Photonic-Assisted Broadband Microwave Receiver with Cross-Channel Interference Suppression

A photonic-assisted broadband microwave receiver is proposed and experimentally investigated. The broadband operation is enabled by a tunable Local Oscillator (LO) implemented by an Optoelectronic Oscillator (OEO) for down-conversion. The OEO utilizes a Microwave Photonic Filter (MPF) based on a phase modulator (PM) and an Optical Bandpass Filter (OBF) for frequency tuning and single mode oscillation. The OEO generates an LO signal with a tunable frequency from 4.94 to 20.30 GHz with a phase noise of -100.19 dBc/Hz at 10-kHz offset frequency. A Fabry-Perot laser diode (FPLD) is utilized in conjunction with the PM to realize a second MPF for photonic-assisted down-conversion, cross-channel interference suppression and image rejection. The receiver down-converts radio frequency (RF) signals from 11.27 to 20.85 GHz to an intermediate frequency (IF) of 2.5 GHz. In a multi-channel microwave communication system, the receiver can select a communication channel by tuning the OEO, and suppresses the interference from other channels. In the experiment, a cross-channel interference suppression ratio of up to 21.95 dB with a channel spacing of around 2 GHz is achieved. The receiver also rejects the image signal in the output with a rejection ratio of up to 21.51 dB. The performance of the receiver is evaluated with signals of different modulation formats, with a maximum symbol rate of 1 GBaud with 16QAM. The receiver features great simplicity for broadband tunability and can find great applications in future microwave systems.