Wideband Photonic Image-Reject RF Receiver Based on Phase Modulation and I/Q Balanced Detection

Abstract

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 ($\lt $0.8 dB) and phase balance ($\lt $0.7 degree) over a wide operating frequency from 8 to 40 GHz are achieved. Due to the using of balanced detection, the dc-offset and even-order distortion are well suppressed. Combined with an analog intermediate frequency (IF) quadrature coupler, the image-reject RF receiver is implemented with an image rejection of 50.3 dB and a spurious free dynamic range (SFDR) of 99.4 dB Hz $^{2/3}$. An RF vector signal with image interference are down-converted to the IF domain. Benefiting from the significant image rejection, a good constellation diagram and a low error vector magnitude (EVM) of the desired signal are obtained.