A Slope Reversal Video Processor Having Amplitude and Pulse Width Discrimination
Frank E. Hoge, B. E. Nelson, D. E. Hines · Review of Scientific Instruments · 1972
A timing discriminator whose output is relatively insensitive to input pulse width and amplitude is described. The video-handling technique is known as slope reversal processing and is based on tapped delay line estimation methods. The concept, design, breadboard construction, and preliminary laboratory test results are reviewed. The processor system features (a) a peak input voltage dynamic range of 80× starting at 100 μV; (b) a four stage preamplifier/line-driver having a voltage gain of 2400×; (c) a tapped delay-line estimator implemented for slope reversal triggering by differential comparison; (d) a nominal ±2.5 nsec shift of the output trigger leading edge over the entire input voltage range, (e) up to 7 dB discrimination against pulse widths less than 35 nsec; and (f) up to one order of magnitude reduction in the false alarm rate compared to a constant fraction system. Deviations in specific portions of the ``walk'' curve are attributed to differential comparator response and preamplifier saturation effects. Design criteria, circuit schematics, and construction details are given. The system is intended for use with pulses having a width of 35 nsec; however, the processor is easily adapted and improved for other pulse widths. The expression for relative pulse width sensitivity is given and experimentally verified.