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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

You may try using feedback system (I assume without loop filter as you are using CPLD, similarly any oversampling may be difficult in CPLD).

Your input x1 feeds the XOR. Your other input x2 feeds through a delay line. The XOR output error feeds back to delay units on x2.

The system if designed carefully should settle and lock when x1 is in phase with x2_d.

When locked the error from XOR is the phase error(in samples).