Abstract: A system for identifying the location of an aircraft on the surface of an airport includes a plurality of low power FM transmitters located along the boundaries of runway and taxiways. Each transmitter provides an FM signal having a common carrier frequency and each FM signal is encoded with unique information indicative of the position of the transmitter on the airport surface. Aircraft and other vehicles containing a conventional FM receiver "capture" only the strongest signal and process the "captured" signal to determine which transmitter was the source of the signal and hence where the aircraft is on the airport surface.

Abstract: A covert radar response system suitable for use with an illuminating coherent radar system having a moving target indicator subsystem shifts the phase and/or frequency of a retroreflected beam to transmit a message to the illuminating system that is not detectable by other observers in the vicinity.

Abstract: An improved radar system utilizing the principle of nonlinear contact effects for detecting and identifying a target, includes two radar transmitters (12,16) at least one of which is a baseband pulse radar transmitter. Both transmitters illuminate the same target and the signals from each transmitter are mixed in a nonlinear junction (40) of the target. Mixing the two signals provides a target return signal whose frequency spectrum contains cross product frequency components having high resolution target data due to the broad spectral content of the baseband pulse, and thus provides a system capable of detecting and identifying the illuminated target.

Abstract: A monopulse optical receiving system is comprised of a plurality of optical sensors for receiving an incident light pulse at angles of incidence within a field of view, and providing in response thereto an output voltage signal whose magnitude is a function of the incident angle, at least two of the sensors being relatively disposed so that a portion of the field of view of one of them overlaps with a portion of the field of view of another one of them to provide an overlapping field of view within which the two sensors provide complementary transmittance gradients, the two sensors further providing mutually complementary voltage signals in response to light incidence within the overlapping field of view, the system further comprising a processing unit which calculates both an immediate coarse angle value for the incident light pulse and a fine angle describing the precise incident angle relative to the coarse angle value.

Abstract: In a track while scan radar system having a tracking processor for providing range and azimuth tracking gates for automatic range and azimuth cursor tracking of a designated target in response to the magnitudes of target return signals received within the tracking gates, circuitry is provided for predicting the magnitudes of succeeding designated target return signals as a function of the actual magnitudes of preceding designated target return signals, and for providing through accumulator circuits to the tracking processor a signal manifestation of each succeeding target return signal occurring within the tracking gates, the magnitude of the signal manifestation being a function of the comparative magnitudes of the predicted and actual target return signal.

Abstract: In a track while scan radar which pinpoints a target location by comparing target return voltage summations in the early half of a range gate with those in the late half of the range gate, and with the target return voltage summations in the left half of a multi-pulse azimuth gate with those in the right half of the azimuth gate, noise and clutter are clipped by means of a clipping signal level which is chosen from the lower value of the summation of the early and late target return voltage summations and the summation of the right and left target return voltage summations, thereby using the noise, clutter and target return signal within the target window in one scan to derive the clipping level for a succeeding scan.

Abstract: In the measurement of the phase difference (proportional to the elevation angle of a target) provided by the radar target signals that are received by each antenna of an antenna array, a comparison of the responses of the signal processing circuitry to the radar target signals and to two signals with an adjustable known phase difference, causes the known phase difference to change until the result of the comparison is a null. The known phase difference, at the time that the comparison provides a null, is equal to the phase difference provided by the radar target signals and is independent of phase errors introduced by the processing circuitry.