Hybrid beamforming

• US 20060269080A1
• Filed: 04/11/2006
• Published: 11/30/2006
• Est. Priority Date: 10/15/2004
• Status: Active Grant

• Current Assignee: Lifesize, Inc. (Enghouse Systems Limited)
• Original Assignee: Lifesize, Inc. (Enghouse Systems Limited)
• Inventors: Oxford, William V., Varadarajan, Vijay
• Granted Patent: US 7,970,151 B2
• Time in Patent Office: Days
• US Class Current: 381/92
• CPC Class Codes: H04M 1/6008 in the transmitter circuit
• CPC Class Codes: H04M 1/6033 for providing handsfree use or a loudspeaker mode in telephone sets arrangements for preventing acoustic echo H04M9/08
• CPC Class Codes: H04R 2201/401 2D or 3D arrays of transducers
• CPC Class Codes: H04R 2227/003 Digital PA systems using, e.g. LAN or internet
• CPC Class Codes: H04R 2420/07 Applications of wireless loudspeakers or wireless microphones
• CPC Class Codes: H04R 27/00 Public address systems circuits for preventing acoustic reaction H04R3/02; circuits for distributing signals to loudspeakers H04R3/12; monitoring or testing arrangements for public address systems H04R29/007; amplifiers H03F
• CPC Class Codes: H04R 29/007 for public address systems public address systems per se H04R27/00
• CPC Class Codes: H04R 3/005 for combining the signals of two or more microphones specially adapted for hearing aids H04R25/407

Abstract

A system such as a speakerphone may include a processor, memory and an array of microphones. The processor may be configured (via program instructions stored in the memory) to perform automatic echo cancellation, self calibration and beam forming. In particular, the processor may receive input signals from the microphone array and operate on the input signals with a highly directed virtual beam which is a composite of two or more beams which are restricted to respective frequency ranges. The two or more beams may include beams of different kinds, e.g., superdirective beams and delay-and-sum beams.

Claims

1. A system comprising:

a set of microphones;

a memory configured to store program instructions;

a processor configured to read and execute the program instructions from the memory, wherein the program instructions are executable to implement;

(a) receiving input signals, one input signal corresponding to each of the microphones;

(b) generating first versions of at least a first subset of the input signals, wherein the first versions are band limited to a first frequency range;

(c) operating on the first versions of the first subset of input signals with a first set of parameters in order to compute a first output signal corresponding to a first virtual beam having an integer-order superdirective structure;

(d) generating second versions of at least a second subset of the input signals, wherein the second versions are band limited to a second frequency range different from the first frequency range;

(e) operating on the second versions of the second subset of input signals with a second set of parameters in order to compute a second output signal corresponding to a second virtual beam;

(f) generating a resultant signal, wherein the resultant signal includes a combination of at least the first output signal and the second output signal.

2. The system of claim 1, wherein the second virtual beam is either a beam having a delay-and-sum structure or an integer-order superdirective beam having an integer order different from the integer order of the first virtual beam.

3. The system of claim 1, wherein the first subset of the input signals corresponds to a first subset of the microphones which are at least partially aligned in a target direction, wherein the second set of parameters are configured so as to direct the second virtual beam in the target direction.

4. The system of claim 1, wherein (b) through (e) are performed in the frequency domain.

5. The system of claim 1, wherein the program instructions are further executable by the processor to provide the resultant signal to a communication interface for transmission.

6. The system of claim 1, wherein the set of microphones are arranged in a circular array.

7. A method comprising:

receiving input signals from an array of microphones, one input signal from each of the microphones;

operating on the input signals with a set of virtual beams to obtain respective beam-formed signals, wherein each of the virtual beams is associated with a corresponding frequency range and a corresponding subset of the input signals, wherein each of the virtual beams operates on versions of the input signals of the corresponding subset of input signals, wherein said versions are band limited to the corresponding frequency range, wherein the virtual beams include one or more virtual beams of a first type and one or more virtual beams of a second type; and

generating a resultant signal, wherein the resultant signal includes a combination of the beam-formed signals.

8. The method of claim 7, wherein the one or more beams of the first type are integer-order superdirective beams.

9. The method of claim 7, wherein the one or more beams of the second type are delay-and-sum beams.

10. The method of claim 7 further comprising:

generating first versions of at least a first subset of the input signals, wherein the first versions are band-limited to a first frequency range;

generating second versions of at least a second subset of the input signals, wherein the second versions are band-limited to a second frequency range different from the first frequency range;

wherein said operating on the input signals with a set of virtual beams to obtain respective beam-formed signals comprises;

operating on the first versions of the first subset of input signals with a first set of parameters in order to compute a first beam-formed signal corresponding to a first of the one or more virtual beams of the first type;

operating on the second versions of the second subset of input signals with a second set of parameters in order to compute a second beam-formed signal corresponding to a first of the one or more virtual beams of the second type.

11. The method of claim 10, wherein the first subset of the input signals corresponds to a first subset of the microphones which are at least partially aligned in a target direction, wherein the second set of parameters are configured so as to direct the first virtual beam of the second type in the target direction.

12. The method of claim 10, wherein the first virtual beam of the first type is an integer-order superdirective beam, wherein the first virtual beam of the second type is either a beam having a delay-and-sum structure or an integer-order superdirective beam having an order different from the order of the first virtual beam of the first type.

13. The method of claim 10, wherein said operating on the input signals with a set of virtual beams to obtain respective beam-formed signals is performed in the frequency domain.

14. The method of claim 10 further comprising:

providing the resultant signal to a communication interface for transmission.

15. The method of claim 10, wherein the array of microphones are arranged on a circle.

16. The method of claim 15 further comprising:

accessing an array of parameters from the memory;

applying a circular shift to the array of parameters to obtain the second set of parameters, wherein an amount of the shift corresponds to a desired target direction.

17. A computer readable memory medium configured to store program instructions, wherein the program instructions are executable to implement:

(a) receiving input signals from an array of microphones, one input signal corresponding to each of the microphones;

(b) generating first versions of at least a first subset of the input signals, wherein the first versions are band-limited to a first frequency range;

(c) operating on the first versions of the first subset of input signals with a first set of parameters in order to compute a first output signal corresponding to a first virtual beam having an integer-order superdirective structure;

(d) generating second versions of at least a second subset of the input signals, wherein the second versions are band limited to a second frequency range different from the first frequency range;

(e) operating on the second versions of the second subset of input signals with a second set of parameters in order to compute a second output signal corresponding to a second virtual beam;

(f) generating a resultant signal, wherein the resultant signal includes a combination of at least the first output signal and the second output signal.

18. A method for configuring a system, wherein the system includes an array of microphones, a memory and a processor, the method comprising:

(a) generating a first set of parameters for a first virtual beam based on a first subset of the microphones, wherein the first virtual beam has an integer-order superdirective structure;

(b) computing a plurality of parameter sets for a corresponding plurality of delay-and-sum beams, wherein the parameter set for each delay-and-sum beam is computed for a corresponding frequency, wherein the parameter sets for the delay-and-sum beams are computed based on a common set of beam constraints, wherein the frequency for the delay-and-sum beams are above a transition frequency;

(c) combining the plurality of parameter sets to obtain a second set of parameters;

(d) storing the first set of parameters and the second set of parameters in the memory of the system.

19. The method of claim 18, wherein the system is a speakerphone.

20. The method of claim 18, wherein the common set of beam constraints includes a pass band width.