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Analog modulation relevant today?

curious_mind

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Elementary question. Is analog transmitter and reciever relevant today or it is completely replaced by digital counter part? I heard that FM is still analog. Is it true?
 

Dominik Przyborowski

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Real world is analog. Even digital signals has to be somehow transmitted through any medium (wire or air), and then we have to deal with losses, jammer, etc.
 

FvM

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The question isn't completely clear. I read it so that it refers to case where the carrier is modulated with an analog audio or video signal rather then a digitally encoded signal. This is the case for AM and FM broadcast and a large part of nautical and aviation voice radio.
 

curious_mind

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Ok, I will put it this way. Classical analog communications have several modulation techniques such as DSB-SC, DSB-FC, SSB-SC, VSB-SC. I guess they are not there today. Similarly FM is have analog and digital counter parts ( I understand that transmission still have to be analog). Which is prevalent today.

I want to map for modulation methods used in the current scenario

Wired Telephony: Is it FSK?
Wireless-mobile : Is it QPSK?
TV: Is it QAM?
Internet:?
Voice: I guess this is still FM (may be analog or digital)
Any other in the list can be added
 

betwixt

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I guess they are not there today.
I guess differently - I would say probably >90% of communications use them.

As FvM stated, you need to distinguish between wired and wireless communications. In wired systems, which are generally short distances, pure digital binary data is used. For just about anything over other distances, a modulated carrier is used and although the modulation may have digital states, the carrier is still very much analog.

Brian.
 

curious_mind

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Do you have comprehensive list of modulation methods used today?
BTW, why is FM angle modulation?. What does angle mean here?
 

frankrose

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For angle modulation wikipedia is your friend. https://en.wikipedia.org/wiki/Angle_modulation

Main reason for analog modulation it is simple, and too many devices are sold, used globally to change it. Other not obvious reason is that analog modulations handle better the attenuation of the channel. If a digitally modulated signal's strength decreases to a relatively low level the performance of the system won't be satisfying. People can tolerate some noise in audio, especially in talk, but with digital communication the intermittently appearing and disappearing voice is annoying, disturbing.

However, digital modulation would have several advantages like it requires smaller bandwidth, thus more channels are available on the same band and/or more useful information in more format could be available (voice, video, books) at the same device. In the future probably everywhere the digital will be the standard trend for commercial radio, TV bands, but safety critical applications will never change (air traffic, long range naval bands for example are analog mods).
 

curious_mind

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Ok, I got it. Back to real basics about FM. I understand the basic equation of FM and tried in matlab. It works. But I have the following query

Basic equation is Acos(2*pi*fc*t+ 2*pi*k*integral (message)*t)

Through maths, it is all clear. Intutively I do not understand why the above equation cannot be Acos(wc*t+ wm*t)
 

curious_mind

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Basically I am interested to know as how 2*pi*k*integral (message)*t term creates chirpiness in the carrier frequency
 

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