GB810057A - Improvements in wide-band directional waveguide couplers - Google Patents

Abstract

810,057. Directional couplers for waveguides. MARIO, G. R. P. June 15, 1956 [June 17, 1955; June 18, 1955], No. 18639/56. Class 40 (8). A wide-band directional waveguide coupler comprises rectangular input and output waveguides 1, 2 coupled by systems of slots 3, 31, 4, 41 to a plurality of cylindrical resonant cavities (e.g. two cavities g, g<SP>1</SP>) having different resonance frequencies, each slot system forming a directional coupling such that a wave propagated in a given direction in the input guide 1 gives rise to a wave propagated in a given direction in each resonant cavity which produces a wave propagated in a given direction in the output guide 2. Each slot system comprises two intersecting slots, the intersection of which lies on an axis of a cylindrical cavity at' a point in a wall of a rectangular guide at which the longitudinal magnetic field is equal and in phase quadrature with the transverse magnetic field. The resonance cavities g, g<SP>1</SP> are spaced apart by a quarter of a wavelength in the rectangular guides, at a frequency intermediate between the resonance frequencies of the two cavities, so that at this frequency the total phase displacement between the input and 3# output waves in the guides 1, 2 is equal to -. <SP>2</SP> Preferably in a construction comprising more than two cylindrical resonant cavities the difference in the resonance frequencies of two adjacent cavities is uniform throughout the coupler. A combination of the directional couplers having a common rectangular input waveguide may be used as a microwave filter enabling a plurality of communication channels in a wide frequency band to be separated, a rectangular output guide particular to a given channel being coupled with the common guide by two cylindrical resonant cavities having resonance frequencies near the respective frequency limits of the given channel.