which can run into discontinuities along the imaginary axis that cause either the transform or its inverse to be divergent.

Briefing it out one of the main areas where Laplace transform is essential is circuit theory; as you probably know Laplace can be used to convert differential equations into algebraic ones this allows for analyzing circuits in there transit state without the need to use the regular methods of solving differential equations, this greatly simplifies the effort needed to analyze and solve whereas Fourier Transform is probably the most important transform because it ties together two of the most used parameters time and frequency, meaning that if you have a signal or waveform in the time domain and you want to see what frequencies does this signal contain you apply the Fourier transform. Looking at the signal in the frequency domain allows us to preform a lot of manipulation on the signal including filtering, sampling, modulation……….etc.

Often a mixture of the two methods proves the most effective. We are interested in functions that depend on time and space. The most physical solution to an equation is one which obeys initial conditions at t=0, and which tends to zero at large distances. This directly corresponds to Fourier transforming with respect to space and Laplace transforming with respect to time!


Part 1:

By Chetana Deshpande.

The field of nanotechnology has, over the last decade, been surrounded by enormous amount of hype. Therefore, it is almost a compulsion to have at least minimal knowledge about this exciting field. Nanotechnology is simply the study of manipulating matter at the nanoscale, i.e., 1-100 nanometers (nm). It focuses on understanding, controlling and exploiting the properties of materials or structures in the nanoscale. A nanometer is one billionth of a meter or about the size of ten hydrogen atoms. One of the most important terms in nanotechnology is ‘nanoparticle’. A nanoparticle is a small object, sized between 1 and 100 nm, which behaves as a whole unit in terms of its properties. A unique feature of a nanoparticle is that it possesses different properties when compared to the same particle on a micro scale. This is due to fact that the ratio of surface area to volume increases drastically in the nanoscale. These properties can be exploited to our benefits.
Nanotechnology finds its application in a vast range including fields like organic chemistry, semi-conductor physics, device physics, molecular biology, micro fabrication, cosmetics, clothing, food packing, disinfectant making, and so on. The list of applications is almost never-ending! But the most important application of nanotechnology is that in the field of medicine. The vision of nanotechnology in medicine can come from several cartoons and science fiction movies like ‘Fantastic Voyage’ where tiny submarines travel through blood eradicating pathogens. The reality is more prosaic, nonetheless exciting. Like any other field, nanotechnology comes with some disadvantages. The first being the safety concerns of nanoparticles. Due to the high surface area to volume ratio, nanoparticles are very reactive or catalytic. They are also small enough to seep through the cell membranes of organisms. This can cause problems like toxicity, respiratory disturbance, etc. The interactions between living cells and nanoparticles are still relatively unknown.
It’s disappointing but a fact that the cases of cancer have drastically increased in the past few years, due to various factors. Cancer is caused by damage of genes which control the growth and division of cells. Cancerous cell need blood supply to grow. A hormone like molecule causes nearby blood vessel to grow towards the cell to supply the oxygen and other nutrients. Cancer can be cured by rectifying the damaging mechanism of the genes or by stopping the blood supply to the cells or by destroying it. Thus, an accurate method of both detection and treatment is required. The conventional methods of detection include observing the physical growth/changes in the organ by X-rays and/or CT Scans and are confirmed by biopsy through cell culture. However the limitation of this method is that it is not very sensitive and the detection is possible only after substantial growth of the cancerous cells. And in most cases, it cannot be treated in an advanced stage. Nanoparticles, as mentioned earlier, can enter the cells and access the DNA which is affected. This can be done in-vitro also. Thus, detection can be done in the incipient stage.

Conventionally, cancer is cured by surgery or radiation therapy. The former causes loss of organ and a chance of reappearance of cancer, while the latter causes a lot of side effects like burning away of healthy tissues (temporary or permanent), etc. Nanotechnology provides nano structures like nano-cantilevers, nanopores, nanotubes, nanoshells and quantum dotes which are prospective structures that would help in detecting and treatment of cancers. A success story in this field is the effective cure of liver cancer using ‘BrachySil’ by a nanotechnology company “pSivida” undertaken in Singapore General Hospital. BrachySil is a tiny structure made up of modified particles of silicon filled with the radioactive isotope of phosphorus 32P. It is injected into the cancer using a fine needle and the radiation is limited to 8mm, hence destroying only cancer cells and not healthy tissues. After 12 weeks of treatment, the cancer reduced by an average of 80% and could eradicate all primitive stage cases. The silicon eventually breaks down and is excreted. The 32P decomposes to stable isotope, after its half-life of 14 days and is used by the body or is excreted. Thus, there is very less scope for side effects. Such an efficient result is not seen in any other treatments of cancer. This method can be used for treating liver and prostate cancer. There is great potential for this treatment to be expanded into all other forms of cancer and tumors.

An image showing a model of BrachySil.

The scope for nanotechnology is very high as there is a lot more to explore in this field. In the subsequent articles, we will try and show you, various other perspectives nanotechnology can have. So, keep visiting us!

Article in British scientific journal, Nature.
Research paper in Forbes magazine.

Open Hardware: The way forward!

by Ashfaq Farooqui

Free and Open Source Software has gained a lot of momentum in the past couple of decades, with accelerating the growth of and development of technology. Though we enjoy the benefits of FOSS on a daily basis the complexity of writing drivers for hardware is increasing with every new piece of hardware coming into the market. Hardware and software have always gone hand in hand, but the last couple of years have seen a massive boom in the software market where major companies were concentrating only on complexity of their software. But of late proprietary companies are entering into legal partner ships with hardware companies to have hardware locks on their software, and also hardware manufactures trying to conceal products for their own benefits.

The four freedoms defined for Free Software can also be used on hardware.

Freedom 0: The freedom to use the product for any purpose.
Once we have bought the product it belongs to us and we have all right to use it for what ever we wish. There are no restrictions, but for the safety of the device we are supposed to use it in a defined manner.

Freedom 1: The freedom to study how the product works, and change it to make it do what you wish.
Lets say for example we have a bicycle, we have all right to modify it and make changes to it and i assume most of us have played around with bicycles to improve them for our own needs.

Freedom 2: The freedom to redistribute copies so you can help your neighbor.

Freedom 3: The freedom to improve the product, and release your improvements (and modified versions in general) to the public, so that the whole community benefits.

The next two laws talk about sharing, though it cannot be done on physical hardware to a very large extent, we shall look into these two freedoms further in the article.

Prior to Integrated circuits most of the devices we had were mechanical and semi transparent, hence users with basic knowledge about the device could repair or replace broken parts and re-purpose. The bicycle is one example which most of us have seen evolve, hobbyists would modify to various designs to suite their needs.

However the has been a rapid change in technology as embedded systems have taken over most of our devices, From the hair dryer to automobiles embedded processors are everywhere. Though it is highly beneficial to have such systems running, they come with a drawback. The simplest drawback being ‘bugs’. No code is perfect, and at some point a bug will show up. The cost of recalling the products to repair them is a herculean task and may cripple the company, hence rarely resorted to. The biggest disadvantage is that no one other than the original manufacturer is capable of repairing it. Now if the source was easily available, it could be rectified by some person and given out to everyone, then installed by the owner if he could simply upgrade the firmware. Now this would benefit everyone. if users were allowed to write firmware, they rate of development would increase to a large extent as we have seen on the application development arena for android platform. Additionally, it would benefit the manufacturers as they could use the community fixes to install in their  subsequent manufacturing runs.

The Open Hardware criteria

Any device made with the intention of benefiting the open hardware community must follow certain rules:

  • All physical designs and schematics must be easily available under a license which allows modification and resale of the new device.
  • All software and firmware must be modifiable by the end user using FOSS tool-chains
  • The owner has the right to repair, modify and re-purpose with legal and social responsibility.

The device must also allow:

  • Updating of all firmware and software by the end-user
  • The user must be allowed to disassemble and reassemble the complete product.

The correlation between the freedoms and open hardware can be made here easily.

Future offerings in Open Hardware domain

Till now we have seen only dealt with what open hardware is. Now given all this how do we hope open hardware to change the world we live in? Now consider for example a cell phone, most of use use a cell phone. The hardware of the cellphone is designed by highly specialized engineers, but if the basic model is given as an open hardware phone, users would add different functionality to the phone according to their needs. For example, a chemical sensor, a heart monitor, and such devices. Now each device would require its own screen buttons, embedded processor, hence it is highly complex for a person trying to make a simple device, instead if given an open phone concept, the developer could use that as a base and create his own device with adequate effort. This type of system can be compared to a ladder where each user/developer ascends the ladder and allows the next person to use his support to go higher. Therefore everyone need not have to do that which is already done, he would need to concentrate on only making what is done better, allowing for a faster growing community.

The market relations in Open Hardware environment

With the arrival of open hardware component manufactures and device manufactures will be forced to change the way they do business. Component manufactures will be selling development kits at a fairly cheap price,  this is already happening with the Arduino boards growing in fame.

Device manufactures will have to decide between being ‘open’ or ‘closed’ this trend is already being seen in the market with all the ‘i’ products coming in with all types of patents and limitations on the end user. Community driven products will reduce expenditures to a large extent as any one can produce the same product, hence stopping monopoly-style-pricing. Since it would be community driven the products would be more of what the user wants and not all unwanted features which are added just to increase the price of the device.

Consumers will be at the benefiting end here, they will have the chance to choose from a wide variety of products and also help in making of these products either by suggesting ideas on mailing lists, supporting projects on kickstarter or by actually making them.

Open Hardware licenses

Though open hardware has been there for a long time there were not many licenses available and people would use the GNU/GPL license or the creative commons.
Due to the special needs of the current advents in the hardware industry a number of licenses have been made to name a few:

  • The TAPR Open Hardware License
  • Although originally a software license, OpenCores encourages the LGPL
  • The CERN Open Hardware License (OHL)

Live Open Hardware projects

The number of current official open hardware projects is increasing day by day, and no definite number can be given.

The most famous projects would be:

  • Arduino- an open source program development board working on ATMEGA controllers
  • Beagle board-a single-board computer based on low-power Texas Instruments processors, using the ARM Cortex-A8 core
  • The maker bot-A device used to print 3D hardware.

Arduino UNO ATMEGA development board

We are now on the brink of a transformation in how physical devices are created and who creates them. The ability to create modern electronic devices is spreading from the hands of large-budget R&D groups of specialized engineers to communities made up simply of the people who want to be involved; engineers, artists, and other creative types .  This transformation will ultimately produce the devices that people want and need, not what focus groups and corporations think is needed. And most importantly this change will transform us into a society of citizen-makers – a people with greater understanding of the things we make and that make us who we are.

Hedy Lamarr: The beautiful inventor

By Aparna Narayanan

Through years of existence, man has come to believe that aesthetic beauty and intellectual congruence are mutually exclusive and that one learns sooner or later, to settle for the one most significant to them. But when these two qualities co-exist, they collide with conformity to lead into something that no man could dream of resisting. Although rare, one could not deny the existence of personalities possessing such qualities.

One such example would be the Austrian-American actress Hedy Lamarr( 1913-2000). Born in Vienna, Austria-Hungary, she is most remembered for her incongruous mixture of mathematical talent and her coveted aesthetic beauty. She joined a famous acting school during her late teens and some people thought her to be the most beautiful actress in Hollywood. In 1933 she starred in the movie Ecstasy, a Czechoslovak film and revealed to the world all her beauty. On August 10 1933, 19 year old Hedy married Friedrich Mandl, an arms manufacturer. Mandl took her to meetings with technicians and partners, where she learned about military technology. In her autobiography, Ecstacy and Me (1966) she mentioned that Benito Mussolini and Adolf Hitler attended Mandl’s extravagant parties. She also stated that she fled to Paris disguised as one of her maids, to obtain a divorce from Mandl. An embellished version of the story states that she attended a party wearing all her expensive jewelry and drugged Mandl with the help of a maid, and later escaped with the jewelry.

She is said to have met her co-inventor George Antheil in the summer of 1940, when they were neighbors in Hollywood. Together they invented a technique for spread spectrum communication and frequency hopping necessary for wireless communication. The idea behind their invention was to make radio-guided torpedoes harder for enemies to detect. Being a composer, George experimented with his music for Ballet Méanique. Here he had coordinated sixteen synchronized player pianos to play simultaneously. He took inspiration from this musical piece to suggest synchronization of rapid changes in radio frequencies. Lamarr’s contribution to the invention was the concept of “Frequency Hopping”. It means transmitting a signal over a random series of frequencies and switching between these frequencies at split-second intervals. The receiver is synchronized with the transmitter and hence ensuring effective recovery of the transmitted signal. This signal might contain commands for directing the torpedo. Eavesdroppers will hear only random blips hence making the detection of these signals by enemies harder. Even if an attempt was made at jamming the signal, it would knock only a few bits out. Frequency hopping is used extensively in Military communication systems. They applied for a patent on “A secret communication system” in 1941. Their frequency hopping idea is also used in Wi-Fi network connections and CDMA used in wireless telephones.

Hedy Lamarr once quoted that “Hope and curiosity about the future seemed better than guarantees. That’s the way I was. The unknown was always so attractive to me and still is”. Her intelligence hidden behind a scintillating exterior goes on to show that her beauty was anything but a façade. A woman like her is sure to instill hope in the hearts of those men whose every dream involves a blend of beauty and intellect; something that everyone talks about,yet hardly ever finds.

Information Source:

American Heritage of Invention & Technology, Spring 1997, Volume 12/Number 4


Dr.Mulugeta, Physics and beyond…

Dr.Mulugeta Bekele, a Physicist from Ethiopia was in Bangalore visiting his alma matter – The Indian Indian Institute of Science in Bangalore, where he pursued his Ph. D. With decades of science work and a life to look up to, Bitstream had an opportunity to interact and interview this humble source of inspiration, embedding a deeply accomplished physicist.

An assimilated interview with Dr. Mulugeta Bekele by Sneha Das of Team Bitstream.

 From being a student to a teacher

 “I wanted to do both math and physics.”

“My parents said that I was born on 22 Oct 1947”. Dr. Mulugeta Bekele started his schooling at the age of four. He joined first grade in the year 1954, and at the young age of 12, in the year 1960, he appeared for the 8th grade national exam.“I failed in my 8th grade. That was the first batch to sit for this 8thgrade national exam. Eight of us sat for the exam and only one passed. I was so small, I didn’t feel anything. So, i took it up again the next year, and all eight of us who took up the exam passed”.

In 1965-66, he joined HaileSelassieIUniversity, now known as Addis Ababa University, then the only university in the country. “In the one year freshman programme we had to take up subjects like physics, math, chemistry, zoology etc. We had to decide which
field to choose the next year.”

View full article »

Demystifying Complex Sinusoids

By Sneha Das and Raghavendra S

“Complex”, the word by itself has an inherent sense which would make one expect complications rather than clear ideas! Blame the English.

And the “i” for imaginary associated with the complex numbers adds further to the disconnect aggravating the already persistent Mathematics reluctance amongst many.

In general, a word of caution about the beauty in Math is in that it is revealed in a slow and seductive process. It certainly requires a little topping of imagination to be able to interpret and appreciate its subtleties.

In this article, in an attempt to present the wonder and beauty of a mathematical nuance we look at complex sinusoids.

Power of the “i”

 The profound Euler’s identity and the polar form representation of complex numbers in the Euler’s formula are some wonders of Mathematics possible because of “i”

where, i=sqrt(-1)

View full article »

DIY Musical Greeting Card

Fall. So it’s that time of the year.  It’s cold and foggy in the northern hemisphere; the skies are all grey and cloudy, the days kind of dull; and all of the staff of bitStream is pinned down under the weight of our fast-approaching endsems, and bitStream has hit a some three-week slowdown. You see, electronic engineering isn’t nearly all that fun when it comes to exams and textbooks. Depressing stuff

And yet, it’s that time of the year – the earth is nearing the completion of the 2016th revolution of the sun since the birth of Jesus, and the entire world’s gearing up for the festivities ahead, with a plethora of festivals and holidays and relatives and family time – you get the drift – lined up. One common thing across festivals and other such special occasions would be the fun. The second would be greeting cards. We all, like it or not, send greeting cards to our near-and-dear ones on several occasions.

When we were little, we used to make these clumsy, fussy, but nonetheless, adorable greeting cards with what little resources we had at hand, crayons, colour-pencils, ruled sheets from our four-ruled ‘hand-writing’ notebooks, with funny caricatures, cute, misspelled messages, kindergarten innocence.  As we grew up, plagued with the shortage of time, the busy individuals that we turned out to be, we skipped all the way to the end to ready- made greeting cards, and earned Archies and Hallmark a fortune; or perhaps got so polished with our skills that our computer-printed greeting cards using word-processing and imaging programs that we nearly outdid the ready-made greeting cards. Yet seldom do the faces of the recipients light-up as they do when they receive these the clumsy, fussy old greetings, than when they’re presented with store bought cards. There lies some kind of charm in fussy DIY craft, when it comes to greeting cards.

Alright,  that’s enough of fanciful writing. The points behind this some close-to-300-word long intro I just typed in are that one, provide an explanation as to why the posts on bitStream have been coming on so painfully slow off late, and two, that we’re going to tell you how to make a DIY musical greeting card.

Okay, so before we get started, thanks go out to our friends at, who came up with this DIY, as well as allowed us to re-post this up here on bitStream; and Lifehacker, where I originally found the link to this article.

Also, all the images,  the code, and the video included in this post, is/are courtesy of Check them out for some other cool DIYs and tutorials involving AVRs and Linux.

Alright,  sodown to the main thing. For this, we’re going to need to following hard and soft resources:

  • Attiny85 – Thru-hole, no frills AVR running at 8MHz
  • Piezzo speaker(s) (x2, in this DIY)
  • Battery holder – Plastic, through hole
  • Coin cell battery
  • Soldering iron, wires, the rest of the usual electronic DIY tools
  • A greeting card, which I shall not tell how to make

Reading this could provide you with some vital background knowledge, about how to put the codes, scripts and libraries to use.

Okay, chop-chop, time to work. The assembling part is incredibly easy, just connect the red wires of the speakers to port 1 and 2 of the Attiny85,  connect the positive terminal of the battery to VCC, ground everything else. Here’s a pin-diagram of the Attiny85 and the assembled circuitry for reference:

Note: After the software part is done, I suggest you place this circuit between two thick cards pasted together. Make a hole on the card that has the message, and right underneath the hole, place a photo-electronic device connected to act as a switch, so the card would automatically play every time somebody opened it.

Okay, now to get to the software part. First, get a MIDI sequence that works for upto a couple of parts. Next, load it into MuseScore, and clean up the chords, so that it doesn’t come up too heavy on the cheap set of speakers we’re using. If you understand musical notations, then make changes as you fancy,  otherwise just leave it that way, and save it as an XML.

Next, use the script to covert it into a header file for the PlayTune library. You should be seeing something that looks like this:

Finally, use this code. Bear in mind, gotafriend.h is the name of the header file generated for the song used in this DIY, in your case, use your own generated header file in your program.

Load the code onto your Attiny85, and you’re good to go.

Here’s a video of the assembled circuit playing ‘You’ve Got a Friend in Me’:

Now, as I mentioned in a note above, use a photo-electronic device as a switch instead of the paper switch, place it under a hole on the side of the message (which is ‘closed’ when the greeting card is ‘closed’). Affix the circuitry on the backside of the card, then conceal the circuitry by pasting a thick card on the back-side, making it the back-cover.

So there’s a DIY musical greeting card you’ve got yourself. There’s one catch in the level of personalization you can give it, and that is, you cannot add spoken messages or audio to this. This is because this is made to custom suit MIDI files, which are basically a representation of music notes, rather than audio. However, if you’re anything of a composer, you can compose your own piece, maybe for that special someone, load it up on the tiny micrcontroller, and there you have super-personal, super-awesome musical greeting card. Nonetheless, if you aren’t much of a Beethoven or a Bach yourself, then I believe we’ve got a workbench in the works that plays an audio message of your choice, so if that’s what you’re looking for, then just hang on for a little, we should be coming up with that some time real soon.

Anyway, back to the context of clumsy DIY cards and musical cards: many people find musical greeting cards annoying, but pre-tweens or (post-)sexagenarians might receive it with a twinkle in their eyes. Also, your relatives from semi-urban/rural locales or those not living on the same edge of technology as you do, might really like it. Either way, no matter who they are, they’ll like it (secretly perhaps), because it’s you who’s made it, with your personalization behind it. So if you make one, no matter whether they liked it, or it pissed the hell out of them, share with us in the comments below!

Music sent over LASER beam

By Aditya Gautam

Transmitting music wirelessly is not nearly a new thing, and while their are somewhat  more practical ways to do it, there’s something damn cool about doing it using a LASER beam.

Not to mention, it’s way simpler than designing a transmission system based on radio-waves, modulation, demodulation, et al. And by simple, I mean really, really simple. Using mostly stuff you’ll easily find around, or over-the-counter in departmental stores. And on the cheap. Probably the single most expensive thing in the setup is the LASER pointer, which you might already have.

Basically, we’re amplitude modulating the LASER beam in accordance with music on your music device. Think you’re great at amplitude modulation, modulation, demodulation techniques, coherent, square law detectors et al? Great. We’ll be using none of that. This uses a very simple circuit, and as long as you can assemble a circuit as per the schematic – although I’ll be walking you through the steps – you’re great to go!

We’re going to be needing a LASER pointer (duh), cells, a potentiometer (47K or 22K should do fine), some wire (wires stripped from an Ethernet cable would be the best), a toggle switch, an audio transformer (one salvaged from an old tape deck/hi-fi system/TV/flicked from your school laboratory should do fine), and a 3.5 mm audio jack.

For the receiver, we’ll be needing a phototransisitor, another 3.5 mm audio jack, a magnifying glass, and a high-gain amplifier (a laptop a mic input or a mic with preamp plus the amp, or a guitar preamp plus a speaker system, or basically any thing that comes with a mic input and speakers should do fine)

I suggest your salvage as many things as possible from old rusty electronic gadgets around your house, flick the rest from your school or college or laboratory. Buy these only if you think it’s absolutely necessary, and if it is worth it .

In addition to all these, you might also want to use a wire cutter and stripper, some insulating tape, soldering iron and solder, a breadboard, alligator clips, and a friend to help you out, though none of these are absolutely necessary. Except maybe the friend, ‘coz it’ll be great fun, then.

So, if you’ve got the things ready, or just want to read this, let’s move on. A disclaimer before you get started, though.

This workbench exercise includes the use of LASERS. Now while diode LASERS used in LASER pointers are relatively safe, do not point it at your eyes. Not even for fun. Take it from someone who’s been lased in the eye. Feels like phosphenes on steroids, for hours together!

Another thing, I’d like to add: while you might as well just connect wires by twisting their ends together, I suggest you use a breadboard, especially if you’re an electronics hobbyist or junkie. A breadboard is to an EE what a slate is to a kindergartner. Plus, it makes everything much more simple, and makes reusing possible, and easy.

So now, to get started (no, actually)

Firstly, we need to modify the LASER pointer. The button cells are probably not going to be sufficient, so we’ll be replacing them with normal AA cells. So, first see what’s the operating voltage of the LASER. It usually should be around 3 to 6 volts. So get as many cells, preferably with a battery compartment/holder, so that its leads would be more convenient to use.

Next, get two leads running out from the positive and the negative battery terminals of the pointer. Connect the wires to the terminals using the alligator clips, or clear tape, or solder them.

And then, we’re going to be externally switching the LASER ON and OFF, so we need to ensure that the local switch on the pointer is always ON. you could do this by simply fastening a tape around the switch, ensuring it is depressed. A slightly more preferable method, in case it’s an old LASER with no use), to hack it open, and short the terminals across the switch, so that it’s always ON.

Next, assemble the circuit as per the following schematic:


View the schematic in full size

Here’s a brief explanation of the setup: To start with, you should do well with any audio transformer, but its the all the more suitable if you use a 8 ohm – 1K-ohm transformer, as its the most easily available audio transformer, as well as the most preferred and widely used audio-transformer, but then again, as I said, any audio-transformer should do just fine.
Connect one of the ends on the 8 Ohm side to the negative terminal of the battery compartment, and also to one terminal of the pot. Connect the other end of the pot to the one terminal of the toggle switch, and the other end of the transformer, on the same side. You could also connect it to the centre tap of the transformer on the same side, as shown in the figure.. Connect the other end of the toggle switch to the the negaive terminal of the LASER. Connect the positive terminal of the LASER to the positive terminal of the battery. This completes the circuit on the primary side of the transformer. On the secondary side, the connections are easier. Connect one end of the transformer to the left terminal of the 3.5 mm jack, the other to the right terminal of the jack. Leave the centre tap terminal of the transformer alone. If your jack comes with a ground terminal as well, just short it with the left terminal of the jack. As simple as that.

The receiver end’s as simple as the secondary side of the audio transformer. Connect the collector of the phototransistor to the left terminal of the audio-jack (shorted with the ground terminal, if it has one), and the emitter terminal to the right terminal of the right terminal of the jack. Done!

That’s it!
Now position your transmitter and receiver across a distance you want to transmit (you can position them as much as a kilometre apart, with excellent quality). Connect the audio jack on the receiving end to the amp. Note that if your pre-amp has a 6.25 mm port, then you’ll have to use a 6.25 mm audio jack on the receiving end instead of the 3.5 mm jack. Now align the transmitter and receivers so that the LASER’s falling positively on the receptor of the photo-transistor. Use the magnifying glass to focus the LASER on to the receptor. Connect the jack on the transmitting end to your iPod, mobile-phone, computer, or anything that can output music through a 3.5 mm jack. Turn up the volume on your music player and the pot, play some bassy music, and stream it across on a LASER beam!

This kind of setup is ideal when your source of music is  on end, and the the listener/speaker at another end, and you don’t want wires all over the place (although you could easily hack this to transmit it through an optical fibre cable).

So what exactly are we doing here? Basically, The transformer modulates the power going to the laser. The signal from the radio is added to and subtracted from the battery power, and the laser gets brighter and dimmer along with the volume of the music or voice in the signal. That’s all the rocket science involved in this!

This workbench exercise is originally the idea of user navaburo, found on instructables.

Head over to his blog and check out some cool electronics and Linux hacks!

So what next?

Well, this is a relatively simple and basic setup for streaming music over a LASER beam, which pretty much any one who can read a simple schematic can pull; for a slightly more advanced version of this, one with much enhanced fidelity, I’m working on a variant of this – except that it’s all digital, so instead of varying the intensity of the LASER, it’s all going to be terms of ON or OFF. So while it does the same thing, it’s actually the whole thing redesigned from near-scratch. Right now, its all in my head now, I’ve got to figure and work out on a few kinks – I seem to have ironed out most, as of now, but I’ll try to still work on it. So in the event that it does work out, I’ll push it here, so do come back and check! See you till then!

e-puzzle 6

Find out and jot down the Electronics related terms that are hidden in the grid.
The remaining letters spell the name of a common electronic component.

looking for answers her roll over here [?]

e-Quiz 1

1. The number of valence electrons in a silicon atom is:

a) Three

b) five

c) eight

d) four

2. When identifying the connections on a large power transistor, a useful tip to remember is:

a) The base is always the middle pin.

b) The collector is usually identified by a metal tab or paint spot.

c) The collector is usually connected to the metal case.

d) The resistance measured between emitter and the metal case will be zero ohms.

3. Which is a type of Electrically-Erasable Programmable Read-Only Memory?

a) Flash

b) Flange

c) Fury


4. The four symbols are: 

a) Capacitor, Microphone, Potentiometer, Electrolytic

b) Electrolytic, Microphone, Resistor, Capacitor

c) Capacitor, Piezo, Resistor, Electrolytic

d) Electrolytic, Coil, Resistor, Capacitor

5. Name the 4 components: 

a) Photo Transistor, switch, capacitor, coil

b) Photo Darlington Transistor, mercury switch, piezo, coil

c) Photo Transistor, reed switch, piezo, coil

d) Photo Darlington Transistor, reed switch, piezo, coil

6. The signal at the collector will be_____ with the base.

a) Inverted.

b) In-phase.

7. What type of switch is an emergency stop?

a) Push to make (PTM)

b) Push to break(PTB)

c) Rocker switch

d) Slider switch

8. The input used by an antenna or cable to a tv set uses___ frequencies.

a) IF

b) RF

c) AF

d) SAP

9. How does a coil react to AC?

a) As the frequency of the applied AC increases, the reactance decreases

b) As the amplitude of the applied AC increases, the reactance increases

c) As the amplitude of the applied AC increases, the reactance decreases

d) As the frequency of the applied AC increases, the reactance increases

10. A two-times increase or decrease in power results in a change of how many dB?

a) 2 dB

b) 3 dB

c) 6 dB

d) 12 dB

Mobile Networks


by Prithvi Ganesh K



Before we hit the secrets behind the networks, I’d like to  throw light on the very basic things we use and the wonders they do because no matter how much u study about them they seem supernatural  A transducer, well we all know what it does, changes one type of energy to another yeah?..just try thinking how that can be made possible. Converting  voice signals to light and electrical signals! Photoresistors which use light to manipulate  resistance. I believe these are the real wonders of the world. If u think similar ,if such concepts intrigue you, bitstream is just the place for you .Stay tuned to our regular updates. Getting back to where we started….


What really happens when a call is made from one mobile network to another?  Instead of boring infographics, let me try and explain it through the game of football instead….


1.  Imagine a call being initiated, just like a goalie looking to pass the ball to his player.

2.  When the number is dialled, the phone sends the request to the cell tower it’s currently connected to – much like the goalie passing the ball to his defender to take forwards.

3.  The call request is forwarded to the base transceiver station (BTS) from the tower.  This is like Xavi making a pinpoint pass through the midfield to another Barcelona player.

4.  From the BTS, the call is connected to the base station controller (BSC), which allots the call a frequency channel to communicate over.  This is akin to a football team keeping their shape, and making sure they stay in their positions (or their allotted “frequency”).

5.  The call is now switched to a mobile switching center (MSC).  If the call is for another user in the same home network, the steps are retraced to the base station of the other user.  This is like reaching the goal mouth of the opponents’ goal and back passing all the way back to your own goal line.

6.  If the call is for a user on another network (another operator), the call is passed from the MSC to a gateway MSC that switches the call to the appropriate operator’s MSC.  Think of it as losing possession to the other team.

7.  Here’s where football stops making sense in the equation.  Instead of the play turning around, imagine if both teams wanted to attack the same goal…  The call is carried forward from MSC to BSC to BTS and all the way to the base station of the called party’s location.

8.  There’s also a home location register (HLR) that each operator maintains, which knows which phone is where (or latched on to which base station).  Also, an authentication center (AuC) checks whether the subscriber being called has the required authorisation and credentials to receive calls.  So if you haven’t paid your bill or furnished proper documents, the AuC is the one who gives you the red card – like a referee does.

9.  When all goes well, the correct subscriber is connected to and you hear ringing at your end, as the networks finally connect the two phones – it’s like a forward taking a shot at the goal.

10.  The called party hears his phone ring.  Think of them as the opponent’s goalie.  If the call goes unanswered or is rejected, it’s like a goalkeeper’s save, and you start from scratch all over again.

11.  When the call is answered, it’s like a goal being scored ,                                                                                                                                                                                                                                                                                                                   and the celebrations begin with a “Hello!”                                                                                                                                                                                                                      

12.  Of course it usually turns out to be a telemarketer, trying to sell you something you don’t really want or need.  So it’s usually the mobile operator and the marketing companies that celebrate most of the calls that get through!

The next time your calling someone try recollecting this whole process(the soccer game) which occurs in a period of 3 SECONDS  :P!!

e-Puzzle 5

This is a circuit that looks very much like the canonical series circuit, but the switches and lights don’t do what’s expected. There has to be a deeper level of knowledge and understanding to figure it out.

Here’s the apparent circuit.

The puzzle is, what components can be added to this circuit (in Fig 1) to give the behavior shown in fig. 2 (All three circuits)? One could think about the effects of common components such as resistors, inductors, capacitors, diodes, transistors, etc. I can tell you it doesn’t involve magnets or radio frequency transmitters. If you figured it out, check the solution. If you haven’t, I can give you three hints:

Hint 1  [?]

Hint 2 [?]

Hint 3 [?]

Fig.  2 [NOTE: These circuits are incomplete. It is merely a depiction of the desired result. Your job is to find out what has to be added to the circuit in fig 1 to achieve this behavior.]

e-Puzzle 4

You are given two small black boxes of alien origin, externally identical but internally containing these circuits. The components are ideal. The boxes are indestructible and impervious to all forms of internal inspection. How do you identify, what box contains what circuit?

Get Your own USB Power Socket

By Yashasvini

Today, almost all computers contain logic blocks for implementing a USB port. A USB port, in practice, is capable of delivering more than 100 mA of continuous current at 5V to the peripherals that are connected to the bus. So a USB port can be used, without any trouble, for powering 5V DC operated tiny electronic gadgets.

Nowadays, many handheld devices (for instance, portable reading lamps) utilize this facility of the USB port to recharge their built-in battery pack with the help of an internal circuitry. Usually 5V DC, 100mA current is required to satisfy the input power demand.

To prepare USB Power Socket we require:

  • Cigar plug
  • Diode-1N4007
  • Resistors
  • 270Ω
  • 820Ω
  • 330Ω
  • Capacitors
    • 470µF
    • 0.1µF
    • 10µF
    • 1µF
  • Zener diode
  • LED
  • USB type A socket View full article »
  • MIicro Electronic Pill

    By Surabhi

    The invention of transistor enabled the first use of radiometry capsules, which used simple circuits for the internal study of the gastro-intestinal tract. They couldn’t be used, as they could transmit only from a single channel and also due to the size of the components. They also suffered from poor reliability, low sensitivity and short lifetimes of the devices. This led to the application of single-channel telemetry capsules for the detection of disease and abnormalities in the GI tract where restricted area prevented the use of traditional endoscopy.

    They were later modified as they had the disadvantage of using laboratory type sensors such as the glass pH electrodes, resistance thermometers, etc. They were also of very large size. The later modification is similar to the above instrument but is smaller in size due to the application of existing semiconductor fabrication technologies. These technologies led to the formation of “MICROELECTRONIC PILL”.

    Microelectronic pill is basically a multichannel sensor used for remote biomedical measurements using micro technology. This is used for the real-time measurement parameters such as temperature, pH, conductivity and dissolved oxygen. The sensors are fabricated using electron beam and photolithographic pattern integration and were controlled by an application specific integrated circuit (ASIC).

    View full article »

    Electronic Watchdog

    By Yashasvini

    Here’s an electronic watchdog for your house that sounds to inform you that somebody is at the gate.The circuit comprises a transmitter unit and a receiver unit, which are mounted face to face on the opposite pillars of the gate such that the IR beam is interrupted when someone is standing at the gate or passing through it.


    • For the transmitter circuit:
    •  IC NE555
    • IR LED
    • Resistors:
    • 1KΩ
    • 20KΩ
    • 22Ω
  • Capacitors:
    • 100µF
    • 0.01µF
    • 100µF
    • 0.1µF

    By Surabhi

    Researchers in the University of Toronto’s Department of Materials Science & Engineering have developed the world’s most efficient organic light-emitting diodes (OLEDs) on plastic. This result enables a flexible form factor, not to mention a less costly, alternative to traditional OLED manufacturing, which currently relies on rigid glass.

    The results are reported online in the latest issue of Nature Photonics.

    OLEDs provide high-contrast and low-energy displays that are rapidly becoming the dominant technology for advanced electronic screens. They are already used in some cell phone and other smaller-scale applications.

    Current state-of-the-art OLEDs are produced using heavy-metal doped glass in order to achieve high efficiency and brightness, which makes them expensive to manufacture, heavy, rigid and fragile.

    “For years, the biggest excitement behind OLED technologies has been the potential to effectively produce them on flexible plastic,” says Materials Science & Engineering Professor Zheng-Hong Lu, the Canada Research Chair (Tier I) in Organic Optoelectronics.

    Using plastic can substantially reduce the cost of production, while providing designers with a more durable and flexible material to use in their products.

    View full article »

    By Surabhi

    In a recent development, it has been found that, Smaller and more energy-efficient electronic chips could be made using molybdenite. In an article appearing online on January 30 in the journal Nature Nanotechnology, EPFL’s (Ecole polytechnique fédérale de Lausanne) Laboratory of Nanoscale Electronics and Structures (LANES) published a study showing that this material has distinct advantages over traditional silicon or graphene for use in electronics applications.

    A discovery made at EPFL could play an important role in electronics, allowing us to make transistors that are smaller and more energy efficient. Research carried out in the Laboratory of Nanoscale Electronics and Structures (LANES) has revealed that molybdenite, or MoS2, is a very effective semiconductor. This mineral, which is abundant in nature, is often used as an element in steel alloys or as an additive in lubricants. But it had not yet been extensively studied for use in electronics.

    100,000 times less energy

    View full article »

    By Surabhi

    Spiders are very agile, and some can even jump. They owe this capability to their hydraulically operated limbs. Researchers have now designed a mobile robot modeled on the same principle that moves spider legs. Created using a 3-D printing process, this lightweight can explore terrain that is beyond human reach..

    Enviably agile and purposeful, the mobile robot makes its way through grounds rendered off-limits to humans as the result of a chemical accident. Depressions, ruts and other obstacles is no match for this eight-legged high-tech journeyman.

    Its mission: With a camera and measurement equipment on board, it will provide emergency responders with an image of the situation on the ground, along with any data about poisonous substances. Not an easy task; after all, it must be prevented from tipping over. But this risk seems a minor one as it confidently and reliably picks its way through the area. As a real spider would, it keeps four legs on the ground at all times while the other four turn and ready themselves for the next step. Even in its appearance, this artificial articulate creature resembles an octopod. And no wonder – the natural specimen provided the model for researchers at the Fraunhofer Institute for Manufacturing Engineering and Automation IPA. This high-tech assistant is still a prototype, but future plans envision its use as an exploratory tool in environments that are too hazardous for humans, or too difficult to get to. After natural catastrophes and industrial or reactor accidents, or in fire department sorties, it can help responders, for instance by broadcasting live images or tracking down hazards or leaking gas.

    View full article »

    e-Puzzle 3

    Your challenge is to design a combo-block with 8 inputs and 1 output. You receive an 8-bit vector, If the vector contains 4 ’1′s or more, the output should be high, otherwise low (This kind of calculation is commonly used for data bus inversion detection).

    What is the best way to design it with respect to minimizing latency (in term of delay units), meaning the lowest logic depth possible?

    Just so we could compare solutions, let’s agree on some metrics. Jus so we could have something to work with. View full article »

    e-Puzzle 2

    Again we are dealing with the poor engineers in the land of Logicia. For some sort of fancy circuitry, a 7-bit binary input is received. As a result it should give the amount of “1″s present in this vector. For example, for the inputs 1100110 and 1001110 the result should be the same and equal to 100 (4 in binary). This time however, the only components they have on their hands are Full Adders. Describe the circuit with minimum amount of parts.



    1) 5 per cent tolerance.

    4) If the picture is stretched or distorted up and down like a fun house mirror the circuit to adjust or repair is?

    3) A connection that shouldn’t be there. (5,7)

    11) Buzzers and LEDs are examples of a

    10 ) Turn a circuit on or off with this.

    15) Temperature changes its resistance.

    14) You do this to fix components on to a chipboard.

    6) A light sensitive resistor (abbreviation). View full article »

    Jonas Smedegaard, Debian and Electronics

    By Sneha Das

    Propagating and sustaining Free Software (Free as in freedom) and the importance of its applicability in learning, development and teaching are important issues that the Free Software Movement globe across has been engaged in, with regular collaborations with various other  Free Software communities.

    While community collaboration is the crucial aspect of this global attempt, today, the Debian Community stands out as the most important of these communities in the Free Software world. Delivering to the world, the Universal Operating System – Debian, dubbed the mother operating system and thousands f packages with diverse applications Debian community is leading the effort of setting software free (again, free as in freedom).

    View full article »

    Iphone 4 SIRI

    By Prithvi Ganesh K

     “Tell my wife I’m running late.” “Remind me to call the vet.” “Any good burger joints around here?” Siri does what you say, finds the information you need, and then answers you! It’s merely a matter of conversing with your phone. Siri (Steve is right inside) iPhone 4S is an application dedicated to Steve jobs .One of the most admirable applications of the present times for the tech savvy .It lets you use your voice to send messages, schedule meetings, place phone calls, and more. Siri isn’t like traditional voice recognition software that requires you to remember keywords and speak specific commands. It understands your natural speech and it asks you questions if it needs more information to complete a task. It is a virtual personal assistant software system. It understands what you say, knows what you mean, and even talks back. For instance…

    You : “Any good burger joints around here?”

    Siri : “I found a number of burger restaurants near you.”

    You : “Hmm. How about tacos?”

    Siri remembers that you just asked about restaurants, so it will look for Mexican restaurants in the neighborhood. And Siri is proactive, so it will question you until it finds what you’re looking for.

    Ask Siri to text your dad, remind you to call the dentist, or find directions, and it figures out which apps to use and who you’re talking about. It finds answers for you from the web through sources like Yelp and Wolfram Alpha. Using Location Services, it looks up where you live, where you work, and where you are. Then it gives you information and the best options based on your current location.

    View full article »

    Dual Tone Multi Frequency: The concept

    By Kiran Vetteth

    Have you ever wondered how you recharge/top-up your cellphone currency through a call line?  How is it that when you call a helpline you can seamlessly navigate through the menu by the mere push of buttons on your keypad? How does the called party/server receive all the digits you pressed accurately? When at times the environment around you causes interference to the call line!

    Well the concept used here is known as Dual Tone Multi Frequency, abbreviated as DTMF. It was developed by Western Electric and first used by the Bell System, later on DTMF was standardized by ITU-T Recommendation.

    Now in every basic telecommunication line, there are 2 channels offered to the subscriber. Apart from the voice channel, which carries audio frequency signals ranging from 300Hz-4000Hz there is also a Dual Tone Multi Frequency Channel having a frequency range of 1906Hz-2574Hz*.

    View full article »

    This time it was ‘Goodbye World’

    In a week’s span, the technological world and hence the society as a whole has lost two icons; Each an icon in his own way. Steve Jobs, the co-founder of Apple died on the 5th of October, and Dennis Ritchie, co-creator of Unix Operating system and the inventor C died on the 12th of October, 2011.

    Dennis Ritchie 1941-2011

    Steve Jobs has been injudiciously celebrated as the greatest inventor of the modern world, and has been posthumously praised to have been the Newton/Einstein/Edison of the 21st century! The corporate mass media has not spared any gimmickry to flatter him.

    On the other hand, the news of the demise of Dennis Ritchie, started circulating online and his admirers globe across, and not the afore mentioned media who were eulogizing him.

    View full article »

    Copper nanowires may be coming to a little screen near you. These new nano-structures have the potential to drive down the costs of displaying information on cell phones, e-readers and I Pads, and they could also help engineers build foldable electronics and improved solar cells, according to new research.

    View full article »

    Scientists at London’s Imperial College have successfully managed to demonstrate digital circuits made from bacteria and DNA.

    They are the most advanced biological logic gates ever created, claims the university.

    “We have demonstrated that we can replicate these parts using bacteria and DNA, we hope that our work could lead to a new generation of biological processors, whose applications in information processing could be as important as their electronic equivalents,” said Professor Richard Kitney from Imperial’s Centre for Synthetic Biology.

    View full article »

    Electronics Crossword


    1.       A transistor amplifier with 85% efficiency is most likely?(4,1)

    6.       Tank Circuits are also called?(4,8)

    7.       A diode used as a voltage regulator?(5)

    9.       A device that measures speed using flickering light?(11)

    10.     A type of cell that cannot be used until it dies?(6,7)

    11.      Diode use for high speed switching?(8) View full article »


    1. Design a circuit with minimum logic that receives a single digit, coded BCD (4 wires) and as an output gives you the result multiplied by 5 – also BCD coded (8 wires).
    2. Due to the war in the land of Logicia there is a shortage of XOR gates. Unfortunately, the only logic gates available are two weird components called “X” and “Y”. The truth table of both components is presented below – Z represents a High-Z value on the output.Could you help the poor engineers of Logicia to build an XOR gate?

    Fourier Analysis: The Mathematical Prism

    Signals and Systems, their analysis and characterization is one of the most passionate tasks any Communications Engineer would want to get drawn into. That given, there has been a thorough understanding of the fundamentals. Otherwise, a scenario of disconnect as it is common with many of us would occur.

    In this post, we try to understand one of the most fundamental concepts of Signals and Systems.

    Frequency Spectrum of signals using the Fourier Analysis: Without a clear understanding of this fundamental concept, the communication student would end up doing just the Algebra with no application whatsoever.

    View full article »

    by Sneha Das


    In this article, we shall highlight upon the draw-backs of Fourier analysis, get a birds eye view of the Short Time Fourier Analysis and try understanding the Uncertainty Principle that governs signals.

    As a prerequisite to be able to interpret this article better, the readers could read through some fundamentals of Fourier Analysis; This article might be helpful


    The Fourier analysis is one of the most boggling discoveries of the 19th century.

    Even the most amazing revelations are not free from flaws, and so does the Fourier analysis. Fourier transforms do not cater any clear information regarding the time at which a particular frequency component is present in the signal. This poses as a serious gap in our understanding when the signal under consideration is of non-stationary in nature, or when the time details of the spectral components are required.

    Thus, when the time localization of the spectral components is needed, a transform giving the Time-Frequency representation of the signal is necessary.

    This is where Short Time Fourier Transforms (STFT) also known as Windowed Fourier Transform comes in.

    In STFT, we assume that some portion of the non- stationary signal is stationary and periodic, and we perform Fourier transform on the stationary portion of the signal separately. By stationary, it is implied that it is a signal whose statistical properties do not change with time. That is the frequency content of the signal is constant at all times.

    If the region where the signal can be assumed to be stationary is too small, then we look at that signal through narrow windows, narrow enough that the portion of the signal seen from these windows are indeed stationary.

    Thus using STFT we get the time localization of the spectral analysis of a signal.

    We would expect the problem to be solved.

    Well, not yet!

    Here comes the Uncertainty Principle of Signals.

    This principle states that “One cannot know the exact time-frequency representation of a signal, i.e., one cannot know what spectral components exist at what instances of times. What one can know are the time intervals in which certain band of frequencies exist, which is a resolution problem.” View full article »