Saturday, 23 April 2016

Practical Application - Modulation Techniques

Signal from device generated is known as base band signal which is not directly transmitted to the desired place but it is modulated before feeding the signal to transmitter. Modulation is a technique of varying any component of carrier signal in proportion to that of base band signal. In this article I have covered several Analog and Digital modulation techniques. Mentioned its basic definition with figure and the important thing, practical application of  that modulation technique.So lets go into brief description and application of some of the techniques.

 Amplitude Modulation

In the simplest way possible, AM can be explained as changing Amplitude of the carrier signal or the high frequency signal with respect to the modulating signal.


1. It is used in Aircraft for communication between station to pilot and vice versa. So why didn't they opt for FM which is less affected to noise as compared to AM. The reason I found is that, AM is used so that multiple stations on the same channel can be  received. While in FM, reception of weaker signal is blocked by the stronger signal which is normally known as capture effect.

2. It is still used in commercial radio broadcasting. But AM having Low frequency, they only broadcast the commentary or news or we can say only vocals will be their. As the frequency is increased, in ground wave propagation attenuation will increase. Hence FM having higher frequency will get more degraded in ground wave as compared to AM. But still use of FM is more than AM. Because it uses direct wave propagation(line of sight).

Frequency Modulation

In case of frequency Modulation, the frequency of Carrier is varied with the instantaneous value of modulating signal.Advantage of FM over AM is that it has ability to reject the noise or in the other way, noise doesn't affect much in FM.


1. The most common application which I don't thing any of you is not aware of this. i.e. FM Radio broadcasting.

2. It was surprise for me also to know that, FM was used in VCR tape recorder. For storing Luminance i.e. the black and White portion of the video is recorded by FM modulation in this analog Tape while the color part is directly recorded by the base band signal. I didn't got more data in this but I came to know that it uses FM for recording.

Quadrature Amplitude Modulation

Till now we have seen that, only single parameter is changed with the instantaneous value of base band signal. But in QAM, two parameters of the signal are changed Amplitude and Phase. In short, QAM is made up of AM and PM. QAM is also known as QPSK(Quadrature Phase Shift Keying) which can be treated as mixture of ASK(Amplitude Shift Keying)  and PSK(Phase Shift Keying).

QAM can be of different types depending upon the number of possibilities of Amplitude and Phase.
For Eg. I have shown two fig. in which first is 8-QAM (2 diff. Amplitude & 4 diff. Phase), and the second fig. is 16-QAM ( 4 diff. Amplitude & 4 diff Phase).


1. NTSC and PAL are color encoding techniques used in analogue TV  and both these encoding techniques uses QAM modulation for encoding the luminance and chrominance information combinedly, for composite video signal.

2. WCDMA(Wideband Code Division Multiple Access) commonly known as 3G connection of our mobile phones also uses QAM. WCDMA uses 64 QAM. 64 QAM has 6 bits per symbol while our 2G connection has only 3 bit per symbol hence 3G is much faster than 2G. 
Amplitude Shift Keying

Till now, the modulation techniques were used for analog signal, but now the modulation techniques we will discuss are used in digital signal modulation. First is ASK, it is very much similar to AM, in which Amplitude of the carrier is varied in proportional to the digital base band signal. As digital signal is a binary signal, so we will have only 2 different amplitude value in ASK. ASK modulation is shown below.


1. ASK Modulation is used in RF Modules. I have used this module many time for making wireless robo car. We need to attach Encoder and Decoder IC to code decode the data. And the digital data from the Encoder is modulated by ASK and than it is transmitted.
2. Some of the RF remotes and RF car keys also uses ASK modulation for transmitting digital data over air. While studying about RF car keys, I found that in some of the car keys, every time the button is pressed different data is transmitted so that one can't just simply copy and transmit the same data to unlock the car.

On Off Keying

On Off Keying(OOK) modulation technique is similar to that of ASK. Difference is that in On Off keying, binary '0' is represented by 0 volt while binary '1' is represented by some fixed amplitude. And frequency in both the cases will be same as carrier frequency.


1.  This modulation technique is used only for low data transfer rate around 100 bits per second. One application of this technique which we use daily is in  IR Remote Control. That remote can be of TV, AC, Radio etc. It works on 38 kHz carrier frequency. 

Frequency Shift Keying

FSK can be related with FM. But this modulation technique is used on digital modulation. In this, frequency of the carrier is changed in accordance with the data bit. For digital '1' frequency will be high while for digital '0' frequency will be low. FSK modulation technique is shown in below fig.


 1. Bluetooth or BLE(Bluetooth Low Energy) which normally used everywhere like in mobile phone, wireless speakers, Laptops, etc uses  GFSK( Gaussian Frequency Shift Keying ) modulation technique for data transmission. Difference between GFSK and FSK is nothing but GFSK has an additional Gaussian Filter to reduce the side band power.

Phase Shift Keying

In phase shift keying, phase of the carrier is changed in accordance with the data or base band signal. For digital data '1', phase shift will be 180 degree while for digital data '0', phase shift will be 0 degree.

QPSK Modulation


1. WiFi has different versions based upon different IEEE standards. Different versions have different speeds and also uses different modulation Techniques. Out of them IEEE 802.11b uses QPSK modulation and 802.11a and g uses 16 or 64 QAM modulation for transmission. Difference between this two is the speed of data transfer. Obviously, 64-QAM is faster than QPSK.

2. Enhanced version of GSM is known as EDGE ( Enhanced Data rates for GSM Evolution ) uses 8-PSK modulation technique for faster data transfer as compared to GSM. GSM uses only 1 bit per symbol for data transfer while EDGE uses 3 bits per  symbol for data transfer. It is commonly called as 2.75G network

Minimum Shift Keying

MSK modulation can be compared with PSK modulation but the difference between them is, in MSK their is no abrupt change in the phase of the carrier signal, rather their is very smooth transition between different phases. It looks similar to that of FSK.


1. MSK is used with Gaussian filter ( commonly known as GMSK ) is used in GSM mobile communication or 2G network. Gaussian filter is used to reduce the side band power of the spectrum. It's data transfer rate is only 1 bit per symbol. Enhanced version of GSM was developed which is known as EDGE( Enhanced Data rates for GSM Evolution ) which uses 8-PSK modulation which uses 3 bits per symbol, faster than GSM.

2. Ships uses GMSK modulation technique for communication with other ships as well as the station. Data like speed of the ship, its current position, Estimated Arrival Time, Type of the ship etc is constantly transmitted through Time division multiplexing. This Tracking system is known as Automatic Identification System (AIS).

This much of data I got when I was researching the topic "Application of modulation techniques". If you know something more than this, do share it with others by commenting below. 


Sunday, 17 April 2016

Practical Application - Description


We all like to come FIRST and if we easily achieve this result by mugging the stuff, than what is the use of understanding the stuff???


“Don’t go for the glory by mugging up, Go for passion and glory will follow.” says Jayraj Sagar

“People mistaken marks as knowledge/talent and that are the reason the past and coming generation both was and is practicing this.” says Parth Kalarthi

“Mugging up is nothing else than writing shit on a piece of a paper.” says Pratheesh Prasad

“Saari mark sheets samosa ki dish saaf karne k kaam aayenge, agar tumhe kuch nahi aata. (All mark sheets would be eventually used as garbage if you don’t know the things practically)” says Makwana Amit

“Sometimes in the battle of coming first, we forget that we are learning it for self development.” says Vijay Dhanwani.

What is the Problem?

In your journey of engineering, we come to learn new techniques, new methods, new technology and new theories many more such stuffs. But the problem is that, we exactly don't know that which of the technique is actually practically used and where it is used. Are we using that devices whose theory we have just studied?? Or are we studying the stuff which was never ever used practically?? 

Due to this lack of practical understanding I personally faced the problem of learning all the theories. I started mugging up all the contents. But soon I realized that why not try to see the actual applications of all this stuffs. So my interest took me on this way of researching and the result was I actually started loving those stuff and understanding that why particular thing is used in this device and It helped me learning new theories very quickly because I can now related the things with the device using particular technique.

 The need

In Digital Communication lecture, all guys were sitting doing their own stuff
rather than focusing on what the professor is saying. Some were acting to be 
focused and very few actually are. The topic which professor was teaching was based 
on Digital Modulation techniques. To be precise, he was teaching QAM (Quadrature Amplitude Modulation). This full form sounds too boring and I personally didn't pay attention to the 
theory and was busy in my mind thinking another stuff. So this is the current phase
 of almost all the students and classes. 

Lets look into another form.

In Digital Communication lecture, all guys were sitting doing their own stuff
rather than focusing on what the professor is saying. Some were acting to  be 
focused and very few actually are. The topic which professor was teaching was based 
on Digital Modulation techniques. To be precise, he was teaching QAM (Quadrature Amplitude Modulation). But this time, before going into theory he asked one question, 

Do you the modulation technique used for 3G  data transfer???
Why 3G data rate is faster than 2G???
This was the technique to draw attention of the student and to excite them. And actually 3G
data transfer or 3G communication uses 64 QAM modulation technique for faster data 
transfer. And I don't think now the professor has to tell the students to pay attention.
And seriously, if the students know the practical application and if they are using 
that techniques, I don't think they were ever going to forget this stuff. And Mugging dies here.

The Motto

As the tagline of my blog says, “If you have knowledge and experience more than others, then share it with others.” I would post the Practical Application of various theories on the blog. Anyone who doesn’t want to be mainstream; anyone who wants to understand the things would be entertained for sure.


It’s quite intricate for me, finding the practical application of every theory but I came up with few interesting ones.As a not so famous quote says that,

So on next Sunday, I'll be posting one article based on practical application of  a particular Theory. And will share all the data gathered which I think will be definitely useful to you.

So this was my thinking based on my experiences and I came to this conclusion of writing such articles. So lets see how much this remedy will cure the disease named Mugging.