US 5,479,177 AGranted

Phased array antenna system to produce wide-open coverage of a wide angular sector with high directive gain and wide frequency bandwidth

AssigneeAIL Systems, Inc.

InventorsRonald M. Rudish, Scott F. Hall

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Abstract

A phased array antenna system capable of scanning at rates faster than the information rate of signals being received to prevent the loss of information during the scanning process. The sensitivity loss due to sampling usually encountered is avoided. The present invention is an improvement on a prior art system that avoids the sensitivity loss in that the present invention also avoids the frequency selectivity inherent in the prior art system. The array antenna system is comprised of the means to form multiple, time-sequenced outputs, each output corresponding to a different beam of sensitivity. The beams scan the full coverage sector and together with the other outputs form a contiguous set of beams that both fill the coverage sector at any one time and also synchronously scan the full coverage sector. A differential delay network incorporating delay lines, envelope detectors and a summing junction is used to combine the outputs from the multiple beams to ensure that the responses to a single emitting source are added in unison in a manner which is not restrictive of frequency bandwidth. This arrangement retains the wide-open angular reception characteristics of a wide-beam omnidirectional antenna, while exhibiting the gain and angular resolution of a multi-element phased array antenna.

Claims4

Dependent claims

Apparatus for eliminating the frequency selectivity of signal energy in high directivity antenna systems having a coverage sector through which the antenna system scans multiple beams at a rate that is faster than the information rate being received, comprising:

(a) a linear phased array antenna comprising a row formed of a plurality of antenna elements, one of said antenna elements at one end of the row being designated the first element, while the remaining elements are designated by succeeding numbers in arithmetic progression across the row of antenna elements, and the antenna elements being considered as being positioned in the azimuth plane for reference purposes;
(b) means for forming a plurality of beams of sensitivity coupled to said antenna elements, said plurality of beams of sensitivity being equal in number to the number of antenna elements in said row, the beams being contiguous and considered as lying in the azimuth plane for reference purposes, with each beam being generally evenly spaced from the adjacent beams in sin .theta. space, where .theta. is the angle away from boresight in the azimuthal plane, the spacing between beam center directions in sin .theta. space being generally proportional to the reciprocal of the number of antenna elements, and the beams, taken together to form a larger composite beam, span the entire azimuth coverage sector;
(c) means coupled to said antenna elements for synchronously scanning each of the beams over the entire coverage sector, the beams maintaining their relative positions adjacent one another in sin .theta. space during scanning, the scanning being carried out periodically at a rate that is at least twice as fast as the highest information rate being received;
(d) means coupled to said antenna elements for accepting signals received by each beam and differentially delaying said signals to cause their modulation envelopes to respond in unison to a single emitting source at a particular azimuth angle within the sector coverage of the antenna system;
(e) means for non-coherently combining said signals after said signals have been differentially delayed, said non-coherently combining means comprising means for envelope detecting and means for combining said envelopes.

2 more elements

A process for eliminating the frequency selectivity of signal energy in high directivity antenna systems having a coverage sector through which the antenna systems scan multiple beams at a rate that is faster than the information rate being received, comprising the steps of:

(a) providing a linear phased array antenna comprising a row formed of a plurality of antenna elements, one of said antenna elements at one end of the row being designated the first element, while the remaining elements are designated by succeeding numbers in arithmetic progression across the row of antenna elements, and the antenna elements being considered as being positioned in the azimuth plane for reference purposes;
(b) providing means for forming a plurality of beams of sensitivity coupled to said antenna elements, said plurality of sensitivity being equal in number to the number of antenna elements in said row, the beams being contiguous and considered as lying in the azimuth plane for reference purposes, with each beam being generally evenly spaced from the adjacent beams in sin .theta. space, where .theta. is the angle away from boresight in the azimuthal plane, the spacing between beam center directions in sin .theta. space being generally proportional to the reciprocal of the number of antenna elements, and the beams, taken together to form a larger composite beam, span the entire azimuth coverage sector;
(c) providing means coupled to said antenna elements for synchronously scanning each of the beams over the entire coverage sector, the beams maintaining their relative positions adjacent one another in sin .theta. space during scanning, the scanning being carried out periodically at a rate that is at least twice as fast as the highest information rate being received;
(d) providing means coupled to said antenna elements for accepting signals received by each beam and differentially delaying said signals to cause their modulation envelopes to respond in unison to a single emitting source at a particular azimuth angle within the sector coverage of the antenna system;
and
(e) providing means for noncoherently combining said signals after said signals have been differentially delayed, said non-coherently combining means comprising means for envelope detecting and means for combining said envelopes.

3 more elements

Dependencies are inferred from the claim text.