Research On Millimeter Wave Monopulse Antenna Feed System Based On Groove Gap Waveguide

The mm-wave monopulse antenna has long-distance and high-resolution detection which is widely used in modern surveillance and tracking radar systems.The detection accuracy of the monopulse antenna is easily affected by the monopulse feeder and monopulse comparator,which are the critical device of the monopulse antenna.Recently,the groove gap waveguide(GGW),features high power capacity,low loss,and easy-to-assemble without needs good electrical contact among different mental parts,is proposed for the millimeter-wave devices and systems.The easy-to-assemble structure of GGW can be used to reduce the assembly difficulty of the high gain monopulse antenna.In this thesis,the research on the design of monopulse feeder antenna and monopulse comaprator is carried out,a dual-circularly polarized monopulse feeder with compact structure and a low-profile broadband monopulse comparator is proposed.In order to realize dual-circularly polarized radiation,the stepped-thickness septum is used to design the dual-circularly polarized monopulse feeder.For obtaining a compact and easily integrated structure,a monopulse comparator with ring-shaped symmetrical planner topology is proposed by using the 3 d B coupler and phase shifter.In order to simplify assemble process of devices,GGW is used to design the required devices of monopulse comparator.Meanwhile,in order to achieve the equal-amplitude distribution in a broad bandwidth,the asymmetrical coupling structure and the novel dispersion-matched transition are proposed to improve the directivity of the 3 d B coupler.Moreover,a ridge waveguide with periodic grooves featuring stable dispersion change is proposed to design the phase shifter,which contributes to reducing the phase unbalance of phase shifter in the broad frequency band.To validate experimentally the design feasibility of the dual-circularly polarized feeder and monopulse comparator,the dual-circularly polarized feeder and monopulse comparator are fabricated.The results show that the amplitude imbalance of the designed monopulse comparator is almost 0.5d B from 27 GHz to 34 GHz,and the measured phase imbalance is less than 3°.From 27 GHz to 31 GHz,the dual-circularly polarized monopulse feed can radiate a symmetrical beam with 32 d B null-depth through the feed of the monopulse comparator,and the gain ratios between the sum and the difference pattern are about 4 d B.The proposed dual-circularly polarized feeder and monopulse comparator characterize broad bandwidth,low loss,and a compact size,which provide a broadband low-profile design scheme for the research of the dual-circular monopulse feeder and monopulse comparator.