Systems and methods for joint angle-frequency determination

Patent metadata

Field	Value
Publication number	US-10145871-B2
Application number	US-201514699871-A
Country	US
Kind code	B2
Filing date	Apr 29, 2015
Priority date	Apr 29, 2014
Publication date	Dec 4, 2018
Grant date	Dec 4, 2018

Abstract

A system for data acquisition and processing includes a selector for obtaining samples from one or more sensors, each of which is configured to collect a sample during one or more sampling intervals forming a dwell period. The selector is configured to obtain only a subset of samples of a complete set of samples that can be collected during a dwell period. A solver is configured to solve an underdetermined system based on the collected samples and a mapping relation/phase function, to jointly determine one or more angles and one or more frequencies of transmissions received by the one or more sensors.

First claim

Accordingly, we claim:

1. A method for determining angle and frequency of transmission from a transmitter, the method comprising:
receiving during a current coherent dwell, sensor data comprising a first plurality of samples, the first plurality of samples comprising N samples collected at a sensor array comprising D sensors, a spacing between a pair of adjacent sensors being Δ;
selecting a second plurality of M samples from the first plurality of samples, M being less than N times D;
determining angle and frequency of transmission of a transmitter located at a range R and an angle θ relative to a plane of the sensor array and transmitting a signal at a frequency f, by minimizing using a solver, an l 1 norm of a product of: (i) a phase functional representing a mapping between time-distance and angle-frequency representations of sensor samples and (ii) the second plurality of M samples, the time-distance representation being based on the spacing Δ, and the angle-frequency representation being based on θ and f.

2. The method of claim 1 , wherein the first plurality of samples corresponds to a single coherent dwell.

3. The method of claim 1 , wherein N is a number of Nyquist intervals in a single coherent dwell.

4. The method of claim 1 , wherein the first plurality of samples comprises:
a first sample, collected by a particular sensor from the D sensors, and associated with a transmission at a first frequency; and
a second sample, collected by that particular sensor, and associated with a transmission at a second, different frequency.

5. The method of claim 1 , wherein selecting the second plurality of M samples from the first plurality of samples comprises filtering the first plurality of samples using a pseudorandom selector.

6. The method of claim 1 , wherein selecting the second plurality of M samples from the first plurality of samples comprises:
ranking the first plurality of samples according to respective signal-to-noise ratios (SNRs) associated with each sample; and
selecting samples corresponding to the M highest ranks.

7. The method of claim 1 , wherein the solver comprises a second order cone programming (SOCP) solver.

8. The method of claim 7 , wherein applying the SOCP solver comprises providing to the SOCP solver a frequency angle solution obtained from samples collected during another coherent dwell prior to the current coherent dwell.

9. A method for determining angle and frequency of transmission from a transmitter, the method comprising:
from a sensor array comprising D sensors, each of which is configured collect a sample during each one of N different sampling periods in one coherent dwell, and a spacing between a pair of adjacent sensors being Δ, obtaining during a current coherent dwell, using a pseudorandom selector, a plurality of M samples, M being less than N times D;
determining angle and frequency of transmission of a transmitter located at a range R and an angle θ relative to a plane of the sensor array and transmitting a signal at a frequency f, by minimizing using a solver, an l 1 norm a product of: (i) a phase functional representing a mapping between time-distance and angle-frequency representations of sensor samples and (ii) the plurality of M samples, the time-distance representation being based on the spacing Δ, and the angle-frequency representation being based on θ and f.

10. The method of claim 9 , wherein obtaining the plurality of M samples comprises:
selecting using the pseudorandom selector at least one of the N sampling periods;
for each selected sampling period, obtaining a sample from at least one of the D sensors; and
at least one of:
(i) selecting at least one of the N sampling periods during each of which a sample is not obtained; and
(ii) during at least one of the selected sampling periods, selecting at least one of the D sensors from which a sample is not obtained.

11. The method of claim 10 , wherein for each selected sampling period, obtaining a sample from at least one of the D sensors comprises rejecting a sample from a sensor if a signal-to-noise ratio (SNR) associated with that sample is less than a specified threshold.

12. The method of claim 9 , wherein the plurality of M samples comprises at least:
a first sample associated with a transmission at a first frequency; and
a second sample associated with a transmission at a second, different frequency.

13. The method of claim 9 , wherein the solver comprises a second order cone programming (SOCP) solver.

14. The method of claim 13 , the processor is further programmed to provide to the SOCP solver a frequency angle solution obtained from samples collected during another coherent dwell prior to the current coherent dwell.

15. The method of claim 13 , wherein applying the SOCP solver comprises providing to the SOCP solver a frequency angle solution obtained from samples collected during another coherent dwell prior to the current coherent dwell.

16. A system for determining angle and frequency of transmission from a transmitter, comprising:
a first processor; and
a first memory in electrical communication with the first processor, the first memory comprising instructions which, when executed by a processing unit comprising at least one of the first processor and a second processor, and in electronic communication with a memory module comprising at least one of the first memory and a second memory, program the processing unit to:
receive in the memory module, during a current coherent dwell, sensor data comprising a first plurality of samples, the first plurality of samples comprising N samples collected at a sensor array comprising D sensors, a spacing between a pair of adjacent sensors being Δ;
select a second plurality of M samples from the first plurality of samples, M being less than N times D; and
determine angle and frequency of transmission of a transmitter located at a range R and an angle θ relative to a plane of the sensor array and transmitting a signal at a frequency f, by minimizing an l 1 norm of the second plurality of M samples by solving an underdetermined linear system comprising a product of: (i) a phase functional representing a mapping between time-distance and angle-frequency representations of sensor samples and (ii) the second plurality of M samples, the time-distance representation being based on the spacing Δ, and the angle-frequency representation being based on θ and f.

17. The system of claim 16 , wherein the first plurality of samples corresponds to a single coherent dwell.

18. The system of claim 16 , wherein N is a number of Nyquist intervals in a single coherent dwell.

19. The system of claim 16 , wherein the first plurality of samples comprises:
a first sample, collected by a particular sensor from the D sensors, and associated with a transmission at a first frequency; and
a second sample, collected by that particular sensor, and associated with a transmission at a second, different frequency.

20. The system of claim 16 , wherein for selecting the second plurality of M samples from the first plurality of samples, the processing unit is further programmed to filter the first plurality of samples using a pseudorandom selection.

21. The system of claim 16 , wherein for selecting the second plurality of M samples from the first plurality of samples, the processing unit is further programmed to:
rank the first plurality of samples according to respective signal-to-noise ratios (SNRs) associated with each sample; and
select samples c

Assignees

• Reservoir Labs Inc
• Significs And Elements Llc

Inventors

• Baskaran Muthu M
• Henretty Thomas
• Johnson Ann
• Langston M H
• Lethin Richard A
• Mcmahon Janice O
• Meister Benoit J
• Mountcastle Paul

Classifications

• G01R25/00

  Arrangements for measuring phase angle between a voltage and a current or between voltages or currents · CPC title

• G01S3/74 Primary

  Multi-channel systems specially adapted for direction-finding, i.e. having a single antenna system capable of giving simultaneous indications of the directions of different signals (systems in which the directions of different signals are determined sequentially and displayed simultaneously G01S3/04, G01S3/14) · CPC title

• G01S7/021

  Auxiliary means for detecting or identifying radar signals or the like, e.g. radar jamming signals · CPC title

• G01R23/02 Primary

  Arrangements for measuring frequency, e.g. pulse repetition rate; Arrangements for measuring period of current or voltage · CPC title