Abstract: In accordance with the principles of the invention, a surveillance radar is provided with a rotating, frequency squinting, end-fed slotted array antenna, which is caused to transmit a plurality of different carrier frequency pulses for successively illuminating specific antenna beam positions during rotation of the antenna. Upon reception of each radar signal return, a signal processor responsive to the frequency of each transmitted pulse and the mechanical pointing angle of the antenna at the time of transmission of each pulse, will determine the frequency dependent squint angle for the transmitted pulse and combine that angle with the instantaneous mechanical pointing angle of the antenna at the time of the pulse transmission, to determine the actual beam pointing angle for each pulse at the time of its transmission. A video signal processor groups together the pulse signal returns from physically adjacent ones of the actual beam pointing angles for common processing, i.

Abstract: A communication system for receiving aircraft reply squits (transmissions) normally used in a radar beacon system for surveilling aircraft in a given geographic area. The communication system includes a plurality of omnidirectional receivers, each receiver having a function of omnidirectionally receiving the aircraft squits and developing therefrom two types of information strings, namely a data string, indicative of a message in the aircraft squit, and a corresponding confidence string indicative of the reliability of the developed data string. A data communication link transmits the data and confidence strings between the plurality of omnidirectional receivers and the master data processor.

Abstract: System for tracking a vehicle equipped with a transponder which emits a first reply signal containing data identifying the vehicle in response to a first interrogation signal and emits a second reply signal containing data specifying the altitude of the vehicle in response to a second interrogation signal, the system including: (a) a squitter transmitter located on the vehicle for interrogating the transponder with the first and the second interrogation signals which are separated in time by a predetermined time spacing interval, in response to which first and second interrogation signals, the transponder transmits the first and second reply signals; (b) a plurality of spaced apart ground receive stations, each of which includes a receiver and decoder for: (i) receiving and decoding data from the first and second reply signals, (ii) determining a time of arrival of the first and second reply signals and the predetermined time spacing interval, and (iii) determining an identity of the vehicle by combining data

Abstract: A radar indicator comprising a source of radar image signals having a first (r,.theta.) format and a digital scan converter responsive to the radar image signals for converting the radar image signals from the first format to digital radar image signals having a second (X-Y) format. The digital scan converter includes an image memory for supplying the digital radar image signals having the second (X-Y) format. A source of external video image signals having the second format, including video synchronization signals is provided. A synchronization signal stripper and clock signal generator circuit is responsive to the video synchronization signals of the external video image signals for generating a clock signal synchronized with the synchronization signals of the external video image signals.

Abstract: A system for locating and identifying aircraft while on an airport. Each aircraft has an IFF transponder which is interrogated from on board the aircraft to produce replies at a slower rate than normal interrogation rates. A plurality of receiving stations at different locations about the airport measure the time of arrival of the replies and decode the replies. The time of arrival information is forwarded to a central receiving station along with the decode reply data. Using conventional correlation techniques, the location of each aircraft is established through the time of arrival information as well as the identity of the aircraft from the decoded reply data.

Abstract: An SSR reply decoding system for separating pulse codes of a series of closely-spaced or overlapping SSR replies is disclosed. A delay line is connected to receive pulses representing the leading edge of each SSR reply code pulse. The delay line has a length corresponding to at least two bracket lengths of an SSR reply. A bracket decoder is connected to respective taps of the delay line for determining the beginning and end of a first SSR reply. A phantom reply detector is connected to the remaining taps for inhibiting the bracket decoder when two replies are represented by pulses in the delay lines, one of the replies having a pulse space from the pulse of another reply equal to a framing pulse period for an SSR reply. The phantom reply detector therefore inhibits the detection of phantom replies. As a discriminate for determining when pulses having the spacing of a framing period belong to different replies, azimuth data is provided which will permit discrimination of these phantom conditions.

Abstract: Tracking system for monitoring aircraft position during simulated training exercises. Standard IFF transponders on the aircraft are periodically enabled by a squitter transmitter mounted on the aircraft. On the ground a plurality of receiving stations are interconnected through a communication link. The transponder replies are received at each receiving station. The time of arrival for each of the transponder replies is measured and communicated to one of the receiving stations. Using Loran techniques, accurate longitudinal and latitude coordinates are determined from the time of arrival data.