Research On Phase Conjugate Circuit Of Retrodirective Antenna

The communication platform of the "Satcom on the move" system such as ship communication and emergency communication has great maneuverability.The nonstationary motion of the platform brings great challenges to the antenna beam alignment of the communication parties and affects the reliability of the wireless communication link.The traditional mechanical beam alignment method will be limited by its adjustment mode and response speed in this scenario,and the electronic beam alignment system corresponds to complex RF links and high cost,thus limiting the widespread use of both on non-stationary platforms.The retrodirective antenna does not need to know the direction of the incoming wave in advance,and does not require complicated digital signal processing.It has the characteristics of fast self-tracking and high cost performance,which reflects the advantages of the mechanical beam alignment system and the electronic beam alignment system.Therefore,it has broad application prospects in the above fields.The performance of the retrodirective antenna depends mainly on the phase conjugate circuit.However,with the development of microwave radio frequency circuits,in order to meet new application scenarios and system indicators,various phase conjugate circuit structures have emerged.In order to further enhance the robustness of the link,promoting the pointing performance of the retrodirective antenna and integrating with modern wireless communication systems,the architecture of the phase conjugate circuit needs to be continuously improved.Based on the research of phase conjugate circuit at home and abroad,this paper studies the improvement of circuit performance index and communication capability,which is mainly divided into the following parts:First,the effects of RF leakage on the phase conjugate performance in the phase conjugate circuit are simulated and analyzed quantitatively by simulation.Then aiming at the RF leakage,the balanced FET resistive mixer circuit based on the first-stage mixing is designed to verify the RF leakage suppression capability.Secondly,based on the sole function of single-stage mixer circuit and high local oscillator frequency,a two-stage mixing phase conjugate circuit with tracking phaselocked loop structure is proposed to down-convert the RF signal to low-IF processing and use in-phase and quadrature modulation for secondary mixing,which embodies the performance advantages of the circuit in interference suppression,link gain control,avoiding high local oscillator frequency and providing duplex communication capability.Thirdly,for the problem that the in-phase quadrature modulation module is sensitive to the amplitude and phase imbalance of the baseband signal,a high IF twostage mixing phase conjugate circuit for improving the intermediate frequency is designed to further improve the interference suppression capability of the circuit.Lastly,In order to improve the communication ability of the phase conjugate circuit,realize the full duplex communication of phase modulation modes such as QPSK and QAM,use the receiving array factor to synthesize the intermediate frequency signal and retain the performance advantage of the secondary mixing frequency,the phase-locked mixing ring structure on the basis of the secondary mixing circuit of the high intermediate frequency is added,forming the multistage mixing phase conjugate circuit.At the same time,the link budget of the design is carried out,and the relationship between the phase-locked loop parameters and data transmission rate is preliminarily analyzed,so as to provide a reference for improving the performance index of the phase conjugate circuit.