How to calculate R and C for Am Demodulation envelope detection?

[Bilal12]

Hello , one question if posible .

How can I calculate the value of R and C for an Am Demodulation envelope detection circuit.

Knowing that the carrier wave is 20KHz, 1Vpp, and the message signal is a 32Hz, 2Vpp, with a 5V DC offset:

and thank you.

 

[Martaine2005]

Hi Bilal12,
Firstly, I would cheat! As the equations turn my brain to mush!

I would stick a 1K and a 1nf to start. Or a varistor. And adjust the cap. Maybe 5nf 10nf.
But have a read of the books as the equations are all there.

Martin

 

[Martaine2005]

It would appear your question has already been answered on another forum!
The equations were there too.
39nf and 5.1K

Martin

 

[Bilal12]

thank you for your replay . but who did you get c=39nf and r=5.1K

 

[Martaine2005]

Have you forgotten all the web sites you asked?

Martin

 

[duke37]

Your circuit looks very strange, shouldn't the ground terminal of the scope be connected to ground.
I would not know how to calculate the values but R needs to discharge C fast enough to follow the wave form. The DC offset will affect the discharge rate and may allow 100% modulation to be detected without distortion.

 

[Martaine2005]

Hi Bilal12,
Have a read of these for the equations.
http://electronics.stackexchange.co...-and-c-for-am-demodulation-envelope-detection
And
https://www.st-andrews.ac.uk/~www_pa/Scots_Guide/RadCom/part9/page2.html
And
http://www-ee.eng.hawaii.edu/~mckell/Teaching-files/EE341L_files/AmpMod.pdf
And
https://en.wikipedia.org/wiki/Envelope_detector
Like I said earlier. My brain turns to mush!!

Martin

 

[Bilal12]

Hi Bilal12,
Have a read of these for the equations.
http://electronics.stackexchange.co...-and-c-for-am-demodulation-envelope-detection
And
https://www.st-andrews.ac.uk/~www_pa/Scots_Guide/RadCom/part9/page2.html
And
http://www-ee.eng.hawaii.edu/~mckell/Teaching-files/EE341L_files/AmpMod.pdf
And
https://en.wikipedia.org/wiki/Envelope_detector
Like I said earlier. My brain turns to mush!!

Martin

ok thank you

 

[Arouse1973]

I think if you started off with an RC of 5 times the 1/fm (modulation frequency) and see how you go. There is a lot of contention over what formula to use. So try this first and see how you get on.
Adam