JP2720845B2 - Adaptive array device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an adaptive array device for spatially receiving signals using a plurality of sensors.

[0002]

2. Description of the Related Art As an application of adaptive array technology for receiving only a specific signal from a plurality of signal sources, a voice emphasis device using an adaptive microphone array, a radio transmitting / receiving device using an adaptive antenna array, and the like are known. .

[0003] Here, a conventional example will be described using an adaptive microphone array that removes ambient noise and emphasizes sound to collect sound.

The microphone array forms a spatial filter by filtering signals collected by a plurality of microphones and then adding the filtered signals. With this spatial filter, ambient noise is attenuated, and only a signal arriving from a predetermined direction, that is, a target signal is received. An adaptive microphone array is a microphone array that changes the spatial filter characteristics adaptively. As a configuration of the adaptive microphone array, “Generalized Sidelobe Canceller” (IEEE, Transactions on Antennas and Propagation (IEEE, Tr
actions on Antennas an
d Propagation), Vol. 30, No. 1, 198
2nd year, pp. 27-34: "Reference 1") is known. The generalized side lobe canceller has a plurality of microphones, a spatial pass filter circuit having a directivity of passing a signal in a predetermined direction by filtering and adding signals from the microphones, and a microphone for each microphone. A spatial cutoff filter circuit group composed of a plurality of spatial cutoff filter circuits having a characteristic of blocking only a signal in a predetermined direction by filtering and adding signals, and each of the spatial cutoff filter circuits A multi-input canceller circuit for removing, from the output of the spatial pass filter circuit, a component having a correlation with the output signal of the spatial cut-off filter circuit by a plurality of adaptive filters using the output as a reference signal.

[0005] However, the space cutoff filter that constitutes the space cutoff filter circuit group used in "Document 1" has two parts.
Since this is a fixed filter using two microphone outputs, the range of the direction in which the signal is blocked (blocking direction) is extremely narrow. Therefore, if the arrival direction of the target signal is slightly different from the direction defined in advance, the target signal largely leaks to the output of the spatial cutoff filter circuit, and a problem occurs that a part of the target signal is also removed in the multi-input canceller circuit. .

In order to solve such a problem of deterioration of the target signal, a method has been proposed in which a spatial cutoff filter circuit group is constituted by a plurality of spatial filter circuits using three or more microphone outputs (IEE, transaction). Antennas and Propagation (IEEE, Transactions on Ant)
Ennas and Propagation), 4th
Vol. 9, No. 9, 1992, pp. 1093-1096: hereinafter "Document 2"). The point of the method shown in "Document 2" is that each spatial cutoff filter circuit constituting the spatial cutoff filter circuit group receives a large number of spatial sample points, that is, a large number of microphone outputs, thereby widening the range of the cutoff direction. Using a wide-angle spatial cutoff filter circuit,
Further, a leak adaptive filter is used as each adaptive filter constituting the multi-input canceller circuit. FIG. 16 is a block diagram showing the configuration of the microphone array proposed in "Document 2". Hereinafter, the related art will be described with reference to the drawings.

FIG. 16 shows a case where a plurality of microphones having the same characteristics are arranged on a straight line at equal intervals. The case where the position of each sensor is sufficiently far from the plurality of microphones and the wavefront of each signal can be regarded as a plane wave will be described. It is also assumed that the signals including both the target signal to be picked up and the ambient noise to be removed are uncorrelated with each other.

A direction expected as a target signal arrival direction obtained by prior knowledge or obtained by a device different from the present device is referred to as a specified direction. In addition, a direction near a specified direction which is likely to be a target signal arrival direction is referred to as a specified direction vicinity, and directions other than the specified direction and the specified direction are referred to as non-specified directions.

First, the operation of FIG. 16 will be described. In the microphone array shown in FIG. 16, outputs from _M microphones l _{0 to} l _M−1 are input to the spatial pass filter circuit 2 and the spatial cutoff filter circuit 12. The spatial pass filter circuit 2 receives signals from the microphones l _{0 to} l _M−1 , and performs filtering and addition so as to pass a signal in a specified direction. Space pass filter circuit 2
Is transmitted to the delay circuit 9. Delay circuit 9
Delays the signal received from the spatial pass filter circuit 2,
It is supplied to the multi-input canceller circuit 13. The delay time of the delay circuit 9 must be determined together with the multi-input canceller circuit 13. The determination method will be described when the multi-input canceller circuit 13 is described. The space cutoff filter circuit group 12 includes a plurality of space cutoff filter circuits. Each of the spatial cutoff filter circuit receives a portion of the signal from a plurality of output signals of the microphone l ₀ ~l _M-1, performs filtering and summed so that signals arriving from the defined direction or defining a direction near canceled. The output group of the plurality of spatial cutoff filter circuits is
It is supplied to the multi-input canceller circuit 13. The multi-input canceller circuit 13 operates to remove components correlated with the output of the spatial cutoff filter circuit group 12 from the output of the delay circuit 9, and outputs the result of the removal to the output terminal 11.

The target signal arriving from the specified direction or the vicinity of the specified direction is included in the output of the delay circuit 9, but not included in the output of the spatial cutoff filter circuit group 12. On the other hand, the ambient noise signal arriving from the non-specified direction is included in both the output of the delay circuit 9 and the output of the spatial cutoff filter circuit group 12. Also, the signal arriving from the specified direction and the signal arriving from the non-specified direction are uncorrelated according to the assumption. Therefore, removing components having a correlation with the output of the spatial cutoff filter circuit group 12 from the output of the delay circuit 9 means that only the ambient noise signal arriving from the non-specified direction is removed at the output 11, and This means that a target signal arriving from near the prescribed direction can be obtained.

Next, the components of FIG. 16 will be described.

First, the configuration of the space pass filter circuit 2 will be described with reference to FIG. FIG. 17 illustrates a configuration example of the space pass filter circuit 2. In the spatial-pass filter circuit 2, the output signal of each of the microphone l ₀ ~l _M-1 in FIG. 16, ₀ M pieces of filter circuit 202 corresponding through the input terminal 201 ₀ ~201 _M-1 ~202 _{M- 1} respectively supplied. Filter circuit group 202 _{0 to} 202
The output signal group of _M-1 is transmitted to the adding circuit 203. The adder circuit 203 includes a plurality of filter circuits 202 _{0 to} 202
The sum of the signals received from _M-1 is calculated, and the result is transmitted to the output terminal 204 as the output of the spatial pass filter circuit 2.

The filter circuit 202 _m (m = 1, 2,...,
M-1) has, for example, an FIR type filter configuration shown in FIG.

Referring to FIG. 18, a filter circuit 202
_{The configuration of m} (m = 1, 2,..., M−1) will be described. An input signal is supplied to the input terminal 301 via the input terminal 201 _m , and a filter output signal is output to the output terminal 305 and transmitted to the addition circuit 203. The signal input to the input terminal 301 has a delay of one sampling cycle.
This is supplied to a tapped delay line composed of at least two delay circuits 302 _{0 to} 302 _G−2 (G is an integer constant of 2 or more). Input signal samples supplied to delay circuit 302 ₀ is transferred to the delay circuit adjacent to each clock. The output signal of each delay circuit 302 _g (g = 0, 1,..., G−2) is supplied to the corresponding multiplication circuit 303 _{g + 1} , and the corresponding tap coefficient supplied from the tap coefficient memory circuit 306 is output. Multiplied. The multiplier circuit 303 _0, an input terminal 30
1 is directly supplied to the signal and multiplied by the tap coefficient supplied from the tap coefficient memory circuit 306. The output signals of the multiplication circuits 303 _{0 to} 303 _G-1 are added to the addition circuit 3
04. The addition circuit 304 includes a multiplication circuit 303
The sum of output signals received from _{0 to} 303 _G-1 is calculated, and the result is output to an output terminal 305. The tap coefficient memory circuit 306 stores tap coefficients such that the entirety of the filter circuits 202 _{0 to} 202 _M−1 has the characteristics described later, and multiplies the tap coefficients by a corresponding multiplication circuit 303 ₀ to
303 _G-1 .

The characteristics of the filter circuits 202 _{0 to} 202 _M−1 are designed so that the output signal of the space-pass filter circuit 2 includes a signal in a specified direction. For example, when the direction orthogonal to the straight line in which the microphones are arranged is taken as the prescribed direction, the integer constant G is set to 2 in all of the filter circuits 202 _{0 to} 202 _M−1 and the multiplication circuit 30 in FIG.
The tap coefficients to be multiplied in the 3 ₀ may be 1 and set. Other design methods include, for example, (multi-dimensional digital signal processing,
Prentice Hall, (Multidimension
nal Digital Signal Procedures
sing, Prentice-Hall, Inc. ) 2
89-315, 1984: "Document 3"
Ya, (IEE, Proceedings of
International Conference on Acoustic Speech and Signal Processing 93, (IEEE, Proceedings of
International Conference
on Acoustics, Speech, andSi
general Processing 93), I-169.
172 pages, 1993: hereinafter "Reference 4").

Next, the configuration of the space cutoff filter circuit group 12 in FIG. 16 will be described with reference to FIG.
In the spatial cutoff filter circuit group 12, "microphone 1" uses two microphone outputs per spatial cutoff filter circuit, but "literature 2" uses three or more microphone outputs per spatial cutoff filter circuit. Microphone output is used. FIG. 19 shows a configuration example in which the number of microphone outputs used per one spatial cutoff filter circuit is Q as the spatial cutoff filter circuit shown in "Document 2". Q is an integer of 3 or more. The spatial cutoff filter circuit shown in "Document 1" corresponds to the case where Q is 2.
19, the output signal of the microphone l _m (m = 0, 1,..., M−1) in FIG. 16 is supplied to the input terminal 901 _m , and the output terminal 905
_m (m = 0, 1,..., M−Q)
It is supplied to the multi-input canceller circuit 13 of FIG.

The filter circuit 906 _{m, q} (m = 0,1,
, MQ, q = 0, 1,..., Q-1) are input terminals 9
The output signal of the microphone l _{m + q} supplied via the signal 01 _{m + q} is filtered according to characteristics described later, and the output signal is transmitted to the addition circuit 907 _m . Adder circuit 90
_7m (m = 0, 1,..., M−Q) calculates the sum of output signals of the plurality of filter circuits 906 _{m, q} (q = 0, 1,. It outputs to the output terminal 905 _m as the output of the cutoff filter circuit. Adder circuit 907 _m (m
= 0, 1,..., MQ) and a plurality of filter circuits 906
_{m, q} (q = 0, 1,..., Q-1) forms a spatial cutoff filter circuit.

Filter circuit 906 _{m, q} (m = 0,1,
, MQ, q = 0, 1,..., Q−1) are the same as those of the filter circuits 202 _{0 to} 202 _M−1 and can be represented as shown in FIG. However, the integer constant G and the characteristic are determined by the filter circuit 906 _{m, q} (m = 0, 1,..., MQ, q =
0, 1,..., Q-1) and filter circuits 202 _{0 to} 202
Different with _M-1 .

Filter circuit 906 _{m, q} (m = 0,1,
, MQ, q = 0, 1,..., Q−1), the output signal of the microphone lm _{+ q in} FIG. 16 is supplied to the input terminal 301 via the input terminal 901 _{m + q} , The filter output signal obtained at terminal 305 is transmitted to addition circuit 907 in FIG.

Filter circuit 906 _{m, q} (m = 0,1,
, MQ, q = 0, 1,..., Q-1) are designed so that not only the specified direction but also signals coming from near the specified direction are cut off at the output terminal 905 _m .
That is, the space cutoff filter circuit group 12 is designed to be a wide angle space cutoff filter circuit group. The design guide is described in “Reference 2”. The greater the number of microphones, the greater the degree of freedom of the spatial cutoff filter characteristics,
This makes it possible to increase the range of the cutoff direction or increase the attenuation rate of a signal arriving from the cutoff direction. Thus,
The spatial cutoff filter circuit group of "Document 2" can cut off the target signal at the output even when the direction of the target signal has an error from the specified direction. As a result, it is possible to prevent the target signal from being removed at the output terminal of FIG. 16 when there is an error between the direction of the target signal and the specified direction.

However, the output group of the spatial cutoff filter circuit of "Document 2" shown here has less spatial freedom than "Document 1". Because the total number of microphones is M
In the case where Q microphone outputs are used for one spatial cutoff filter circuit group constituting the spatial cutoff filter circuit group 12, the spatial degree of freedom of the output of the spatial cutoff filter circuit group is (M−Q + 1). Yes, "Document 1" has Q =
2, because “Document 2” corresponds to the case where Q ≧ 3.
In the case of the configuration shown in FIG. 19, the spatial degree of freedom directly appears in the number of output terminals 905 _m of the spatial cutoff filter circuit group 12.

Next, the configuration of the multi-input canceller circuit 13 will be described with reference to FIG. In the multi-input canceller circuit 13 is supplied as a reference signal to the leakage adaptive filter 7 ₀ to _7-MQ for each output signal of the spatial cutoff filter circuit group 12 corresponding output signal of the delay circuit 9 are supplied to a subtracting circuit 10 . Leak adaptive filter 7 ₀
7 to 7 _MQ filter the corresponding output signal of the spatial cutoff filter circuit group 12 received as the reference signal, and transmit the output signal to the addition circuit 8. Adding circuit 8, the sum of the output signals received from the leak adaptive filter group 7 ₀ to _7-MQ is calculated, and transmits the result to the subtracting circuit 10. Subtraction circuit 10
Subtracts the sum calculated by the adder circuit 8 from the signal supplied from the delay circuit 9 and outputs the result to the leak adaptive filter group 7
_The signal is transmitted as an error signal common to all of _{0 to} 7 _{M- Q} and is output to an output terminal 11 as an output signal of the entire apparatus. Leak adaptive filter group 7 ₀ to _7-MQ subtraction circuit 10
The tap coefficient is updated based on the error signal received from.

The tap total leakage adaptive filter 7 ₀ to _7-MQ is determined by the distance between the most distant microphone. This is for signals coming from any direction,
The phase difference between the microphone output in order to enable compensation in leakage adaptive filter 7 ₀ to _7-MQ.

The delay time of the delay circuit 9 is determined based on the microphone groups l _{0 to} l _M−1 from the space-pass filter circuit 2 and the delay circuit 9.
And delay path to the subtraction circuit 10 through a spatial cutoff filter circuit group 12 from the microphone group l ₀ ~l _M-1, the leakage adaptive filter group 7 ₀ to _{7-M- Q,} to the subtraction circuit 10 via the adder circuit 8 It is set so that the delay of the route to be reached is equal. The delay time of the space-pass filter circuit 2 is determined by the filter circuit groups 202 _{0 to} 20 constituting the space-pass filter circuit 2.
It is determined by the delay characteristic of 2 _M−1 and the delay time of the adder 203. The delay time of the spatial cutoff filter circuit group 12 is
The filter circuit group 906 _{m, q} (m = 0,1,..., M−1, q = 0,1, 1) constituting the space cutoff filter circuit group 12
.., MQ) and the delay time of the adder 907. Leak adaptive filter group 7 ₀ to _7-MQ delay time is determined by the tap total.

With this configuration, the leak adaptive filter group 7
_{From 0 to} 7 _MQ , an error signal, that is, a signal at the output terminal 11 is used to convert a reference signal into a spatial cutoff filter circuit group 12.
Operates so as to remove components having a correlation with the output signal group. The reason for using a leak adaptive filter instead of a normal adaptive filter will be described later.

FIG. 20 is described with reference to FIG. 21 the structure of a leakage adaptive filter 7 ₀ to _7-MQ. FIG.
Represents an example of a block diagram of an adaptive filter. Leak adaptive filter 7 ₀ to _7-MQ as tap coefficient updating circuit 326 in FIG. 14, an adaptive filter is used to leak with tap coefficient updating circuit shown in FIG. 21. In FIG. 20, an input terminal 321 is connected to a spatial cutoff filter circuit group 12
Is supplied as a reference signal. Output terminal 32
5 outputs a filter output signal, which is transmitted to the addition circuit 203.

The configuration of the adaptive filter will be described with reference to FIG. The reference signal input to the input terminal 321 is a delay circuit 32 that generates a delay of one sampling cycle.
2 _{0 to} 322 _L−2 (L is an integer constant representing the total number of taps) and is supplied to a tapped delay line. Delay circuit 322
_The input signal sample supplied to ₀ is transferred to an adjacent delay circuit every clock. Each delay circuit 322 _l (l
= 0, 1,... L-2)
_{l + 1} , and is multiplied by the corresponding tap coefficient supplied from the tap coefficient update circuit 326. Multiplication circuit 323
_{To 0} , the signal input to the input terminal 321 is directly supplied, and is multiplied by the tap coefficient supplied from the tap coefficient update circuit 326. The output signals of the multiplication circuits 323 _{0 to} 323 _L−1 are supplied to the addition circuit 324. Adder circuit 324
Calculates the sum of the output signals received from the multiplication circuits 323 _{0 to} 323 _L−1 , and outputs the result to the output terminal 325.

A description will be given of a leaky tap coefficient updating circuit used as the tap coefficient updating circuit 326 with reference to FIG. FIG. 21 is an example of a block diagram of a tap coefficient updating circuit with leak when an LMS algorithm is assumed as the tap coefficient updating algorithm. Input terminal 327
Is supplied with an error signal from the subtraction circuit 10 in FIG. The input terminal 402 _0, supplied signals supplied to the input terminal 321 of FIG. 20 is directly input terminal 402 _l (l
= 1, 2,..., L−1) includes the delay circuit 322 of FIG.
An output signal of _l-1 is supplied. Output terminal 401 _l (l =
0, 1,..., L−1) are transmitted as tap coefficients to the multiplying circuit 323 _l in FIG.

The error signal supplied to the input terminal 327 is
The signal is transmitted to the multiplication circuit 407. The multiplication circuit 407 multiplies the error signal by the step size μ, and transmits the result to all the multiplication circuits 406 _{0 to} 406 _L−1 having the same number as the total number of taps. The multiplication circuit 406 _l (l = 0, 1,..., L−1)
A signal supplied from the multiplier circuit 407 multiplies the delay signal supplied via a terminal 402 _l, and supplies to the adding circuit 405 _l results. The adder circuit 405 _l includes the multiplication circuit 4
A signal supplied from the 09 _l, adds the signal supplied from the multiplier circuit 406 _l for transmission to the delay circuit 403 _l.
The output signal of the delay circuit 403 _l, together with is transmitted to the terminal 401 _l as a tap coefficient is supplied to the multiplying circuit 409 _l. The multiplication circuit 409 _l multiplies the output signal supplied from the delay circuit 403 _l by the leak control coefficient α,
And transmits to the adding circuit 405 _l.

The tap coefficient updating circuit with leak is configured such that the leak control coefficient α to be multiplied by the multiplier circuits 409 _{0 to} 409 _L-1 is 1
It is a slightly smaller positive constant, and includes an addition circuit 405 _l , a delay circuit 403 _l , and a multiplication circuit 409 _l (l = 0, 1,...,
L-1) constitutes a leak integration circuit. In FIG. 21, a portion surrounded by a dashed line is a leak integration circuit. The normal adaptive filter corresponds to the case where α is set to 1, and is not a leak integrating circuit but a normal integrating circuit.

The properties of the leak integrating circuit will be described using equations. Multiplication circuit 405 _l (l =
0,1, ..., the signal supplied to the summing circuit 405 _l from _{L-1) x 1 (k} ), the output signal of the delay circuit 403 _l y
₁ (k). Sample number (k + 1) delay in (1-sampled period) circuit 403 _l of the output signal y ₁
(K + 1) is represented by the equations (1) and (2).

Y ₁ (k + 1) = x ₁ (k) + αy ₁ (k) (1) = x ₁ (k) + y ₁ (k) − (1−α) y ₁ (k) (2) Normal integration In the circuit, since α = 1, the third on the right side of equation (2)
The term becomes 0. On the other hand, in the leak integration circuit,
(2) the third term on the right side of the equation, acts to reduce the output signal of y ₁ (k + 1) That the delay circuit 403 _l. With this function, the growth of the tap coefficient is suppressed in the leak adaptive filter as compared with the normal adaptive filter. Also, the strength of suppressing the growth of the tap coefficient is
It is proportional to the value of (1-α) and the magnitude y ₁ (k) of the tap coefficient.

[0033] If instead of leakage adaptive filter 7 ₀ to _7-MQ, and used the normal adaptive filter, the target signal is leaked to the output of the spatial cutoff filter circuit group 12 due to the effects of errors in the microphone arrangement and characteristics In such a case, even if the amount of leakage is small, a phenomenon occurs in which the tap coefficient grows endlessly and the target signal is removed. However, in the configuration of FIG. 16, the growth of the tap coefficients is suppressed because it uses leakage adaptive filter group 7 ₀ to _7-MQ, can leak amount to prevent removal of the target signal if slightly.

[0034]

In the prior art described above, in order to reduce the deterioration of the target signal when there is an error between the arrival direction of the target signal and the specified direction, even in such a case, the space is cut off. In order to sufficiently cut off the target signal at each output of the filter circuit group 12, a space cutoff filter circuit having a wide range in a cutoff direction is used. In this conventional example, the range of the cutoff direction needs to be particularly widened in order to reduce the removal of the target signal even when the error between the target signal arrival direction and the specified direction is large. This means that the number Q of microphones required for one space cutoff filter circuit constituting the space cutoff filter circuit group 12 increases. Therefore, when the total number of microphones is fixed, the degree of spatial freedom for removing ambient noise is reduced, which causes a problem that the performance of removing ambient noise is reduced. Alternatively, in order to maintain the ambient noise elimination performance, it is necessary to increase the total number of microphones, which causes a problem that the hardware scale increases.

It is an object of the present invention to provide an adaptive array device which realizes signal reception with a small amount of target signal degradation even with a large error between the arrival direction of the target signal and the specified direction with a small number of sensors.

[0036]

SUMMARY OF THE INVENTION According to the present invention, a plurality of sensors arranged at spatially different positions and a group of output signals from the plurality of sensors are respectively filtered and added, so that the signals are added in advance. A first space-pass filter circuit having directivity for passing a signal coming from a prescribed direction, a first delay circuit for receiving and delaying an output signal of the first space-pass filter circuit, A plurality of sensor outputs are newly selected from the outputs of the sensors, and each is filtered and added, so that a spatial cutoff filter circuit group including a plurality of spatial cutoff filter circuits that cuts off only signals arriving from a predetermined direction. A first leak adaptation filter comprising a plurality of leak adaptation filters for receiving and filtering output signals of the plurality of spatial cutoff filter circuits on a one-to-one basis. Filter group, an addition circuit for calculating the sum of the output signals of the first leak adaptive filter group, and the sum calculated by the addition circuit is subtracted from the output signal of the first delay circuit. And transmitting the subtraction result as a common coefficient update error signal to all of the first leak adaptive filter groups.
In the adaptive array device using the generalized side lobe canceller, the spatial cutoff filter circuit receives output signal groups from the plurality of sensors, performs filtering on each of the output signal groups, and performs addition in advance. A second spatial pass filter circuit having directivity for passing a signal coming from a prescribed direction, a second delay circuit for receiving and delaying output signals of the plurality of sensors on a one-to-one basis, A second leak adaptive filter for receiving and filtering the output signal of the second spatial pass filter circuit, and subtracting the output signal of the second leak adaptive filter from the output signal of the second delay circuit, and calculating the result of the subtraction. A second subtraction circuit that transmits a signal to be subtracted to the leak adaptive filter that supplies the signal as an error signal for updating the coefficient. Second constituting a blocking filter circuit
Is shared by all of the spatial cutoff filter circuits.

The present invention also provides a group of norm-constrained adaptive filters for controlling tap coefficients such that the norm of the tap coefficients of each filter is equal to or less than a positive constant determined for each filter, instead of the first leak adaptive filter group. It is characterized by having.

Further, the present invention includes a tap coefficient constrained adaptive filter group in which the change range of the tap coefficients of the filter is limited to a range determined for each tap, instead of the second leak adaptive filter group. Features.

Further, the present invention is characterized in that the first space-pass filter circuit and the second space-pass filter circuit are shared.

Further, the present invention is characterized in that a configuration for outputting only one sensor signal among the plurality of sensors is used as the first space pass filter circuit.

Further, the present invention is characterized in that a configuration for outputting only one sensor signal among the plurality of sensors is used as the second space pass filter circuit.

[0042]

According to the present invention, in each of the spatial cut-off filter circuits constituting the spatial cut-off filter circuit group, the characteristic is such that a signal arriving from a specified direction and near the specified direction is passed and a signal arriving from a non-specified direction is attenuated. The output signal of the second leak adaptive filter or the tap coefficient constrained adaptive filter using the output signal of the second spatial pass filter having the reference signal as a reference signal is subtracted from the signal obtained by delaying the signal of each sensor, and the result of the subtraction is obtained. In addition to the output of the spatial cutoff filter circuit, the coefficient of the second leak adaptive filter or the tap coefficient constrained adaptive filter is updated as an error signal. As a result, in the output of the spatial cutoff filter circuit, components having correlation with the signal arriving from the specified direction and the vicinity of the specified direction are sufficiently removed, and the signal arriving from the vicinity of the specified direction at the multi-input canceller circuit output is prevented from being removed. Is done. Further, in the multi-input canceller circuit, the first leak adaptive filter or the norm constrained adaptive filter is used to suppress the tap coefficient from growing excessively, and to suppress the tap coefficient from the vicinity of the specified direction slightly remaining in the output of the spatial cutoff filter circuit. It is possible to prevent the signal from removing the signal from the vicinity of the specified direction. Further, in the spatial cutoff filter circuit group according to the present invention, the degree of freedom of the space is less reduced.

[0043]

Embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing a first embodiment of the present invention. 1 and FIG. 16 which is a block diagram of a conventional example.
Are the same except for the space cutoff filter circuit group 12, so that the detailed operation will be described below focusing on this difference.

The space cutoff filter circuit group 12 according to the present invention comprises:
By receiving and filtering and adding the output groups of the microphone groups l _{0 to} l _M−1 , directivity that allows signals arriving from a predetermined direction to pass and attenuates signals arriving from directions other than the predetermined direction spatial-pass filter circuit 3, a plurality of delay for receiving and delaying an output signal of each of the microphone group l ₀ ~l _M-1 circuit 4 ₀ ~4 _M-1 having
Delay circuit group composed of
And leakage adaptive filter group constituted from a plurality of leakage adaptive filter 5 ₀ ~5 _M-1 the output signal is a reference signal,
Signal from the output signal of each of the plurality delay circuits 4 ₀ ~4 _M-1, subtracts the output signal of the corresponding leakage adaptive filter of leakage adaptive filter group 5 ₀ ~5 _M-1, the subtraction result is subtracted And a plurality of subtraction circuits 6 _{0 to} 6 _M−1 that transmit an error signal for updating the coefficient to the leak adaptive filter that has supplied the signal and also transmit the output signal of the spatial cutoff filter circuit group 12 to the multi-input canceller circuit 13. And a subtraction circuit group.

First, the whole of the space cutoff filter circuit group 12 will be described with reference to FIG.

The spatial pass filter circuit 3 receives the output groups of the microphone groups l _{0 to} l _M−1 , filters and adds the signals, thereby passing a signal arriving from a predetermined direction and passing the signal from a direction other than the specified direction. incoming and the output signal obtained by attenuating the signal and supplies it to leak adaptive filter group 5 ₀ ~5 _M-1 as the reference signal. Leak adaptive filter 5
_m (m = 0, 1,..., M−1) filters the output from the spatial pass filter circuit 3 received as the reference signal, and transmits the output signal to the subtraction circuit 6 _m . Delay circuit 4 _m
(M = 0,1, ..., M -1) delays the signal supplied from the microphone l _m, and transmits to the subtraction circuit 6 _m. The subtraction circuit 6 _m (m = 0, 1,..., M−1)
_m, the output signal of the leak adaptive filter 5 _m is subtracted from the signal supplied thereto, and the result is transmitted to the leak adaptive filter 5 _m as an error signal. Supply. Leak adaptive filter 5 _m (m = 0, 1,..., M−
1) is the coefficient updated by the error signal received from subtracting circuit 6 _m.

In this configuration, the leak adaptive filter 5
_m (m = 0, 1,..., M−1) operates so as to remove, from the error signal, that is, the output signal of the subtraction circuit 6 _m , a component correlated with the reference signal, that is, the output signal of the space-pass filter circuit 3. I do. As a result, in the output of the subtraction circuit _6m , that is, the output of the spatial cutoff filter circuit group 12, signals arriving from the specified direction and the vicinity of the specified direction are removed, and signals arriving from the non-specified direction remain. Therefore, the spatial pass filter circuit 3, the delay circuit 4 _m , the leak adaptive filter 5 _m , and the subtraction circuit 6 _m can be regarded as constituting a kind of spatial cutoff filter circuit.

The leak adaptive filter 5 _m (m = 0, 1,
..., M-1) taps total number N of and, the delay circuit 4 _m delay time is set so as to enable removal of the signals arriving from the prescribed direction near. That is, the total number N of taps of the leak adaptive filter 5 _m (m = 0, 1,..., M−1) is
The number is made sufficiently large so that a signal arriving from the vicinity of the prescribed direction can be removed. The delay circuit 4 _m (m = 0, 1,..., M−
1) the delay time of the spatial-pass filter circuit 3 from the microphone group l _m, a delay of the route leading to leakage adaptive filter group 5 via the _m subtraction circuit 6 _m, the subtracting circuit via a delay circuit 4 _m from the microphone group l _m The delay of the path to 6 _m is set to be equal.

The reason why a leak adaptive filter is used instead of a normal adaptive filter will be described later.

By this space cutoff filter circuit group 12,
Even when the arrival direction of the target signal does not match the specified direction and is near the specified direction, the target signal is removed from the output of the space cutoff filter circuit group 12. As a result, even if there is an error between the arrival direction of the target signal and the specified direction, the removal of the target signal at the output terminal 11 in FIG. 1 is prevented.

Next, each component of the space cutoff filter circuit group 12 will be described.

The configuration of the spatial pass filter circuit 3 is the same as the configuration of the spatial pass filter circuit 2 in the conventional example.
It can be represented as in FIG. However, the characteristics of the spatial filter need not be the same in the spatial pass filter circuit 3 and the spatial pass filter circuit 2. The input relationship of the spatial pass filter circuit 3 is the same as that of the spatial pass filter circuit 2. Output relationships are different, the output obtained at the output terminal 204 of the spatial-pass filter circuit 3 is supplied as a reference signal to the leakage adaptive filter 5 ₀ to 5 _M-1 in FIG. 1. The filter circuit 202 _m (m = 1, 2,...,
The configuration of M-1) is the same as that of the spatial filter circuit 2, and the description is omitted.

The space-pass filter circuit 3 is designed to pass a target signal arriving from a specified direction and a vicinity of the specified direction, and attenuate a signal arriving from a non-specified direction.
For example, in the description of the conventional example, the spatial pass filter circuit 2
You can use the design method introduced in.

[0055] Configuration of the leak adaptive filter 5 ₀ ~5 _M-1 is the leakage adaptive filter 7 ₀ to _7-MQ described in the conventional example
In FIG. 20 showing an example of the configuration, the number of taps L is given by replacing the total number L with N. Since the operation is the same, detailed description is omitted.

The leak adaptive filter 5 _m (m = 0, 1,
, M-1), the input terminal 321 in FIG.
The signal from the spatial pass filter 3 of FIG. 1 is supplied as a reference signal. Reference signal is filtered, the output signal is transmitted to the subtraction circuit 6 _m in FIG. 1 via the output terminal 325. The input terminal 327, the output signal of the subtracting circuit 6 _m is supplied.

[0057] Hereinafter, will be described in detail the nature of the subtraction circuit 6 ₀ ~6 _M-1 of the output signal derived from the nature of the leak adaptive filter. The leak adaptive filter, the leakage adaptive filter 7 ₀ to _7-MQ conventional example as described with reference to FIG. 21, to suppress the strength of the growth of the tap coefficients is proportional to the magnitude of the tap coefficients. Therefore, when the value of the optimum tap coefficient (the tap coefficient that minimizes the error input) is large, it becomes difficult for the tap coefficient to approach the optimum tap coefficient. As a result, the tap coefficients after convergence have a large error with respect to the optimal tap coefficients. This means that the leak adaptive filter 5 _m (m = 0, 1,..., M−1) has a correlation between the error signal, that is, the output signal of the subtraction circuit 6 _m , and the reference signal, that is, the output signal of the space-pass filter circuit 3. This means that when a certain component is removed, the amount of removal differs depending on the magnitude of the tap coefficient. That is, components that require large tap coefficients for removal are not so much removed, but components that can be sufficiently removed with small tap coefficients are largely removed. By the way, the amount of the signal arriving from the vicinity of the prescribed direction is substantially equal to the amount included in the output of the spatial pass filter circuit 3 and the amount included in each microphone output l _{0 to} l _M-1 .
The maximum value of the tap coefficient required for the removal is as small as about 1. Thus, at the output of the subtraction circuit 6 ₀ to 6 _M-1, signals arriving from the prescribed direction near is largely removed. On the other hand, the amount of the signal arriving from the non-specified direction included in the output of the space-pass filter circuit 3 is equal to each microphone output l _0.
Since it is smaller than the amount included in l _M−1 , the maximum value of the tap coefficient required for the removal is much larger than 1. Thus, at the output of the subtraction circuit 6 ₀ to 6 _M-1, the removal amount of signals arriving from the defined outer direction is small. For the above reasons,
At the output of the subtraction circuit 6 ₀ to 6 _M-1, defines the direction and defining signals arriving from the direction near but not little residual signals arriving from the defined outer direction is relatively large residual.

[0058] If it is assumed that uses the normal adaptive filter in place of the leak adaptive filter 5 ₀ ~5 _M-1, since the tap coefficients of the adaptive filter can endlessly growth, at the output of the subtraction circuit 6 _m, defined direction Not only the signal arriving from the vicinity but also the signal arriving from a non-specified direction is removed. In this case, the multi-input canceller circuit 13 cannot remove a signal arriving from a non-specified direction, that is, ambient noise. The present invention avoids this problem by using a leaky adaptive filter instead of a normal adaptive filter.

As is apparent from the above description, the ambient noise arriving from an undefined direction is largely removed at the output terminal 11 of the multi-input canceller circuit 13. On the other hand, regarding the target signal, even if there is an error between the arrival direction and the specified direction, since the reference signal contains only a small amount, it is hardly removed at the output terminal 11 of the multi-input canceller circuit 13. .

Based on the above description, differences between the embodiment and the conventional example will be summarized. In the conventional example of "Reference 2" shown in FIG.
In order to prevent a phenomenon that the target signal is removed at the output terminal 11 when there is an error between the prescribed direction and the arrival direction of the target signal, a plurality of microphones requiring a large number of microphone outputs are required in order to prevent a phenomenon that the target signal is removed at the output terminal 11. It consisted of a fixed spatial filter. Therefore, the spatial degree of freedom in the output group of the spatial cutoff filter circuit group 12 is smaller than that in "Reference 1." This means a reduction in spatial freedom to remove ambient noise. As a result, when the total number of microphones is fixed, the performance of ambient noise removal deteriorates. Alternatively, it is necessary to increase the total number of microphones in order to obtain a certain ambient noise removal performance.

On the other hand, in the present invention shown in FIG.
The spatial cutoff filter group 12 includes the leak adaptive filters ₅₀ to
It is composed of a plurality of variable spatial filters using 5 _M−1 , and the degree of freedom in the spatial cutoff does not decrease as compared with the method of “Reference 2”. Therefore, it is possible to prevent the removal of the target signal at the output terminal 11 with a smaller number of microphones than in the conventional example shown in "Reference 2."

FIG. 2 is a block diagram showing a second embodiment of the present invention. The first embodiment and differs from the second embodiment shown in FIG. 1, the multi-input canceller circuit 13, the leakage adaptive filter 7 ₀ to _7-M-1 norm constraint adaptive filter 14 ₀ in FIG. 2 in FIG. 1 １４14 _{M- 1} .

Norm-constrained adaptive filters 14 _{0 to} 14 _M-1
Configuration of, in FIG. 20 illustrating a configuration example of a leak adaptive filter 7 ₀ to _7-MQ described in the prior art is given by the tap coefficient updating circuit 326 and norm constraint tap update circuit.

In the norm-constrained tap updating circuit, the p-th norm L _P (p is an integer constant of 1 or more) of the tap coefficient is a positive constant Θ
Is controlled so as not to exceed. However, the tap coefficients to the filter is L, p-th power norm L _P is calculated as follows.

[0065]

(Equation 1)

Where w _l is the l-th tap coefficient,
| W _l | represents the absolute value of w _l. Also

[0067]

[Outside 1]

Represents a p-th root. The fact that L _P is limited to Θ or less means that each tap coefficient cannot grow to a certain degree or more, and when the target signal leaks to the output group of the spatial cutoff filter circuit as in the first embodiment. However, the effect of suppressing the removal of the target signal in the multi-input canceller output 11 is produced.

The norm-constrained tap updating circuit will be described with reference to FIG. FIG. 3 is a block diagram of a norm-constrained tap update circuit when an LMS algorithm is assumed as the tap coefficient update algorithm. Input terminal 3
27 is supplied with an error signal from the subtraction circuit 10 of FIG. The input terminal 402 _0, supplied signals supplied to the input terminal 321 of FIG. 20 is directly input terminal 402 _l (l
= 1, 2,..., L-1) is the delay circuit 322 of FIG.
An output signal of _l-1 is supplied. Output terminal 401 _l (l =
0, 1,..., L−1) are transmitted as tap coefficients to the multiplying circuit 323 _l in FIG.

The error signal supplied to the input terminal 327 is
The signal is transmitted to the multiplication circuit 407. The multiplication circuit 407 multiplies the error signal by the step size μ, and transmits the result to all the multiplication circuits 406 _{0 to} 406 _L−1 having the same number as the total number of taps. The multiplication circuit 406 _l (l = 0, 1,..., L−1)
A signal supplied from the multiplier circuit 407 multiplies the delay signal supplied via a terminal 402 _l, and supplies to the adding circuit 405 _l results. The adder circuit 405 _l includes the multiplication circuit 4
The signal supplied from 24 _l and the signal supplied from multiplication circuit 406 _l are added, and the result is transmitted to delay circuit 403 _l and transmitted to constraint control coefficient generation circuit 428. The delay circuit 403 _l the signal received from the adder circuit 405 _l to 1 sampling period delay, to transmit the output signal to the multiplication circuit 424 _l. The multiplying circuit 424 _l includes the signal received from the delay circuit 403 _l and the constraint control coefficient generating circuit 42.
8 multiplies the restraint control coefficient β supplied from the supplies the result to the adder circuit 405 _l, transmits as a tap coefficient to the terminal 401 _l. Constraint control coefficient generation circuit 428
Calculates the restraining control coefficient β from a signal group received from the adder circuit 405 ₀ ~405 _L-1, and supplies the 424 ₀ ~424 _L-1.

FIG. 4 shows a configuration example of the constraint control coefficient generation circuit 428. The p-th norm calculation circuit 510 receives the output signal of the adder group 405 _l (l = 0, 1,..., L−1) through the input terminal 501 _l and calculates its p-th norm L _p I do. The calculation result of the p-th norm L _p is calculated by a division circuit 506.
Is transmitted to The division circuit 506 converts the limit value の of the p-th norm given to the terminal 507 into a p-th norm calculation circuit 51
The result is divided by the p-th norm L _p received from 0, and the result is transmitted to the minimum value selection circuit 508. Minimum value selection circuit 508
Is the result of the division received from the division circuit 506 and the terminal 509
And outputs the smaller value to the output terminal 502 as the constraint control coefficient β. Output terminal 5
02 is transmitted to the multiplication circuit groups 424 _{0 to} 424 _L−1 in FIG. 3 and is multiplied by the signal received from the delay circuit 403 _l . As described above, the constraint control coefficient generation circuit 408 reduces all tap coefficients so that L _p becomes Θ or less when the p-th norm L _p exceeds a certain positive constant 正.

In the L _p norm calculation circuit 510 of FIG.
The multiplication circuit 503 _l (l = 0, 1,..., L−1) receives the output signal of the addition circuit 405 _l of FIG. 3 via the input terminal 501 _l , calculates its p-th power, and adds the result. The signal is transmitted to the circuit 504. The adder circuit 504 includes p-th power circuit groups 503 _{0 to} 503
The sum of the p-th power values received from 03 _L−1 is calculated, and the result is transmitted to the p-th root circuit 505. The p-th root circuit 505 calculates the p-th root of the value received from the adding circuit 504. The output signal of the p-th root circuit 505 is a p-th power norm L _p, is transmitted to the divider circuit 506.

FIG. 5 is a block diagram showing a third embodiment of the present invention. The difference between the first embodiment and the third embodiment shown in FIG.
In the leakage adaptive filter 5 ₀ to 5 _M-1 in FIG. 5, is to be replaced by the tap coefficients constraint adaptive filter 15 ₀ ~15 _M-1.

Tap coefficient constrained adaptive filters 15 ₀ to 15
Structure of _M-1, in FIG. 20 illustrating a configuration example of a leak adaptive filter 7 ₀ to _7-MQ described in the conventional example, the tap total number L to N, the tap coefficient updating circuit 326 to the tap coefficient Constrained tap update circuit Given by substitution.

Tap coefficient constraint filter 15 ₀ -15 _M-1
In this example, coefficient maximum absolute values Φ _{0 to} Φ _N−1 are provided for each tap as the upper limit of the absolute value of the tap coefficient. Coefficient maximum absolute value Φ ₀ ~Φ _N-1 for each tap, the subtraction circuit 6 _0-6 of FIG. 5
_The decision is made in consideration of signal elimination in _M-1 . That is, when a signal exists only in a certain direction, the subtraction circuit 6
_m (m = 0, 1,..., M−1)
Consider whether or not the output signal of _{m and} the output signal of the tap coefficient constrained adaptive filter 15 _m can be equal.

Since the signal arriving from the vicinity of the prescribed direction should be removed by the subtraction circuit 6 _m , the maximum coefficient absolute value of the tap which plays a major role in the removal is determined by the output signal of the tap coefficient constraint adaptive filter 15 _m. a sufficiently large value to become equal to the output signal of the delay circuit 4 _m. On the other hand, since a signal arriving from a non-specified direction should not be removed, the maximum absolute value of the tap coefficient which plays a major role in the removal is determined by the output signal of the tap coefficient constrained adaptive filter 15 _{m and} the delay circuit 4 _m . Use a small value that is not equal to the output signal. For example, the tap coefficient constraint adaptive filter 15
_m (m = 0, 1,..., M−1) maximum coefficient absolute value Φ ₀
Φ _N-1 is the output signal amplitude of the delay circuit 4 _m with respect to the output signal amplitude of the spatial pass filter circuit 3 (= input signal amplitude of the tap coefficient constrained adaptive filter 15 _m ) when a signal exists only in a certain direction. It can be determined using the ratio (directional output ratio).

For the n-th tap of the tap coefficient constrained adaptive filter 15 _m , if the tap is a center tap (center tap) for removing a signal arriving from the specified direction, the direction in the specified direction slightly greater than the output ratio and the coefficient maximum absolute value [Phi _n. If the tap is a main tap (near the center tap) for removing a signal arriving from the vicinity of the specified direction, a value slightly larger than the maximum value of the directional output ratio in the vicinity of the specified direction is determined by the coefficient maximum absolute value Φ. _Let it be _n . For other taps, the maximum coefficient absolute value Φ increases as the distance from the center tap increases.
Decrease _n .

The maximum coefficient absolute value Φ ₀係数
According [Phi _N-1, when the absolute value of the n-th tap coefficient w _n exceeds the coefficient maximum absolute value [Phi _n is the absolute value of the tap coefficient to reduce the tap coefficients to be equal to or less than the [Phi _n.

[0079] As described above, by limiting the tap coefficients, respectively, in the output of the subtraction circuit 6 ₀ ~6 _M-1 in FIG. 5, is largely removed signals arriving from the prescribed direction near the prescribed direction outside Incoming signals are not significantly removed. The multi-input canceller circuit 13 supplied with this output as a reference signal removes the target signal from the multi-input canceller output 11 even if there is an error between the target signal arrival direction and the specified direction, as in the first embodiment. This has the effect of being suppressed.

The tap coefficient constrained tap updating circuit will be described in detail with reference to FIG. FIG. 6 is an example of a block diagram of a tap coefficient update circuit with tap coefficient constraints when an LMS algorithm is assumed as the tap coefficient update algorithm. The input terminal 327 has a subtraction circuit 1 shown in FIG.
An error signal is supplied from 0. The input terminals 402 _0,
The signal supplied to the input terminal 321 of FIG. 20 is directly supplied, and the output signal of the delay circuit 322 _n-1 of FIG. 20 is supplied to the input terminal 402 _n (n = 1, 2,..., N−1). You.
The signals obtained at the output terminals 401 _n (n = 0, 1,..., N−1) are used as tap coefficients as multiplication circuits 323 _{n in} FIG.
Is transmitted to

The error signal supplied to the input terminal 327 is
The signal is transmitted to the multiplication circuit 407. The multiplication circuit 407 multiplies the error signal by the step size μ, and transmits the result to all of the multiplication circuits 406 _{0 to} 406 _N−1 having the same number as the total number of taps. The multiplication circuit 406 _n (n = 0, 1,..., N−1)
The signal supplied from the multiplication circuit 407 is multiplied by the delay signal supplied via the terminal 402 _n , and the result is supplied to the addition circuit 405 _n . Adding circuit 405 _n transmits a signal supplied from the limiter circuit 434 _n, adds the signal supplied from the multiplier circuit 406 _n to the delay circuit 403 _n. The delay circuit 403 _n delays the signal supplied from the addition circuit 405 _n by one sampling cycle, and transmits the output signal to the limiter circuit 434 _n . Limiter circuit 434 _n
Is the signal received from the delay circuit 403 _n, performs limiter below in accordance with the coefficient maximum absolute value [Phi _n supplied from the constraints generation circuit 438. Results of the limiter operation is transmitted as a tap coefficient to the terminal 401 _n is supplied to the adding circuit 405 _n.

The limiter circuit 434 _n (n = 0, 1,...,
FIG. 7 shows an example of the input / output characteristics of N-1). Delay circuit 403
absolute value of the input signal received from the _n time is smaller than the coefficient maximum absolute value [Phi _n outputs the same signal as the input signal, the absolute value when the factor greater than the maximum absolute value [Phi _n of the input signal and the sign input signal A signal having the same absolute value as Φ _n is output.

FIG. 8 is a block diagram showing a fourth embodiment of the present invention. The difference between the third embodiment and the fourth embodiment is that
In the multi-input canceller circuit 13 is that the leakage adaptive filter 7 ₀ ~7 _M-1 in FIG. 5 is replaced with the norm constraining the adaptive filter 14 ₀ ~14 _M-1 in FIG. 8. This difference is the same as the difference between the first embodiment and the second embodiment.
The effect is the same.

FIG. 9 is a block diagram showing a fifth embodiment of the present invention. The difference between the first embodiment and the fifth embodiment shown in FIG. 1 is that in FIG. 9, the output of the spatial pass filter circuit 2 is shared as the output of the spatial pass filter circuit 3 in the spatial cutoff filter circuit group 12. That is. However, since the characteristics of the space-pass filter circuit 2 are shared with the space-pass filter circuit 3, not only the signal arriving from the vicinity of the specified direction is allowed to pass but also the signal arriving from the non-specified direction is attenuated. In the fifth embodiment, the space-pass filter circuit 3 can be omitted by sharing the space-pass filter, and there is an effect that the calculation amount and the hardware scale are reduced as compared with the first embodiment. According to the same principle, the second embodiment
With respect to 4 to 4, a configuration in which the space-pass filter circuit 3 and the space-pass filter circuit 2 are shared can be considered.

FIG. 10 is a block diagram showing a sixth embodiment of the present invention. The difference between the third embodiment and the sixth embodiment shown in FIG. 5 is that the spatial pass filter circuit 2 in the third embodiment is replaced with a configuration for directly outputting the output signal of one microphone. It is that you are. In the third embodiment, the output signal of the spatial pass filter circuit 2 is supplied as the input signal of the delay circuit 9, whereas in the sixth embodiment, the microphone l _{C is used} as the input signal of the delay circuit 9. The signal output from is supplied directly.
In the sixth embodiment, since the space-pass filter circuit 2 in the third embodiment is not required, there is an effect that the calculation amount and the hardware scale are reduced.

Incidentally, as the microphone l _C for supplying the input signal of the delay circuit 9, any _one of the microphones l _{0 to} l _M-1 can be used. For example, when M is an odd number, the microphone l _{((M-1) / 2)} can be used as the microphone l _C.

FIG. 11 is a block diagram showing a seventh embodiment of the present invention. The difference between the fourth embodiment and the seventh embodiment shown in FIG. 8 is that the space-pass filter circuit 2 in the fourth embodiment is replaced with a configuration for directly outputting the output signal of one microphone. It is that you are. In the fourth embodiment, the output signal of the spatial pass filter circuit 2 is supplied as the input signal of the delay circuit 9, whereas in the seventh embodiment, the microphone l _{C is used} as the input signal of the delay circuit 9. The signal output from is supplied directly.
This difference is the same as the difference between the third embodiment and the sixth embodiment, and the effect is the same.

According to the same principle, a configuration in which the spatial pass filter circuit 2 is replaced with a configuration for directly outputting the output signal of one microphone can be considered in the first or second embodiment.

FIG. 12 is a block diagram showing an eighth embodiment of the present invention. The difference between the third embodiment and the eighth embodiment shown in FIG. 5 is that the spatial pass filter circuit 3 in the third embodiment is replaced by a configuration for directly outputting the output signal of one microphone. It is that you are. In the third embodiment, the tap coefficients constraint adaptive filter group l5 ₀ ~l5
Space-pass filter circuit 3 as input signal common to _M-1
In the eighth embodiment, the signal output from the microphone l _C is directly supplied, whereas the output signal of the microphone l _C is supplied. In the eighth embodiment, since the spatial pass filter circuit 3 in the third embodiment is not required,
There is an effect that the amount of calculation and the hardware scale are reduced.

The tap coefficient constraint adaptive filter group 15
₀ As ~l5 _M-1 Microphone l _C supplies a common input signal, it is possible to use any of the microphone from the microphone l ₀ ~l _M-1. For example, if M is an odd number, microphone l _{C
((M-1) / 2)} can be used.

FIG. 13 is a block diagram showing a ninth embodiment of the present invention. The difference between the fourth embodiment and the ninth embodiment shown in FIG. 8 is that the space-pass filter circuit 3 in the fourth embodiment is replaced with a configuration for directly outputting the output signal of one microphone. It is that you are. In the fourth embodiment, tap coefficient constrained adaptive filter groups 15 _{0 to} 15
Space-pass filter circuit 3 as input signal common to _M-1
In the ninth embodiment, the signal output from the microphone l _C is directly supplied, whereas the output signal of the microphone l _C is supplied. This difference is the same as the difference between the third embodiment and the eighth embodiment, and the effect is the same.

According to the same principle, a configuration in which the spatial pass filter circuit 3 is replaced with a configuration for directly outputting the output signal of one microphone can be considered in the first or second embodiment.

FIG. 14 is a block diagram showing a tenth embodiment of the present invention. The sixth embodiment shown in FIG.
The difference from the sixth embodiment is that the spatial pass filter circuit 3 in the sixth embodiment is replaced with a configuration for directly outputting the output signal of one microphone. In the sixth embodiment, a tap coefficient constraint adaptive filter group 15 ₀
While the output signal of the spatial pass filter circuit 3 is supplied as an input signal common to ~ 15 _M-1 , the signal output from the microphone l _C is directly supplied in the tenth embodiment. I have. In the tenth embodiment,
Since the space-pass filter circuit 3 in the sixth embodiment is not required, the effect of further reducing the calculation amount and the hardware scale is produced.

The tap coefficient constraint adaptive filter group 15
₀ as a microphone for supplying a common input signal to ~l5 _M-1, it can be any microphone from the microphone l ₀ ~l _M-1. In Figure 14, a microphone for supplying a common input signal to the tap coefficients constraint adaptive filter group l5 ₀ ~l5 _M-1, the microphone provides an input signal of the delay circuit 9, by using a common microphone l _C However, different microphones can be used.

FIG. 15 is a block diagram showing a twelfth embodiment of the present invention. The seventh embodiment shown in FIG.
The difference from this embodiment is that the spatial pass filter circuit 3 in the seventh embodiment is replaced with a configuration for directly outputting the output signal of one microphone. This difference is the same as the difference between the sixth embodiment and the tenth embodiment, and the effect is the same.

According to the same principle, in the first or second embodiment, the space-pass filter circuit 2 is replaced by a configuration for directly outputting the output signal of one microphone, and the space-pass filter circuit 3 is replaced by a single microphone. A configuration in which the output signal is directly output can be considered.

In the above, the embodiment of the present invention has been described with respect to the case where the microphone arrangement is a straight line and the specified direction is orthogonal to the microphone arrangement line. However, even when the microphone arrangement and the specified direction are different. The characteristics of the filter circuits 202 _{0 to} 202 _M-1 in the spatial pass filter circuit 2 are designed so as to pass the signal arriving from the prescribed direction, and the spatial cutoff filter circuit group 12 is designed to block the signal arriving from the prescribed direction. By designing, it is possible to cope with the same configuration in principle.

In addition, even if the microphone characteristics and the amplifier circuits of the microphones are different from one another, the same configuration can be used in principle by changing the characteristics of the space pass filter circuit 2 and the space cutoff filter circuit group 12. .

Further, even when the position of the signal source is not sufficiently far from the microphone array and the wavefront of the signal is not a plane wave, the microphone arrangement can be changed, and the spatial pass filter circuit 2 and the spatial cutoff filter circuit group 12 can be properly adjusted. By designing, it is possible to cope with the same configuration in principle.

In the above description, only an FIR type filter is used as a filter circuit such as an adaptive filter. However, other filter circuits such as an IIR type and a lattice type can be realized.

While the microphone array has been described as an example, the present invention can be applied to an antenna array and the like based on the same principle. Further, many algorithms other than the LMS algorithm used as an example can be applied to the tap coefficient updating algorithm.

[0102]

As described above, according to the present invention,
Even when there is an error between the arrival direction of the target signal and the specified direction, signal reception with little deterioration of the target signal can be performed with a small number of sensors.

[Brief description of the drawings]

FIG. 1 is a first embodiment of the present invention.

FIG. 2 is a second embodiment of the present invention.

FIG. 3 is a block diagram illustrating an example of a norm-constrained tap coefficient updating circuit in the norm-constrained adaptive filter of FIG. 2;

FIG. 4 is an example of a block diagram of a constraint control coefficient generation circuit in FIG. 3;

FIG. 5 is a third embodiment of the present invention.

6 is a block diagram of a tap coefficient constrained tap coefficient updating circuit in the tap coefficient constrained adaptive filter of FIG. 5;

FIG. 7 is a graph showing an example of input / output characteristics of the limiter circuit in FIG. 6;

FIG. 8 is a fourth embodiment of the present invention.

FIG. 9 is a fifth embodiment of the present invention.

FIG. 10 is a sixth embodiment of the present invention.

FIG. 11 is a seventh embodiment of the present invention.

FIG. 12 is an eighth embodiment of the present invention.

FIG. 13 is a ninth embodiment of the present invention.

FIG. 14 is a tenth embodiment of the present invention.

FIG. 15 is an eleventh embodiment of the present invention.

FIG. 16 is a block diagram showing a configuration of a conventional example.

FIG. 17 is an example of a block diagram of a space-pass filter circuit in FIG. 16;

18 is an example of a block diagram of the filter circuit in FIG.

19 is a block diagram showing a configuration example of a spatial cutoff filter in FIG.

FIG. 20 is a block diagram illustrating an example of a leak adaptive filter in FIG. 16;

FIG. 21 is a block diagram illustrating an example of a tap coefficient updating circuit with leakage.

[Explanation of symbols]

_{1 0} ~1 _M-1 microphone 2,3 spatial pass filter circuit 4 ₀ ~4 _M-1, 9 delay circuits _{5 0 ~5 M-1, 7} 0 ~7 M-1 leak adaptive filter 6 ₀ to 6 _{M- 1} , 10 Subtraction circuit 8 Addition circuit 11 Output terminal 12 Spatial cutoff filter circuit group 13 Multi-input canceller circuit 14 _{0 to} 14 _M-1 norm constrained adaptive filter 15 ₀ to 15 _M-1 Tap coefficient constrained adaptive filter 201 _{0 to} 201 _{M -1} microphone signal input terminal 202 _{0 to} 202 _M-1 filter circuit 203 addition circuit 204 spatial filter output terminal 301, 321 input terminal 302 _{0 to} 302 _G-2 , 322 _{0 to} 322 _L-2 delay circuit 303 _{0 to} 303 _{G -1,} 323 _{0 ~323 L-1} multiplier circuits 304, 324 adder circuits 305, 325 output terminals 306 tap coefficient memory circuit 326 tap coefficient updating circuit 327 error signal input terminal 40 ₀ to 401 _L-1 delay signal input terminals 402 ₀ ~402 _L-1 tap coefficient output terminal 403 ₀ ~403 _L-1 delay circuits 405 ₀ ~405 _L-1 addition circuit _{406 0 ~406 L-1, 409} 0 ~ of 409 _L-1 multiplier circuits 407,424 ₀ ~424 _L-1 multiplier circuits 434 ₀ ~434 _N-1 limiter circuit 428 restraining control coefficient generation circuit 438 constraints generating circuit 501 ₀ ~501 _L-1 signal from the adder circuit Input terminal 502 Constraint control coefficient output terminal 503 _{0 to} 503 _L-1 p-th power circuit 504 Addition circuit 505 p-th root circuit 506 Division circuit 507 Norm constraint value input terminal 508 Minimum value selection circuit 509 Constant input terminal 510 p-th norm calculation circuit 901 ₀ ~901 _M-1 microphone signal input terminal 905 ₀ ~905 _MQ spatial cutoff filter circuit output terminal _{906 m, Q (m = 0,1} , ..., MQ, q = 0,1
…, Q-1) Filter circuit 907 _{0 to} 907 _MQ adder circuit

Claims (6)

(57) [Claims] 1. A plurality of sensors arranged at spatially different positions, and a group of output signals from the plurality of sensors, each of which is filtered and added, so that a signal arriving from a predetermined direction is obtained. A first space-pass filter circuit having directivity to pass the signal; a first delay circuit for receiving and delaying an output signal of the first space-pass filter circuit; and a plurality of signals newly output from the plurality of sensors. A plurality of spatial cutoff filter circuits, each of which is selected from the sensor outputs, and is filtered and added, thereby blocking only a signal arriving from a predetermined direction. A first leak adaptive filter group consisting of a plurality of leak adaptive filters for receiving and filtering the output signal in a one-to-one manner; An adder circuit for calculating the sum of output signals of the leak adaptive filter group; subtracting the sum calculated by the adder circuit from the output signal of the first delay circuit, outputting a subtraction result as a received signal, And a first subtraction circuit that transmits a common coefficient update error signal to all of the first leak adaptive filter groups. An adaptive array device using a generalized side lobe canceller, A second spatial pass filter circuit having directivity such that a signal coming from a direction defined in advance is passed by receiving and filtering the output signal groups from the plurality of sensors and adding them, A second delay circuit for receiving and delaying the output signal of the sensor of the first one-to-one basis, and an output signal of the second space-pass filter circuit A second leak adaptive filter for receiving and filtering, and a leak adaptive filter that supplies a signal for subtracting an output signal of the second leak adaptive filter from an output signal of the second delay circuit, and subtracting a result of the subtraction. And a second subtraction circuit that transmits the error signal for updating the coefficient to the second spatial pass filter circuit. The second spatial pass filter circuit configuring the spatial cutoff filter circuit is shared by all of the spatial cutoff filter circuits. An adaptive array device characterized by the above-mentioned. 2. A group of norm-constrained adaptive filters for controlling tap coefficients such that the norm of tap coefficients of each filter is equal to or smaller than a positive constant determined for each filter, instead of the first leak adaptive filter group. The adaptive array device according to claim 1, wherein: 3. A tap coefficient constrained adaptive filter group in which a change range of a tap coefficient of a filter is limited to a range determined for each tap, in place of the second leak adaptive filter group. The adaptive array device according to claim 1. 4. The adaptive array device according to claim 1, wherein said first space-pass filter circuit and said second space-pass filter circuit are shared. 5. The first space-pass filter circuit according to claim 1,
The adaptive array device according to claim 1, 2 or 3, wherein a configuration for outputting only one sensor signal among the plurality of sensors is used. 6. The second spatial pass filter circuit,
The adaptive array device according to claim 1, 2, 3, or 5, wherein a configuration for outputting only one sensor signal among the plurality of sensors is used.