DE2063271B2 - ADAPTIVE COMPENSATION Echo suppressor - Google Patents

Description

3 4

is adjustable and the first input of the multiplier The individual output signals W ₁ (Y) ... w _n (i) des

with the associated output of the branching network branching network 21 ... 29 result in

Works connected and the second input of the multi-passage through the actuators 61 ... 69 which through

plizierers by the residual echo in the outgoing the summing 7 summarizing signals

Direction of the four-wire path is controllable, this is 5 ^ ₁ · Vf ₁ (O ... g _n · w _n (t), so that at the output of the

The object is achieved in that in each case between the output of the adder 7, the simulated echo signal
of the branching network and the first input of the

Multiplier a sign evaluator switched on %, _f *. _ - ^ s ₍ \

^is ·, -ι

The measures according to the invention result in 10

achieves that the multi is formed at the second inputs. For setting the actuators 61 ... 69

This is only controlled by the correlator, whichever is specified

positive and equally large negative value are essentially made up of a number of multipliers

so that the multiplier consists of an extremely simple 41 ... 49.

Way as a pure polarity reversal for the analog output 15 According to the invention, the respective first input signal of the respective output of the branching the multiplier 41 ... 49 can be implemented via a sign network. At the same time assess 31 ... 39 with one of the outputs of the arises the advantage of a much more precise setting branching network 21 ... 29 connected so that for the transfer function to be simulated, than with z. B. at the first input of the multiplier 41 which is a similar measure in the way of supplying the input signal SIgU [W ₁ (I)] for processing. Residual echo signal to the respective second inputs The second inputs of the multipliers 41 ... 49 of the multipliers. are on the other hand via the amplifier 9 with the

The following is the invention on the basis of an in strengthening k from the signal e (t) of the outgoing

the drawing shown block diagram of the direction 6 of the four-wire path controlled so that on

Compensation echo suppressors according to the invention the analog signal k · e (t) for multiplication

kers explained in more detail. with the value sign [w {(f)] is present. Because the multipliers

The drawing shows, as an excerpt from a 41 ... 49, only an analog value with a

Long-distance telephone connection via one or more predetermined positive or equal negative

Runtime-affected four-wire lines have to multiply the transition by value, they can be turned into extremely

a four-wire line with an incoming Rieh- 3 ° simple way as a pure polarity reversal for the analog

direction 1-2 and an outgoing direction 5-6 to a signal k ■ e (t) . The resulting

Two-wire line 4 via a replica output signals of the multipliers 41 ... 49 are

equipped fork 3. The echo counter is then closed via an integrating element 51 ... 59

handle on the one hand in the incoming direction 1-2 an actuating signal processed in such a way that if there is an under-

and on the other hand, in the outgoing direction, a break in the signal to be integrated k e (t) sign

switches, but between this echo counter wi (t) the corresponding instantaneous control value is transferred

pusher and fork 3 remains constant for a long time. After all, they control

longer four-wire line can be located. Integrating elements 51 ... 59 the actuators 61 ... 69

The adaptive quadrupole of the echo canceller has a value gi that corresponds to the respective integrated control

for example, from a filter bank with a larger 40 signal is proportional.

Number of filters connected in parallel on the input side

21 ... 29, then from the downstream invention have shown that the inclusion of a

Actuators 61 ... 69 and a subsequent sign evaluator in each case in the supply of the

Summer 7. The input of this quadrupole is from output signals of the branching network to the

the signal x (t) of the incoming direction 1-2 45 multipliers with simultaneous analog control

fed; the output of the quadrupole feeds a simulated second input of the multiplier through the

Iated echo signal £ (i) via the differential amplifier 8 residual echo signal is a much better replica of the

echo signal simulated in the subtracting sense in the outgoing direction results in the switching on of a

5-6 a. In the balanced state, the quadrupole has the corresponding sign evaluator in the supply line

approximately the same transfer function as the 5 ° of the residual echo signal to the respective second inputs

Transfer function of the echo path from the input of the multipliers.

of the quadrupole via fork 3 back to the differential The simulated echo signal £ (0 as output signal

amplifier 8, so that at the output of the difference of the summer 7, for example, as shown in the drawing

amplifier 8 provides extensive compensation of the over, over a differential amplifier 8 in the outgoing

the fork 3 trampled echoes takes place. 55 Direction 5-6 of the four-wire path are fed in,

The most favorable conditions for the setting of the signal coming from fork 3 .KO as actuators 61 ... 69 by means of the sum to be described of the residual echo signal coming through the fork correlation elements result from the use of z {t) and that of the Two-wire line 4 coming of a branching network, which system with signal n {t) of the nearby participant contains the one input orthogonal impulse responses. Such a 60 of the differential amplifier 8 and the simulated echo branching network can be fed as in the present signal £ (/) to the other input of the differential amplifier example through filter kers connected in parallel on the input side. The input of the amplifier 9 21 ... 29, but z. B. also through a pure transit time is then the output signal e (t) = y (t) - £ (0 of the member with a larger number of taps (see. Differential amplifier 8).
Sondhi, FIG. 2) or through Laguerre networks 65 In a further embodiment of the invention, the (cf. Sondhi, p. 506) will be implemented. In the general setting process of the actuators 61 ... 69 by means of a, however, the condition that the impulse responses of the decision device 10 for those time intervals of the filters are linearly independent of one another is sufficient. valle frozen in which the signal e (t) is replaced by the

interference signal n {t) arriving from the nearby participant becomes unusable for the correlation. This decision circuit 10 is controlled both from the incoming direction 1 and from the outgoing direction 6 of the four-wire path and is able to throttle the amplifier 9. The throttling of the

amplifier 9 is expediently carried out in such a way that its gain k always becomes 0 when the signal x (t) on the incoming direction 1 is smaller than the signal e (t) on the outgoing direction 6, and also when the signal x {t) falls below a certain predetermined level threshold.

1 sheet of drawings

Claims (3)

ϊ 2 partial or total suppression of intermediate patent claims: comments from the currently listening participant arise. 1. Compensation echo canceller for a Compensating echo canceller is used as a message transmission system with a two- 5 rend of the entire conversation connection the part-wire-four-wire transition, with one of the recipients, both transmission directions uneinge-signals of the incoming direction of the quadruple available. Such compensation wire path powered branch network with echo barriers are inter alia by the article a series of outputs that systems with "An Adaptive Echo Canceller" by M. M. S ο η d h i linearly independent impulse antio from "The Bell System Technical Journal", 1967, Words correspond, is provided, each on a page 497 to 511, known. With echo cancellers this Adjustment element are fed to an adder, type becomes the speech signal of the distant participant the output signal of which is passed as a simulated echo signal through an adaptive quadrupole that passes through in the subtracting sense the signals of the outgoing correlator is set in such a way that the the direction of the four-wire path is added, 15 transfer function of the four-pole to that of the echo each adjustment element through the integrated path, i.e. mainly to that of the fork transition The output signal of a multiplier is adjustable approx. As a result of this adaptation process delivers and the first input of the multiplier with which the quadrupole a simulated echo signal which is im associated output of the branching network subtracting the speech signals of the near connected and the second input of the multi-20 subscriber is supplied, so that an extensive by the residual echo in the outgoing compensation of the echo signals without any influence Direction of the four-wire path is controllable, since the speech signals of the near one are present at the same time characterized in that it is achieved between participants. the respective output of the branching network - the quadrupole of the above-mentioned reference exists Work (21 ... 29) and first input of the multi-25 from a branching network with a number of plizierers (41 ... 49) have signed outputs, the systems with one another linear (31 ... 39) is switched on. correspond to independent impulse responses. the 2. Echo canceller according to claim 1, characterized in that signals from these outputs are each via an adjusting element characterized in that one of the signals is fed to a summer. The correlator, in turn incoming and outgoing direction of 30 consists of an equal number of multipliers, Four-wire path controlled decision-making device, each with an output of the branching network (10) is provided, which connects the supply of the work and through the residual echo in the Residual echo signal to the second inputs of the outgoing direction of the four-wire path controlled Multiplier (41 ... 49) is able to throttle. are. The outputs of these multipliers are 3. Echo canceller according to claim 2, characterized in each case 35 averaged and controlled via an integrator characterized in that the decision device then the associated setting member. (10) from the signal, which by subtracting a relatively very large circuit technology of the uncompensated signal the outgoing niche effort of the correlator cause the Direction (5) of the four-wire path with the simu- multiplier, which is the instantaneous value of the product lated echo signal arises, is controlled. 40 must generate from two analog quantities that one How the multipliers work in four quadrants result. Now it is from the cited reference known, the residual echo signal to the multipliers via a limiter (infinite clipper) and a subsequent The invention relates to a compensating 45 to feed the amplifier, whereby it is achieved Sation echo canceller for a message over- that mostly at the second inputs of the multiplier transmission system with at least one two-wire - a certain positive or negative signal value Four-wire transition. is applied, depending on whether the instantaneous value of the Echo suppressors or echo cancellers are generally residual echo signal is positive or negative.
50 The object of the invention is to provide a compensation set that specifies delay-affected four-wire routes, such as echo cancellers with a correlator, e.g. B. submarine cable or satellite connections included. With quick setting of the coefficients of the telephony connections, actuators with less circuitry, especially on the hybrid circuits, require more than 55 orders of this kind. double the running time of the four-wire connection delayed Based on a compensation echo counter back to the speaking subscriber and can here, pusher for a message transmission system with partly under the pretense of statements by the partner, a two-wire-four-wire transition, in which one of so annoying appear that a normal the signals of the incoming direction of the four-way conversation becomes impossible. Conventional 60 wireline powered branching network with a Echo suppressors prevent the reflected speech signals from the series of exits that systems communicate with one another distant participant usually corresponds to linearly independent impulse responses on their return, to the speaking participant that it is provided with the help of a sum weighing device each via an adjustment member the instantaneous transmission converters are supplied, its output signal as Determine direction and the transmission path of the 65 simulated echo signal in the subtracting sense Block the transmission direction that is not currently required. Signals of the outgoing direction of the four-wire path However, these measures can cause significant damage, with each adjustment member being affected by the Mutilations of speech and continue to use the integrated output signal of a multiplier