Abstract: A surface acoustic wave interferometer direction finding and frequency idification method and apparatus is disclosed. The invention utilizes a plurality of dispersive delay lines in order to represent a multiplicity of signals, having different frequencies and angles of arrival at a plurality of antennae, by a train of pulses which retain phase information. Analysis of the interpulse spacing among the pulses in this pulse train, which represents the difference in frequency among the multiplicity of signals arriving at the antennae of the invention, and a pulse comparison of the signals at each of the antennas, allows selective correlation of signal with angle of arrival.

Abstract: Apparatus is disclosed for implementing a unique data compaction technique hich is capable of significantly reducing the storage requirements for alpha-numeric data-sets. The results of a computer simulation which demonstrates the power of this technique are provided. In addition, the logic circuitry required to implement this data compaction technique for the transmission of data over a communications link is given.

Abstract: Hijacked vehicles, or the like, are identified by illuminating a transpon mounted to the vehicle by a beam of microwave energy, e.g., from a helicopter flying over the traffic. The transponder includes non-linear diodes which reradiate a signal back towards the helicopter. Means are disclosed for modulating the return signal with a 16-bit identification code, each bit of which is transmitted as a 31-bit pseudo-random code.

Abstract: Incoming radio frequency signals from one or more remote transmitters, that may be changing or "hopping" in frequency, are received at two closely spaced antennas. A pair of Chirp-Z transform processors are respectively coupled to said antennas. The transform processors are operated in synchronism and produce a pair of sampled comb filter output responses, each of which comprises a multiple of frequency "bins" distributed over a given spectrum. The bins are read out of the Chirp-Z processors in a synchronous sequential order, and each bin is represented by a pair of signals in phase quadrature. The phase quadrature signals of corresponding bins are multiplied in a predetermined manner and the products thereof are selectively added and subtracted to provide a predetermined function (tan .PHI.) of the phase difference (.PHI.) between the signals incident on the pair of antennas. This predetermined function is coupled to a processor that calculates a trigonometric function (sin.sup.