Abstract: The phase change to be measured is multiply measured at artificially incred and decreased values and then averaged to result in greater accuracy. Delayed versions of the reference and input signals are compared in dual channels to the undelayed input signal and the undelayed reference signal, respectively. Resulting time-lengthened and time-shortened phase measurement signals from the dual comparator channels are algebraically combined to provide an analog output signal having an average magnitude accurately proportional to the true phase difference between the undelayed reference and the undelayed input signals. Increased linearity/reproducibility results where relatively high frequency signals (e.g., up to 70 MHz or more) are to be phase compared. An optional voltage clamp on the comparator channel outputs further improves linearity/reproducibility where very small phase differences are being measured.