Help me understand how this circuit for measuring the doppler effect works

[freeindy]

Hi.

I have a problem understanding the circuit I have attached. As i understand, the signal that is received (in sinusodial form) is being "converted" to a pulse length depending on the incoming signal's frequency. Am I right on this? Can anyone explain me maybe in more detail about what is really going on. Would appreciate it lot.

The circuit is to measure the doppler effect on moving targets. The signal is sent by a certain frequency (36 Mhz) and recieved by the circuit attached.

Thanks

Indy

 

[renwl]

Receiver

is the signal received by photodiode?

 

[Jim cage]

Re: Receiver

It looks like a downconverting scheme from RF to IF frequency which is determined by the series LC tank.

 

[freeindy]

Re: Receiver

Hi lads, Thanks for your reply.

Renwl: Yes, the signal is received by the photodiod.

Jim:
Yeah, it looks like that. I think the downconverted frequency is what charge/discharge the capacitor at the end to give a pulse. But the values seems odd to me. The reason is, the resonance freq of the tank circuit is 159 Mhz and incoming freq. is 36 Mhz. what is the IF freq?

Indy