Patent GB-1184462-A (GB)
Title: Improvements relating to Multi-Source Signal Coupling
IPC: H03H7/48
Filed: 1967-04-26
Abstract: 1,184,462. R.F. couplings; automatic phase control systems. COMPAGNIE FRANCAISE THOMSON HOUSTON - HOTCHKISS BRANDT. 26 April, 1967 [2 May, 1966], No. 19311/67. Headings H3A and H4A. [Also in Division H1] In an electric circuit comprising at least one input and one output hybrid junction and an adjustable phase shifter in one of the paths connecting the input and output hybrid junctions, two input points of the input hybrid junction being connected (with or without relative fixed phase shift) to respective radio power sources and two output points of the output hybrid junction being connected to useful and dummy loads respectively, a circuit detects the amplitude difference of the signals from the radio power sources and automatically adjusts the phase shifter to maintain maximum ratio of power in the useful load to that in the dummy load. In an embodiment phase-locked transmitters T1, T2 of equal power feed a hybrid junction 10 connected to points 18, 19 and including an adjustable phase shifter 20; points 16, 17 are connected to an aerial 3 and dummy load 9 respectively. When the phase shifter is adjusted for 90 degrees shift the output signals reach hybrid junction 15 in phase and the aerial receives the combined power from both transmitters and none is lost to load 9. If the relative powers of the transmitters change the phase shifter is re-adjusted to give total power feed to the aerial. Automatic re-adjustment of the phase shifter can be derived from diodes 56, 58, D.C. amplifier 68 and reversible motor 72; a rate feedback is afforded by a generator 76. To cater only for a complete failure of one transmitter an " on-off " phase shifter is provided utilizing a trombone coaxial phase shifter, Fig. 1a (not shown). Transmitter phase-locking.-The outputs of probes 48, 50 are applied to a hybrid junction 52, one via a 90-degree phase shift. A phase shifter 43 is controlled by the voltage from a tapping on the resistor 52R to restore in-phase transmitter outputs by variation of varactorcontrolled phase shifter 43. In another embodiment each transmitter comprises sound and vision channels and associated diplexer, Fig. 3 (not shown). In a modification the sound units of both transmitters are connected to a first hybrid junction and the outputs of the hybrid junctions are diplexed via adjustable phase shifters to a third hybrid junction to which the aerial and dummy load are connected, Fig. 4 (not shown): should either vision transmitter fail, the system by phase shift re-adjustment can radiate the power from the remaining vision transmitter plus the power from both sound transmitters, and similarly in the case of failure of one sound transmitter &c. In one modification failure of either diplexer is catered for, Fig. 5 (not shown); in another modification concurrent failure of one transmitter and a diplexer is allowed for and utilizes two further hybrid junctions, Fig. 6 (not shown). An arrangement is described where there are three transmitters, Fig. 7 (not shown). Various alternative forms of hybrid junction may be utilized, Figs. 8, 9, 10 (none shown).