how to seperate mixed signal

Discussion in 'Wireless & RF Design' started by meguro, Mar 24, 2009.

  1. meguro

    Thread Starter New Member

    Mar 4, 2009
    My circuit is:
    In the transmitter:

    audio signal (500Hz - 40KHz) -> FM Modulation (around 400KHz, square wave) -> mixed with low frequency signal(20Hz or 50Hz, square wave) by using opamp summing circuit

    In the receiver:
    mixed signal -> low pass filter to get low frequency signal (OK)
    mixed signal -> high pass filter to get FM modulation signal (X)

    My question is:
    How to get the FM modulation signal from the mixed signals? I tried RC High pass filter. There was sharp edge of low frequence signal passed through the HPF.