GB1294502A - Frequency variable directional filter - Google Patents

Abstract

1294502 Band separation devices HITACHI ELECTRONICS CO Ltd and NIPPON TELEGRAPH & TELEPHONE PUBLIC CORP 21 May 1970 [24 May 1969] 24749/70 Heading H1W A frequency variable directional filter comprises two parallel rectangular waveguides 7, 8 between which is interposed at least one resonator consisting of a ring shaped rectangular waveguide so as to provide a common wall coupling region acting as a directional coupler, the operating frequency being varied by means of adjustable dielectric or metal posts 12 inserted into the resonator from the surface of a waveguide wall. A wide-band input at port A is divided such that non-resonant frequencies leave port C while frequencies corresponding to resonance of the ring-shaped resonator appear at port B. In the embodiment shown the resonator comprises portions 9 & 91 which are interdigitated by slotted waveguide portions 10 1 , 10 2 , 10 3 located in the H-planes of resonators. Dielectric posts 12 made e.g. of polystyrene, and inserted into the resonators to vary the resonance frequency are of limited diameter to reduce wave energy loss through the resonator bores in which the posts are located. The posts are separated by #/4 where # is the resonance wavelength and each post may be of different diameter to reduce the total reflection from the posts. In an alternative arrangement the waveguides 7, 8 and the resonator have common walls provided with coupling holes.