Abstract: A variable threshold detecting circuit for use with radar signals where a given target will appear with the same intensity on the screen whether the target is nearby or far away. The 1/R.sup.4 decrease in amplitude of the returned radar signal is compensated for by discharging an integrating circuit and using the output voltage of the integrating circuit as the threshold to a threshold detector for passing only the radar signals exceeding the threshold.

Abstract: A digital radar including (i) a digital memory whose stored array of digital words represents radar searched space and (ii) display smoothing apparatus receiving the memory data and quadrupling the number of digital words available for display. Typical of the preferred embodiment, a four digital word group comprising W.sub.a, W.sub.b, W.sub.c, and W.sub.d, and representing four mutually contiguous searched space segments is used to produce the average of W.sub.a and W.sub.b, the average of W.sub.a and W.sub.c, and the average of all four in the group. The averages and the memory words are painted on a display in their appropriate locations.

Abstract: A postdetection, digital radar signal processor for producing information for a PPI type display on a conventional CRT. Each line of the polar or PPI type display represents a summing of past and present returns received at substantially the same antenna position during past and present antenna scans. SUThis invention relates to electronics and more particularly to digital processors for use with radar systems.Storage tubes, or electrostatic memory tubes, are widely used for radar indicators. The information painted thereon is retained by electric charges and thus such tubes can provide to the operator a continuous map of the system observed space. However, storage tubes are expensive, unstable, and have limited dynamic range. They also require critical adjustments.Previous attempts to replace the storage tube in airborne weather radar applications with a conventional CRT (cathode ray tube) and digital memory have had some success and also some shortcomings.

Abstract: An input tracking threshold detector includes a first circuit receiving input signal, a feedback signal, and a predetermined gating signal. The first circuit outputs a binary signal which during gating signal enablement intervals is indicative of the relative amplitudes of the input and feedback signals. The feedback signal is developed from the first circuit output by a second circuit whose output signal amplitude is indicative of the duty cycle of its input.