Analysis Of The Feed Structure Of Millimeter Wave Radial Line Slot Antennas

Millimeter wave systems have many distinct advantages,such as miniaturizing system components, increasing frequency bandwidth, providing higher detectability, not easily influenced by atmosphere conditions, etc. Therefore, they are widely used in communication, radio astronomy and military fields. A rectangular waveguide slot array has been greatly developed after World War II, but it has conventionally a disadvantage in terms of complicated structures, especially in high frequency band. A radial line slot antenna (RLSA) is a high gain, high efficiency and low cost planar antenna, which is suitable for mass production and commercial uses.In this thesis, a rectangular-to-radial waveguide transition adapter is proposed as a feeder of radial line slot antennas. Without the disk at the bottom of the adapter, the return loss becomes much smaller. The feed structure is analyzed by a combined method of FEM based on the weak form of Helmholtz equations and mode expansion method. The results are compared with those obtained by Ansoft HFSS. Parameters of the transition are optimized to get a broadband performance in Ka band. Results show that, the frequency bandwidth is about 10.0% while the return loss below -20dB.