JPH02112326A - Echo canceller controller - Google Patents

Abstract

PURPOSE:To prevent the disturbance of an echo paths model part and to cancel an echo even when an excessive signal is inputted by controlling the echo cancel ler so as to stop the correction of the echo path model part when a speech receiving signal level has possibility to exceed the excessive load level of the echo path. CONSTITUTION:An echo canceller controller consists of a reception signal level measuring circuit 1, a deciding circuit 2 and a control circuit 3. The deciding circuit 2 compares the reception signal level measured by the receiving signal level measuring circuit 1 with a threshold level set beforehand. By the compari son, when the reception signal is inputted to an echo path, and the presence of the possibility to cause excessive load distortion is decided, the output of an echo path characteristic measuring part 11 of an echo canceller 10 is con trolled, and the correction of an echo path model part 12 of the echo canceler 10 is stopped. Thus, even when the excessive signal is inputted, the echo canceler 10 can be controlled so as to sufficiently cancel the echo.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an echo canceller control device that controls an echo canceller used in a communication line.

[Conventional technology]

In recent years, the presence of echoes that occur in long-distance communication lines, especially in long-distance communication lines due to the rapid increase in satellite 1111 signals, has increased.
Due to the large amount of line delay, it poses a major problem in terms of call quality. Conventionally, echo suppressors have been used to control echoes, but since they are based on switching operations, they have had the problem of causing disturbances such as disconnection at the beginning of speech and click noise. Echo cancellers were developed to solve this problem.

An example of such an echo canceller is shown in FIG. This echo canceller 10 is used with an echo path 20 connected between a receive signal output terminal 15 and a transmit signal input terminal 16. The echo canceller 10 has an echo path model section 12 having an adaptive filter (echo path model) therein. Based on the call signal, the characteristics from the receive signal output terminal 15 to the send signal input terminal 16 are measured by the echo path characteristic measuring section 11, and the echo path model section 2 is adjusted to the measured echo path characteristics. By passing the received signal through this echo path model section 12, a pseudo echo that approximates the echo signal is created, and this pseudo echo is subtracted from the actual echo signal.
Echo is canceled.

The receiving signal input terminal 1 of such an echo canceller 10
The reception signal inputted from 4 is sent to the reception signal output terminal 15 and simultaneously sent to the echo path model section 12. The signal output from the receive signal output terminal 15 passes through the echo path 20 and is input as an echo to the transmit signal input terminal 16 of the echo canceller 10.

On the other hand, by passing the received signal input to the echo path model section 12 through an adaptive filter having the same characteristics as the echo path 20, a false echo identical to the echo input to the transmit signal input terminal 16 is obtained. This pseudo echo is subtracted by the subtractor 13 from the actual echo signal input from the transmit signal input terminal 16. As a result, the transmitted signal whose echo has been canceled by the subtractor 13 is outputted from the transmitted signal output terminal 17.

[Problem to be solved by the invention]

When an excessive signal is input to the reception signal input terminal of the conventional echo canceller described above, nonlinear distortion will occur in the echo path if there is a device with a small overload margin in the echo path. That is, when an excessive signal that causes a signal to clip is applied to the input of a conventional echo canceller, this clipped signal causes waveform distortion on the echo path, exceeding the overload level of the echo path and generating nonlinear distortion. However, since the echo canceller has an internal linear filter to cancel echoes on the assumption that the echo path characteristics are a linear system, when nonlinear distortion occurs, the echo canceller operates as if noise were input to the echo path. That is, as a result of the occurrence of this nonlinear distortion, the error in the measurement result of the echo path characteristic measuring circuit becomes large, the operation of the echo path characteristic measuring circuit is disturbed, and it becomes impossible to measure the echo path characteristic satisfactorily. As a result, the characteristics of the echo path model are disturbed, and there is a drawback that the echo cannot be canceled sufficiently.

SUMMARY OF THE INVENTION An object of the present invention is to provide an echo canceller control device that eliminates such drawbacks and controls an echo canceller so that even if an excessive signal is manually applied to the echo canceller, the echo can be sufficiently canceled.

[Means to solve the problem]

The present invention includes an echo path characteristic 1111tll foot section that measures the characteristics of an echo path, and an echo path model section that corrects the echo path model based on the measurement to match the echo path, and outputs a received signal to the echo path. An echo canceller control device for controlling an echo canceller, comprising: a measuring means for measuring a level of a received signal input to the echo canceller; and a determination as to whether the received signal is an excessive signal based on the level measured by the measuring means. The present invention is characterized by comprising a determining means, and a control means for controlling the echo path characteristic measuring section to stop modification of the echo path model section when the determining means determines that the received signal is an excessive signal.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing one embodiment of the present invention.

This embodiment is used by being connected to an echo canceller 10 similar to that shown in FIG.

This echo canceller control device is comprised of a received signal level measuring circuit 1, a determination circuit 2, and a control circuit 3.

In the echo canceller control device having such a configuration,
The received signal level measuring circuit 1 uses a received signal inputted to the receiving side input terminal 14 of the echo canceller 10 as a human input signal. The received signal level measuring circuit 1 constantly measures the level of the received received signal.

The determination circuit 2 compares the received signal level measured by the received signal level circuit 1 with the threshold 1 hold level that has been set as a diagonal. The threshold level of , ゛, is a value like the 9th order.

In other words, if there is a possibility that nonlinear distortion will occur when a received signal of a level higher than J-' is inputted to the echo path 20 via the canceller 10, the value corresponding to this level is set to It is set as a hold level. Judgment circuit 2ba1. Through this comparison, it is determined whether or not there is a possibility that when the received signal level is input to the echo path 20 and causes waveform distortion, the overload of the echo path 20 exceeds one novel level and nonlinear distortion occurs.

The control unit 3 controls the output of the echo path characteristic measuring unit 11 of the echo canceller IO when the second determination circuit 2 determines that there is a possibility of causing overload distortion when the received signal causes waveform distortion in the echo path. °ζ, echo canceller 1
The modification of the echo path model section 12 of 0 is stopped.

Next, the operation of this embodiment will be explained.

The received signal input to the receiving side input terminal 14 of the echo canceller 10 is simultaneously input to the received signal level measuring circuit 1 of the echo canceller control device of this embodiment. The level of the received voice (No. 13) is constantly measured.The determination circuit 2 compares the received voice signal level measured by the received voice signal level measurement circuit 1 with the preset threshold 1 hold level, and determines the next level. In other words, the receiving signal output from the receiving side output i of the echo canceller 10:Ai 15 is input to the echo path 20 and causes waveform distortion, exceeding the overload level of the echo path 20. Determine whether there is a possibility of nonlinear distortion occurring. Determination circuit 2
If it is determined that there is a possibility of nonlinear distortion occurring when the received signal causes waveform distortion in the echo path, the control circuit 3 controls the echo path characteristic measuring section 11 of the echo canceller 10 based on this determination. Furthermore, this control 11
Accordingly, the echo path characteristic measuring section 11 controls the echo path model section 12 to stop the modification of the value of the adaptive filter in the echo path model section 12. The echo path model section 12 stops correcting the value of the adaptive filter and sets it to the value of the adaptive filter before overload distortion occurs. can be excluded.

Then, in the subtraction unit 13, sufficient echo cancellation can be performed.

In this way, according to this embodiment, when the received signal level is input to the echo path and waveform distortion occurs in the echo path, there is a possibility that the overload level of the echo path will be exceeded.
Since the echo canceller is controlled to stop modifying the echo path model section, disturbances in the echo path model section can be prevented, and even if an excessive signal is input, echoes can be sufficiently canceled.

〔Effect of the invention〕

As explained above, according to the present invention, there is an effect that the echo canceller can be controlled so that even if an excessive signal is input, the echo can be sufficiently canceled.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG. 2 is a block diagram showing an example of an echo canceller. 1 ・ ・ ・ 2 ・ ・ ・ 3 ・ ・ 10 ・ ・ 11 ・ ・ 12 ・ 13 ・ ・ 20 ・ ・ Received signal level measurement circuit Judgment circuit Control circuit Echo canceller Echo path characteristic measurement section Echo path model part subtraction part echo path

Claims (1)

[Claims] (1) An echo path characteristic measurement unit that measures the characteristics of an echo path, and an echo path model unit that corrects the echo path model based on the measurement to match the echo path, and controls an echo canceller that outputs a received signal to the echo path. An echo canceller control device, comprising: measuring means for measuring the level of a received signal input to the echo canceller; and determining means for determining whether the received signal is an excessive signal based on the level measured by the measuring means. and control means for controlling the echo path characteristic measuring section to stop correction of the echo path model section when the received signal is determined to be an excessive signal by the determining means. Device.