JPH04207635A - Two-way talking detection circuit for echo canceler - Google Patents

Abstract

PURPOSE:To reduce a tide required for discriminating a level of a signal at 2-way talking by providing a control circuit which controls a variable attenuator, discriminates an output of a comparator circuit and stops the estimate operation of an echo canceler or releasing the stop to the detection circuit. CONSTITUTION:A reception signal is attenuated by a variable attenuation circuit 90 and when no RT signal exists, the attenuation is 0dB. An Rout signal is stored at any time for M times by a 1st storage circuit 40 and a 1st power measurement circuit 100 converts a signal for M times newest into power. A Sin signal is stored at any time for M times by a 2nd storage circuit 41, a signal for newest M times is converted into power by a 2nd power measurement circuit 101, and a division circuit 30 divides an output of the power measurement circuit 100 with an output of the power measurement circuit 101, an output of the division circuit 30 is averaged for N times by an averaging circuit 50 and the output of the averaging circuit 50 and the output of the division circuit 30 are compared by a comparator circuit 60. When a value subtracting the result of averaging from the result of division is smaller than a negative value, the comparator circuit 60 estimates it to be in the 2-way talking state. Thus, the 2-way talking state is detected in a shorter time.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an echo canceler that cancels echoes caused by impedance mismatching of a hybrid transformer, and more particularly to a two-way conversation detection circuit of the echo canceller.

A conventional echo canceller makes the 5out signal zero by estimating the impulse response of the echo path in the absence of the RT multiplication signal (transmitted signal of the receiving side speaker). The presence of the RT multiplied signal interferes with the estimation. Therefore, a two-way call detection circuit is used that detects a state where the RT double signal is present, that is, a two-way call state, and stops the estimation operation. In echo cancellers for telephone lines, there is usually a loss of 6 dB or more due to the noise margin of the communication channel. Therefore, when there is no RT double signal, the 'Sin signal is Rout
It becomes 6dB or more smaller than the signal.

On the other hand, during two-way communication, the Rout and Sin signals are approximately equal. This is used to detect the state of two-way communication.

Specifically, as shown in Figure 2, Rout, Sin, 5
Level measurement circuit 35.36.37 to measure the level of out signal
Find it by Using the results, the determination circuit 45 compares the power of each signal.

If it is determined that there is a two-way conversation, the estimation operation is stopped to prevent the estimation from being disturbed.

Problems to be Solved by the Invention In the conventional method, since there are variations in the magnitude of the Rout, Sin, and 5out signals, an average is taken to determine the magnitude. Therefore, there is a problem that it takes time to determine that a two-way conversation is occurring, which interferes with the estimation and deteriorates echo cancellation.

The present invention has been made in order to solve the above-mentioned problems inherent in the conventional technology, and therefore, an object of the present invention is to provide a novel two-way call detection circuit that makes it possible to shorten the time required for this determination. It's about submitting.

Means for Solving the Problems In order to achieve the above object, the two-way conversation detection circuit of the echo canceller according to the present invention estimates the echo of the received input signal to the transmitted input signal using an adaptive FIR type filter, and In an echo canceller capable of subtracting an estimated echo from an input signal to obtain a transmission output signal and stopping the estimation, a variable attenuator outputs a reception input signal to a reception input of the echo canceller, and a reception output of the echo canceller is divided into M times. a primary storage circuit for storing, a primary power measurement circuit for measuring the power of the output of the primary storage circuit, a secondary storage circuit for storing M transmission inputs of the echo canceller; a secondary power measurement circuit that measures the power of the output of the storage circuit; a division circuit that divides the output of the primary power measurement circuit by the output of the secondary power measurement circuit; and an average of the outputs of the division circuit. an averaging circuit that compares the output of the dividing circuit with the output of the averaging circuit; and a comparator circuit that controls the variable attenuator and determines the output of the comparator circuit to stop the estimation operation of the echo canceller. and a control circuit for canceling the stoppage.

Embodiment Next, a preferred embodiment of the present invention will be specifically explained with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of an echo canceller two-way call detection circuit according to the present invention.

Referring to FIG. 1, the received signal is attenuated by a variable attenuation circuit 90 ranging from OdB to several dB. When there is no RT-fold signal, the attenuation amount is OdB. The Rout signal is stored M times by the first storage circuit 40 at any time. The latest M signals are converted into power by the first power measurement circuit 100. Sin
The signal is stored M times by the second storage circuit 41 at any time.

The latest M signal is converted into power by the second power measurement circuit 101. A division circuit 30 divides the output of the power measurement circuit 100 by the output of the power measurement circuit 101, and an averaging circuit 50 averages the output of the division circuit 30 N times. This averaging circuit 5
The output of 0 and the output of the division circuit 30 are compared by a comparison circuit 60.

When the value obtained by subtracting the average result from the division result becomes smaller than a certain negative value, the comparator circuit 60 estimates that a two-way conversation is occurring.

(1) 2-impulse response estimation operation stop process control circuit 70
receives a signal from the comparison diagram F#I60 indicating that a two-way conversation is in progress, and stops the estimation operation of the echo canceller 80. At the same time, the control circuit 70 sets the amount of attenuation of the variable attenuation circuit 90 to a certain value. By doing so, if the value of the comparison circuit 60 becomes a smaller negative value, it is determined that the RT multiplication signal exists, that is, a two-way communication state is established. If it is determined that a two-way conversation is occurring, the estimation operation of the echo canceller 80 continues to be stopped.

(2) Impulse response estimation operation stop cancellation process If the result of the comparison circuit 60 returns to the original value when it is estimated to be in a two-way communication state, it is determined that there is no RT multiplication signal, and the control circuit 70 cancels the estimation operation stop and sets the reduction/representation of the variable attenuation circuit 90 to OdB.

When it is determined that a two-way communication is in progress (at this time, the result of the comparison circuit 60 is spread over the area above and below centering on O), when the RT multiplication signal disappears, the result of the division circuit 30 becomes larger. , the result of the comparison circuit 60 will touch a positive value and approach its f&O. The control circuit 70 determines this process,
The estimated operation of the echo canceller 80 is canceled.

As described in detail, according to the present invention, it is possible to detect a two-way conversation state in a shorter time, and it is possible to suppress deterioration in the amount of echo cancellation caused by a two-way conversation state.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing one embodiment of the present invention, and FIG.
The figure is a block diagram showing a conventional two-way call detection circuit. 5.15... Receiving side speaker, 10.25... Hybrid transformer, 30... Division circuit, 35.36.37.
・Level measurement circuit, 40. 41.. Memory circuit, 45. Judgment circuit, 50.. Averaging circuit, 60 Comparison circuit, 70
...Control circuit, 55.8C1...Echo canceller, 90...Variable attenuation circuit, 100.101...Power measurement circuit Patent applicant NEC Corporation

Claims (1)

[Claims] An echo canceler that can estimate the echo of the received input signal into the transmitted input signal using an adaptive FIR type filter, subtract the estimated echo from the transmitted input signal, and stop the estimation of the transmitted output signal. a variable attenuator that outputs to the reception input of the canceller; a primary storage circuit that stores M reception outputs of the echo canceller; and a primary power measurement circuit that measures the power of the output of the primary storage circuit. , a secondary storage circuit that stores M transmission inputs of the echo canceller; a secondary power measurement circuit that measures the power of the output of the secondary storage circuit; a division circuit that divides the output of the primary power measurement circuit; an averaging circuit that averages the output of the division circuit; a comparison circuit that compares the output of the division circuit with the output of the averaging circuit; and the variable attenuation circuit. 1. A two-way call detection circuit for an echo canceller, comprising a control circuit that controls the echo canceller and judges the output of the comparison circuit to stop or release the estimated operation of the echo canceller.