GB1415803A - Waveguide filters - Google Patents

Abstract

1415803 Waveguide harmonic filters MARCONI CO Ltd 31 May 1974 [15 June 1973] 28505/73 Heading H1W A dissipative harmonic filter (harmonic pad) comprises a rectangular waveguide 1 having, in one or both narrow walls, slits 4 parallel to the minor cross-sectional axis, the slits being covered by one or more absorptive pads 5. The width of the slits is preferably less than twice the thickness of the waveguide walls and they may be spaced apart by two slit widths. They may extend the full width of the guide wall. The pad 5 may be made of silicone rubber loaded with ferrite, or a ceramic material loaded with ferrite or with carbonyl iron. It is stated that the filter passes fundamentals and all harmonics propagated in any TE mo mode but attenuates all other modes. As shown in Fig. 2, a number of such filters 6, 7, 8 &c. may be arranged in axial alignment with the cross-sections of adjacent filters relatively rotated through an angle of between 20 and 40 degrees. The fundamental of the TE mo mode propagates unchanged through such an arrangement, but harmonics of this mode are partially converted at each transition to TE mn waves (n>0) which are absorbed by the successsive filters.