how to measure a really small phase difference?

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freewing

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how to measure phase difference

I want to measure the phase difference between two signals. The phase difference is only 0.002 rad. So I think a binary PD is a good choice since it has a high gain when the phase difference is small. Since the two signals are ~100MHz signal, then half-rate binary PD can make it. But for normal half-rate binary PD, I/Q reference signals are needed. This will make things complex. So is there any other simple way to measure such a small phase difference?
 

measure phase difference

You can consider another option:

Have a look at Analog Devices AD8302.
This IC allows you to measure phase difference between two RF signals up to 2.5GHz with sensitivity 10mV per 1deg.
A comprehensive article on this issue you can find here:
https://www.analog.com/library/analogDialogue/archives/35-05/AD8302/

Good luck ..
 

measuring phase difference

Wow, that's a time delay of only one millimeter at the speed of light. What on earth are you measuring?

If you have two RF mixers and a 100.001 MHz oscillator, you could mix your two signals down to 1 kHz where the phase difference would be much easier to measure. You'll need to carefully balance the line lengths.

How about measuring *changes* in phase difference instead of trying to measure the absolute phase difference? Then you wouldn't need to balance the lengths or worry about drift.
 

measure phase difference rf

Actually, the two signals are on the chip and my phase detection circuit is also on-chip. When the phase difference is expressed in time domain, it's roughly 10ps. So I still think it's doable. Think about the CDR circuit for serial link and backplane communications. Now I just don't know which kind of phase detector is better.
 

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