GB835575A - An improved multiplexing and filtering device for the u.h.f. band - Google Patents

Abstract

835,575. Waveguide circuits. STANDARD TELEPHONES & CABLES Ltd. Dec. 14, 1956 [Dec. 21, 1955], No. 38287/56. Addition to 769,668. Class 40 (8). [Also in Group XL (c)] In a U.H.F. multiplex transmit-receive arrangement isolation of the different frequency bands in the transmitted and received waves is achieved by means of the multiplexers described in the parent Specification whilst separation of the transmitted and received waves, which are orthogonally polarized, is achieved by means of a mode filter. A horn radiator 10, Fig. 1, used for both transmission and reception, is connected to a symmetrical waveguide 8 in which a number of parallel conductive vanes 11, forming a mode filter, are arranged. These allow the passage of the received, horizontally polarized wave to a multiplexer 13 whilst forming a short-circuit for the transmitted, vertically polarized wave. The transmitted wave is coupled from a rectangular waveguide 7 into the waveguide 8 by means of a vertical probe 9. A transmission multiplexer 3 is coupled to the waveguide 7. Both multiplexers consist of two or more cavities each tuned to a different frequency, each connected on the one hand to a separate transmitter or receiver and coupled on the other hand by apertures to a common transmitting or receiving wide-band waveguide. The latter may be a ridged waveguide and may be connected to the waveguide 8 by means of probe couplings and a coaxial line (Fig. 4, not shown). In the modification of Fig. 5, the waveguides 7 and 8 are provided with double ridges in the form of horizontal, conductive laminae 23, 24 which are spaced apart by a small gap in the region of the coupling aperture 22 and recede from each other on either side of the aperture. The ridges also act as a mode filter.