GB1067167A - Improvements to transmission devices - Google Patents

Abstract

1,067,167. Waveguide hybrid junctions COMPAGNIE FRANCAISE THOMSONHOUSTON-HOTCHKISS BRANDT. Nov. 14, 1963 [Nov. 20, 1962], No. 45035/63. Heading H1W. [Also in Division H4] A diplexing circuit uses hybrid circuits consisting of four coaxial line arms coupled to a common section of waveguide. The rectangular waveguide 31, Fig. 3, contains a T-junction 32, 34, 35 symmetrically disposed between the broad walls, and a further coaxial terminal 33 disposed either in the end wall or (as shown) in the broad wall of the waveguide axially displaced from the T-junction. If the terminals are correctly matched and the waveguide is operated in the H 01 mode, input energy from terminal 32 is divided in phase between symmetrical terminals 34, 35 and none is coupled to terminal 33. Two such waveguides (G 1 , G 2 , Fig. 1) are provided with respective symmetrical terminals (2, 4) and (2<SP>1</SP>, 4<SP>1</SP>) interconnected by coaxial lines (Co 1, Co 2) of equal length, whereby a signal (e.g. a television vision signal) fed to terminal (1) is wholly coupled to terminal (1<SP>1</SP>). A further signal of a different frequency (e.g. a television sound signal) fed to terminal (3<SP>1</SP>) divides equally in antiphase between the lines (Co 1, Co 2) and is reflected back to waveguide (G 2 ) by rejection filters (Crs 1, Crs 2). Since the filters are staggered by one quarter-wavelength from the waveguide (G 2 ), the reflected signals are in phase at the T-junction (5<SP>1</SP>) and are coupled to the terminal (1<SP>1</SP>). The latter may be connected to an aerial feeder. Any portion of the signal not reflected by the filters is dissipated in a load (8). The coaxial arms also contain band-pass filters (Cfi 1, Cfi 2) for the signal fed to the terminal (1).