GB1359939A - Electromagnetic waveguide transmission devices - Google Patents

Abstract

1359939 Branching filters; waveguide constructions WESTERN ELECTRIC CO Inc 12 April 1972 [16 April 1971 (2)] 16808/72 Heading H1W A waveguide band-separation filter or mode transformer comprises a segmental circular waveguide for transmission of the circularelectric TE 01 mode and band-pass filters mounted on the chordal surface of the segmental guide. As shown, the waveguide 10 is of semi-circular cross-section and is coupled by a slot 16 on the centre line of the diametral surface 12 to the first cavity 50 of a band-pass filter. This comprises rectangular cavities 50, 53, tuned to a desired band and coupled to an output (or input) waveguide 26. A band-stop filter, tuned to the same band as the bandpass filter 20, comprises rectangular cavities 51, 52 coupled to the waveguide 10 by central slots 17 ,18 and resonant respectively in the H 101 and H 102 modes. Energy in bands outside the regime of filters 20 and 30 is transmitted without change between ports 1 and 3 of the waveguide 10. Modifications are described in which the axes of the cavities of the bandpass and band-stop filters lie perpendicular to the axis of the waveguide 10. Such cavities may have either a rectangular or a circular crosssection. When the arrangement is used as a mode transformer (see Fig. 5, not shown), the port 3 may be terminated by a piston and the band-stop filter omitted. The whole of the input energy then passes into the band-pass filter. In the multiplexing arrangement of Fig. 4, a wideband input at A is divided into sub-bands by diplexers 71 and low-pass filters 66. Each subband is further sub-divided by channel-dropping filters 70 connected to amplification or utilization devices 65. The channels may be recombined in an output arrangement which is identical to the input arrangement and it is apparent that the whole multiplexing arrangement operates reciprocally. The device of Fig. 3, may be made by an electroforming process using non-destructible stainless steel mandrels for the formation of cavities 50, 51, 52, 53 and waveguide 26. The electroform consists of two slabs with mating surfaces co-inciding with the common median plane of the cavities and the waveguide (see Fig. 6, not shown). The curved wall of waveguide 10 is provided by a further electroform and the chordal wall 12 by the undersurface of the lower of the two slabs providing the filters. The slabs are located by pin-and-slot, and a sealing gasket is located in a peripheral groove in the upper slab.