JP2003169001A5 - - Google Patents

Description

[0004]
This FG / BG method is a duo filter method including a semi-fixed filter 1 which performs convolution operation to calculate an estimated echo, and an adaptive filter 2 which performs adaptive calculation according to the fluctuation of the characteristic of the loop path. In step 3, the impulse response (loop path transfer characteristic) of the loop path is estimated, and the estimated value j is input to the adaptive filter 2 on the BG side. The BG-side adaptive filter 2 outputs the BG-side estimated echo signal h obtained by adaptively calculating the input signal d from the input terminal 13 of the first channel system using the estimated value j. Further, the BG side estimated echo signal h is subtracted from the input signal c from the input terminal 12 of the second channel system in the subtractor 11. If the impulse response of the looped path is estimated well, the echo signal e (if there is no input signal f from the other party's terminal, the echo signal e is input to the input signal c from the input terminal 12 of the second channel system. The BG side estimated echo signals h are almost equal. If the characteristic of the adaptive filter 2 on the BG side is close to the characteristic of the true loop path, the coefficient of the adaptive filter 2 on the BG side is transferred to the coefficient of the semi- fixed filter 1 on the FG side, and the semi- fixed filter 1 on the FG side The FG side estimated echo signal i is output. Generally, the fact that the adaptive filter 2 on the BG side approaches the characteristic of the true looping path is the difference a between the input signal c at the input terminal 12 of the second channel system and the estimated echo signal h on the BG side. This is done by comparing the power with the input signal c from the input terminal 12 of the second channel system. Here, the transfer is performed under the following conditions .

[0010]
That is, in order to solve the above problem, an echo canceller device according to the present invention is provided in a transmission system in which a received signal received via a first communication system is looped into a second communication system via a coupling path.
BG-side adaptive filter for calculating an estimated BG-side echo by performing adaptive calculation on an input signal to the first communication system according to a change in characteristics of the loop path in the first communication system;
An FG-side semi-fixed filter that calculates an FG-side estimated echo by performing a convolution operation using a required coefficient on an input signal to the first communication system;
An input signal to the first communication system is equal to or greater than a predetermined threshold value, and an error of the BG-side estimated echo is equal to or less than a predetermined first margin, and an error of the FG-side estimated echo is equal to A transfer determination circuit that transfers a coefficient of the BG-side adaptive filter as the required coefficient of the FG-side semi-fixed filter when a transfer condition that is less than or equal to a predetermined second margin is satisfied;
Subtraction means for subtracting the interference signal from the first communication system to the second communication system by subtracting the FG side estimated echo from the input signal to the second communication system by a subtractor,
And an echo canceller device,
The pseudo echo path between said subtractor second echo canceler input unit of the communication system side is provided, in the initial operating state, the first or margin error of the BG side estimated echo is the predetermined And the error of the estimated FG side echo is equal to or greater than a predetermined second margin, and the transfer condition is satisfied.

[0014]
BEST MODE FOR CARRYING OUT THE INVENTION
An embodiment of the present invention will be described based on FIG. As an embodiment, an echo canceller apparatus having a hybrid circuit 15 and having a function of connecting to a system that switches to a two-wire line or a four-wire line while operating an echo canceller will be described. FIG. 1 shows an embodiment thereof, and the same reference numerals as in FIG. 2 denote the same parts in FIG. Reference numerals 16 and 17 in FIG. 1 denote 2-line to 4-line changeover switches, 18 and 19 denote transmission lines of a 4-wire line, and 22 denotes a transmission line of the 2-line line.
In FIG. 1, f and n are signals from the other terminal, d is a signal to the other terminal, c is a signal of the sum of the loop signal and the input signals f and n from the other terminal, 20 is a pseudo loop path, and 21 is the pseudo loop Adder which adds pseudo echo signal g by loop path, loop signal e by and loop back signal e, and signal f, n from the remote terminal, h is an estimated echo signal obtained by estimating loop network by adaptive filter based on signal d to the remote terminal, i Is an estimated echo signal obtained by estimating a loop-around signal by a semi-fixed filter based on the signal d to the opposite terminal.

[Description of the code]
1 semi-fixed filter 2 adaptive filter 3 impulse response estimation circuit 4 transfer determination circuit 5 input determination circuit 6 error comparison circuit 7 power comparison circuit 8 determination circuit 9 and 10 subtractor 11 first communication system output terminal 12 second transmission line 20 pseudo echo path input terminal 13 the first input terminal 14 and the second communication system of the output terminal 15 hybrid circuits 16 and 17 two-wire four-wire changeover switches 18 and 19 4-wire circuit of the communication system of the communication system 21 Adder 22 2-wire circuit a Error signal (ch)
b Error signal (ci)
c Input signal from the input terminal of the second communication system c 'Signal value d Input signal from the input terminal of the first communication system e Loop signal f , n Input signal from the remote terminal g Pseudo echo signal h Adaptive calculation Estimated echo signal i Estimated echo signal k, k 'margin
Estimated value from j estimation circuit
m Control signal from transfer judgment circuit

Claims (4)

In a transmission system in which a received signal received via a first communication system is looped into a second communication system via a loop-around path,
BG-side adaptive filter for calculating an estimated BG-side echo by performing adaptive calculation on an input signal to the first communication system according to a change in characteristics of the loop path in the first communication system;
An FG-side semi-fixed filter that calculates an FG-side estimated echo by performing a convolution operation using a required coefficient on an input signal to the first communication system;
An input signal to the first communication system is equal to or greater than a predetermined threshold value, and an error of the BG-side estimated echo is equal to or less than a predetermined first margin, and an error of the FG-side estimated echo is equal to A transfer determination circuit that transfers a coefficient of the BG-side adaptive filter as the required coefficient of the FG-side semi-fixed filter when a transfer condition that is less than or equal to a predetermined second margin is satisfied;
Subtraction means for subtracting the interference signal from the first communication system to the second communication system by subtracting the FG side estimated echo from the input signal to the second communication system by a subtractor,
And an echo canceller device,
The pseudo echo path between said subtractor second echo canceler input unit of the communication system side is provided, in the initial operating state, the first or margin error of the BG side estimated echo is the predetermined And an error of the estimated FG side echo is equal to or greater than a predetermined second margin, and the transfer condition is satisfied. The lower limit value and the upper limit value of the loop signal by the pseudo loop path are within the operable level range of the BG side adaptive filter under the condition that the error of the BG side estimated echo is equal to or more than the predetermined first margin. The echo canceller device according to claim 1, wherein each of the echo cancelers is regulated according to conditions. The loop path is a hybrid circuit, and the output of the first communication system is the 4-wire input to the hybrid circuit, and the 4-wire output from the hybrid circuit is an input to the second communication system. The echo canceller device according to claim 1, wherein the echo canceller device is configured to: The echo canceller device according to claim 1 or 2, wherein the loop line is an acoustic echo path formed between an output of the first communication system and an input of the second communication system. .