Simplified Doppler Frequency Shift Measurement Enabled by Serrodyne Optical Frequency Translation

摘要

A simplified Doppler frequency shift (DFS) measurement approach based on Serrodyne optical frequency translation is reported. A sawtooth wave with high amplitude is sent to one phase modulation arm of a Mach-Zehnder modulator in conjunction with the transmitted signal to implement the Serrodyne optical frequency translation, as well as the optical phase modulation of the transmitted signal on the frequency-shifted optical carrier. The echo signal is applied to the other arm of the modulator. The lower first-order optical sidebands from the modulator are selected by an optical bandpass filter and detected in a photodetector. By measuring the frequency of the output low-frequency signal, the value and direction of the DFS can be determined. DFS from -100 to 100 kHz is measured for 6- to 17-GHz microwave signals with a measurement error of +/- 0.03 Hz and a measurement stability of +/- 0.015 Hz in 30 min when a 500-kHz sawtooth wave is used.

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