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Altera_Forum
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15 years ago

How to determine if 2 signals are in quadrature

Hello friends, I need to determine if two signals are precisely on 90 deg. phase. In fact, there is a xor phase comparator and I try to catch lock condition as indicator (for viewing purposes, ...
Altera_Forum's avatar
Altera_Forum
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15 years ago

A criterion "precisely on 90 deg. phase" won't work. If you measure phase, you have to specify a phase tolerance that is accepted as locked state. To measure a phase difference in digital signal processing, you need an oversampling clock.

If you have an analog VCO, an obvious method is to do also the phase limit comparison in the analog domain, based on the low-pass filtered XOR comparator output.