NL8204100A - INTERFERENCE ELIMINATOR. - Google Patents

Description

*.

VO 3625

Regarding; Interference interference.

The invention relates to an interference cancellation device.

In a communications system, echoes typically occur from electrical signals on a receive signal rooster at a hyhride junction meet an incorrectly matched impedance and are partially reflected over a transmit signal rooster to the removed source. As a result, the reflected signal or echo is fed to the removed end of the transmitter some time after the original signal has been transmitted. As the distance between the talking and listening subscribers increases, the echo takes a long time to match the speaking subscriber and consequently the echo becomes, at least subjectively, more disturbing to the speaking subscriber.

An attempt has been made to control ultrasounds in general. An echo controller described in U.S. Patent No. K,005,277 includes a speech signal operated device known as an echo canceller. More specifically, csavat echo cancellation is a type of selective damping, which is performed in response to speech levels in the transmission, such that the echo, which would otherwise be returned to the speaker, is suppressed. Such a device suffices normally for terrestrial communication paths, whereby the echo delay in the circulating propagation time between the source of the signal and the return of the echo is not great. However, in communication lanes via satellite links, the transmission delays are much longer and the echo is more distracting and they even interrupt a conversation by cutting the returning signal at intervals before the two subscribers say that they say double speech.

On the other hand, in plants of interrupting the outgoing cock, another echo control device, commonly known as an echo canceller, more specifically builds a replica signal of the echo signal and algebraically extracts the estimate from the echo canceller. outgoing signal to obtain a canceled echo signal 8204100-2. Most conventional ecBo clearance devices, such as, for example, the inridating, are often described in Lat. U.S. Patent 3 ^ 99 * 999 builds the replica syntBetiscB using a tapped delay line with adjustable multipliers 5 in an adaptive positive torque system, also a called transverse filter. The multipliers are automatically adjusted by a controller signal, which comes from a Bet difference between the echo and the Bet replica signal.

Ideally, the Bybride, which is present in the interconnection between U-wires and 2-wires between the signal paths and the sender / receiver Bet, allows a maximum of 6 dB of Bet receiving signal to leak to the transmission signal path. In practice, Bet also appears that a Bybride may be connected in an incorrect mode or that Bet is not associated with its balance network network. Betgene 15 leads to a network equalization disturbance, during which a large part of Bet's receiving signal will leak to the transmission signal path. Frequently, the known ecBo clearance instructions keep this strong ecBo signal for speech at Bet's near end and recognize this signal as such, whereby Bet ecBo signal is not recorded.

According to the invention, an interference cancellation device for Bet in Primary includes an interference signal of a first signal passing along a transmit signal path of a signal in one. nearby end. standing transmitter / receiver is propagated, first members to subtract an interference replication signal from the 25 first signal to generate a signal with reported interference, replica generator members which respond in response to an input signal on a receive signal path of the transmitter / receiver and Bet signal with Detected Interference Bet Interference Replication Signal Raise, A Detector For Bet Interfering With The Replication Generator Bodies Setting 30 When A Signal From The Transmit Signal Path Is Greater Than A Predetermined Value, These Devices Am A Preliminary Interference Replication Signal From Bet Actual Interfering Interference Signal From The Transmitter / Receiver subtract in order to generate the first signal, and supply the first signal 35 to the replica generator members when the interference signal in the first signal is less than required, thereby causing the replica generator members to be pre limiting interference replication signal, and in plants thereof, supplying the raised interference signal to the replica generator members when the interference breakdown in the first signal is at least as large as required, thereby causing the replica generator members to generate the interference replica signal.

In an embodiment of the present invention, an ecbo cancellation process is split into two stages, each providing a first preliminary cancellation and a final cancellation. A nearby speech detector responds to the preliminary signal with a raised echo, which is detected by the first stage in plants of the actual returning echo signal, as in the known apparatuses. Therefore, there is less chance that the speech detector 15 at the near end will have a strong eco signal for speech at the near end.

In accordance with the invention, use is made of the fact that since only e-mails modify an echo cancellation device at a given time, a number of components of a two-stage ecbo-2Q cancellation device can be shared. More specifically, a single transverse filter and a single accumulator adjustment of the bet at each stage of the ecbo canceling device can output canceled echo signal,

The invention will be explained in more detail below with reference to the drawing. 1 shows a two-stage echo cancellation device according to the invention; and FIG. 2 is another embodiment of a two-stage echo cancellation device.

The following description and accompanying illustrations illustrate the invention of an echo cancellation system located in the interconnection point between 2 wires and b wires of a telephone chain. In general, the invention can be used to control a random type of analog or digital interference signal, which occurs, for example, in radar, satellite, sonar, radio, television systems and the like, 8 2 0 4 1 0 0 • - - k -

It is therefore clear that the following explanation of the beer is given only by way of example and should not be taken in a limiting sense since the invention is applicable in all those instances. where a disturbing signal is present.

Ideally, an echo cancellation device should be provided, only the correlation properties between an incoming signal x (t) arising at the farthest end and the "reverse echo signal y (t) used to control The adjustment process of a prone transverse filter, with the correlation signal (t} being defined by

T

<p (t) = f x (t) y (t-r) dT. (1} 0

When using a correlation detector, the time required for the cancellation device to provide a predetermined degree of cancellation is determined by the bandwidth or bit rate of the incoming signal, the resulting maximum sample rate of the incoming signal, the relative noise level and the speech at the near end. When using the granulation process, the adaptation time from the phone user's viewpoint becomes excessive in the presence of high noise levels and typical levels of speech at the near end. In conventional conventional ecbo canceling devices, the use of a speech detector at the nearby end is obstructed to hinder the adaptation process when speech is at this end. Likewise, these speech detectors cannot interfere with high level eco signals and speech at the near end and such will erase the known echo cancellers in an incorrect manner in the presence of arc level eco signals.

The object of the invention is to solve this problem by splitting the cancellation problem into two stages. An arrangement selected by example, illustrating the interference-canceling features of the invention, as applied to the specific example of an echo cancellation arrangement, is shown in FIG. 1. 35 A single transmission station is shown in fiber for connecting 8204100 - 5 -

A transmitter / receiver 10, which is present at the adjacent end, with a receiving signal path 12 and a transmitting signal path 1 ^ via a hybrid power supply 16. A balance power supply 17 is connected to the hybrid power supply 16 for the impedance of the transmitter / receiver 10 as well possible to adjust 5.

As shown in FIG. 1, an ecbo cancellation device includes an ecboreplication generator 18, which is present between the receive signal path 12 and the transmit signal path 1¾, a first combination device 20, a second combination device 22, switching means 2k 10, and a controller 26. The ecboreplica generator 18 responds to the input signal x (k}, which approaches the transmitter / receiver 10 present at the nearest end over the receive signal path 12 and processes samples of the input signal x (k) in accordance with equation (1) in order to scatter as an output signal of the echo signal 15 present on the transmit signal path 1¾, this scatting being determined as the preliminary echo replica signal y1 (k).

The ecboreplica generator 18, which can digitally include a number of delay elements, multipliers and integrators, which form a transverse filter in conjunction with an accumulator, thereby providing the pulse response of the signal applied thereto as an input signal and has been described in more detail in the Dutch patent application ........

From the output of the eco-replicator generator 18, the preliminary echo replica signal yy (k) is then applied as an input signal 25 to the switching members 2k, which are set in the position shown in FIG. 1 when the process is initiated. Thus, the preliminary echo replica signal y ^ k] is supplied through the switching means 2k as a first input signal to the first combination device 20, the other input signal for the first combination device 20 being the actual returning echo signal y (k] the output of the bypass 16 occurs. The first combination device 20 then subtracts the preliminary eco-signal y, i from the actual returning echo signal y (k) am as the output signal to form the difference thereof, referred to as the primary signal e ^ k] with raised echo.

8204100 -6-

The preliminary signal e.j (k) with canceled eciio is propagated along the transmission signal and supplied as an input signal to so many the second combination device 22 as the switching means 2k.

The switching means 2b, which are set in the position shown in FIG. 1, supply the preliminary signal e ^ (k) with canceled echo as an input signal, together with the input signal x (k) to the echo replicator generator 18. In accordance with the echo replica generator 18, the preliminary echo (k) signal with canceled echo serves to adjust the input signal x (k) to form an improved value for the preliminary echo replica signal y ^ (k), wherein this adjustment process is described in more detail in the above-mentioned patent application.

The preliminary signal e ^ (k) with canceled echo or alternatively the preliminary echo replica signal y ^ Ck] (as indicated by the dotted equation in Fig. 1) is also applied as an input signal to the controller 2β, which is also on the input signal x (k) responds. The controller 26 controls the adjustment process performed by the echo replicator generator 18 by comparing either e ^ (k) or y ^ (k) with a predetermined value of x (k) and serves to determine the position of the switching members 2k change when either e ^ (k) or y ^ (k) exceeds a predetermined threshold. That is, the controller 26 operates according to whether the relationship ej (k]> Ax (k) or y1 (k)> Bx (k] operates, A or B being selected such that the preliminary signal e ^ (k) with canceled echo causes sufficient cancellation of the actual returned echo signal y (k} to allow a normal speech detector present at the near end to operate properly. It is clear that the controller 26 may include any known device capable of performing a threshold detection.

When the predetermined threshold value is exceeded, the controller 26 activates the switching members 2b, whereby the first cancellation stage is terminated because the preliminary signal (k) with canceled echo is no longer on as an input signal and the preliminary echo replica signal y ^ (kl no longer as an output signal 35 is present from the echo replicator generator 18. The final value 820 4 1 0 0 - 7 - of the preliminary echo replica signal y \ j (fc) is stored in a freely accessible memory 28 and is always supplied as an input signal via the switching means 2k applied to the first combination device 20. Therefore, the first combination device 20 will continue to generate the preliminary signal e ^ (k) with canceled echo, which travels along the transmit signal path 1¼ to the second combination device 22. The moment the switches 2k are activated to initiate the second stage of cancellation, the preliminary ecii oreplica signal y ^ (k) supplied by the echo replication generator 18 via the switching means 2k as a second input signal to the second sync credit 22. The second co-ordinator 22 subtracts this eco-replica signal from the preliminary echo signal with the echo canceled to form the final echo signal (k) with the echo canceled, which travels back along the remainder of the transmission signal path. farthest end receiver / transmitter (not shown) is propagated.

The final signal e, -, (k] with canceled echo is also applied via the other position of the switching members 2k (indicated by a dotted line in Fig. 1) as the new input signal to the echo replicator generator 18, replacing the preliminary signal e ^ (k) with canceled echo. The echo replicator generator 18 therefore affects x (k) in relation to e ^ k) to provide a final output choreplica signal 7g (ki. The end echo replica signal e ^ (k} is then transmitted via the other position of the switching members 2k (indicated by a dotted line in Fig. 1 25), as the second input signal applied to the second co-ordinator 22, in which the signal of the preliminary signal e1 (k1) is subtracted with raised echo to form a leveled value for the final signal eg (k) with canceled echo. The above-described process then continues, with the final signal eg (k) with canceled echo sent to the echo replication enerator 18 is fed back to continuously adjust the final echo replica signal 7g (k) during the period that the input signal x (k) is present or until the threshold requirement of the controller 26 is no longer met, as will be the case with a slowly with the time-varying actual value of y (k). More in 8204100

R V

- 8 - in particular, if at a time during the adjustment Tan the final signal e2 (k} with canceled echo or e ^ (k) becomes smaller than Ax (k) or y1 (k) becomes smaller than Bx (k), the controller 26 re-activates the switching means 2k, whereby the preliminary signal ee1 (k) with the echo canceled is again fed as an input signal to the echo replica generator 18. As described above, the preliminary signal e ^ (k ) with canceled echo are adjusted in association with the input signal x (k) until once again the predetermined threshold value of the controller 26 is exceeded and the switching members 10 2k are activated, so that the final signal e2 (k) with canceled echo again as an input signal is applied to the echo replicator generator 18. The controller 26 will continue to control the value of either (k) or y ^ (k) as described above and the input signal to and the output signal from the echo replicator generator 18 as necessary. according to the predetermined threshold value.

The absence of an input signal x (k) or alternatively the presence of a speech signal present at the near end is detected by a speech detector 30 located at this end. The presence of the speech at. the near end can be detected, for example, by comparing either the preliminary echo replica signal or canceled signal y ^ (k) or e ^ (k) with either the input signal x (k) or the actual returning echo signal y (k) using methods which are known per se in the current speech detector systems and which are explained in more detail in the above-mentioned patent application. For example, e.g. the speech detector 30 U store elapsed values of the input signal x (k) and determine whether speech is present at the near end when the current value of the preliminary echo-canceled signal is greater than half the maximum value of the H-stored 30 values of the input signal. When the speech detector 30 essentially recognizes speech at the near end, an inhibit signal is transferred to the echo replicator generator 18, thereby breaking the connection between the echo replicator generator 18 and the transmit signal 1b, as a result of which a further change in the the information stored in the echo replicator generator 18 is obstructed, allowing the speech present at the proximate end to propagate unaltered 8204100-9 to the removed transmitter / receiver.

Another echo cancellation system is found in FIG. 2, in which controller 26 and speech detector 30 are combined into a single detector / controller 32, which can perform the same functions as the individual components present in FIG. 1. -without the detector / controller 32 responds to the input signal x (k), the preliminary signal e ^ (k) with canceled echo and in other operating modes to the convenient returned echo signal y (k) and the preliminary echo replica signal (k) When the detector / controller 32 is a controller, it compares the preliminary signal e ^ (k) with canceled echo with the input signal x (k) in a mode, as already described above for fig. position of the switching members 2k is changed in accordance with the relationship e1 (k] <Ax (k), the threshold value A being selected at the user's discretion.

The detector / controller 32 may also compare the input signal x (k) with the preliminary echo replica signal y ^ (k) (indicated by a dotted connection in Fig. 2) and activate the switching means 2b according to the threshold decision y ^ (k) <Bx (k). In another configuration, the detector / controller 32 can determine the time derivative of the preliminary echo (k) signal with canceled echo to produce a change of the echo cancellation signal de ^ (k) / dt. The detector / controller 32 then compares the echo cancellation signal de ^ (k) / dt with a predetermined constant C and changes the position of the switching members 2k according to the relationship de. (K) 25 ^ t "<C. (21

The value of C is chosen such that the velocity change of e (k) falls below a certain value, it is assumed that sufficient preliminary echo cancellation has taken place. In its capacity as a speech detector at the proximate end, the detector / controller 32 interferes with the echo replication generator 18 according to one of the methods described above in reference to FIG.

According to the invention, a two-stage echo cancellation process is obtained, in which only a single echo replication generator is used in plants of a separate echo replication generator for each stage, a saving which makes it possible for the invention can be realized on an integrated integrated chain. Furthermore, it is clear that the invention may be retested with respect to digital to analog signals, the only difference in construction being the device within the echo replication generator.

8204100

Claims (6)

1. Interference Elimination Device for Let in Relief Canceling an interference signal from a first signal which is propagated along a transmit signal line from a transmitter / receiver fiber located at a near end, including first members 5 cm from an interference replica signal from the first signal. in order to provide a signal with a sustained interference, replica generator means which, in response to an input signal on a receive signal path from the transmitter / receiver and generate a signal with a sustained interference, generate an interference replica signal, and a detector 10 am a setting of the replica generator means Lelemmeren when a signal from the transmit signal path is greater than the predetermined value characterized by second means (201 for Let subtract a preliminary interference replica signal (y \ j (k) l from Let actual returning interference signal (y (kll nit de subtract transmitter / receiver in order to let ee First signal (to generate, and switch organs (2 ^. 26} to apply the Let first signal to the replica generator members (18) when the interference cancellation in the Let first signal is less than necessary, thereby causing the replica generator members to generate preliminary interference replica signal and in plants 20 thereof To let signal with Live interference ( e2 (kll to be applied to the replica generator when the interference cancellation in the first signal is at least as large as necessary, thereby causing the replica generator means to generate interference replica signal (y2 (k) l, 2. Lifting device according to claim 1, characterized by 25 storage means (28) for storing a last value. of Let preliminary interference replica signal and Let supply this value to the second members (20) when Let signal with supplied interference is supplied to the replica generator members, 3. Disposal device according to claim 2, characterized in that the storage elements consist of a freely accessible memory. Upgrading device according to claim 1, 2 or 3, characterized in that the switch members respond to the input signal (m (k) 1 and the first signal Let first signal (e ^ (k) 1) on the replica generator in response to the input signal (m (k) 1). 12 - supplying means when the first signal is less than a predetermined input value to the input signal, and instead supplying the signal (e ^ k)] to the replication generator means with blunt interference when the first signal is at least equal to 5 the roughly determined value of the input signal. Canceling device according to claim 1, 2 or 3, characterized in that the switching members respond to the input signal (x (k] 1 and the preliminary interference replica signal (yj (k)) the first signal (e ^ k)) in response to the input generator members. supplying the 10 preliminary interference replica signal is less than a predetermined input value of the input signal and, instead, supplying the signal (e ^ k)) with interleaved interference to the replica generator means of the preliminary interference interference signal being at least equal to the predetermined interference value certain sensed value of 15 the input signal. Canceling device according to claim 1, 2 or 3, characterized in that the switching means, in response to the first signal (e ^ (k)), determine the time derivative for forming a signal change with interfered interference, the first signal on supplying the 20 replica generator means when the signal change with canceled interference is greater than a predetermined value and instead supply the signal (e ^ k) 1 with lost interference to the replica generator means when the signal change with raised interference is at most equal to the predetermined value 25 value. The cancellation device according to any one of the preceding claims, characterized in that the detector (30] responds to the input signal (x (k]] and the preliminary interference replica signal (y ^ -kl). The cancellation device according to any one of claims 1 to 6, characterized in that the detector (30) responds to the input signal (x (k)) and the first signal (e ^ (kl). 8204100