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# [Moved] Orcad space amplitude modulation simulations: Why is the RC out voltage is so small?

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#### tempvipguest

##### Newbie level 5
[Moved]Orcad pspice amplitude modulation simulation:why the RC out volt. is so small?

Hi,
I am simulating Amplitude Modulation circuit in Cadence.Here is the simulation sch:

V1 pulse freq=1GHz,Vpp=1v.V2 pulse freq=100KHz,peak to peak voltage is 0.1v.when the amplitude modulation sigal Vmod go through the RC filter,the demodulation signal Vlpf peak to peak is 50mV,and DC offset is about 600mV. what is the problem?Vlpf peak to peak should be 0.1v,and DC offset should be about 1V.

Could anyone help?Thanks!
pspice simulation file attached below:
View attachment carrier bak.rar

Re: [Moved]Orcad pspice amplitude modulation simulation:why the RC out volt. is so sm

LPF out is average of "mod" voltage, not peak. Review the waveform and you'll understand why the output can't be 1 V.

tempvipguest

### tempvipguest

Points: 2
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Re: [Moved]Orcad pspice amplitude modulation simulation:why the RC out volt. is so sm

Does it mean i need an envelope detector here not a lpf if i want to demodulate the v2(V2 pulse freq=100KHz,peak to peak voltage is 0.1v.)? Do you have any good envelope detector to advise?
Thanks for your help.

Re: [Moved]Orcad pspice amplitude modulation simulation:why the RC out volt. is so sm

I'm not sure if you want to design real circuits or functional models of amplitude modulation. The answer will be respectively different. A typical "real" enevlope detector is comprised of a diode, a capacitor and a resistor. https://en.wikipedia.org/wiki/Envelope_detector

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