GB855026A - Improvements in or relating to wave guide transition devices - Google Patents

Abstract

855,026. Waveguide couplings. WESTERN ELECTRIC CO. Inc. Dec. 19, 1958 [Dec. 31, 1957], No. 41005/58. Class 40(8). A waveguide transition device comprises a hollow conductive waveguide or resonator, of circular transverse cross-section, a hollow conductive waveguide of rectangular cross-section supportive of electromagnetic wave energy of a type wherein the maxima and minima locations in time and space of the magnetic field component intensities coincide with the minima and maxima locations, respectively, of the electric field component intensities, means for establishing a standing wave in said rectangular waveguide, and means for coupling between said circular waveguide or resonator and rectangular waveguide comprising a multiplicity of coupling apertures disposed through a common metallic wall portion with each of said apertures positioned at a lull in the field pattern of said standing wave. In one arrangement, Figs. 1 and 1A, a circular waveguide 11 is coupled to a surrounding annular rectangular waveguide 13 through rectangular apertures 15 to 21 spaced apart one guide wavelength in the annulus 13. A rectangular waveguide 12 forms an E-plane Tee junction with the annulus 13. Energy passing down guide 12 divides into two equal portions on reaching the Tee junction, the polarities of the electric fields of the two portions being 180 degrees out of phase, as indicated by the arrows 10. The two portions meet at the opposite side of the annulus 13 to produce an electric field lull at this point and are reflected to set up a standing wave in the annulus 13. The apertures 15 to 21 are thus all located at electric field lulls so only magnetic coupling is possible to the waveguide 11 and a TE 01 wave is excited therein. A band reflection filter 22 located an odd number of quarter wavelengths at the circular waveguide frequency from the coupling apertures ensures that all the energy is propagated to the left in the drawing. The apertures 15 to 21 may each be located a quarter guide wavelength from the positions shown, in which case they will be at magnetic field lulls and a TM 01 wave will be excited in the waveguide 11. In alternative embodiments (Figs. 4 and 5, not shown) an annular cavity resonator forming a bandpass filter is provided between the waveguides 11 and 13. Coupling apertures are provided in a common wall of the waveguide 13 and the cavity resonator, which is coupled to the waveguide 11 by means of a gap interrupting the waveguide. The ends of the cavity resonator may be formed by movable plungers or pistons for tuning purposes. In a further alternative embodiment, Fig. 6, a circular waveguide 61 is terminated by a conductive plate 62 provided with circular apertures which communicate with an annular rectangular waveguide 63 forming an H-plane Tee junction with a rectangular waveguide 64. A conductive ring iris 66 and a round plate 67 separated by a dielectric spacer 68 form a resonant cavity with the end plate 62. In a similar arrangement (Fig. 8, not shown) the annulus 63 and waveguide 64 are modified to form an E-plane Tee junction.