Homogeneous Lens Multibeam Antenna And Single-channel DBF Multibeam Antenna Research

Multi-beam antennas can form multiple beams in different directions with just a single antenna aperture. They can minimize the volume and cost of the antenna system and realize wide-angle coverage, which make them a key technique in wireless communication and modern radar systems. Therefore, multibeam beam antennas have wide applications. This dissertation focuses on the design of multi-beam antennas, espically the homogeneous dielectric lens antenna, which can realize wide-angle coverage, and the single-channel DBF antnna. The main achievements are as follows.1. Spherical lens can only be used to generate multiple beams in one dimension previously. By parallel displacing multilayer feed antennas in another dimension, scanning in two dimensions is realized. The relationship between displacement of feed antenna and scan angle is analyzed based on the coordinate transformation approach and by using a ray-tracing method. For millimeter-wave applications, a Ka-band lens antenna with8×2feed arrays has been fabricated. Measurements show that scan coverage of128°in azimuth and30°in elevation is achieved.2. A novel homogeneous spheroidal lens antenna is proposed to overcome the shortcoming of the spherical lens. The spheroidal is a circle in the top view and an ellipse in the side view. The beamwidth in E-and H-planes can be individually controlled and wider coverage is obtained through adjusting the axial ratio of the ellipse. The system is analyzed through a ray-tracing method. Spherical lens antennas that can realize two-dimentional coverage and full360°coverage in the azimuth are fabricated at Ku-band. Measurements on the latter design show that the side lobe levels of the20beams are all below-17dB and the gain differences are all within±0.4dB.3. Based on the time sequence phase weighting (TSPW) technique, a new type of digital beamforming (DBF) multibeam antenna array is proposed. Cost and power consumption are usually very high in traditional DBF antenna array due to the fact that each of the array elements is followed by an RF channel. The proposed scheme can decrease the sensitivity to wave front distortion when compared with other methods. A proof-of-concept prototype of eight-element receiving array at X-band has been fabricated and tested. Measured results confirm the validity and advantages of the proposed scheme.4. A calibration method is proposed for the single RF receiver digital beamforming (DBF) antenna array. The influence of the imperfection in phase weighting is analyzed. The on-line test of the0/π phase shifters is carried out based on a known incident plane wave. After errors of all the phase shifters are obtained, the amplitude-phase distribution on the aperture could be corrected. The corrected data are then used to finally obtain the multi-beam patterns. Simulated and measured results validate the efficiency of the proposed calibration method.