Investigation of ultra-wideband channelization and down-conversion technology based on microwave photonics

Addressing the needs for wide instantaneous bandwidth, parallel reception, and down-conversion processing in fields such as wireless communications and spectrum sensing, Radio Frequency (RF) channelization technology is receiving widespread attention. To achieve instantaneous ultra-wideband signal reception in the C, X, and Ku bands, research on 4- channel optical channelization has been conducted, with each channel having a bandwidth of 4 GHz and a 1 GHz overlap between adjacent channels. Due to the optoelectronic/electro-optic conversion losses and active optical noise present in microwave photonic links, the broadband frequency conversion link introduces significant noise figures and in-band gain fluctuations. By incorporating balanced detection technology in the coherent detection link, the relative intensity noise introduced by the laser is reduced, ensuring the signal-to-noise ratio (SNR) of the module output signal. Additionally, antialiasing filtering is performed using intermediate frequency (IF) band-pass filtering in the electrical domain, achieving high flatness, high suppression ratio, high isolation, and steep edge channel division. This effectively overcomes the poor filtering characteristics of a single optical filter, with the full IF band gain fluctuation being ±3 dB. To verify the accuracy of signal detection, the module was integrated into the system for experimental testing, achieving effective detection of signals in four channels, with a frequency measurement accuracy better than 1 MHz.