Design of improved 8 mm band multimode matching feed

摘要

An improved 8 mm band multimode matching feed is designed in this paper, which eliminates the rectangular step structure in the original multimode matching feed, which has large difficulty in processing, then reducing the difficulty of processing and production costs. The improved feed uses the rectangular-to-circular mode converter structure and variable angle cone structure to achieve the transition from the rectangular waveguide dominant mode TE10 mode to the circular waveguide dominant mode TE11 mode, then TE11 mode be synthesized with a high-order mode TM11 mode which is motivated by a variable angle cone structure. The improved feed is similar to, or even better than the original feed in the directivity pattern, gain and voltage standing wave ratio (VSWR). The gain of feed is approximately 13 dB, the VSWR is less than 1.13 and the equal level of E plane and H plane is -15 dB. Measured results are same with the simulation results.