Integrated Duplex Filtering Feeds For Ring-Focus Reflector Antennas

Duplex antennas have compact structures and high efficiencies,which can reduce the size and weight of wireless communication equipment.It has important application requirements in small integrated wireless communication equipment.Most of the satellite antenna feeders require duplex,broadband,lightweight and compact characteristics.In satellite antennas,the common one is VSAT,which is the abbreviation of"Very Small Aperture Terminal"(Very Small Aperture Terminal)in English,or small station for short.It refers to a class of intelligent small or miniature earth stations with very small aperture antennas.Traditionally designed VSAT feeds often do not have the characteristics of duplex and compactness.In order to meet these specific requirements,duplexers and other components are usually added to the feed,which will increase the volume and cost of communication equipment,and also bring about problems of large loss and difficult matching.Therefore,in the reflector antenna,how to design a reasonable feed to realize a miniaturization and integration of communication equipment and reduce the cost of communication equipment is the design focus of this article.In this paper,the feed of reflector antenna is designed step by step,and the following three tasks are completed:1.A duplex pyramid horn antenna based on an E-plane split waveguide is designed,The feasibility of the scheme as a reflector antenna feed is verified.As the feed source of the reflector antenna,because it needs to generate a wide beam and reduce the shielding of the reflector,a small-diameter horn is used in the design.Compared with the traditional design of the feed of the ring focus reflector antenna,the duplexer is integrated in the hollow waveguide which is used to transmit signals,and two signals are split in the E-plane of the waveguide to realize the integrated design of the duplexer and the feed horn.When the feed design scheme is applied to the ring focus reflector antenna,there is no need for additional duplexers,and the overall volume and weight can be reduced It can also solve the problems of large loss and difficult matching.Each channel filter of the duplexer in the feed is a third-order equal-ripple filter.The k-converter is realized by inserting an inductive diaphragm into a section of waveguide,and the resonant unit is realized by using a half wavelength rectangular waveguide.The results of simulation and actual measurement are in good agreement.The results show that the designed frequency division duplex filter feed achieves high isolation between ports.The isolation between the receiving channel ports is greater than 43d B,and the isolation between the transmitting channel ports is greater than 45d B.The return loss in the transmitting and receiving channels is better than 10d B.The gain of the receiving port is up to8.75d Bi,and the gain of the transmitting port is up to 9.5d Bi.2.A homopolarized duplex horn feed for ring focus reflector antenna is designed.After verifying the feasibility of E-plane split waveguide duplex pyramid horn antenna as reflector antenna feed,the designed dual horn feed with the same polarization is applied to the ring focus reflector antenna while improving the isolation.The same E-plane split waveguide duplex structure and the feed integration design of the reflector antenna are adopted.By increasing the filter order of duplexer,so as to increase the length of the feed support rod,the feed can not only play the role of adjustable length support for the secondary reflector of the ring focus reflector antenna,but also can separate the transmit and receive signals to achieve high isolation,so as to realize the communication equipment miniaturization and integration,reduce the cost of communication equipment.The feed isolation exceeds 84d B and the gain reaches 10.3d Bi in the receiving channel,and 75d B and 12.9d Bi in the transmitting channel.The gain of receiving channel and transmitting channel can reach 34.75d Bi and 36.45d Bi respectively.3.A circularly polarized duplex feed for ring focus reflector antenna is designed.At the splitting point of E-plane split waveguide duplexer,a stepped tapered diaphragm is used to realize linear polarization to circular polarization,so that the TE₁₀mode and TE₀₁mode in the waveguide are equal in size,and the phase difference is 90 degrees.Finally,a duplex circular polarization reflector antenna is optimized.The isolation of feed in receiving channel is more than 72d B,the gain is up to 10.8d Bi,and the axial ratio is less than 3d B.The isolation of feed in transmitting channel is more than 68d B,the gain is up to 12.5d Bi,and the axial ratio is less than 2d B.The gain of receiving channel and transmitting channel can reach 34.6d Bi and36.48d Bi respectively.Through a systematic study on the theoretical principles of the above three duplex filter feeders,the design theory and basic knowledge of the integrated feeders of the Ring-Focus Reflector Antenna are thoroughly understood.An integrated duplex feed for the reflector antenna is designed,and the function of duplex filter and self-support for the secondary reflector are realized.