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Design >> RF Design >> question about vco loaded
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Message started by James Bond on Jul 12^th, 2007, 4:43am

Title: question about vco loaded
Post by James Bond on Jul 12^th, 2007, 4:43am

Hi all,

I am simulating the vco, polyphase and passive mixer together.

I have an output amplitude 1.75Vpp from vco, after the polyphase filter,
it becomes 800mVpp. But when I connect this output to mixer, it becomes
340mVpp which is not enough to drive mixer.

It seems that a isolation amplifier would be useful placed between
polyphase filter and mixer. But I am not sure how to build this kind of
large input signal and high speed amplifier or I should use just a LC tank
network to amplify the signal?

Could you please give me some suggestions? Thank you vey much.

Title: Re: question about vco loaded
Post by mobil on Sep 20^th, 2007, 10:32pm

As u said, the buffer is needed between VCO and Mixer. And it's better to design VCO with buffer at the beginning