Simple photonics-based microwave frequency and power measurement system

This paper presents a microwave photonic system for measuring both the frequency and power of an RF signal. It is based on a dual-parallel Mach-Zehnder modulator (DP-MZM) and an optical bandpass filter (OBPF). The OBPF selects an RF modulation sideband produced by the two sub-MZMs inside the DP-MZM. Applying a sawtooth wave with an amplitude of twice the modulator half-wave voltage <i>V_π,DC</i>, which is equivalent to sweeping the modulator bias voltage over the range ±<i>V_π,DC</i>, results in the generation of a low-frequency sinusoidal wave after photodetection. The frequency and power of the system input RF signal can be determined by using a low-cost off-the-shelf gain and phase detector to measure the peak voltage and the phase of the low-frequency sinusoidal wave. The system has a simple and compact structure, a fast response time, a wide frequency operating range and a robust performance. Experimental results are presented that demonstrate RF signal frequency and power measurements in the ranges of 5 to 20 GHz and -10 to 17 dBm, respectively.