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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, 7:49pm

Title: peculiar vco phase noise
Post by mixed_signal on Oct 18^th, 2013, 7:49pm

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, 5:40am

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, 10:27am

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, 12:36pm

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.