can somebody explain this circuit!

Attached is a 300MHz ASK receiver circuit. I spent more than 2 hours looking to the circuit but i couldnt understand how the circuit can generate stream of pulses to the decoder. :sad:

can somebody explain it in a simple way, specially the part from the electrolytic cap upto the decoder. :razz:
cheerz

View attachment reciever1.bmp

Dear xpower
Hi
It seems simple . first stage is signal detector ( it will give you your detected message signal that is digital . and second stage is a simple amplifier to increase the amplitude . and latest stage is ADC
Best Wishes
Goldsmith

goldsmith said:

Dear xpower
Hi
It seems simple . first stage is signal detector ( it will give you your detected message signal that is digital . and second stage is a simple amplifier to increase the amplitude . and latest stage is ADC
Best Wishes
Goldsmith

Click to expand...

thanks Goldsmith :razz: but i need simple description of the operation like... first stage detect the 300 MHz signal and pass it to the electrolytic cap which can pass the signal (in a low frequency form) to the self biased transistor... etc. the end result that the output of the second transistor should be stream of pulses with response to the received signal.

am so demanding! :lol:

Hi again
Well , no problem , sorry if my last notes weren't clear . As you probably know , first stage is an oscillator , it will oscillate at your carrier frequency , and as you know the ASK , is similar to an AM modulation with this difference that the message signal isn't analog . it is a coded signal or a pulse chain . so , if you selected FC+FM at your transmitter , this oscillator will do this :
Your received signal*oscillator frequency and it will take difference of them , that will consequence Fm ( your message signal , which is an square wave ( approx) , and this signal will go through c2 (c2 is coupling capacitor ) and Q2 which biased at automatic bias , will amplify it ( at CE arrangement ) and at the another pin of c5 you'll have a pulse train , and c10 is just a filter to eliminate the eventual noises ( HF noises ) and at las you have a digital to analog converter that will give you an analog signal instead of your digital signal .
I hope you got it .
Best Wishes
Goldsmith

i was thinking its an ASK receiver, but what youve explained is an FSK receiver, is it?

No , FSK= frequency shift keying , and FSK , is FM modulation with this difference that the message signal isn't analog , and the frequency of carrier will change with changing the message signal that is an square wave ( coded signal ) .
( at both ASK and FSK , the carrier is a sine wave ) but message is a pulse signal . and at ASK the amplitude will have variation ( according to the pulse signal ) but at FSK frequency will have changes . don't confuse about them !
Best Wishes
Goldsmith