Patent GB-781057-A (GB)
Title: Improvements in or relating to the comparison and measurement of signals in electrical pulse systems
Inventor: MELLING WILLIAM PHILIP
IPC: G01R29/00
Filed: 1952-02-22
Abstract: 781,057. Pulse amplitude measurement. ELLIOTT BROS. (LONDON), Ltd. May 22, 1953 [Feb. 22, 1952], No. 4788/52. Class 37. In apparatus for comparing and measuring the amplitudes of signal pulses which are separated by an appreciable time interval and can only be detected after amplification, the input pulses are amplified and supplied to a storage circuit which establishes a voltage proportional to the amplitude of each pulse persisting over the succeeding time interval between pulses, and a locally generated reference train of voltage pulses of amplitude progressively increasing or decreasing over a range including the maximum and minimum signal pulse amplitudes and timed to recur between successive signal pulses is amplified in the same amplifier as the signal pulses alternately therewith, the stored voltage being applied to one input of a voltage comparator whose other input is supplied with the amplified reference pulse train so that an output pulse is produced at the instant of equality between the two inputs which is utilized to indicate the signal pulse amplitude by opening a gate circuit from the local reference train generator at the instant of equality, or to similarly arrest an integrating linear voltage rise generator started at the commencement of the local reference train, whereby to derive a unidirectional voltage corresponding to the pulse amplitude. Fig. 1 shows a device wherein an input signal pulse 8 whose amplitude is to be measured is fed into an amplifier 3 (which may include a detector) and the output is directed by an electronic switch 4 synchronized by pulses on line 21 to a storage circuit 5 producing a voltage proportional to the amplified signal pulse, which persists over the succeeding pulse interval and is supplied to one input of a voltage comparator circuit 6. Immediately after the arrival of pulse 8, a pulse is supplied to line 21 by a synchronizing generator (not shown) and triggers a linear voltage rise generator 7 comprising a circuit integrating a reference direct voltage. Simultaneously the reference generator 1 is triggered to produce a train of pulses each having the same duration as the input signal pulse 8 and increasing linearly from zero to a maximum value, which passes through attenuator 2 and amplifier 3 to electronic switch 4, which has meanwhile been turned over by the sync. pulse to connect the amplifier output direct to the second input of the comparator circuit 6. At equality between the stored voltage and the reference pulse train, the comparator generates a pulse which stops the operation of the linear voltage rise generator 7, whose final output voltage is proportional to the input pulse amplitude and is capable of direct measurement or comparison with a further output similarly proportional to the amplitude of another input pulse. Fig. 3 shows a modification in which the linear voltage generator 7 is replaced by an electronic circuit 17 supplied with the output of the reference pulse train generator 1 and triggered by the output pulse of the comparator to produce an output voltage proportional to the instantaneous amplitude of the reference pulse train, from which with a knowledge of the attenuator characteristics the amplitude of the input signal pulse may be determined. If the input pulse 8 comprises a pulse of modulated R.F. waves, the reference train must also comprise pulses of modulated R.F. If the amplifier 3 has high gain, random output noise may be excluded by a low-pass filter in the amplifier output; errors due to the filter time delay being mitigated by increasing the number of reference train pulses and subtracting a constant compensating voltage from the output of the linear voltage rise generator 7.