Detection of narrow pulses

An electronic circuit arrangement for detecting the presence 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:

• pulse curvature discriminating means for discriminating against pulses in the waveform having a curvature less sharp than that sharp peak curvature characteristic of a desired pulse;
• pulse width discriminating means for discriminating against pulses in the waveform having a width greater than that width characteristic of a desired pulse;
• and pulse symmetry discriminating 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;
• which arrangement is such that the pulse curvature and pulse width discriminating means are provided in parallel, and the pulse symmetry discriminating means is serially thereafter, and is thus effective for pulses in the waveform which have not yet been discriminated against, the pulse curvature discriminating means including 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 it 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.

In an electronic circuit for detecting, in an input signal, the presence of narrow pulses while discriminating against other pulses which do not have all of the characteristics of amplitude to width ratio, width and symmetry of said narrow pulses, the combination of:

• first means for determining if the time period required, for a first differential of an input signal pulse, to pass between predetermined positive and negative values is less than a first predetermined value and for producing a first pulse signal when said time period is less than said first predetermined value;
• second means for determining if the time period required, for a second differential of said pulse, to pass from a first to a second zero crossing is less than a second predetermined value and for producing a second pulse signal when such time period is less than said second predetermined value;
• third means for determining if said first pulse signal occurs within a further time period, of a third predetermined value, commencing at the instant of said first zero crossing and for producing a third pulse signal when said first pulse signal occurs within said further time period;
• and
• pulse generating means for producing a narrow output pulse when said second pulse signal occurs within another time period of a fourth predetermined value commencing with said third pulse signal.