Signal direction processing for an antenna array

Patent metadata

Field	Value
Publication number	US-10705176-B2
Application number	US-201514882034-A
Country	US
Kind code	B2
Filing date	Oct 13, 2015
Priority date	Oct 13, 2015
Publication date	Jul 7, 2020
Grant date	Jul 7, 2020

Abstract

Systems and methods are provided for determining a direction of a signal received at an antenna array. An antenna array includes a plurality of antenna elements, including a reference element. A signal combiner element is configured to combine weighted signals from a subset of the plurality of antenna elements to provide a composite output. An adaptive processing component is configured to determine an optimal set of weights for the subset of the plurality of antenna elements. An angle of arrival search component is configured to find a direction of minimum gain given the optimal set of weights.

First claim

Having described the invention, the following is claimed:

1. A system for determining a direction of a signal of interest having known properties from a signal received at an antenna array comprising:
an antenna array, comprising a plurality of antenna elements, including a reference element, each of the plurality of antenna elements providing one element of a vector of signal values;
a signal combiner element configured to combine weighted signals from a subset of the plurality of antenna elements to provide a composite output;
an adaptive processor configured to determine a set of weights for a subset of the plurality of antenna elements by correlating a reference signal, received at the reference element, to the composite output, such that the set of weights provides a response pattern having a well-defined null in the direction of the signal received at the antenna array, wherein correlating the reference signal to the composite output comprises calculating a product of an inverse of a matrix derived from the vector of signal values and an expected value of the product of the vector of signal values and the output of the reference element; and
an angle of arrival search component configured to search the response pattern to find a direction of minimum gain, representing the direction of the signal of interest, the angle of arrival search component calculating a gain for each of a plurality of angles of arrival from the set of weights and selecting an angle of arrival of the plurality of angles of arrival having a smallest gain as the direction of the signal of interest;
wherein the adaptive processor determines a cross-correlation of the vector of signal values and a complex conjugate of a locally generated replica signal that is linearly proportional to the signal of interest to determine the matrix derived from the vector of signal values.

2. The system of claim 1 , wherein the adaptive processor is configured to determine the matrix derived from the vector of signal values as a cross-correlation, such that the adaptive processor is configured to calculate the set of weights, w , as, w =(E[ q q *]) −1 E[ x r*], where x is the vector of signal values, the superscript * denotes a complex conjugate of a term, q =E{ x p*}, p is the locally generated replica of the signal of interest, and r is the output of the reference element.

3. The system of claim 1 , wherein the adaptive processor is configured to determine the matrix as a sum of a cross-correlation and an approximation of a covariance matrix of thermal noise in the receiver, such that the adaptive processor is configured to calculate the set of weights, w as, w =(E[ q q *]+C n ) −1 E[ x r*], where x is the vector of signal values, the superscript * denotes a complex conjugate of a term, q =E{ x p*}, p is the locally generated replica of the signal of interest, C n is the approximation of a covariance matrix of the thermal noise in the receiver, and r is the output of the reference element.

4. The system of claim 1 , wherein the angle of arrival search component is configured to iteratively search across a range of possible angles, such that a first search is performed at a coarse quantization level to narrow the range of possible angles and a final search is performed at a fine quantization level to determine the angle of arrival.

5. The system of claim 4 , wherein the first search is performed in increments of ten degrees, and the final search is performed in increments of one hundredth of a degree.

6. A method for determining a direction of a signal of interest having known properties from a signal received at an antenna array comprising:
receiving a signal at a plurality of antenna elements as a vector of signal values, the plurality of antenna elements including a reference element that provides a reference signal;
applying weights to received signals at a subset of the plurality of antenna elements;
combining the weighted signals from a subset of the plurality of antenna elements to provide a composite output;
determining an optimal set of weights for the subset of the plurality of antenna elements that minimize a mean squared error between the composite output and an output of the reference element, such that the optimal set of weights provides a response pattern having a well-defined null in the direction of the signal received at the antenna array, wherein determining the optimal set of weights comprises:
determining a cross-correlation of the vector of signal values and a locally generated replica signal that is linearly proportional to the signal of interest;
determining a matrix from the cross-correlation; and
determining the set of weights as a product of an inverse of the matrix determined from the cross-correlation and an expected value of the product of the vector of signal values and the reference signal; and

determining an angle of arrival for the signal of interest from the set of weights, said determining the angle of arrival comprising:
calculating a value for the gain for each of a plurality of angles of arrival from the set of weights; and
selecting an angle of arrival of the plurality of angles of arrival having a smallest gain as the angle of arrival of the signal.

7. The method of claim 6 , wherein determining the angle of arrival for the signal from the set of weights by searching the response pattern comprises iteratively searching across a range of possible angles, the iterative search comprising:
selecting the plurality of angles of arrival to represent a coarse quantization level to narrow the range of possible angles; and
selecting the plurality of angles of arrival to represent a fine quantization level to determine the angle of arrival.

8. The method of claim 6 , wherein determining the matrix from the cross-correlation comprises determining the matrix as the cross-correlation, such that the set of weights, w , is determined as, w =(E[ q q *]) −1 E[ x r*], where x is a vector of signal values from the subset of plurality of antenna elements, the superscript * denotes a complex conjugate of a term, q =E{ x p*}, p is the locally generated replica of the signal of interest, and r is the output of the reference element.

9. The method of claim 6 , wherein determining the matrix from the cross-correlation comprises determining the matrix derived from the vector of signal values as a sum of the cross-correlation and an approximation of a covariance matrix of thermal noise in the receiver, such that the set of weights, w , is determined as, w =(E[ q q *]+C n ) −1 E[ x r*], where x is a vector of signal values from the subset of the plurality of antenna elements, the superscript * denotes a complex conjugate of a term, q =E{ x p*}, p is the locally generated replica of the signal of interest, C n is an approximation of a covariance matrix of the thermal noise in the receiver, and r is the output of the reference element.

10. The method of claim 6 , wherein the subset of the plurality of antenna elements is an improper subset of the plurality of antenna elements.

11. A system for determining a direction of a signal of interest having known properties from a signal received at an antenna array comprising:
an antenna array, comprising a plurality of antenna elements, including a reference element;
a signal combiner element configured to combine weighted signals from a subset of the plurality of antenna elements to provide a composite output;
an adaptive processor configured to determine a set of weights for the subset of the plurality of antenna elements that minimize a mean squared error between the composite output and an output of the reference element, by calculating the set

Assignees

• Mesecher David K
• Northrop Grumman Systems Corp

Inventors

• Mesecher David K

Classifications

• G01S3/46 Primary

  using antennas spaced apart and measuring phase or time difference between signals therefrom, i.e. path-difference systems · CPC title

• H04B7/086

  using weights depending on external parameters, e.g. direction of arrival [DOA], predetermined weights or beamforming · CPC title

• H04B7/0854

  using error minimizing algorithms, e.g. minimum mean squared error [MMSE], "cross-correlation" or matrix inversion · CPC title

• H01Q3/2611

  Means for null steering; Adaptive interference nulling · CPC title

• H01Q3/2629

  Combination of a main antenna unit with an auxiliary antenna unit · CPC title