Re: convert FM signal into bit sequence

VSP wrote:
hi all, Please help me out here. I am basically trying to successfully transmit
and receive a sequence of bits. Let me go about this a bit
systematically.

AIM: To transmit a sequence of bits BACKGROUND: I have chosen to use FM Transmission. So from the sequence of
bits that i have, I generate an AM wave* (it is similar to a square wave
since there are only two amplitude levels +5v and 0v), which I feed into
an FM Transmitter that I have bought. At the other end, the reciever
catches the FM signal. So far OK but now comes the problem - I HAVE TO
SOMEHOW RECONVERT THIS FM SIGNAL INTO THE SEQUENCE OF BITS.

*The FM Transmitter requires an AM input so, I have to first generate an
AM wave

Therefore, my basic problem is to convert an FM wave into the sequence of
bits that it is meant to convey.

All suggestions are welcome. If you have a much better way of
accomplishing the whole aim, it is mighty welcome.

There are two misconceptions here.

A. The input to the FM modulator is not an AM modulated carrier, but a baseband (i.e., unmodulated) signal.

B. The FM modulator won't take kindly to a real square-wave input. The transition between should take many cycles of the carrier to avoid generating "splatter".

C. While it's true that the modulator's output will alternate between two frequencies and hence be FM, this particular kind of operation is called "frequency-shift keying", or FSK. It can be demodulated with an ordinary FM discriminator (or any other FM detector) or with a pair of filters, one for each stable carrier frequency. The filter with the greater output indicates the input frequency.

Google "FSK demodulation"

Jerry
--
Engineering is the art of making what you want from things you can get.
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