JP3016312B2 - Nonlinear processor control circuit of echo canceller - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-linear processor control (NLP) circuit of an echo suppressor used for satellite communication or conference telephone.

[0002]

2. Description of the Related Art On the signal receiving side, an echo suppressor is used to cancel a received signal sneaking into a transmission signal side due to impedance mismatch of a hybrid transformer, that is, to cancel an echo. This circuit is provided on the signal side, and suppresses a signal which is not completely canceled by the echo canceller at the time of single talk (there is no signal on the transmitting side), that is, a signal for suppressing a residual signal.

Conventionally, the NRP of this type of echo canceller
The circuit has the configuration shown in FIG. In FIG. 3, the transmission signal of the transmission-side speaker 21 passes through the hybrid transformer 22, becomes the transmission input signal 201, passes through the echo canceller main body 23, becomes the transmission output signal 202, and enters the NRP circuit side. Here, the transmission signal is through, but the residual signal of the echo is further suppressed and transmitted as an output signal 203 to the transmission line side.

[0004] The received input signal 204 from the transmission path side is NR
At the same time as the level is detected by the P circuit 24 and the echo canceller main body 23, the signal is transmitted to the transmitting speaker 21 through the hybrid transformer 22. When the signal passes through the hybrid transformer 22, the signal is wrapped around due to impedance mismatch with the speaker 21 on the transmitting side, that is, an echo 205 is generated and the input signal 204 is wrapped around to the transmitting side. The echo suppressor main body 23 estimates the echo by an adaptive FIR filter with reference to the reception input signal 204 and the transmission output signal 202, and cancels the estimated echo by subtracting the estimated echo from the transmission input signal 201. However, the echo cannot be completely canceled. The residual signal is output as a transmission output signal 202.

Next, the operation of the NLP circuit 24 will be described. First, a first stage is to detect a state in which single talk and echo have been canceled, and a second stage is to suppress a residual signal and use it as a transmission output signal in that state.
In this first stage, a certain time-averaged level measurement of the received input signal 204 (referred to as the RIN signal) is performed by the level measuring circuit 30, which includes the transmitted output signal 202, in this case a residual signal (referred to as the E signal). The time-averaged level measurement is performed by the level measurement circuit 27, and the level is determined.
When the N signal is higher than a certain level and the E signal is lower than a certain level, the level determination circuits 28 and 29 determine the state in which single talk and echo have been canceled, respectively. In the second stage, the switching circuit 26 switches whether the E signal is suppressed by the suppression circuit 25 and transmitted as the output signal 203 or whether the E signal is transmitted without being suppressed without being suppressed based on the determination in the first stage.

[0006]

In the conventional method, the suppression of the residual signal is limited to the time of single talk and the echo cancellation state. For example, line noise or room noise from the transmitting side speaker is included in the transmission input signal. When there is such a component, after the single talk and echo cancellation state, when both the reception signal and the transmission signal become silent, this noise component becomes the transmission output signal. The transmission output signal replaces the signal in which the residual signal is suppressed with the signal in which the noise component remains, giving the listener a sense of incongruity and deteriorating the communication quality. Also, during a two-way call (a state in which a received signal and a transmitted signal are interlaced), the state of single talk and echo cancellation may be interrupted, which also has the problem of deteriorating call quality.

[0007]

Means for Solving the Problems] nonlinear processor control circuit of the echo canceller of the present invention, sends the No. receiving Sing Sing
Shin output signal feed a residual signal by subtracting the estimated echo and the estimated from the feed No. Sing Sing estimated by the adaptive FIR type filter with reference to the Sing Sing Nos feed and No. receiving Sing Sing echo sneaking into signal side A suppression circuit for inputting the transmission output signal of the echo canceller unit and outputting the transmission output signal as a predetermined level ;
The input level is higher than the reference value, which is higher than the reference value.
If the threshold is less than "1",
“0” is “2” when it is between the two high and low reference values.
A first level detector for outputting a first switching signal, the inputs receiving Sing Sing No. and with said transmission output signal detects the level difference this level difference is larger than a predetermined reference value to
A second level detection unit that outputs a second switching signal, which is set to “0” when it is smaller and “1” when it is smaller, and an output of the suppression circuit.
A signal and the transmission output signal, the first switching signal
And the second switching signal, and the first switching signal is
In the case of "1", regardless of the value of the second switching signal,
And outputs the transmission output signal, and the first switching signal is "0".
In the case, the suppression circuit is independent of the value of the second switching signal.
Output signal of the road, and when the first switching signal is "2",
If the second switching signal is "1", the transmission output
If the signal is "0", the output signal of the suppression circuit
And a switching circuit for outputting the output .

[0008]

Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram of the present embodiment, and FIG.
FIG. 6 is a characteristic diagram showing a criterion for level determination in FIG. In FIG. 1, a transmitting side talker 1, a hybrid transformer 2, and an echo canceller main body 3 have the same configuration as the conventional example shown in FIG.

The operation of the NLP circuit 4 will be described below. The level measurement circuit 7 receives the transmission output signal 102 (in this case, the residual signal of the echo 105), averages the level over time, and outputs a level signal 106. The level judging circuit 8 compares the level signal 106 to be higher or lower than two reference levels (TH-L, TH-H, TH-L <TH-H). , And a switching signal of “1” when it is larger than TH-H, and a switching signal of “2” when it is TH-L to TH-H. The level measuring circuit 10 receives the input signal 104, and outputs a level signal 107 obtained by time-averaging the level. The level comparison circuit 9 compares the level signal 107 with the level signal 10 of the level measurement circuit 7.
6 and a signal level difference between them (level signal 10
When the 6-level signal 107) is greater than the reference level A, the switching signal is "0", and when it is smaller, the switching signal is "1".
Output to

The switching circuit 6 receives these two switching signals and makes the determination shown in FIG. That is, when the decision 1 level signal 106 is smaller than TH-L, the residual signal is suppressed regardless of other decisions (NLP-O
N).

Decision 2 If the level signal 106 is greater than TH-H, the residual signal is not suppressed (NLP-OFF) regardless of other decisions.

Judgment 3 When the level signal 106 is TH-L to TH-H
, The level signal 106 -the level signal 107
Is larger than the reference level A, NLP-ON.

If the difference between the level signal 106 and the level signal 107 is smaller than the reference level A, NLP-OFF.

The switching circuit 6 switches the output signal or the residual signal, ie, the transmission output signal 102, which has been suppressed by the suppression circuit based on this determination, without changing the output, or as it is, and outputs it as the output signal 103.

[0015]

As described above, in the present invention,
Since the first condition for suppressing the residual signal is only the level of the residual signal, the received signal and the transmitted signal are suppressed even when there is no sound, so that a noise component such as a line can be removed. Further, by setting the second condition for suppressing the residual signal to be the difference between the level of the received input signal and the level of the residual signal, there is no interruption during two-way communication and the effect of reducing the deterioration of communication quality is eliminated. There is.

[Brief description of the drawings]

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

FIG. 2 is a characteristic diagram showing switching conditions in FIG.

FIG. 3 is a block diagram of a conventional example.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 transmitter speaker 2 hybrid transformer 3 echo canceller main body 4 NLP circuit 7, 10 level measurement circuit 8 level determination circuit 9 level comparison circuit 6 switching circuit 5 suppression circuit 101 transmission input signal 102 transmission output signal (residual signal) 103 NLP output signal 104 Receive input signal

Continuation of the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H04B 1/76-3/44 H04B 3/50-3/60 H04B 7/005-7/015

Claims (2)

(57) [Claims] 1. A echoes around to receive Sing Sing No. is sent Sing Sing No. side with reference to the Sing Sing Nos feed and No. receiving Sing Sing estimated by the adaptive FIR type filter estimation with the estimated from the feed No. Sing Sing echo canceller unit the transmission receives the output signal and suppressing circuit that suppresses to a predetermined level, the type a transmission output signal input level to high and low two predetermined output as signal output signal feed a residual signal by subtracting the echo Input level.
If the value is larger than the higher reference value, "1" is the lower value
If the value is smaller than the reference value of “0”, the two
A first level detector which if in the middle of Jun'ne outputs the first switching signal is "2", the type receiving Sing Sing No. and with said transmission output signal detects the level difference this level
If the difference is larger than a predetermined reference value, "0"
A second level detector that outputs a second switching signal that is set to “1”; an output signal of the suppression circuit and the transmission output signal;
And the first switching signal and the second switching signal
For reference, when the first switching signal is “1”, the second switching signal is “2”.
Before outputting the transmission output signal regardless of the value of the switching signal
When the first switching signal is "0", the second switching signal
Output the output signal of the suppression circuit regardless of the value of
When the first switching signal is “2”, the second switching signal is
If "1", the transmission output signal is "0",
A non-linear processor control circuit for an echo canceller, comprising: a switching circuit for outputting an output signal of the suppression circuit . Wherein said first level detector receives the output of the first level measurement circuit and said first level measuring circuit for outputting the time-averaged certain level of the transmission output signal <br/> and a level determining circuit for outputting the first switching signal, the second level detector and the second level measurement circuit before <br/> SL to output the time-averaged is a level of the received signal enter the output of the first level measurement circuit and the second switch
2. The non-linear processor control circuit for an echo canceller according to claim 1, further comprising a level comparison circuit for outputting a signal .