Tunable OEO-based photonic RF receiver with image frequency rejection.

A tunable optoelectronic oscillator (OEO)-based photonic radio frequency (RF) heterodyne receiver with the capability of image frequency rejection is proposed and experimentally demonstrated. The OEO incorporating a dual-electrode Mach-Zehnder modulator (DEMZM) operates as a high quality local oscillator (LO) and a broadband mixer simultaneously, with one electrode port of the DEMZM used for the feedback of the generated LO signal and the other port for receiving external RF signals. Two channels of immediate frequency (IF) signals can be achieved in optical domain by beating the +1-order sideband of LO with the +1-order sideband of input RFs and beating the -1-order sideband of LO with the -1-order sideband of input RFs correspondingly. Through setting the bias angle of the DEMZM at π/4 or 5π/4 and quadrature combining of the two channels of the IF signal, the combined IF signal down-converted from the target RF signal gets enhanced due to the in-phase sum of two channels, while the combined IF signal down-converted from the image frequency can be rejected due to out-of-phase sum of two channels. In the experiment, the input RF signals with operating frequency range from 8.85 to 14.85 GHz are successfully received with the image rejection ratio reaching 42.6 dB, and the spurious free dynamic range of the system is better than 94.8  dB Hz.