Phase meter based on zero-crossing counting of digitized signals

Abstract

We developed a compact and easy-to-use phase meter based on a zero-crossing counting algorithm for digitized signals. Owing to the algorithm, the phase meter has low-noise and wide dynamic range. Low-noise differential phase measurements can be done for square waves (-204 $\mathrm{dBra}{\mathrm{d}}^2/Hz$ for a 1-kHz, 1-${\mathrm{V}}_{\mathrm{p}-\mathrm{p}}$ signal, 10 Hz-1 kHz offset, with cross-correlation) as well as sinusoidal waves, with a measurement error of $<1\times 10^{-4}$ rad. We also demonstrated a direct phase measurement of an optical-beat note from a free-running laser over 10 decades (0.25 mHz-10 MHz) with a wide dynamic range of ~280 dB at 0.25 mHz. The phase meter can be an alternative for conventional phase meters and frequency counters in wide range of experiments.

Submitted to Review of Scientific Instruments. Some Errors and typos are corrected (v2)