need help in this circuit - Zero Bias Schottky Detector


Joined Jun 22, 2012
Its an AM detection circuit, the diode is a half wave rectifier and the RC filter removes the carrier, so the result is the original modulation audio.


Joined Aug 1, 2013
Can any one explain how this circuit detects RF signals
The word "detect" used here does not mean what you think. It is not determining the presence or absence of a signal. In radio, a detector is a circuit that extracts the modulated signal (audio, video, whatever) from the carrier wave. The schematic shows a basic AM (amplitude modulation) detector.



Joined Mar 14, 2008
Looks like it detects by diode rectification of the RF waveform

Google that is mainly for AM modulation.
My company used a similar circuit to detect the level of microwave radiometer signals on an earth orbit weather satellite except it used back (tunnel) diodes, instead of Schottkys, for better sensitivity.
Basically it generated a slowly varying DC level ( a few hundred Hz) in proportion to the intensity of the black body radiation in the microwave spectrum from earth.


Joined May 3, 2013
How it is used to detect the mobile signals
If there's a RF input, you will get a DC output.

If you have a good tuned filter at the input, you can detect a transmission over a particular radio spectrum.

Else, you can get DC even from random RF signals, like a motorbike passing by .....


Joined Dec 13, 2013
actually, schotkey diodes have a higher minimum rf voltage for detecion than the older germanium diodes. if you apply a little bias to them, they will detect down to almost zero volts.