Accumulation Of Uniform Multi-beam Imaging Reflector Antenna Research

The multi-beam antenna is an important part of the project"The theory and key technologies of the passive realtime imaging system", which supported by The Nature Science Foundation of China. The multi-beam antenna provides the receiving front-end for the passive imaging system, which is the major development direction of the passive realtime imaging system. Because of the widespread application of the passive imaging system in areas such as military, counter-terrorism and so on, the overseas countries carry on strict blockade to this technology. In order to meet the modern technology requirement and break the technology blockade, developing the passive millimeter imaging system in domestic has very important engineering significance.The method to realize the uniform multi-beam is studied deeply in this thesis. The major work and original innovation points are as the follows:1. The multiple beams reflector antenna is one of the key technologies for the passive imaging system, and the parabolic reflector is illuminated by the frontend feeds. The 29 independent beams covering±10°are obtained by 29 horn feeds in a curved plane. The nonuniformity of the beam gain is less than 1dB, the nonuniformity of beam width is less than 0.21°, and the sidelobe level is less than -14dB.2. A novel method-the Method of Moving Reference Point (MMRP) is proposed in this thesis. Using the new method the phase centre of any kind of antennas can be obtained as long as its far field radiation expression is determined, and we can determine the more ideal phase deviation according to the engineering requirements by choosing the better phase center position and angle width.3. Another new method-based on the combination of comercial software and numerical calculation is proposed to analyse the reflector antenna in this thesis. Using this new method, it does not need to consider the specific form of feeds, where their aperture field distributions are obtained by commercial software. The high order modes and edge diffraction fields of the feed are also considered by this method, thus the design of the reflector antenna is more accurate.4. The effects of the spacial choherence and the coupling between the feeds are considered in this thesis. A coherent wave beam can be obtained by the multi-feed reflector antenna when the spacing between the feeds is small. By increasing the spacing between the feeds,the effect of the coherence is reduced gradually. Through out the study of the compling effect of feeds located at the middle and edge of the array, it is found that compling effect to the uniformity can be neglected.