Patent GB-871332-A (GB)
Title: Detector sampling means
IPC: H04L5/12
Filed: 1958-02-11
Abstract: 871,332. Diplex transmission systems. COLLINS RADIO CO. Feb. 11, 1958 [July 26, 1957], No. 4481/58. Class 40 (4). [Also in Group XL (c)] Means for sampling a periodically integrated signal comprises a dual polarity gate arranged to be opened by timing pulses at the end of the period of integration and fed with said integrated signal to produce an output pulse whose polarity is determined by that of the integrated signal, said output pulse being fed via a gate opened in synchronism with the timing pulses to a toggle circuit. The invention is applied to the reception of twinplex signals in which the phase of the received signal is varied by one of four prescribed amounts from the phase previously obtaining, in accordance with the four combinations of mark and space on two channels. Phase detector, Fig. 3.-As shown the radio receiver output 12 is fed to gate 27a, 27b, which are opened during alternate periods by outputs from the bi-stable circuit 20 controlled by timing pulses F 1 , to feed resonating circuits 26a, 26b which resonate by virtue of their high Q achieved by amplified positive feedback through gates 28a, 28b. Thus during one period an A.C. signal, having the phase of the input, builds up in amplitude and during the next period stays at constant amplitude until the end of the period. The gate 28a is then momentarily operated in such a manner as to reverse the phase through it so that the feedback is now negative and the oscillation is damped out so that it may not interfere with the phase of the next signal which is about to be received. During the constant amplitude period of resonator 26a, the phase of this signal is compared with that of the next pulse which is building up in resonator 26b comparison being effected in detector 32a which gives a sawtooth output rising to a maximum at the end of the period. The polarity of the detector output indicates a mark or a space in channel 1. A similar phase detector 36b is provided for channel 2 but the output from resonator 26a is fed thereto over a 90-degree phase shifter 33. It is demonstrated that in this case the output pulses from the phase detector represent the original signal alternately erect and inverted so that compensation must be effected later on. The phase detector outputs of several received radio waves may be combined at 36a, 36b in a diversity system, the combined outputs feeding outputs 37a, 37b. Signal sampling circuit. First embodiment, Fig. 4.-Inputs 37a, 37b are sawteeth having positive or negative polarity, the former directly and the latter after alternate inversions representing spaces and marks in channels 1 and 2. Pulses F 1  after amplification are applied to gates 41a, 41b (which when opened thereby are capable of passing signals of either polarity) the gates being opened at the maximum points in the sawteeth. The outputs of the gates operate bi-stable circuits 44a, 44b which are triggered to give one or other output polarity depending on the input polarity. The output of 44b feeds a balanced modulator fed by pairs of pulses on F 2 <SP>1</SP> so as to transmit the input signals erect and inverted thereby compensating for the inversion mentioned above. Second embodiment, Fig. 5.-The sawtooth wave from the phase detectors 37a, 37b feed gates 51a, 51b which are opened by timing pulses, each gate having two mutually inverse outputs such as 52a, 53a which open either gate G1 or gate G2 according to the polarity on terminal 37a. As before these gates open at the maximum of the incoming sawtooth. The outputs of these gates trigger the bi-stable state toggle circuit 56a to produce positivegoing signals at 57a, 58a according as the signal is mark or space. The right-hand circuit operates similarly for the second channel appropriately operated inverters 61a, 61b being inserted in both leads for reasons previously mentioned. Specification 828,782 is referred to.