Patent GB-836930-A (GB)
Title: Locking-oscillator phase-pulse generator
IPC: H04L5/12
Filed: 1957-08-20
Abstract: 836,930. Multiplex transmission systems. COLLINS RADIO CO. Aug. 20, 1957 [Jan. 16, 1957], No. 26301/57. Class 40 (4). [Also in Group XL (c)] In a diplex system in which binary coded inputs to each channel are combined to phase shift a stable oscillator frequency by amounts which correspond to the four possible combinations of the two inputs, the phase comparison is made between two adjacent pulses derived from the stable oscillator frequency, and each pulse acts as a phase reference for the immediately following pulse. As shown in Fig. 1, a reference frequency 8#, which may be an audio frequency is generated at 10 and applied to the phase detectors 13p, 13q in phaselocking circuits P and Q respectively. Each phase-locking circuit includes a normally open gate 17p, 17q, whereby the output of the phase detector 13 controls a reactance 19 in the frequency determining circuit of an oscillator 11p, 11q, producing a frequency f. The output frequency of the oscillator is multiplied by eight by a frequency multiplier 12 and applied as the other input to the phase detector 13. Timing pulses, which are synchronous with the binary input pulses are applied to a bistable circuit 28, whereby the output gates 21, 22 are alternately opened to pass the output of the corresponding oscillator 11. The square-wave outputs of the bistable circuit 28 are also utilized to control pulse-forming circuits 36, 37, which through the respective gates 17p, 17q control the phaselocking circuits P, Q, the arrangement being such that when the output gate 21 is initially opened the gate 17q is momentarily closed to disable the phase-locking circuit Q. Similarly, when the gate 22 is initially opened, the gate 17p is momentarily closed. When the output gate 21 is opened a pulse of frequency f is applied to the output circuit 32 and to channel 1 and channel 2 phase-shifting circuits 41h, 42h, in a phase-determining circuit H which also receive binary coded input pulses from channels 1 and 2. The phase-shifted outputs of the circuits 41h, 42h, are combined vectorially at 43h and utilized to control the phase of the oscillator 11q, the phase-locking circuit Q being at that instant disabled. The phase-shifter 41h is arranged to provide a O degree shift for a mark on channel 1, Fig. 3, and a 180 degree shift for a space on channel 1, the phase-shifter 42h providing a 90 degree shift for a mark on channel 2 and a 270 degree shift for a space on channel 2. When combined at 43h the output to the oscillator 11q may have a shift 45, 135, 225 or 315 degrees, according to the combined signal appearing on channels 1 and 2 at that instant, and the phase of the oscillator 11q is correspondingly adjusted to form the new reference and then locked by the phase-locking circuit Q. The vector O represents the phase of the input frequency from the oscillator 11p. The next pulse from the bistable circuit 28 opens the gate 22 and closes the gate 17p to momentarily disable the phase-locking circuit P. An output pulse of frequency f and the appropriate phase is applied via the gate 22 to the output line 32 and is also applied to the phase shifters 41k, 42k together with the binary input pulses now appearing on input channels 1 and 2. As in the previous case, the phase-shifted outputs of the phase-shifters 41k, 42k are combined at 43k and shift the phase of the output frequency from the oscillator 11p accordingly, and the cycle is then repeated.