Research On Integrated Substrate Gap Waveguide-fed Millimeter Wave Slot Circularly Polorized Antenna

With the official arrival of the 5G era,in-depth research on millimeter wave antennas has become increasingly important.As a device for receiving and transmitting electromagnetic waves in a wireless communication system,an antenna is a vital device.The antenna is developing in the direction of miniaturization,integration,broadband and circular polarization of antenna because the integration and miniaturization of the circuit.Microstrip slot antennas have the advantages of wide bandwidth and low profile,but the slot antenna is bidirectional radiation and electromagnetic wave leakage is serious in high frequency.In order to improve the defects of the slot antenna while achieving circular polarization performance,this paper uses the integrated substrate gap waveguide structure to study the circular polarization application of the slot antenna.The main work is as follows:(1)A wide-slot circularly polarized antenna based on the center-feed of integrated substrate gap waveguide is proposed.The antenna is composed of integrated substrate gap waveguide,and a rectangular slot is etched on the ground of the transmission waveguide,and then a rectangular perturbation patch is added to the slot to realize the radiation of circularly polarized waves.Firstly,the formation mechanism of the circular polarization of the antenna is explained by characteristic mode analysis,and then the left / right circular polarization of the antenna is explained by the electric field distribution at the slot.Next,the performance of the antenna is simulated and analyzed.The simulation results show that the center frequency of the antenna is 28 GHz,the impedance bandwidth(| S11 | <-10dB)is 22.8-32 GHz,the absolute bandwidth is 9.2 GHz,and the relative bandwidth is 32.86%.The 3dB axial ratio bandwidth is 27.6-31 GHz,the absolute axial ratio bandwidth is 3.4GHz,and the relative axial ratio bandwidth is 12.14%.The antenna gain is greater than 6.7dBi in the 3dB axial ratio bandwidth range.Finally,the proposed antenna is processed and verified.The test results show that the test results of the designed antenna are in good agreement with the simulation results.Compared with the published circularly polarized antennas,the proposed antenna has the advantages of broadband,small size and high gain.(2)A wide-slot circularly polarized antenna based on the eccentric-feed of integrated substrate gap waveguide is proposed.The only difference between the two antennas is that the eccentrically fed antenna uses an offset microstrip line to feed the slot,changing the antenna's feeding position to adjust the impedance matching to widen the impedance bandwidth.Simulation results show that the center frequency of the antenna is 28 GHz,with a wide impedance bandwidth(| S11 | <-10dB)of 23.9-35 GHz,the absolute bandwidth is 11.1GHz,and the relative bandwidth is 39.64%.The 3dB axial ratio bandwidth is 26.8-30.8GHz,the absolute axial ratio bandwidth is 4GHz,and the relative axial ratio bandwidth is 14.29%.The antenna gain is greater than 6.6dBi in the 3dB axial ratio bandwidth range.Process and verify the proposed antenna.The test results show that the test results of the designed antenna are in good agreement with the simulation results.Both simulation and test results show that the proposed eccentrically fed circularly polarized antenna has a wider bandwidth(impedance bandwidth and axial ratio bandwidth)compared to the centrally fed circularly polarized antenna.(3)A narrow slot circularly polarized antenna based on integrated substrate gap waveguide feeding is proposed.The difference between this antenna and the wide-slot antenna in the previous two chapters is the width of the slot.The circular polarization principle of the two is the same by adding a perturbation structure to separate two degenerate modes by 90 ° to achieve circularly polarized wave radiation.Simulation results show that the center frequency of the antenna is 25 GHz,the impedance bandwidth(| S11 | <-10dB)is 24.2-26.2GHz,the absolute bandwidth is 8GHz,and the relative bandwidth is 8%.The 3dB axial ratio bandwidth is 25.6-26.2GHz,the absolute axial ratio bandwidth is 0.6GHz,and the relative axial ratio bandwidth is 2.4%.Simulation results show that compared with the two wide-slot circularly polarized antennas,the proposed narrow-slot circularly polarized antenna has a narrower bandwidth(impedance bandwidth and axial ratio bandwidth).