Research Of An Ka_band Dual Aperture Dual Model Feed

With the development of single-pulse technology, people raised more demands for tracking accuracy and speed of radar. Single pulse feed of the millimeter-wave band had an advantage in large information capacity and fast data processing speed. Thus it gets more and more attention. This paper analyzed and designed the dual-port dual-mode feed for Ka-band. and was focused on aspects below: the band broadening of feed, interaction between X-band feed and Ka-band feed for the radiation field, band broadening of folded magic T, band broadening of 3d B bridge, and single pulses contradictions between sum and difference.Firstly, this paper analyzed the works principle of dual-port dual-mode feed and built dual-port dual-mode feed model with HFSS, guaranteeing its structure to work with X-band feed composed together to form a single pulse dual-band feed. Then it specifically analyzed the physical structure of the feed, and it is mainly composed by device of sum and difference, a transition section. Device of sum and difference was made of folding magic T and 3d B bridge. It calculated primary pattern function of the dual-port dual-mode feed by use of caliber field method, so we get primary pattern of feed. In this paper, device of sum and difference feeders of the dual-port dual-mode feed were the focus of research and design.Secondly, we designed network of sum and difference by magic T and 3d B bridge, a thorough analysis for impedance characteristics of folded magic T and 3d B bridge was did. As the result of magic T internal discontinuities, It generated refection. So we added capacitance or inductance to offset the reflection. By adjusting metal separators between ports of 3d B bridges,we could guarantee amplitude and phase characteristics of 3db bridge.It is joined with the transition section between the feeder and network of sum and difference, and it can improve impedance matching.On the other hand it change four speakers into two speakers.In the transition section, purpose of Wave type device is the formation of high-order mode TE20. Because effective aperture ratio of the sum channel and the difference channel is 1: 2, so it met conditions of optimum irradiation. It solved contradictory problems between sum and difference, so It improved the single pulse fed efficiency. Since the X-band and Ka-band feed worked in a radiation aperture, It increased the difficulty of deployment. So we adjusted the radiating aperture by adding the deployment of a metal plate and a choke groove, we could make feeds of X and Ka band can work normally.Finally, the feed was processed and tested. It showed absolute bandwidth of the entire feed is 2GHz, It increased 1.4GHz of absolute bandwidth than the introduction of the feed from Swiss before. Each port isolation was higher than 25 d B, and zero depth of azimuth and elevation difference pattern was less than-25 d B, but zero depth offset achieve maximum 5° in the measure. Most data of the experiences and simulation data fit better, and deviations of the test and simulation may be related with Machining and measured processing.