Research And Design Of Empty Substrate Integrated Waveguide High-Order-Mode Millimeter Wave Antenna

Millimeter wave antenna structures are widely used in fields such as satellite communication and biomedicine.With the determination of the 5G millimeter wave communication frequency band,more scholars have invested in the research of millimeter wave antennas.Substrate integrated cavity waveguide(ESIW)has the advantages of low cost and low dielectric loss,and it is a feasible approach for designing low-cost millimeter wave antenna structures.In addition,high-order-mode cavities can replace feeding networks,reduce energy loss in the antenna feed section,and reduce the difficulty of antenna fabricating.The ESIW high-order-mode antenna arrays operating in the n257(26.5GHz～29.5GHz)and n258(24.25GHz～27.5GHz)bands of 5G millimeter wave are researched in this paper.The main research contents and innovations of this paper are as follows:1.An ESIW hybrid high-order-mode millimeter wave dual-polarized slot antenna array is proposed.By combining the cross slot with the highorder-mode electric field at the end of the orthogonal arranged waveguides,the high isolation between the two orthogonal polarizations is realized,and the hybrid electric field mode composed of characteristic modes such as TE140 mode and TE340 mode with different resonant frequencies are excited in the feeding cavity.The resonant frequencies of different characteristic modes are used to broaden the impedance bandwidth of the antenna subarray,and the stability of antenna gain in the working frequency band can also be ensured.On this basis,by adjusting the relative position of the subarrays,the grating lobe suppression of the array radiation pattern is realized.The low-grating-lobe dual-polarized antenna structure is fabricated and measured,and the results show that the overlapping impedance bandwidth in both polarization directions of the antenna is 22.5%(23.59GHz～29.58GHz),and the maximum measured gain in the two polarization directions can reach 20dBi and 20.2dBi,respectively.In addition,the gain distribution in the operating frequency range is stable.The measured results prove that the antenna structure can meet the dual polarized radiation requirements in the frequency range of 24.25GHz～29.5GHz.2.An ESIW hybrid high-order-mode millimeter wave circularly polarized antenna array is proposed.The aperture and elliptic cavity are used as the circular polarization radiation structure,and the hybrid electric field modes are excited to broaden the subarray impedance bandwidth and maintain the stability of the subarray gain.The sequential rotation feeding network is used to feed the multiple subarrays with the same amplitude and the phase difference of 90 degrees,so that the axial ratio bandwidth and impedance bandwidth of the antenna array can be greatly broadened.The simulation results show that the overlapped bandwidth of the impedance and the axial ratio of the antenna array is 18.2%(24.5GHz～29.4GHz),and the maximum gain is 21.4dBic.In addition,the gain of the array varies less than 3dB within the overlapped bandwidth range.The simulation results meet the requirements of circular polarization radiation in the working band.3.An ESIW high-order-mode self-sequential rotating millimeter wave circularly polarized antenna array is proposed.The high-ordermode electric fields,which are orthogonal with phase difference of 90 degrees and mode changes with frequency,are excited in the feeding cavity by using cross slots of unequal length to feed the circularpolarized radiation elements arranged above the cavity,thus realizing self-sequential rotation and broadened axial ratio bandwidth of the circularly polarized subarray.The impedance bandwidth of the antenna subarray is improved by using diverse resonating frequencies of the hybrid electric field modes.The self-sequential rotation circularly polarized array is formed by combining the subarrays with the sequential rotation feeding network.The antenna structure is fabricated and measured,and the results show that the overlapped bandwidth of the impedance and the axial ratio of the antenna array is 24.9%(23.04GHz～29.6GHz),and the maximum gain is 19.1dBic.In addition,the gain distribution in the operating frequency range is stable.The measured results prove that the antenna structure can meet the circularly polarized radiation requirements in the frequency range of 24.25GHz～29.5GHz,and the effect of self-sequential rotation technology on improving the axial ratio bandwidth of circularly polarized antennas.