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Design >> RF Design >> peculiar vco phase noise
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Message started by mixed_signal on Oct 18^th, 2013, 6:49pm

Title: peculiar vco phase noise
Post by mixed_signal on Oct 18^th, 2013, 6:49pm

Hi,
The phase noise of my vco looks weird with a peaking near the center.
The vco is followed by a Power amplifier �followed by offchip matching network. I have control �on the matching network components.

Is it parasitic oscillation? How can I fix this? Any materials that discuss solving such issue?

Title: Re: peculiar vco phase noise
Post by raja.cedt on Oct 20^th, 2013, 4:40am

Hello,
I haven't seen this kind of results till now, very strange for me. Could be some spur from supply noise or may be bandwidth was too low, which is giving huge peaking.

� What is your Bandwidth and reference frequency?

Thanks,
Raj.

Title: Re: peculiar vco phase noise
Post by mixed_signal on Oct 20^th, 2013, 9:27am

Hi Raja,
I forgot to mention that this is an injection locked oscillator locking to the third harmonic of 800 MHz i.e. 2.4GHz.
But I heard some saying about parasitic oscillation

Title: Re: peculiar vco phase noise
Post by tm123 on Oct 21^st, 2013, 11:36am

Does your design use a switching power supply? Looks to me there is a spur at ~3KHz, although the magnitude is not too large. If your oscillator has poor 'pushing' you can get a spur from power supply ripple.