Design and implementation of dual mode feed horn for broadband wireless local loop antenna

The electrical design of primary feed antennas involves a number of dependent factors. A primary feed can be any type of elementary antenna: dipole, slot, horn, and so on. And the principal characteristics to consider are matching of the feed to the feed guide, radiation pattern, polarization etc. Although a conical horn antenna as primaly feed for reflector antenna has characteristics of axis symmetry beam, its beamwidth of E-plane and H-plane is. not equal and sidelobe level is very high. These problems could be solved with multimode or dual mode horn antenna. A corrugated horn antenna among the various multimode horn antennas has profitable characteristics such as axis symmetry beamwidth and excellent cross polarization property, but it has disadvantages of heavy weight, big size and difficulties in fabrication process[1]. In this paper, we designed dual mode horn antenna as a primary feed for broadband wireless local loop(24.25-26.7GHz) antenna. The dual mode horn was first descibed by P. D. Potter[2]. This horn has a very simple design. It may be used as feed element in reflector antennas where low cross polarization property is required. As the radiation pattern of this simple horn is almost rotationally symmetrical, it may also replace the single conical horn to obtain a higher aperture efficiency of the reflector[3- 5]. If we consider the cross-polar component and sidelobe, a dual mode horn would be a good choice. A most important application of a dual mode horn is as a feed of cassegrain reflector or parabolic reflector, built, and tested with relatively good success in their performance.