Research On Antenna Adaptive Impedance Matching Network

Impedance matching is one of the most important technical problems in RF systems.It is mainly used in various fields such as offshore operations,communications equipment,military equipment,and aerospace,etc.Among them,adaptive impedance matching has become one of the research hotspots in the microwave field.There are three types of matching networks:lumped parameters,distribution parameters,and mixed parameters.The paper studies the adaptive matching network and its application in antennas.The main tasks completed are as follows:The lumped,distributed,and mixed parameter matching networks were studied by ADS software.The ?-type and T-type topologies can provide greater freedom for impedance matching adjustment.The varactor are loaded into a lumped parameter matching network and a hybrid parameter matching network respectively,and an adaptive matching of the time-varying load impedance of the antenna is achieved through a simulation example.The basic genetic algorithm is improved.The main parameters(such as the number of individuals,the maximum number of iterations,the selection probability,the mutation probability,and the crossover probability)in the algorithm are discussed to influence the performance of the improved genetic algorithm,and the values of the modified parameters are determined.An improved genetic algorithm was used to optimize the time-varying load impedance of a 2.4 GHz antenna,and compared with the ADS software's own optimization algorithm.The antenna return loss,convergence iteration number and program running time t obtained by the improved genetic algorithm are better than the ADS's own optimization algorithm.An electromagnetic simulation software HFSS was used to model a microstrip patch antenna with a center frequency of 2.4GHz.The adaptive mixed T-type and ?-type matching networks were loaded respectively to perform joint simulation with the antenna.Set the variable capacitance range of the T-type matching network to 1?5pF,the step length to 0.5pF,when C1=1pF,the return loss S11=-30.996dB;set the ?-type matching network variable capacitance to 1?6pF The step length is 0.5pF.When there is only one variable capacitor,the return loss corresponding to C1 = 6pF is S11 =-18.71dB;when there are two variable capacitors,C1 = 3pF,C2 = 6pF,and the corresponding echo Loss S11 =-30.006dB.It shows that the mixed parameter matching network can achieve antenna adaptive impedance matching.