From the receiver circuit below, which is exactly the part that demodulates the RF signal?

I know, a typical circuit used for an envelope detector is composed of a resistor, a capacitor and a diode. Is that similar?

I' m a newbie and any help would be appreciated.

enter image description here


1 Answer 1


The demodulation is done inside the chip - the chip produces the output lines that control the motor and this is the general clue about where AM demodulation is done.

Bear also in mind that the likely type of modulation is OOK (on-off keying) and this makes demodulation a lot easier because you are detecting the presence or non-presence of the carrier. Counting the number of modulated pulses that the transmitter emits is the likely method of decoding data from the transmitter.

  • \$\begingroup\$ As I 'm trying to decode the circuit, what is the purpose of part between antenna and ic, in general? \$\endgroup\$
    – dempap
    Dec 16, 2013 at 19:57
  • \$\begingroup\$ I'm not 100% sure but I think it is a self oscillating mixer stage - the antenna signal gets mixed with a low amplitude oscillator and the signal gets down converted (mixed) to a lower frequency. This is speculation. Either that or it is a limiter circuit cum AGC. Not sure really. \$\endgroup\$
    – Andy aka
    Dec 16, 2013 at 20:33

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