Electronics > RF, Microwave, Ham Radio

Harmonics of a fundamental frequency

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0xFFF0:
Hi all, I don't have a good spectrum analyzer and have a question: Do the harmonics of a fundamental frequency actually have more jitter or is it all 100% phase-locked?

ejeffrey:
Mostly harmonics will be synchronous with the fundamental.  However that corresponds to more phase noise because 1 picosecond of jitter is more radians of a 3 GHz third harmonic than the 1 GHz fundamental. 

gf:

--- Quote from: 0xFFF0 on October 22, 2021, 03:21:53 pm ---Hi all, I don't have a good spectrum analyzer and have a question: Do the harmonics of a fundamental frequency actually have more jitter or is it all 100% phase-locked?

--- End quote ---

The terms "fundamental" and "harmonics" are defined for periodic waveforms (see https://en.wikipedia.org/wiki/Fundamental_frequency).
An ideal periodic waveform does not have jitter, and a jittery waveform is strictly no longer periodic, but rather has a spread spectrum in the frequency domain.

RoGeorge:

--- Quote from: 0xFFF0 on October 22, 2021, 03:21:53 pm ---Hi all, I don't have a good spectrum analyzer and have a question: Do the harmonics of a fundamental frequency actually have more jitter or is it all 100% phase-locked?

--- End quote ---

You are asking about jitter, which is about the time domain, yet talking about a spectrum analyzer and asking about phase, thought a SA usually measures the magnitude of the harmonics in the frequency domain, and does not measure the phase.  An SA is to display the power distribution of the given signal into its harmonics, and phase doesn't matter.

Time jitter and phase noise are not the same.  In general, the longer you wait to measure time deviations, the larger the observed time jitter (relative to where you would expect an edge of a signal to be).

Harmonics are "phase-locked" with the fundamental, or else (if the phase of harmonics wouldn't be locked) that would mean that the fundamental changes its shape in time, so it wouldn't be a periodic function any more.



What exactly do you want to measure, or to find out, or in what context is the question you were asking?

radiolistener:

--- Quote from: 0xFFF0 on October 22, 2021, 03:21:53 pm ---Do the harmonics of a fundamental frequency actually have more jitter or is it all 100% phase-locked?

--- End quote ---

For what reason do you need it? If you want to use it for frequency multiplier, the output phase noise will depends on both - phase noise of the the source clock and phase noise of multiplier.

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