Cascaded adaptive beamforming system

Patent metadata

Field	Value
Publication number	US-9482736-B1
Application number	US-201514703989-A
Country	US
Kind code	B1
Filing date	May 5, 2015
Priority date	Mar 15, 2013
Publication date	Nov 1, 2016
Grant date	Nov 1, 2016

Abstract

A system and device phase-aligns and sums signals from a very large array of sensors, such as microphones or ultrasonic transducers, without prior knowledge of time delays of signals reaching each sensor, so as to accommodate effects of reverberant fields or acoustic or ultrasonic media containing multiple reflectors or scatterers and/or having heterogeneous, unknown acoustic properties.

First claim

What is claimed is:

1. A cascaded adaptive beamforming system comprising:
a plurality of sensors configured to receive signals and to produce corresponding sensor output signals; and
a beamforming processor configured to process the sensor output signals to produce a beamformed output signal, the beamforming processor having a cascade arrangement with a first cascade level and a plurality of succeeding cascade levels, the first cascade level and each succeeding cascade level including a beamforming element configured to perform beamforming on two input signals to produce a phase-aligned composite signal, each beamforming element including (i) a filter structured to estimate time delay between the two input signals and adaptively phase-align the two input signals, and (ii) a summer for combining the two input signals, after correction for the time delay by the filter, to produce the phase-aligned composite signal.

2. A cascaded adaptive beamforming system according to claim 1 , wherein the phase-aligned composite signal is sum of (a) a delayed version of a first one of the two input signals phase-aligned with a second one of the two input signals and (b) the second one of the two input signals.

3. A cascaded adaptive beamforming system according to claim 1 , wherein, for each beamforming element, the beamforming processor is configured to perform a time delay estimation based on the two input signals and to produce the phase-aligned composite signal based on the time delay estimation.

4. A cascaded adaptive beamforming system according to claim 3 , wherein the beamforming processor is further configured to output the time delay estimation for a use other than beamforming of the signals.

5. A cascaded adaptive beamforming system according to claim 1 , wherein, for each beamforming element, the beamforming processor is configured to implement an adaptive filter for at least one of (1) outputting a time delay estimation based on the two input signals, (2) outputting the phase-aligned composite signal, or (3) outputting adaptive filter weights of the adaptive filter.

6. A cascaded adaptive beamforming system according to claim 5 , wherein each adaptive filter is an LMS filter.

7. A cascaded adaptive beamforming system according to claim 6 , wherein each LMS filter has length 2.

8. A cascaded adaptive beamforming system according to claim 1 , wherein, for each beamforming element, the beamforming processor is configured to implement a first adjustable time delay element for adding an adjustable amount of delay to a first input signal of the two input signals, a second adjustable time delay element for adding an adjustable amount of delay to a second input signal of the two input signals, and a summer configured to combine the outputs of the first and second adjustable time delay elements to produce the phase-aligned composite signal.

9. A cascaded adaptive beamforming system according to claim 1 , wherein, for each beamforming element, the beamforming processor is configured to perform upsampling and interpolation on each of the two input signals to allow for phasealignment of the signals when the time delay between the two input signals is less than one sample time.

10. A cascaded adaptive beamforming system according to claim 1 , each beamforming element of the succeeding cascade levels further including delay lines to prevent beamforming at each of the succeeding cascade levels from commencing prior to beamforming at each preceding cascade level.

11. A cascaded adaptive beamforming system according to claim 1 , wherein:
each beamforming element at the first cascade level being configured to perform beamforming on a pair of distinct sensor output signals and produce a phase-aligned composite signal; and
each beamforming element of succeeding cascade levels being configured to perform beamforming on a pair of distinct phase-aligned composite signals from a preceding cascade level to produce a phase-aligned composite signal.

12. A cascaded adaptive beamforming system according to claim 1 , wherein:
for a single beamforming element at the first cascade level, the beamforming processor is configured to perform beamforming on a distinct pair of the sensor output signals and to produce a phase-aligned composite signal; and
for a single beamforming element at each succeeding cascade level, the beamforming processor configured to perform beamforming on a pair of input signals consisting of the phase-aligned composite signal from a preceding cascade level and a distinct sensor output signal to produce a phase-aligned composite signal.

13. A cascaded adaptive beamforming system according to claim 1 , wherein:
for each beamforming element at the first cascade level, the beamforming processor is configured to perform beamforming on a pair of sensor output signals to produce a phase-aligned composite signal, wherein the beamforming processor is configured to process one of the pair of sensor output signals in each of two beamforming elements at the first cascade level; and
for each beamforming element at each succeeding cascade level, the beamforming processor is configured to perform beamforming on a pair of phase-aligned composite signals from a preceding cascade level and to produce a phase-aligned composite signal, wherein the beamforming processor, at each succeeding cascade level is configured to process one of the pair of phase-aligned composite signals from the preceding cascade level in each of two beamforming elements at the succeeding cascade level.

14. A cascaded adaptive beamforming system according to claim 1 , wherein the beamforming processor comprises a real-time computing architecture in which the beamforming elements are implemented in hardware and the beamforming elements at each cascade layer operate in parallel.

15. A cascaded adaptive beamforming system according to claim 14 , wherein the beamforming processor comprises a plurality of FIFO buffers for storing and delaying the phase-aligned composite signals between cascade levels.

16. A cascaded adaptive beamforming system according to claim 1 , wherein:
the plurality of sensors are further configured to transmit signals;
the signals received by the sensors include reflections of the signals transmitted by the sensors; and
the beamforming processor is configured to produce the signals transmitted by the sensors using at least one of (1) estimated time delays from beamforming of the sensor output signals or (2) filter weights from beamforming of the sensor output signals.

17. A cascaded adaptive beamforming system according to claim 1 , wherein the beamforming processor comprises a computer processor and a memory storing computer program instructions that, when implemented on the computer processor, implement the beamforming elements in the cascade arrangement.

18. A cascaded adaptive beamforming processor for processing sensor output signals from a plurality of sensor elements and producing a beamformed output signal from the sensor output signals, the beamforming processor comprising:
a plurality of beamforming elements coupled in a cascade arrangement having a first cascade level and a plurality of succeeding cascade levels, the first cascade level and each succeeding cascade level including a beamforming element configured to perform beamforming on two input signals to produce a phase-aligned composite signal from the two input signals, each beamforming element having (a) a filter structured to estimate time delay between the two input signals, (b) two adjustable time delay elements structured to ph

Assignees

• Dartmouth College

Inventors

• Ray Laura
• Ou Teresa
• Schafer Carsten
• Abdeen Alaa
• Hall Harrison

Classifications

• G01S3/808 Primary

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