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biff44
Joined: 24 Dec 2004
Posts: 1834
Helped: 244
Location: New England, USA
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 15 Feb 2005 22:31 phase measurement |
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| If I have two 20 MHz signals, and I want to simply and cheaply ($5 for instance in large quantity) measure the relative phase difference down to a 0.1 degree accuracy between the two signals, how would you guys do it? Some timer circuit, some dsp chip?
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boy
Joined: 30 Sep 2002
Posts: 563
Helped: 39
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15 Feb 2005 22:43 phase measurement |
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| i dont know my idea gonna work. I would use a mixer, LPF and ADC. The output if LPF will give you cos(Phi).
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flatulent
Joined: 19 Jul 2002
Posts: 4875
Helped: 324
Location: Middle Earth
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15 Feb 2005 23:00 Re: phase measurement |
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| A phase-frequency detector as used in synthesizers will have an output proportional to the phase difference. The expensive part will be the ADC to measure the output and the microprocessor or PIC to do the translation from measured voltage to degrees of phase difference.
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biff44
Joined: 24 Dec 2004
Posts: 1834
Helped: 244
Location: New England, USA
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16 Feb 2005 0:16 Re: phase measurement |
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I thought about the mixer already, but I doubt you could cal out the dc offset over temperature and compensate for AM to PM conversion.
Digital phase detector, interesting...
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16 Feb 2005 0:16 Ads |
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RFDave
Joined: 18 Feb 2004
Posts: 346
Helped: 45
Location: NE USA
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16 Feb 2005 4:19 Re: phase measurement |
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Take a look at the AD8302. Single chip that gives you amplitude and phase difference between 2 signals. Only good to +/- 1 degree though.
Dave
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