Detection of narrow pulses

Claim 2

1 An electronic circuit arrangement for detecting the present of sharply peaked, relatively narrow, Gaussian pulses in an electrical waveform signal of the sort emanating from a limited bandwidth receiver having low pass filter characteristics, which arrangement comprises: means for discriminating against pulses in the waveform having a curvature less sharp than that sharp peak curvature characteristic of a desired pulse; means for discriminating against pulses in the waveform having a width greater than that width characteristic of a desired pulse; and means for discriminating against pulses in the waveform which are not roughly symmetrical about their peak value, and thus which do not have a symmetry characteristic of a desired pulse.

Claim 3

2 An arrangement as claimed in claim 1, wherein the curvature and width discriminating means are provided in parallel, and wherein the symmetry discriminator means is thereafter effective for pulses in the waveform which have not yet been discri1 599 459 minated against.

Claim 4

3 An arrangement as claimed in either of the preceding claims, wherein the curvature discriminator means employs a first differentiator to which the input waveform is applied, and a first timing means for discriminating against pulses in the output of this first differentiator which fail to pass from a negative threshold level to a positive threshold level within a predetermined time related to the sharp peak curvature characteristic of a desired pulse, which first timing means is the combination of a positive threshold detector and a negative threshold detector (both connected to derive input signals from the first differentiator), a first monostable circuit connected to derive input trigger signals from the negative threshold detector, and a first AND gate the first input of which is the first monostable's output and the second input of which is the output of the positive threshold detector.

Claim 5

4 An arrangement as claimed in claim 3, wherein the width discriminating means employs a second differentiator (deriving its input from the first differentiator) and a second timing means to discriminate against pulses in the output of the second differentiator which are too wide, which second timing means is the combination of a zero crossing detector deriving its input from the second differentiator, a second monostable circuit triggered by the output of the zero crossing detector, and a second AND gate deriving its first input from the zero crossing 35 detector and its second input from the output of the second monostable.

Claim 6

An arrangement as claimed in claim 4, wherein the symmetry discriminating means is a third timing means which discri 40 minates against input pulses which are not roughly symmetrical about their peak value, which third timing means is the combination of a third monostable circuit (also triggered by the output of the zero crossing detector), 45 a third AND gate the first input of which is the third monostable's output and the second input of which is derived from the output of the first AND gate, a fourth monostable circuit triggered by the output 50 of the third AND gate, and finally a fourth AND gate the first input of which is the fourth monostable's output and the second input of which is connected to the output of the second AND gate (the one which 55 derives one of its inputs from the output of the zero crossing detector).

Claim 7

6 An electronic circuit arrangement for detecting the presence of sharply peaked, relatively narrow, Gaussian pulses in an 60 electrical waveform signal as claimed in any of the preceding claims and substantially as described hereinbefore. D.G ROUSE Agent for the Applicant. Printed for Her Majesty's Stationery Office, by Croydon Printing Company Limited, Croydon, Surrey, 1981. Published by The Patent Office, 25 Southampton Buildings, London, WC 2 A l AY, from which copies may be obtained.