| Millimeter wave waveguide slot antennas have wide applications in military field for the advantages of compact structure, low feeder loss, high radiant efficiency, large power capacity and good stability and so on. In this paper, the circular polarization and the wide beamwidth characteristics of waveguide slot antenna are discussed and an innovative millimeter wave waveguide antenna structure of circular polarization and wide beamwidth is presented. Firstly, a circular polarization scheme is proposed and validated by simulations and tests. Secondly, the implementation method of wide beamwidth waveguide slot antenna is detailedly discussed. In the end, two different antenna design schemes are raised and can be chosen according to different applications. The main research works are summarized as follows:1. A novel configuration for millimeter wave waveguide antenna of circular polarization is designed, containing a rectangular feed waveguide and a antenna radiating element. One end of rectangular feed waveguide shorted out, while the radiating element is composed by a rectangular radiation cavity and L-shaped slots. The energy coupling between the radiation cavity and the feed waveguide is attributed to the cross slot on the broad wall. The designed antenna has a good circular polarization performance with small size and all-metal construction, which can be applied in severe environment. In this paper, the principle and structure of the antenna are detailedly introduced and its structure parameters are discussed and optimized. The measured results of the antenna are also included. The simulated and experimental results show an axial ratio bandwidth at30GHz of300MHz and the gain greater than8dBi.2. Further research on implementation of wide beamwidth is carried out and two antenna structures of wide beamwidth are proposed based on the design of the millimeter wave circular polarization waveguide antenna. The first antenna improves the slot structure of the circular polarization antenna unit by applying L-shaped slots. It has a150MHz circularly polarized bandwidth with a beam width better than100°, uniform pattern and gain greater than zero in hemisphere area. The second antenna composes of circular polarization antenna units, feeding with waveguide branching. With eight-shaped beam shape on horizontal plane, its maximum radiation direction can be adjustable. By introducing principle and simulation optimizing for two antennas, the operation characteristics, advantages and disadvantages of the two antenna structures are discussed respectively in this paper. |
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