Research On 2.45GHz Circular Polarization Direction-Finding Antenna Array

With the rapid development of direction finding technology,electronic reconnaissance and direction finding has become an important technology in the field of military electronic countermeasures.In order to realize direction finding in complex electromagnetic environment,it is usually necessary for direction finding antenna to have the characteristics of anti-interference and high precision.The circularly polarized array antenna has important research value because it has the characteristics of high gain,anti-interference and beam scanning,which satisfies the working requirements of the direction finding antenna.Based on the study of the principle of microstrip antenna and phased array antenna,a circularly polarized direction finding array antenna system at 2.45 GHz is designed in this paper.The main work is as follows:1.A circularly polarized array antenna at 2.45 GHz is designed.The antenna consists of a 4×8 circularly polarized antenna array and hybrid ring.The circularly polarized antenna is fed by slot coupling.Circular polarization is achieved by cutting angle on the patch.The feed network consists of a 1.25? hybrid ring loaded with two one-quarter power dividers.The power divider uses a quarter impedance converter for impedance matching.The radiation mode of the antenna is changed by switching the feed port of the hybrid ring.The simulation results show that sum and difference ports of antenna achieve impedance matching,higher isolation and the axis ratio of the array antenna is less than 3dB,which achieves better circular polarization performance.The gain of the antenna is 14.4 dB,and the depth of sum and difference is greater than 25 dB,meeting the design requirements of direction finding antenna.2.A phase shifting circuit at 2.45 GHz is designed.Based on the principle of reflective phase shifter,a series scheme of analog phase shifter and digital phase shifter is designed to realize adjustable phase shifting by adjusting the bias voltage of the diode in the circuit.The simulation and test results show that the return loss at the input and output ports is greater than 10 dB,the fluctuation of insertion loss is less than 2.5 dB at 2.45 GHz.Phase shifter can realize continuous phase modulation about 285°.Finally,phase shifter is connected with each outport of a quarter power divider to realize adjustable four-way output phase.The designed phase shifter meets the requirements of beam scanning of antenna array.3.Finally,the designed antenna array,hybrid ring,phase shifter and Power divider are arranged reasonably to get the direction finding antenna system.The simulation results show that beam scanning of-30 °~+30° can be achieved by changing the bias voltage of each diode in the phase shifter.During the scanning period,the axis ratio is less than 3dB.In summary,a direction finding antenna system is designed.The designed antenna not only achieves the scanning range of(±30 degree),but also has better circular polarization performance in the scanning range,which has certain engineering application value.