GB907117A - Dual frequency feed horn - Google Patents

Abstract

907,117. Aerials. BENDIX CORPORATION. Feb. 9, 1961 [March 9, 1960], No. 4873/61. Class 40 (7). The invention relates to horn aerials capable of radiating energies of two different frequencies and orthogonal polarizations such as are used in co-operation with a reflecting surface to form shaped beams. The aerial comprises a flared rectangular horn 12 with a plurality of spaced parallel conductive plates 27 projecting inwardly from opposite walls. The horn is fed from a waveguide 11 which is provided with conductive plates 25 attached to opposite walls and parallel to those in the horn. Probes 17 and 22 feed the waveguide with energy at two different frequencies and with orthogonal propagating modes. The lower frequency energy is introduced by probe 17 and as its electrical vector lies in the direction of arrow 16 it is substantially unaffected by the plates and propagated with a pattern dependent on the horn wall design. Matching rods 21 match the waveguide to the horn at this frequency. The higher frequency energy introduced by probe 22 is prevented from passing back into the closed end of waveguide 11 containing probe 17 by bars 32 joining the rear ends of the wave-guide plates 25. The size of the guide is effectively reduced to the space not occupied by the plates for this energy and the plates are tapered at 26 to form a horn section for it. Plates 27 reduce the radiating aperture for high-frequency energy and in order to suppress undesirable modes a structure 29 is provided consisting of a conductor 29 centrally positioned by support members 31 which are connected together at an obtuse angle and conductively connected to the horn walls. In order to match the high-frequency structure it is preferred to make the central pair of plates 25 narrower than the others and to taper them to the horn-waveguide junction at a smaller angle.