Filtering Sum of Three Different Sinusoids

[Tolunay Aydın]

Hello everyone, i generated 3 different frequency sinusoids and summed them with wien bridge oscillators.1 represents 'on' for a wave 0 represents 'off'.I need to see 0 Volts at the output if and only if 101 and 000 situations.Otherwise(111 110 011 010 100 001) i should observe combination of sinusoids at the output.I tried to connect a bandpass filter to the end of summing amplifier.However, in this case i see nothing at the output for 100 and 001 cases.Thanks for your help.

 

[Harald Kapp]

Which frequencies do you use?
If they are spaced well apart (in terms of frequency), you will require 3 bandpass filters, each tuned to one of the frequencies. The output of the filtes should be rectified and low-pass filtered to detect the envelope curve of the signal. A Schmit-Trigger circuit can restore a clear digital 0 or 1 signal from that.
If the frequencies are near neighbours, building the requisite filtes will be a challenge as each filter should only detect a single frequency, not the neighbours.