Research On Millimeter-wave Substrate Integrated Complementary Source Antennas And Arrays

The sufficient spectrum resources of millimeter-wave frequency band can fulfill the requirements of high-capacity,high-data rate broadband wireless communications.As key components of communication systems,millimeter-wave antennas and arrays have become a research hotspot in recent years.Complementary source antenna is a kind of antenna which combines electric current and equivalent magnetic current source to realize electromagnetic radiation.It has the advantages of wide bandwidth and stable radiation characteristics and is suitable for millimeter-wave communication applications.However,the existing millimeter-wave complementary source antennas are relatively complex,not easy to integrate at low cost,and its radiation characteristics are obviously insufficient compared with the antennas in low-frequency band of the same kind.In this paper,the millimeter-wave complementary source antennas are studied.Methods of polarization control,gain enhancement,antenna miniaturization and bandwidth broadening of the millimeter-wave substrate integrated complementary source antennas are proposed.A low-cost printed circuit board process is utilized to realize a variety of millimeter-wave complementary source antennas and arrays with wide bandwidth,multi-polarization,stable gain and low backward radiation characteristics.The research enriches the types of millimeter-wave antennas and improves the antenna performance.The research results can provide theoretical and technical support for the design of millimeter-wave antennas in applications including the fifth-generation mobile communication.The main innovations of this paper are as follows:1.A millimeter-wave substrate integrated horizontally polarized end-fire magneto-electric dipole antenna is designed.By loading metal patches at the open end of a substrate integrated waveguide with broad wall perpendicular to the dielectric substrate,the vertical equivalent magnetic current source and the horizontal electric current source required for radiation are realized.In order to facilitate the antenna feeding,a substrate integrated 90° twist waveguide structure is designed.On this basis,a miniaturized substrate integrated Butler matrix beamforming network with multi-layer folding structure is designed.Compared with the traditional single-layer structure,the horizontal dimension of the Butler matrix can be reduced by 45%.By combining the designed antenna with the beamforming network,a two-dimensional multi-beam antenna array with horizontal polarization is realized.The experimental results show that the array has a bandwidth of 22.1%and a gain up to 13.1 dBi,and can achieve beam coverage in the range of about 70°.2.A design method of millimeter-wave substrate integrated circularly polarized end-fire complementary source antenna is proposed.By etching the antipodal slots on the upper and lower broad wall of the open-ended substrate integrated waveguide,the horizontal in-phase current radiation is realized.Two orthogonal electric field components are realized by combining the horizontal equivalent magnetic current formed by the electric field on the open-ended substrate integrated waveguide.The amplitude and phase of the radiation field produced by the two kinds of sources can be adjusted by changing the size of the etching slots.The designed antenna has impedance bandwidth of 64%and 3 dB axial ratio bandwidth of 51%.In order to further enhance the gain of the antenna and reduce the backward radiation,a planar dielectric rod structure is introduced in front of the antenna aperture.The overlapped bandwidth of impedance and axial ratio of the loaded antenna is 41%,the gain is up to 12 dBic,and the front-to-back ratio of the radiation patterns is 20 dB.3.In order to further enhance the radiation gain of antenna elements,the concept of complementary source is extended from the design of point source to the design of aperture antenna.A millimeter-wave substrate integrated complementary source planar horn antenna is proposed.By loading dipole arrays on the radiation aperture of H-plane hom antenna,the linear complementary source radiation is realized.The antenna has an impedance bandwidth of 44%.The gain of the antenna is 12 dBi and the radiation front-to-back ratio is larger than 10 dB.Based on the proposed complementary source horn antenna,a 1 x 4 horn array is designed,with the array element spacing of 2.3?0.The phase corrected structure is used to further improve the amplitude and phase distribution on the aperture of the horn.Thus,an improved aperture efficiency of the hom element and suppressed sidelobe level of the horn array are obtained,The designed horn antenna array has a bandwidth of 33%,gain up to 14.6 dBi and sidelobe level lower than-10 dB.4.The method of further reducing the profile of millimeter-wave substrate integrated end-fire complementary source antenna is studied.Based on the image theorem,a millimeter-wave magneto-electric monopole antenna is proposed.By properly increasing the size of the metal layer at the bottom of the antenna,the dipole loaded at the open-ended substrate integrated waveguide can be replaced by monopole.While the thickness of the substrate integrated waveguide can be reduced and the height of the antenna can be further reduced by adopting top-loaded structure at the monopole.The profile of the antenna is reduced from 0.51?0 of the original end-fire magneto-electric dipole to 0.19?0 of the magneto-electric monopole.The antenna has a 60.7%working bandwidth and stable radiation characteristics.The Ka-band antenna can cover all the existing 5G millimeter-wave communication bands with a low profile of only 1.7 mm.On this basis,the influence of metallic ground and dielectric radome on antenna characteristics in mobile terminal applications is further studied.The simulated and experimental results can provide technical support for the practical applications of this kind of antenna.5.In order to solve the problem that the bandwidth of the antenna is limited by the single-mode operating frequency band of the substrate integrated waveguide,a millimeter-wave magneto-electric dipole antenna fed by the substrate integrated coaxial line working in TEM mode is studied and designed.The required antenna mode of the magneto-electric dipole is successfully stimulated by loading the electric dipole on the open-ended substrate integrated coaxial line.The transition from coplanar waveguide to substrate integrated coaxial line is designed to facilitate the antenna feeding.The antenna is compact with working bandwidth of 73.7%.The radiation patterns are stable within the wide bandwidth with low cross polarization and backward radiation.