Maximum likelihood angle estimation of wideband signals using phased array antennas

Patent metadata

Field	Value
Publication number	US-9391365-B2
Application number	US-201313889144-A
Country	US
Kind code	B2
Filing date	May 7, 2013
Priority date	Apr 21, 2011
Publication date	Jul 12, 2016
Grant date	Jul 12, 2016

Abstract

A method for estimating a target direction of a wideband signal received on an electronically steered array includes: applying convolutional or stretch processing to spatial frequency data of the wideband signal; initializing a stabilization direction to a beam pointing direction; stabilizing the spatial frequency data to the stabilization direction; compressing the spatial frequency data to a plurality of frequency range or time bins; selecting range or time bins and forming a covariance matrix; calculating an estimated target direction using the covariance matrix; determining if a stabilization direction accuracy condition is met; recalculating the stabilization direction based on the estimated target direction if the stabilization direction accuracy condition is not met; and iteratively repeating until the stabilization direction accuracy condition is met.

First claim

What is claimed is:

1. A system for estimating a target direction, the system comprising:
an electronically steered antenna array configured to receive a wideband signal;
a processor configured to convolutional or stretch process spatial frequency data of the wideband signal;
a beam stabilizer configured to:
stabilize the convolutional or stretch processed spatial frequency data in a stabilization direction;
compress the convolutional or stretch processed spatial frequency data to a plurality of frequency range or time bins; and
select range or time bins and form a covariance matrix;

a steering angle calculator configured to estimate the target direction using the covariance matrix;
a stabilization angle accuracy threshold calculator configured to determine whether a stabilization direction accuracy condition is met; and
a stabilization angle updater configured to update the stabilization direction to the estimated target direction,
wherein the steering angle calculator is configured to initialize the stabilization direction to a beam pointing direction, and
wherein the steering angle calculator, the stabilization angle accuracy threshold calculator, and the stabilization angle updater are configured to iteratively update the stabilization angle and to recalculate the estimated target direction until the stabilization accuracy condition is met.

2. The system of claim 1 , wherein the beam stabilizer is further configured to:
calculate the convolutional or stretch processed spatial frequency data using processing parameters and antenna direction cosine;
calculate derivatives of the convolutional or stretch processed spatial frequency data and antenna pattern values using antenna parameters;
solve for a plurality of stabilization coefficients using normalization constants; and
apply the plurality of stabilization coefficients to the convolutional or stretch processed spatial frequency data to generate stabilized spatial frequency data.

3. The system of claim 1 , wherein the steering angle calculator comprises:
a steering vector calculator configured to calculate a steering vector using the stabilized spatial frequency data;
an angle correction calculator configured to calculate an angle of arrival correction using the steering vector; and
an angle of arrival accuracy calculator configured to compare the angle of arrival correction with an angle of arrival accuracy condition.

4. The system of claim 1 , wherein the beam stabilizer comprises:
a stabilization coefficient calculator configured to calculate a plurality of stabilization coefficients; and
a combiner configured to combine the spatial frequency data with the plurality of stabilization coefficients to generate stabilized spatial frequency data.

5. The system of claim 1 , wherein the steering angle calculator is configured to:
initialize a steering angle to the stabilization direction;
calculate a plurality of steering vectors using the steering angle;
calculate an angle of arrival correction;
determine if an angle of arrival accuracy condition has been met;
update the steering angle based on the angle of arrival correction if the angle of arrival accuracy condition has been met;
iteratively repeat calculating the steering vectors using the steering angle, calculating the angle of arrival correction, determining if the angle of arrival accuracy condition has been met, and updating the steering angle using the steering vectors, and updating the steering angle based on the angle of arrival correction until a steering angle accuracy condition is met; and
output the updated steering angle as the estimated target direction when the steering angle accuracy condition is met.

6. The system of claim 1 , wherein the target direction comprises a plurality of target directions.

7. The system of claim 1 , wherein the beam stabilizer is further configured to compress the convolutional or stretch processed spatial frequency data by applying an inverse Fourier transform to the stabilized spatial frequency data.

8. A system for stabilizing wideband spatial frequency data of a wideband signal for estimating a target direction on an electronically steered antenna array, the system comprising:
a beam stabilizer configured to stabilize the spatial frequency data in a stabilization direction;
a steering angle calculator configured to estimate the target direction using the stabilized spatial frequency data;
a stabilization angle accuracy threshold calculator configured to determine whether a stabilization direction accuracy condition is met; and
a stabilization angle updater configured to update the stabilization direction to the estimated target direction,
wherein the steering angle calculator is configured to initialize the stabilization direction to a beam pointing direction and
wherein the steering angle calculator, the stabilization angle accuracy threshold calculator, and the stabilization angle updater are configured to iteratively update the stabilization angle and to recalculate the estimated target direction until the stabilization accuracy condition is met.

9. The system of claim 8 , wherein the steering angle calculator comprises:
a steering vector calculator configured to calculate a steering vector using the stabilized spatial frequency data;
an angle correction calculator configured to calculate an angle of arrival correction using the steering vector; and
an angle of arrival accuracy calculator configured to compare the angle of arrival correction with an angle of arrival accuracy condition.

10. The system of claim 8 , wherein the beam stabilizer comprises:
a stabilization coefficient calculator configured to calculate a plurality of stabilization coefficients; and
a combiner configured to combine the spatial frequency data with the plurality of stabilization coefficients to generate stabilized spatial frequency data.

11. The system of claim 8 , wherein the steering angle calculator is configured to:
initialize a steering angle to the stabilization direction;
calculate a plurality of steering vectors using the steering angle;
calculate an angle of arrival correction;
determine if an angle of arrival accuracy condition has been met;
update the steering angle based on the angle of arrival correction if the angle of arrival accuracy condition has been met;
iteratively repeat calculating the steering vectors using the steering angle, calculating the angle of arrival correction, determining if the angle of arrival accuracy condition has been met, and updating the steering angle using the steering vectors, and updating the steering angle based on the angle of arrival correction until a steering angle accuracy condition is met; and
output the updated steering angle as the estimated target direction when the steering angle accuracy condition is met.

Assignees

• Raytheon Co

Inventors

• Hansen Charles T

Classifications

• G01S7/295

  Means for transforming co-ordinates or for evaluating data, e.g. using computers · CPC title

• G01S13/4454

  phase comparisons monopulse, i.e. comparing the echo signals received by an interferometric antenna arrangement · CPC title

• H01Q3/00 Primary

  Arrangements for changing or varying the orientation or the shape of the directional pattern of the waves radiated from an antenna or antenna system {(means for positioning H01Q1/125)} · CPC title

• G01S13/42

  Simultaneous measurement of distance and other co-ordinates (indirect measurement G01S13/46) · CPC title

• G01S13/02

  Systems using reflection of radio waves, e.g. primary radar systems; Analogous systems · CPC title