The Design Of Pattern Reconfigurable Antenna Based On Non-foster Circuit

With the advent of the 5G era,the application of reconfigurable pattern antennas has become more and more widespread.This thesis mainly uses the "negative delay" characteristics of non-Foster elements,and provides a reflection phase with a positive slope by non-Foster loadon the parasitic element.It is used to offset the phase dispersion caused by the negative slope propagation phase,and can realize the null or beam steering by adjusting the non-Foster load impedance to provide the required phase for thenull or beam in a specific direction.Based on parasitic element technology and non-Foster circuit theory,this thesis predominately researches the pattern reconfigurable antenna based on non-Foster circuit.The primary contents are as follows:1.A conical antenna based on non-Foster circuit is designed.First,a conical antenna was designed,and the S parameter and radiation pattern of the antenna are obtained by simulation.Secondly,according to the parasitic array theory,analyze the array factor to determine the phase required by the antenna.Then,the combination of non-Foster load is analyzed to determine the structure of the non-Foster load.Finally,according to the theory of negative impedance converter,the non-Foster circuit is designed,and the non-Foster circuit and the conical antenna are co-simulated,and the null steering of the antenna pattern is realized through the varactor diode.The simulation results show that the radiation pattern gains of the non-Foster circuit loaded conical antenna is greater than 2 d Bi in the frequency band from 200 MHz to 380 MHz.And after adjusting the varactor diode,the null angle of the radiation pattern is from 90°to about 45°,the null steering of the pattern is realized.An active conical antenna is processed,and the results of physical test are consistent with the simulation results,which proves the reliability of the design scheme.2.A bulb-monopole antenna based on non-Foster circuit is designed.Firstly,a bulb-monopole antenna is designed and simulated.Secondly,the combined structure of the non-Foster load is determined by the parasitic array theory.Finally,a suitable NIC circuit structure is selected to design the non-Foster circuit,and the antenna and circuit are co-simulated in ANSYS Designer.The simulation results show that the non-Foster circuit loaded bulb-monopole antenna is greater than 2 d Bi in the operating band from180 MHz to 350 MHz.By changing the bias voltage of the varacor diode,the beam angle of the antenna radiation pattern changes from 90° to about 65°,the function of reconfigurable radiation pattern beam is realized.In this thesis,two reconfigurable pattern antennas are designed based on non-Foster circuits.By loading a non-Foster circuit and adjusting the loaded,null steering and beam steering can be realized respectively.