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 dBrad2/Hz for a 1-kHz, 1-Vp-p signal, 10 Hz-1 kHz offset, with cross-correlation) as well as sinusoidal waves, with a measurement error of <1 × 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.
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