Research On I/Q Imbalance Compensation Technology Of Dual Optical Frequency Comb Channelized Receiver

Dual optical frequency comb channelized receivers,based on the I/Q(Inphase/Quadrature)demodulation architecture,have a great advantage in broadband radio frequency signal reception due to the strict coherence between the comb teeth,and have a wide range of application prospects in radar,electronic warfare,and other fields.However,due to the I/Q imbalance problem caused by the physical imperfections of the optoelectronic device,the suppression performance of the system on the image frequency will be reduced in practical applications,thereby bringing the problem of adjacent channel signal crosstalk to the dual optical frequency comb channelized receiver and bringing interference to the signal frequency identification,which seriously affects the application and promotion of the dual optical frequency comb channelized receiver.To solve the problem of I/Q imbalance in dual optical frequency comb channelized receivers,this thesis first designs and builds a dual optical frequency comb channelized receiver,and analyzes the reasons for I/Q imbalance.Considering the multi-channel and large instantaneous bandwidth characteristics of the dual optical frequency comb channelized receiver,this thesis uses simulation and experimental methods,and compares the existing I/Q imbalance compensation schemes for other communication receiver types.Then an I/Q imbalance compensation is designed based on the wideband conjugate model and the second-order statistical characteristics of signals in the digital domain,which can not only carry out good image frequency suppression for single-tone signals,multi-tone signals,and 1 GHz bandwidth linear frequency modulation signals,but also solve the problem of adjacent channel signal crosstalk in dual optical frequency comb channelized receivers.This enables the dual optical frequency comb channelized receiver to receive multi-frequency and large-bandwidth radio frequency signals in parallel and multichannel.Through experimental testing,after the I/Q imbalance compensation of the adaptive filter,the image rejection ratio of the single-tone test signal received by the dual optical frequency comb channelized receiver is increased from 27 d B to more than 81 d B;the image rejection ratio of the linear frequency modulation test signal of 1 GHz bandwidth is increased from 22 d B to the noise power level,with an image frequency rejection ratio of more than 30 d B;and the image rejection ratio of the 10-tone signal with 1 GHz bandwidth is increased from 27 d B to more than 72 d B.Finally,the FPGA hardware system for the 20-tap complex adaptive filter is designed and verified based on the System Generator platform,and the functional simulation is completed in VIVADO.Through simulation testing,the image rejection ratio of the single-tone test signal actually received by the dual optical frequency comb channelized receiver is increased from 27 d B to 84 d B;the image rejection ratio of the linear frequency modulation test signal of the 1 GHz bandwidth is increased from 22 d B to the noise power level,with an image frequency rejection ratio of more than 31 d B;and the image rejection ratio of the 10-tone signal of the 1 GHz bandwidth is increased from 27 d B to more than40 d B.Although the hardware system has a lower image frequency rejection ratio for multi-tone signals than the 128-tap adaptive filter,in general,this work demonstrates the potential and feasibility of implementing I/Q imbalance compensation on hardware systems.