simfund

Dear all,

I simulate the QVCO using spectreRF. I have set the fundamental frequency = 4GHz. Actually, this circuit should operate at 4GHz. After simulating, it give the fundamental frequenyc is 2GHz (-80dB). The 2nd harmonic is 4GHz (the one I wanted). It gives -3dB. Actually, what is my problem? Why it will give out a strange frequency to me?

thanks

wccheng

i think u need to increase the sampling frequency of ur simulation.

khouly

Increase the estimated osc frequency.This should be as close as possible to wanted one..

How could I increase the sampling rate of the simulation setting?

Look at this ...

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However, my predicted osc freq is around 4GHz. If I set this is too high, willi it cause problem?

Do you design a prescaler (divider by 2) follow the VCO?

surely NO.