All-Optical and Broadband Microwave Image-Reject Receiver Based on Phase Modulation and I/Q Balanced Detection

Image-reject radio frequency (RF) receiver is the backbone of modern RF systems, but often suffers from limited bandwidth, local oscillator (LO) leakage, even-order distortion, and I/Q imbalance. A wideband photonic image-reject RF receiver based on two phase-modulators (PMs) in a Sagnac loop and an I/Q balanced detector is proposed. In the experiment, excellent I/Q amplitude balance (<; 0.8 dB) and phase balance (<; 0.7 degrees) over a wide operating frequency from 8 to 40 GHz are achieved. Due to balanced detection, the even-order distortion and dc-offset are significantly suppressed. Combined with an analog intermediate frequency (IF) quadrature coupler, the image-reject RF receiver is implemented with a spurious free dynamic range (SFDR) of 99.4 dB·Hz
^2/3
and an image rejection of 50.3 dB. An antenna remoting RF vector signal with image interference is down-converted to the IF domain. Benefiting from the significant image rejection and Sagnac loop architecture, a good constellation diagram and a low error vector magnitude (EVM) of the desired signal are obtained.