USA As Represented by Secretary of the Navy

Ford Aerospace & Communications Corporation

Boeing North American, Inc.

Loral Aerospace Corp.

Louis J Avila

John E Merritt

Norman G Hempling

Joseph S Kaufmann

Prentiss N Robinson

C Web Westerman

The objectives of the invention are met by an improved radar tracking system and a process of radar tracking. In the improved system and process, an estimate of a target range and a range uncertainity swath from a first radar system is inputted into a second radar system along with a duty factor. The second radar system determines a set of zero eclipse intervals and respective ranges of range pulse repetition frequencies that solves a first set of equations. A usable range pulse repetition frequency is chosen from the results. Next, an estimated target Doppler frequency region and a Doppler uncertainity swath is inputted into the second radar system. The second radar system is instructed to determine a set of clear Doppler frequency region intervals, and respective ranges of Doppler frequency pulse repetition frequencies by solving a second set of equations. A usable pulse repetition frequency is chosen that is present in at least one of the ranges of range pulse repetition frequencies and that is present in at least one of the ranges of Doppler frequency pulse repetition frequencies. The second radar system is then instructed to track the target using the usable pulse repetition frequency.

Pulse repetition frequency section method and system

Apparatus and methods of achieving accurate, unambiguous angle information with a minimum number of antenna elements. The present invention resolves the ambiguities inherent in a long baseline phase interferometer by employing a minimum number of antennas to form shorter baselines. The present invention employs roll motion (antenna rotation) to reorient interferometer baselines and a signal processor to measure the roll angle. Taking interferometer phase data with at least two orientations of the interferometer baselines permits resolution of the ambiguities. This also allows the use of long antenna baselines thereby achieving high angular accuracy with angle ambiguities resolved using only two antenna elements per spatial angle. This reduces system complexity and reduces the required clear aperture area, factors of great significance in missile systems. The invention takes phase data at two or more interferometer baseline orientations and forms a set of simultaneous equations involving the phase ambiguities. These equations are solved to produce unambiguous target direction vectors. The interferometer may employ four antennas to obtain maximum accuracy angle data unambiguously and simultaneously in both azimuth and elevation. However, three antennas may also be used with some loss in angle accuracy.

Interferometer ambiguity resolution using missile roll

A circuit for extending the frequency range of a digitally generated FM signal (f). A digital frequency generator (1) generates a precise FM waveform at a frequency up to about 50 MHz. Coupled to the FM signal (f) is a phase lock loop (53, 55, 57) comprising a voltage controlled oscillator (VCO) (57) whose output frequency can be much higher than the frequency of the FM signal (f). In a first embodiment, a crystal oscillator (61), mixer (59), and low pass filter (63) are used to bring the output (f') of the VCO (57) down into the range of the digital frequency generator (1). In a second embodiment, an analog frequency divider (73) is used to bring the output (f') of the VCO (57) into the range of the digital frequency generator (1). In a third embodiment, the single sideband (SSB) generator (37) from the digital frequency generator (1) and a counter (66) are used in a partly analog, partly digital, negative feedback loop.

Frequency extended digitally generated FM

A system using two concentric fuzing beams in warhead implementation to mure the effective length of the target relative to the missile along the trajectory to prevent drop out of small targets.

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Costa Mesa, CA, United States of America

Louis J Avila