US 5,493,306 AGranted

Phased array antenna system to produce wide-open coverage of a wide angular section with high directive gain and moderate capability to resolve multiple signals

AssigneeEaton Corporation

InventorsRonald M. Rudish, Scott F. Hall

Life of this patent

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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 phased array is configured to add the capability to provide moderate multi-dimensional separation of multiple signals and to eliminate the sensitivity loss due to sampling usually encountered with such rapid-scan systems. The array antenna system is comprised of the means to form multiple, time sequenced responses, each response corresponding to a different beam of sensitivity. The beams scan the full coverage sector and together with each other form a contiguous set of beams that both fill the coverage sector at any one time and also synchronously scan the full coverage sector. The beams are differentially delayed to permit the beam responses from any particular incident signal to be added in unison, giving rise to a compressed pulse whose time of occurrence is related to the signal angle of incidence. The means for beam addition selectively forms a coherent sum at only one of its multiplicity of output ports, the particular port being a periodic function of the signal frequency. The ambiguities which arise in frequency measurement capabilities due to the periodicity are resolved by auxiliary means for coarse frequency measurement, however, the ambiguities do degrade frequency resolution of multiple signals. This arrangement retains the wide-open angular reception characteristics of a wide-beam or omnidirectional antenna, while exhibiting the gain and angular resolution of a multi-beam phased array antenna, and most of the frequency resolution avail able from a channelized receiver.

Claims4

Dependent claims

An apparatus for adding the capability to separate multiple signals and for eliminating the sampling loss of signal energy in 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 compressing 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) by 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 being generally evenly spaced from the adjacent beams in sin .theta. space, where .theta. is the angle away from broadside 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 beam signals to cause their modulation envelopes to respond in unison to a single emitting source at a particular azimuth angle to within the sector coverage of the antenna system;
(e) means for coherently combining said beam signals after said signals have been differentially delayed, said means for combining being arranged to cause coherent addition selectively at different output ports of said combiner for different signal frequencies;
and
(f) means for measurement of the approximate frequency of said combined beam signals for eliminating ambiguities in determination of signal frequency.

4 more elements

A process for adding the capability to separate multiple signals and for eliminating the sampling loss of signal energy in 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 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 the 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) 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 broadside 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) differentially phase shifting signals received by said antenna elements at rates exceeding 4 .pi. radians per cycle of the highest frequency present in the information content of the incident electromagnetic wave 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) accepting signals received by each beam and differentially delaying said beam 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) accepting beam signals that have been differentially delayed and coherently combining said beam signals to cause coherent additions selectively at different output ports for different signal frequencies thereby providing a method for determination of signal frequency with fine precision;
and;
(f) measuring the approximate frequency of the beam signals at each output post for eliminating ambiguities in determination of signal frequency.

4 more elements

Dependencies are inferred from the claim text.

Facts

Application: 07/094,265Filed 28 Aug 1987
Granted: 20 Feb 1996
Term ends: Not estimatedThe source records don’t support an estimate.

Classification7 codes

H01Q 3/42
By electrical means: using frequency-mixing
G01S 7/021
Of systems according to group G01S13/00: auxiliary means for detecting or identifying radar signals or the like, e.g. radar jamming signals
G01S 13/426
Simultaneous measurement of distance and other co-ordinates: scanning radar, e.g. 3D radar
H01Q 3/2682
Varying the relative phase or relative amplitude of energisation between two or more active radiating elements; varying the distribution of…