Research On Quadrature Phase-shifting Filtering Feeding Network And Its Antenna Application

With the continuous development of today’s information world,circularly polarized filtering antennas have become an indispensable part of modern wireless communication systems,which are responsible for radiating and receiving radio waves,and are widely used in telephone communications,broadcasting,navigation,radar,remote sensing,satellite communications and other fields.In recent years,circularly polarized filtering antennas are more popular and adopt multi-feed point antenna structure,which has high requirements for the design and performance of the entire quadrature phase-shifting filtering feeding network.This paper designes the quadrature phase-shifting filtering feeding network,then three different feeding networks are developed,and one of them is applied to the design of a circularly polarized filtering antennas.The main work of this paper is as follows:(1)A three-port dual-mode quadrature phase-shifting filtering feeding network is designed,and the quarter-wavelength terminal open-circuit transmission line and the designed short-circuit stubloaded dual-mode resonator are integrated with two sets of coupling lines,which can output 0°,90°phase filtering signals.It operates at a center frequency of 2 GHz with a relative bandwidth of 7.5%,an in-band insertion loss of approximately 3.2 d B,an amplitude difference of 0 d B±0.09 d B,and a phase difference of 90°±0.9°.(2)A three-port three-mode quadrature phase-shifting filtering feeding network is designed,and the designed three-mode resonator is integrated with a quarter-wavelength terminal open-circuit transmission line and two sets of coupling lines,which can output 0° and 90° phase filtering signals at equal amplitude.Its working center frequency is 2 GHz,with a relative bandwidth of 11.5%.The passband insertion loss is approximately 3.2 d B.The amplitude difference is 0 d B± 0.4 d B,and the phase difference is maintained at 90 ° ± 0.4 °.If a wider bandwidth quadrature phase-shifting filtering feeding network is required,only a multi-mode resonator with a wider bandwidth can be designed.(3)A five-port dual-mode quadrature phase-shifting filtering feeding network is designed.Firstly,the voltage electric field distribution of one-half wavelength terminal open-circuit transmission line is analyzed,and the open-circuit stub-loaded dual-mode resonator is designed.They are integrated with two sets of coupling lines to design a five-port dual-mode quadrature phaseshifting filtering feeding network.And the feeding network was physically processed,with a working center frequency of 2 GHz and a measured relative bandwidth of approximately 4%.The insertion loss is approximately 7 d B.The amplitude difference is 0 d B± 0.5 d B,and the phase difference is maintained at 90 ° ± 5 °,which can achieve filtering signals output at 0 °,90 °,180 °,and 270 °.(4)A circularly polarized filtering antenna based on L-type probe feeding has been designed.Firstly,the three-port dual-mode quadrature phase-shifting filtering feeding network is optimized and improved,and the isolation resistor is added to better apply it to the designed circularly polarized filtering antenna.Secondly,a double-layer circularly polarized filtering antenna is designed,and it is processed and tested after simulation and optimization.The measured impedance bandwidth of the antenna is 1.90 GHz-2.10 GHz,and the 3 d B axial ratio bandwidth is 1.50 GHz-2.50 GHz.The highest measured gain in the passband is 6.84 d Bi,and the gain curve in the passband is flat.The frequency band edge is steep,and it has good frequency selectivity,which can achieve good circularly polarized filtering antenna performance.