Research On Planar Array Antenna Based On Horn Elements

Recently, with the rapid development of radio techonology, the requirements for electrical performance of the antenna are increasingly enhanced. The high capacity of mobile communication systems require antenna systems that must be portable, low-profile and light weight. Traditional reflector antennas can’t already meet these above requirements. However, planar array antennas own above these characteristics.In this paper, the engineering application practices of the current satellite communication antennas and radar antennas are taken as our research backgrounds. The particular implementation methods of the dual polarization and circular polarization, and the requirements of low sidelobe in the design of array antenna are investigated. Several typical planar array antennas are designed and optimized by using the horn as the basic antenna element, combined with the research methods of electromagnetic simulations and experimental validations. The main work is as follows:(1) To achieve the planar array antenna with dual polarization and low sidelobe, the pyramid horn antenna feeded by probes is used as the basic radiation element, and the feed network of array antenna is constructed by using the low loss and quasi-air coaxial line. The antenna array design of low sidelobes in pitch planes is achieved by using weighted passive networks. Meanwhile, the isolation degree of antenna polarization port is enhanced and the cross polarization level is reduced by using the reversed phase feeding. The antenna with low sidelobe and wide beam is achieved by adding the choke groove near arrays. The measured results indicate that the cross polarization inhibition degree of antenna is more than 35 d B and the polarization port isolation degree is less than-30 d B. The antenna has many characteristics such as dual-polarized and co-aperture radiation, high polairtion purity, and compact structure.(2) To realize the circular polarized radiation array antenna, the circular polarized radiation element of ladder horn feeded by one-armed planar spiral is designed and optimized, and the wideband electromagnetic characteristics of main electrical parameters(the radiation pattern, axial ratio, and standing wave) for the radiation element are analyzed. On the basis of unit design, the 8x8 array antenna is designed and fabricated. Measured results show that the voltage standing wave ratio(VSWR) of the antenna array is less than 1.5 in the operation bandwidth, the 3d B axial-ratio bandwidth is more than 23%, and the cross polarization level is less than-15 d B. This paper proposes the rotating and reversed phase feeding method to reduce the cross polarization level of submatrix. The measured results of the sample are good agreement with simulated results, which verifies the effectiveness of array antenna design.(3) In order to overcome the dual circular polarized antenna array technology at K-band, this paper proposes a waveguide array antenna structure with dual circular polarizations. The high-efficiency co-aperture dual-polarized radiation element, wide-band circular polarizer, and low loss waveguide feed network are analyzed and designed. The measured results show that the proposed waveguide array antenna has the characteristics of high-efficiency, wide-band axial ratio, and high-isolation. Moreover, the aperture efficiency of the array antenna is bigger than 76%, the 3d B axial-ratio bandwidth is 16.5%, and the port isolation in the operation bandwidth is more than 25 d B. This antenna has good engineering application prospects in satellite communication systems for small aperture antennas.(4) To meet the technology requirement of the low sidelobe radar antenna, this paper proposes a pyramidal horn antenna element feeded by the shorting termination, and constructs the low sidelobe antenna array(16x16) of self-supporting structure of square coaxial transmission line feed network filled by air. Coaxial line filled with air has the characteristics of low loss and easy fabrication. Amplitude weighting for antenna aperture is realized by using the unequal power divider network. The port mismatch problem of power divider with the large power divide ratio is solved by loading tunning nails. The measured results of the antenna sample show that the relative bandwidth for VSWR less than 2 is 7.5%, and the gain at the center frequency is 31.8 d B, and the gain in the operation frequency band is higher than 31.5 d B. Finally, the measured side-lobe level in the E-plane is less than-28 d B and the measured side-lobe level in the H-plane is less than-29.5 d B. The designed antenna structure is compact and low-cost, which has a high practical value.The main work of this thesis is based on the application background of antenna array, which has application values in areas of satellite communications and radar detection antenna systems.