JPH0263225A - Echo controller - Google Patents

Abstract

PURPOSE:To avoid a broken signal line and to prevent the occurrence of intermission or cut-off of speech head or speech tail by erasing a detouring signal only. CONSTITUTION:A detouring signal is a pseudo reception signal in an adaptive filter 110. n-Set of transmission signals are stored in n-stage of shift registers 20, the inverse characteristic of an impulse response of an echo path is stored in a shift register 21, a multiplier 40 and an accumulator 30 convolute signals and the echo is suppressed by subtracting a reception signal delayed by n-stage from the pseudo reception signal at a shift register 22. The output of a subtractor 51 is divided by the power of a transmission input via a power calculation section 72 and a reciprocal computing element 60 at a multiplier 42 and the content of the shift register 21 is corrected. Thus, the occurrence of intermission or cut-off of speech head or speech tail is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an echo control device, and particularly to a control device for echoes generated by 2114 line conversion or the like.

[Prior Art] Conventionally, as a method for controlling this type of echo, an echo canceler is used that generates a pseudo echo signal through an adaptive filter based on a received input signal, and subtracts it from the transmitted input to cancel the echo. There is.

[Problems to be Solved by the Invention] As shown in FIG. 2, in the two-wire/four-wire converter 90, a signal input to the two-wire input/output terminal 1 is transmitted to the transmission output terminal 2, and is input to the reception input terminal 3. If the transmitted signal is completely transmitted to the two-wire input/output terminal 1 and there is nothing that goes around to the transmission output terminal 21, the echo control device 100 is no longer necessary.

However, in reality, the impedance matching of the converting section is often insufficient, and there is a drawback that the signal input to the receiving input terminal 3 goes around to the transmitting output terminal 2.

Echo suppressors are available as a solution to these drawbacks. However, since the echo suppressor cuts Route 02, it has the drawback of causing jerks and truncations at the beginning and end of speech.

The purpose of the present invention is to eliminate these drawbacks of the conventional ones,
Without cutting the signal path, there are
An object of the present invention is to provide an echo control device that does not cause word endings to be cut off.

[Means for Solving the Problems] According to the present invention, there is provided a first n-stage shift register that holds n continuous time transmission input signals, and a second shift register that holds inverse characteristics of the transfer function of the echo path. an n-stage shift register; a first input signal that switches between the latest transmission human input signal and the output of the first shift register;
a first multiplier that multiplies the output of the first shift register and the output of the second shift register; an accumulator that cumulatively adds n outputs of the first multiplier; a third 0-stage shift register that holds the input signal; a subtracter that subtracts the output of the third shift register from the output of the accumulator to obtain a transmission output signal; a first power calculation unit that calculates a multiplicative sum; a reciprocal calculation unit that calculates the reciprocal of the output of the first power calculation unit; and a second multiplier that multiplies the output of the subtracter and the output of the reciprocal calculation unit. , a second switch that switches between the output of the second multiplier and a zero signal, a third multiplier that multiplies the output of the second switch and the output of the first shift register, and the third multiplier. an adder that adds the output of the first multiplier to the output of the multiplier of
a third power calculation unit that calculates the sum of squares of the latest n pieces of the transmission output signal, and a third power calculation unit that compares the outputs of the second and third power calculation units. There is obtained an echo control device characterized in that it includes a comparator that switches the second switch to a zero signal when the output of the second switch is larger.

〔Example] Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a block diagram of an embodiment of the present invention, and FIG. 2 is a diagram showing the basic configuration of the present invention for explaining its operation.

In FIG. 1, 20 is a first n-stage shift register that holds n continuous time transmission input signals, 21 is a second n-stage shift register that holds the inverse characteristic of the transfer function of the echo path, and 10 switches the latest transmitted human input signal and the output of the first shift register 20, and switches the output of the first shift register 20.
40 is a first multiplier that multiplies the output of the first shift register 20 and the output of the second shift register 21; 30 multiplies the output of the first multiplier 4o by n times; an accumulator that performs cumulative addition; 22 is a third n-stage shift register that holds the received input signal; 51 is a subtracter that subtracts the output of the third shift register 22 from the output of the accumulator 30 to obtain a transmission output signal; 72 is the latest n number 2 of the transmission input signal
60 is a reciprocal calculator that calculates the reciprocal of the output of the first power calculator 72; 42 is a second power calculator that multiplies the output of the subtracter 51 and the output of the reciprocal calculator 60; a multiplier; 11 is a second switch that switches between the output of the second multiplier 42 and a zero signal; 41 is a third multiplier that multiplies the output of the second switch 11 and the output of the first shift register 20; 50 is an adder that adds the output of the first multiplier 40 to the output of the third multiplier 41; 71 is a second power calculation unit that calculates the sum of squares of the latest n received input signals; 70
80 is a third power calculation unit that calculates the latest sum of squares of n transmission output signals, and 80 compares the outputs of the second and third power calculation units to calculate the output of the third power calculation unit. When the larger
This is a comparator that switches the second switch to a zero signal.

In FIG. 2, the wrap-around of the two-wire/four-wire converter is a linear conversion, so the wrap-around signal y (z) is expressed as follows.

Y (Z) ---I((Z) -X (Z)
(1) The wrap-around signal becomes a pseudo reception signal (Z) in the adaptive filter 110.

Father (Z) -G (Z) -Y (Z)
(2) Therefore, the residual signal E (Z) is E (Z) - Father (Z) - Z" X (Z)
(3) −(Z) −H(Z) X(Z) −Z”
It becomes X(Z) (4). To obtain E(Z)-0, ``go +g-, z-++... (
5) By approximating the valve Σ g+ 2', the adaptive filter becomes a finite-order impulse response.

From FIG. 1, the n-stage shift register 20 has y(1),
...y (1-n+1) n transmission signals are stored, the inverse characteristic G (Z) of the impulse response of the echo path is stored in the shift register 21, and the multiplier 40 and the accumulator 3
Y (1) and g (1) are convolved at 0, and father (1) - Σ g (1) ・ y (1 - j)
(7)”+0. The echo is suppressed by subtracting the received signal delayed by n stages in the shift register 22 from the pseudo received signal determined by equation (7).

e (i) = '2 (i) - χ (i - ++)
(8) The output of the subtracter 51 is the power calculation unit 72,
The multiplier 42 divides the power of the transmission input that has passed through the reciprocal calculator 60, and the contents of the shift register 21 are modified as follows.

g (D −g (D+ “°e(i) °Y(toha(j −0...n)) (9) Also, the contents of the shift register 21 only need to be updated when there is a signal at the receiving input. Therefore, the receiving power level and the transmitting output level are calculated by the power calculation units 70 and 71, double talk is detected by the comparator 8o, and the stop of correction is controlled.

[Effects of the invention] As explained above, the present invention eliminates only the wrap-around signals and does not cut the signal path like an echo suppressor, so it has the effect of not causing jitter or cutting at the beginning or end of a speech. be.

41.42: Multiplier, 50, 51: Adder, 60: Reciprocal calculator, 70, 71.72: Power calculation unit, 80: Comparator, 90: Two-wire four-wire converter, 100: Echo control device, 1
10: Adaptive filter.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG. 2 is a diagram showing the principle of the present invention.

Claims (1)

[Claims] 1, a first n holding n continuous time transmit input signals
a second n-stage shift register that maintains an inverse characteristic of the transfer function of the echo path; and switching the latest transmission input signal and the output of the first shift register to the first shift register. a first switch for input; a first multiplier that multiplies the output of the first shift register and the output of the second shift register; and an accumulation that cumulatively adds n outputs of the first multiplier. a third n-stage shift register for holding the received input signal; a subtracter for subtracting the output of the third shift register from the output of the accumulator to obtain a transmission output signal; a first power calculation unit that calculates the sum of squares of n pieces; a reciprocal calculation unit that calculates the reciprocal of the output of the first power calculation unit; and a second power calculation unit that multiplies the output of the subtracter and the output of the reciprocal calculation unit. a multiplier; a second switch that switches between the output of the second multiplier and a zero signal;
a third multiplier that multiplies the output of the second switch by the output of the first shift register; an adder that adds the output of the first multiplier to the output of the third multiplier; a second power calculation unit that calculates the latest n sums of squares of the input signals; and a third power calculation unit that calculates the latest n sums of squares of the transmitted output signals.
and a comparator that compares the outputs of the second and third power calculation units and switches the second switch to a zero signal when the output of the third power calculation unit is larger. An echo control device characterized by: