Microwave Channelizer Based on Polarization Multiplexing and Photonic Image-Reject Mixing

Microwave channelization based on coherent optical frequency combs (OFCs) enables processing of ultra-wideband RF signals using low-frequency components. The channel number usually equals to the comb line number of the OFCs and the bandwidth for the microwave input is determined by the frequency spacing of the OFCs. However, the generation of coherent OFCs with large comb lines and large frequency spacing is extremely challenging, limiting greatly the potential of the OFC-based channelizer. In this paper, we propose and demonstrate a microwave photonic channelizer based on polarization multiplexing and photonic image-reject mixing, which can divide a broadband signal into four channels using only one optical carrier and two orthogonal-polarization photonic LOs. The requirement of the comb line number is efficiently reduced by the polarization multiplexing, and the in-band interference is greatly suppressed by the photonic image-reject mixing. A proof-of-concept experiment is carried out. An RF signal with 4.8-GHz bandwidth centered at 10 GHz is successfully divided into 4 channels with 1.2-GHz bandwidth. The in-band interference is effectively suppressed for each channel.