Patent GB-811815-A (GB)
Title: Pulse generating apparatus
IPC: G04F10/06
Filed: 1957-03-28
Abstract: 811,815. Radio navigation. SPERRY RAND CORPORATION. March 28, 1957 [March 28, 1956], No. 10185/57. Class 40 (7). Relates to a Loran receiver of the type disclosed in U.S.A. Specification 2,651,033 for measuring the time interval between A and B pulses of equal recurrence frequency f transmitted from spaced points in which locally generated A and B pedestal trigger pulses are adjusted to coincide with the received A and B pulses, the time interval between the pedestal trigger pulses being indicated by a calibrated delay device. According to the present invention coarse A and B pedestal trigger pulses, Figs. 2 (d) and 2 (g) are derived in the usual manner from one output of an oscillator and divider unit 10, Fig. 1, the interval between the pulses being determined by a coarse delay device controlled by a potentiometer 38, and sequential pulse trains e and f each of recurrence frequency nf, e.g. 1000 c/s, are derived from another output of the oscillator unit 10, the relative timing of the pulse trains e and f being determined by a precision phase shifter 14 ganged to the coarse delay control 38; a precision A pedestal trigger pulse, Fig. 2 (h), is then derived by selecting that pulse in the pulse train e which immediately succeeds the coarse A pedestal trigger pulse and a precision B pedestal trigger pulse, Fig. 2 (h) is derived by selecting the pulse in pulse train of which immediately succeeds the coarse B pedestal trigger pulse. The time interval between the precision A and B trigger pulses is indicated by a counter 46 and dial 22 ganged to the phase shifter 14. As shown, the oscillator unit 10 produces a pulse output, Fig. 2 (a) of recurrence frequency 2 ( f ) and a pulse output, Fig. 2 (c), of recurrence frequency mf. The pulse output a is applied to a generator 32 producing a squarewave output b of recurrence frequency f which is applied to the coarse A and B pedestal trigger pulse generators 34, 36, the resultant A pedestal trigger pulse Fig. 2 (d) '  being delayed relative to the negative step in waveform b by a fixed amount and the resultant B pedestal trigger pulse, Fig. 2 (g), being delayed relative to the positive step in waveform b by a variable amount determined by a variable-duration pulse generator controlled by the potentiometer 38. The pulse output c of recurrence frequency nf is converted by means of a tuned amplifier 12 into a corresponding sine wave which, during the negative portion of waveform b, is applied directly to a pulse generator 30 giving the pulse train e and, during the positive portion of waveform b, is applied to the pulse generator 30 through the phase shifter 14 giving the pulse train f; this selection is effected by a relay 26 controlled by the square wave b. The precision A and B pedestal trigger pulses, Fig. 2 (h), are derived from the signals d, e, f and g in a selector circuit 42 which may comprise (1) a bistable circuit which is triggered on by a coarse pedestal trigger pulse and triggered off by the next succeeding pulse from the pulse train e orf ; or (2) a gating circuit which is opened by each coarse pedestal trigger pulse. The phase shifter 14 may be of the type disclosed in U.S.A. Specification 2,627;598.