Noise at resonance frequency - RF Cafe Forums
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Post subject: Noise at resonance frequency Posted: Mon Sep 26, 2005 11:27 am
I have build a VCO for a mixer IC. When i am viewing the output power of VCO with Spectrum analyzer then there is a lot of noise at and around desired resonance frequency. I am using a DC supply of +- 5V and a regulated supply from 0V to 1.5V to check the response of VCO resonance frequency. Noise is less when i am operating with 0V or 1.5V regulated voltage, but if i give around 0.7V of regulated supply then noise gets worse. I have also tried connecting capacitors with my regulated supply but to no improvement. Can anybody please suggest that how can i get rid of the noise ?
Post subject: VCO noisePosted: Wed Sep 28, 2005 3:13 pm
I'm a bit confused. Do I understand that you are running the oscillator proper from +/- 5V regulated, and that you're changing the control voltage (from a different supply?) from 0 to 1.5V?
If your VCO uses a varactor diode, you need to make sure that it's never forward biased. That means avoiding the range of 0 to at least 0.7 V