GB1356884A - Broadband waveguide circulators - Google Patents

Abstract

1356884 Waveguide junction circulation WESTERN ELECTRIC CO Inc 27 June 1972 [29 June 1971] 30044/72 Addition to 1305006 Heading H1W The bandwidth of an H -plane waveguide junction-circulator is improved by providing two gyromagnetic elements of different (resonant) lengths. The invention is an improvement on that described in Specification 1,305,006 according to which an element (or elements) extends along the axis of symmetry of the junction and is proportioned such that the reflection coefficients for the two counter-rotating resonant modes and that of the in-phase mode are spaced by 120 degrees over a wide band. As shown in Fig. 4, two such elements 52, 54 of unequal size are separated by a dielectric gap and form quarter-wave resonant sections for the counter-rotating modes at two spaced frequencies whereby the operating bandwidth of the circulator is extended. In addition, the resonant frequencies of the in-phase modes of the two elements are determined by quarterwavelength conductive pins 44, 53 whereby further extension of the bandwidth is obtained. In a modification of this construction (Fig. 8, not shown) one of the gyromagnetic elements rests on a conductive disc which behaves as an impedance transformer and smooths the phase/ frequency characteristic determined by the various resonances. The operation of the construction of Fig. 5 is similar to that of Fig. 4 but, in this case, the two elements 55, 56 extend from a central conductive septum and are spaced from the walls 40, 41 of the junction by dielectric discs 58, 59. In the construction of Fig. 6, the elements 71, 72 are resonant in a halfwave mode and are terminated at both ends by dielectric spacers 73, 74, 75. In the construction of Fig. 7, the elements 84, 85 extend into cavities 82, 83 whose depths determine the resonant frequencies of the in-phase modes of the two elements. The resonant frequencies of the counter-rotating modes are determined by the total lengths of the elements.