Abstract: Weather radar is currently evolving towards acquiring multi-polarization information. This paper proposes a novel scheme for a pentapolarization dual-channel weather radar antenna feed system, which conveniently achieves five polarization operating modes through a "Pentapolarization Switch Assembly". A design example for a C-Band 3.2-meter antenna is provided, demonstrating that this design scheme is novel and feasible.

The radar transmitter protection unit is comprised of a three-port circulator and a high-power load. It protects the transmitter from potentially abnormal high reflections originating from the antenna feed system.

  The feeder system’s power-feeding device consists of components that form two channels connecting the triple-polarization state switching switch and the dual-polarized feed source. These include a four-port circulator, a TR discharge tube, a limiter forming the transceiver duplexer, a dual-channel azimuth rotary joint, an elevation rotary joint, sampling couplers, and straight, bent, and twisted waveguides of varying lengths. The azimuth rotary joint and elevation rotary joint are critical components that enable normal power transmission to the antenna as the entire system rotates in azimuth and elevation directions. Sampling couplers can measure or monitor the transmission loss and phase consistency between the two signal paths, assisting in determining whether the feeder system is operating normally.

  The polarization conversion device is realized through a specially designed five-polarization state switching switch assembly developed by Hengda Company. When the transmitter signal is switched to horizontal polarization, the transmitted signal is channeled through the H path to radiate via the antenna’s H polarization. When the transmitter is switched to vertical polarization, the transmitted signal is channeled through the V path to radiate via the antenna’s V polarization. When the transmitter is switched to H and V dual polarization, the transmitted signal is equally divided and fed in-phase through both the H and V channels to radiate simultaneously via the antenna’s H and V polarizations; in this case, the actual radiation corresponds to a 45° oblique polarization wave. When the transmitter is switched to left-hand or right-hand circular polarization, the transmitted signal is equally divided and fed in quadrature through the H and V channels to radiate via the antenna’s H and V polarizations. When the phase difference between the electromagnetic waves is +90°, the actual radiation corresponds to a left-hand circularly polarized wave; when the phase difference is -90°, the actual radiation corresponds to a right-hand circularly polarized wave. Thus, conversion among five polarization states—horizontal polarization, vertical polarization, 45° oblique polarization, left-hand circular polarization, and right-hand circular polarization—is achieved. Under all five polarization states, both H and V channel receivers can receive echo signals either separately or simultaneously.

 

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