A Precise 360 Degrees-Range Phase Detector Based On An N-Path Filter

A technique for using an N-path filter to precisely measure the phase difference between a pair of periodic signals with the same frequency is presented. It is shown that using the N-path filter and a variable delay cell within a feedback circuit allows for accurate measurement of the phase difference for a two-decade range of amplitude of one of the signals. Simulations demonstrate sub-1 degrees phase resolution for 100 MHz input signals with amplitudes as low as 10 mV. The circuit dissipates 12.6 mW from a 1.8 V supply.