Want hlp in dsigning of a binary ASK modem or Power Line Modem. I have a project of designing a binary ASK modem, with a microphone as an input and a speaker as an output.
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Study these links ….
Amplitude-shift keying (ASK) is a form of amplitude modulation that represents digital data as variations in the amplitude of a carrier wave. In an ASK system, the binary symbol 1 is represented by transmitting a fixed-amplitude carrier wave and fixed frequency for a bit duration of T seconds. If the signal value is 1 then the carrier signal will be transmitted; otherwise, a signal value of 0 will be transmitted.
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The purpose of the device is to transmit the speech (voice) from a Microphone to a nearby speaker using the binary amplitude shift keying modulation/demodulation.
so when I speak from the microphone I can hear my voice from the speaker, but the way of transmitting the voice should be by Binary Amplitude Shift Keying modulation/ demodulation. so of course I will need an analogue to digital converter at the transmitter to convert the speech waveform from the mic to binary(1 and 0),
So if there is a mic with ADC comes in one part that is fine, i will need a mixer to modulate the binary signal on a carrier signal and then the output from the mixer should go to a bandpass filter and then goes to the demodulator to recover the binary signal and then to lowpass filter and then to DAC (Digital to Analogue converter) so then the voice signal can be heard from the speaker. It should be a small device which can be built on a Vera board and has all the components on the same board from the mic to the speaker (any small speaker).
So I don’t want to buy a ready modem, what I want is to construct a simple one that do the job of transmitting the speech from one end to another end (speaker),let’s say 15-20 cm away through a hardwire channel, It has the same idea of the intercom but here we should use modulation and demodulation theories, so we can call it modem!
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