JPS601986B2 - Adaptive echo canceller - Google Patents

Description

【発明の詳細な説明】 この発明は長距離電話回線に挿入される反響制御装置の
一つである適応型反響消去装鷹に関するものである。DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an adaptive echo canceller, which is one type of echo control device inserted into a long-distance telephone line.

適応型反響消去装置は内部に反響路の特性を近似する疑
似反響路を少なくとも一つ持ち疑似反響路の特性に近づ
けるべく逐次的に修正を行うことにより反響路特性を合
成するように構成されている。The adaptive echo canceller has at least one pseudo echo path that approximates the characteristics of the echo path, and is configured to synthesize the echo path characteristics by sequentially making corrections to approximate the characteristics of the pseudo echo path. There is.

しかしながら反響路には送信側通話者の音声が反響と一
体となって存在するため反響路の特性を知るためには、
送信側入力、言いかえれば反響賂出力に反響のみが存在
し、送信側通話者の音声が存在しない期間を検出し、疑
似反響滋の惨正を停止させる機能が必要である。この機
能を果たすのが、双方向通話検出器あるいは重畳通話検
出器と呼ばれるものである。双方向通話検出器は通常送
信側信号レベルと受信側レベルとを、比較し、受信側レ
ベルの方が大きい時に受講一方向通話状態であると判定
し、前記修正回路を動作させるよう制御している。しか
しながらそのような構成であるためしベル検出器の動作
時間だけ同時通話状態の検出が遅れるのは避けられない
。そこで、送信側と受信側の両方に遅延回路を挿入し、
疑似反響路の入力を遅延回略の後から取り、双方向通話
検出器の入力を遅延回路の前から取り、遅延回路の遅延
時間を双方向通話検出器内のレベル検出器の動作時間よ
り長く選ぶことによって前記の欠点を補うような構成の
反響消去装置が考案されている。本明細書ではこのよう
な制御方式を遅延制御と呼ぶことにする。しかしながら
このような反響消去装置は必然的に回線遅延の増大を併
うため、実用の菱贋としては無理がある。そこで本発明
の目的は、前記双方向通話検母器の時間遅れを取り除く
ことが可能、即ち、遅延制御による利点を保ちながらし
かも回線に遅延時間を全く与えない形式の反響消去装置
を提供するものである。However, in the echo path, the voice of the sender is present along with the echo, so in order to know the characteristics of the echo path,
There is a need for a function to detect periods when only echoes are present in the transmitter's input, or in other words, in the reverberant output, and no voice from the transmitter's caller is present, and to stop the scourge of false echoes. A device that performs this function is called a two-way conversation detector or a superimposed conversation detector. The two-way conversation detector usually compares the signal level on the transmitting side and the level on the receiving side, determines that a one-way conversation is occurring when the receiving side level is higher, and controls the above-mentioned correction circuit to operate. There is. However, with such a configuration, it is unavoidable that the detection of the simultaneous call state is delayed by the operating time of the bell detector. Therefore, we inserted delay circuits on both the transmitting and receiving sides,
The input of the pseudo echo path is taken after the delay circuit, the input of the two-way speech detector is taken before the delay circuit, and the delay time of the delay circuit is longer than the operating time of the level detector in the two-way speech detector. Echo canceling devices have been devised that are selectively configured to compensate for the above drawbacks. In this specification, such a control method will be referred to as delay control. However, since such an echo canceling device inevitably increases line delay, it is difficult to use as a practical counterfeit device. SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an echo canceling device that can eliminate the time delay of the two-way call analyzer, that is, maintains the advantages of delay control and does not impart any delay time to the line. It is.

前記遅延制御を用いた反響消去装置の欠点は、疑似反響
路と反響消去減算器から成る反響消去部全体が遅延され
た信号で動作するため、出力信号が必然的に遅れてしま
うことにある。A drawback of the echo canceling device using the delay control is that the entire echo canceling section, which consists of the pseudo echo path and the echo canceling subtractor, operates with a delayed signal, so the output signal is inevitably delayed.

本発明による反響消去装置では、遅延制御された反響消
去部とは別に、修正回路を持たない第二反響消去部を設
け、前記遅延制御による第一反響消去部の疑似反響路か
ら反響路成分を第二反響消去部の疑似反響路へ転送し、
第二反響消去部自体は遅延回路を通さない受信側信号及
び送信側信号を入力とし、反響消去を行うことを特徴と
する。次に図面を用いて更に詳細に説明する。In the echo canceling device according to the present invention, a second echo canceling unit without a correction circuit is provided separately from the delay-controlled echo canceling unit, and the echo path component is extracted from the pseudo echo path of the first echo canceling unit using the delay control. Transfer to the pseudo echo path of the second echo canceller,
The second echo canceller itself is characterized in that it receives as input the receiving side signal and the transmitting side signal that do not pass through the delay circuit, and performs echo cancelling. Next, a more detailed explanation will be given using the drawings.

第１図は従来の遅延制御型の反響消去装置の一例である
。受信側信号は受信側入力端子１００から入り受信側出
力端子２００を経て近端話者に至る。受信側信号の反響
と近端話者の送話信号を含む送信側信号は送信側入力端
子３００より入り送信側出力端子４００から遠端話者へ
至る。遅延回路２０と２１は、それぞれ送信側信号と受
信側信号を遅らせて疑似反響路１１に与えるため設けら
れている。双方向通話検出器３川よ、送信側信号と受信
側信号をそれぞれ送信側遅延回路２０と受信側遅延回路
２１の前から取り出しているため、結果的に疑似反響路
１１よりも時間的に早く信号を検出することができる。
双方向通話検出器３０の出力は、その動作時間のため真
の双方向通話状態の開始時刻より遅れて双方向通話を検
出するが、予想されるその検出時間より長い遅延時間を
送信側遅延回路２０と受信側遅延回路２１に与えておけ
ば、双方向通話による疑似反響路の乱れを未然に防ぐこ
とが可能である。双方向通話検出器３０の出力は、疑似
反響路修正回路１０を、双方向通話時に動作しないよう
に制御する。疑似反響路１１の出力は、反響消去減算器
１２において遅延された反響と送話信号のうち反響のみ
を消去する。反響消去減算器１２の出力には、送話信号
のみが残り送信側出力端子４００へ導かれる。疑似反響
路修正回路１０は、修正情報として、反響消去減算器１
２の出力則ち残留反響と受信側信号とを用いて疑似反響
路１１を修正する。第１図の回路では双方向通話検出遅
れによる疑似反響路の誤った修正は送信側遅延回路２０
と受信側遅延回路２１により防ぐことが可能であるが、
反面、明らかに送信側の遅延時間が遅延回路２０１こよ
り増加する。第２図は、本発明の一実施例である。受信
側伝送路則ち端子１００から端子２００、送信側伝送路
即ち端子３００から端子４００ともに遅延回路は含まな
い。送信側遅延回路２川またゞ第１疑似反響路１１、疑
似反響路修正回路１０反響消去減算器１２から成る第一
反響消去部５０を遅れて動作させるために設けてある。
受信側遅延回路２１‘ま、第一疑似反響路１１において
合成される反響路特性に送信側遅延回路２０の遅延時間
が含まれるのを差し引くために設けられた遅延回路で遅
延時間は、送信側遅延回路２０と全く同値に選ぶことに
よって前記の目的を達する。FIG. 1 is an example of a conventional delay control type echo canceler. The receiving side signal enters from the receiving side input terminal 100 and reaches the near-end speaker via the receiving side output terminal 200. A transmitting signal including an echo of the receiving signal and a near-end speaker's transmitted signal enters from the transmitting input terminal 300 and reaches the far-end speaker from the transmitting output terminal 400. Delay circuits 20 and 21 are provided to delay the transmitting side signal and the receiving side signal and apply them to the pseudo echo path 11, respectively. Two-way conversation detector 3: Since the transmitting side signal and the receiving side signal are taken out before the transmitting side delay circuit 20 and the receiving side delay circuit 21, respectively, they are taken out earlier than the pseudo echo path 11 in time. signal can be detected.
Although the output of the two-way conversation detector 30 detects two-way conversation later than the start time of a true two-way conversation state due to its operation time, the output of the two-way conversation detector 30 has a delay time longer than the expected detection time. 20 and the receiving side delay circuit 21, it is possible to prevent disturbance of the pseudo echo path due to two-way communication. The output of the two-way conversation detector 30 controls the pseudo echo path correction circuit 10 so as not to operate during a two-way conversation. The output of the pseudo echo path 11 cancels only the echoes out of the delayed echoes and the transmitted signal in the echo canceling subtracter 12. Only the transmitting signal remains at the output of the echo cancellation subtractor 12 and is guided to the transmitting side output terminal 400. The pseudo echo path correction circuit 10 uses an echo cancellation subtractor 1 as correction information.
The pseudo echo path 11 is modified using the output of 2, that is, the residual echo and the receiving side signal. In the circuit shown in FIG.
This can be prevented by the receiving side delay circuit 21, but
On the other hand, the delay time on the transmitting side clearly increases compared to the delay circuit 201. FIG. 2 is an embodiment of the present invention. The receiving side transmission path, ie, from terminal 100 to terminal 200, and the transmitting side transmission path, ie, from terminal 300 to terminal 400, do not include a delay circuit. Two transmitting side delay circuits are provided to operate the first echo cancellation unit 50, which is composed of a first pseudo echo path 11, a pseudo echo path correction circuit 10, and an echo cancellation subtractor 12, with a delay.
The receiving side delay circuit 21' is a delay circuit provided to subtract the delay time of the transmitting side delay circuit 20 from being included in the echo path characteristics synthesized in the first pseudo echo path 11. The above objective is achieved by choosing the delay circuit 20 to have exactly the same value.

双方向通話検出器３０の出力は第１図と同様に疑似反響
路修正回路１０を制御し、双方向通話時誤った修正を行
なわないようにする。The output of the two-way communication detector 30 controls the pseudo echo path correction circuit 10 in the same manner as in FIG. 1, to prevent erroneous correction during two-way communication.

第２図が第１図と違う点は第一疑似反響路１１から反響
路特性を取り入れ、遅延回路２１を通さない受信側信号
を入力とする、第二疑似反響路４０とその出力を遅延回
路２０を通さない送信側信号から差し引く第二反響減算
器４１とから成る第二反響消去部５１が設けられ、第二
反響減算器４１の出力を送信側出力信号として端子４０
０へ導く点である。遅延回路２０と遅延回路２１の遅延
時間を等しく選べば疑似反響路１１の反響路特性は、端
子２００から反響路を通り端子３００へ至る。反響路成
分と全く同値になるから、第二疑似反響路４０で反響路
特性として、用いても何ら支障はない。たメー反響路が
フェーズロール（Ｐｈａｓｅｒｏｌｌ）のような時間的
に変動するような非直線性を持った場合疑似反響路４０
とは時間的に違った信号で動く第１疑似反響路１１の特
性がそのまま第２疑似反響路４０で使えるとは限らない
のでフェーズロールへの追従性は第１図の回路より送信
側遅延回路２０と受信側遅延回路２１のもつ遅延時間だ
け悪くなることが予想される。しかしそのような非直線
性を持つ反響路は現実には少数であり、それ以外の反響
路に対しては、本発明による反響消去装置は、第１図と
同等の双方向通話状態に対する疑似反響路防護性能、即
ち遅延制御による利点を保ちしかも回線遅延増大という
欠点のない反響消去機能を有するため例えば海底ケーブ
ル回路のような比較的時間遅延の小さい長距離電話回線
あるし、は拡声電話器のり島音防止への応用等に有効で
ある。第３図は第２図の回路に疑似反響路間の反響路特
性の転送を行うゲート４２を付加し、さらに双方向通話
検出器３０の出力によりゲート４２を制御するように構
成し、本発明の効果を得るようにした実施例である。The difference between FIG. 2 and FIG. 1 is that the echo path characteristics are taken in from the first pseudo echo path 11, and the receiving side signal that does not pass through the delay circuit 21 is input, and the second pseudo echo path 40 and its output are connected to a delay circuit. A second echo canceller 51 is provided, which includes a second echo subtracter 41 that subtracts from the transmitting side signal that does not pass through the terminal 40, and outputs the output of the second echo subtracter 41 as the transmitting side output signal.
This is the point that leads to 0. If the delay times of the delay circuit 20 and the delay circuit 21 are selected to be equal, the echo path characteristics of the pseudo echo path 11 extend from the terminal 200 through the echo path to the terminal 300. Since it has exactly the same value as the echo path component, there is no problem in using it as the echo path characteristic in the second pseudo echo path 40. If the mechanical echo path has non-linearity that fluctuates over time, such as a phase roll, a pseudo echo path 40
Since the characteristics of the first pseudo-reverberation path 11, which moves with a temporally different signal, cannot necessarily be used as is in the second pseudo-reverberation path 40, the ability to follow the phase roll is better than the circuit shown in FIG. It is expected that the delay time of the delay circuit 20 and the receiving side delay circuit 21 will be worse. However, in reality, there are only a few echo paths with such non-linearity, and for other echo paths, the echo canceling device according to the present invention can eliminate pseudo echoes for a two-way conversation situation equivalent to that shown in FIG. For example, there are long-distance telephone lines with relatively small time delays, such as submarine cable circuits, and loudspeaker telephones, because they have an echo cancellation function that retains the advantages of road protection performance, that is, delay control, and does not have the disadvantage of increased line delay. It is effective in applications such as preventing island sound. FIG. 3 shows a configuration in which a gate 42 for transferring the echo path characteristics between the pseudo echo paths is added to the circuit shown in FIG. This is an embodiment in which the following effects are obtained.

なお、第３図においては、第２図において設けられてい
た受信側遅延回路２１に相当する遅延回路は設けられて
いない。この相異により第一疑似反響路１１の反響路特
性としては、送信側遅延回路２川こよる遅延時間分を含
むことになるが、第二疑似反響路４０への転送には既知
である遅延時間分の反響路特性を取り除いて転送するこ
とは容易である。例えば第一疑似反響路１１が重畳積分
を用いて反響合成を行う型であった場合、反響路特性は
、現実の反響路のィンパルス応答そのものとなる。ィン
パルス応答において遅延時間は単にタップの平行移動の
みを意味するから遅延時間に相当するだけ移動したタッ
プから転送することにより目的は蓬せられる。もちろん
第２図と同様に、受信側遅延回路を用いて構成できるこ
とは言うまでもなく、本図は例を示したにすぎない。ゲ
ート４２は双方向通話検出器３０の制御により受信側一
方向通話時には第一疑仏則反響路１１から第二疑似反響
路４０へ送信側遅延回路２０‘こよる遅延時間分を取り
除いた反響路特性を転送し、送信一方向および双方向同
時通話状態には第二疑似反響路４０から第一疑似反響路
１１へ前記遅延時間分を付加した反響路成分を転送する
ように構成されている。双方向通話検出器３０は、送信
側入力信号レベルが受信側入力信号レベルより小さくか
つ送信側入力信号レベルがしきし、値よりも大きい時受
信一方向通話と判定する。Note that, in FIG. 3, a delay circuit corresponding to the receiving side delay circuit 21 provided in FIG. 2 is not provided. Due to this difference, the echo path characteristics of the first pseudo echo path 11 include the delay time caused by the two transmitting side delay circuits, but the known delay in transfer to the second pseudo echo path 40 It is easy to remove and transfer the echo path characteristics for hours. For example, if the first pseudo echo path 11 is of a type that performs echo synthesis using convolution, the echo path characteristics will be the impulse response of the actual echo path itself. In impulse response, the delay time simply means parallel movement of the taps, so the purpose can be achieved by transferring from a tap that has moved by an amount corresponding to the delay time. Of course, it goes without saying that the structure can be constructed using a receiving side delay circuit as in FIG. 2, and this figure merely shows an example. The gate 42 is controlled by the two-way call detector 30 to provide a reverberation path from the first pseudo-reverberation path 11 to the second pseudo-reverberation path 40 by removing the delay time caused by the transmission-side delay circuit 20' during one-way communication on the receiving side. The characteristics are transferred, and the echo path component to which the delay time has been added is transferred from the second pseudo echo path 40 to the first pseudo echo path 11 in the transmission one-way and two-way simultaneous communication states. The two-way call detector 30 determines that a one-way call is received when the transmitting side input signal level is lower than the receiving side input signal level and the transmitting side input signal level is higher than a threshold value.

・双方向通話検出器３０は送信側信号レベルと受信側レ
ベルを入力とする公知の双方向通話検出器ならいずれも
回線に遅延を生ずることなく遅延制御が行えるという本
発明による効果を得ることができるのは明らかであり、
またヒステリシスあるいはハングオーバ時間等を設けて
誤検出を防ぐことが可能なのは言うまでもない。- If the two-way conversation detector 30 is a known two-way conversation detector that inputs the transmitting side signal level and the receiving side signal level, it will be possible to obtain the effect of the present invention that delay control can be performed without causing a delay in the line. It is clear that you can
It goes without saying that false detection can be prevented by providing hysteresis or hangover time.

第３図においてゲート４２を設けて第二疑似反響路４０
から第一疑似反響路１１への経路を設けてあるのは万が
一の双方向同時通話の誤検出により第一疑似反響路が乱
れた場合、第二疑似反響路の反響路成分の方が良好に反
響を消去できる事実により双方向通話状態と認められた
時には、第二疑似反響路４０から第一疑似反響路１ １
へ反響成分を転送し、前記の乱れを未然に防ぎ、再び受
信一方向通話状態となった時に早く第一疑似反響路１
１が収束するようにするためである。なお第３図では、
疑似反響路修正回路１０は常時修正を行うように綾成さ
れているがレベル検出時間、あるいはしきし、値条件等
をゲート４２の制御信号の条件とは変えた別の双方向通
話検出器を付加し、疑似反響路修正回路１０の修正係数
を制御することも有効である。In FIG. 3, a second pseudo echo path 40 is provided with a gate 42.
The reason why there is a path from the path to the first pseudo-echo path 11 is that in the unlikely event that the first pseudo-echo path is disturbed due to false detection of simultaneous two-way communication, the echo path components of the second pseudo-echo path will be better. When a two-way communication situation is recognized due to the fact that echoes can be eliminated, the second pseudo-echo path 40 is connected to the first pseudo-echo path 1.
The echo component is transferred to the first pseudo echo path 1 to prevent the above-mentioned disturbance, and to quickly transfer the echo component to the first pseudo echo path 1 when the receiving one-way communication state returns.
This is to ensure that 1 converges. In addition, in Figure 3,
Although the pseudo echo path correction circuit 10 is designed to perform constant correction, a separate two-way communication detector whose level detection time, threshold, value conditions, etc. are different from the conditions of the control signal of the gate 42 is used. It is also effective to add this and control the correction coefficient of the pseudo echo path correction circuit 10.

【図面の簡単な説明】[Brief explanation of drawings]

第１図は従来の遅延制御を用いた適応型反響消去装置で
あって１００は受信側入力端子、２００は受信側出力端
子、３００は送信側入力端子、４００送信側出力端子、
１０は疑似反響路修正回路、１１は疑似反響路、１２は
反響消去減算器、２０は送信側遅延回路、２１‘ま受信
側遅延回路、３０は双方向通話検出回である。 第２図は本発明の一実施例であって、１０川ま受信側入
力端子、４００は送信側出力端子、１０は疑似反響路修
正回路、１１は第一疑似反響路、１２は第一反響消去減
算器、２川ま送信側遅延回路、２１は受信側遅延回路、
３０は双方向通話検出器、４０は第二疑似反響路、４１
は第二反響消去減算器であり、１０，１１，１２から成
る部分５０が第一反響消去部、４０と４１から成る部分
５１が第二反響消去部である。 第３図も本発明による反響消去装置の一実施例であって
、１０川ま受信側入力端子、２００は受信側出力端子、
３０川ま送信側入力端子、４００送信側出力端子、１０
は疑似反響路修正回路、１１は第一疑似反響路、１２は
第一反響消去減算器、２川ま送信側遅延回路、３０は双
方向通話検出器、４０‘ま第二疑似反響路、４１は第二
反響消去減算器、４２はゲート回路であり、１０，１１
，１２から成る部分５０が第一反響消去部、４０，４１
から成る部分５１が第二反響消去部である。 第１図 努２図 第３図FIG. 1 shows an adaptive echo cancellation device using conventional delay control, in which 100 is a receiving side input terminal, 200 is a receiving side output terminal, 300 is a transmitting side input terminal, 400 is a transmitting side output terminal,
10 is a pseudo echo path correction circuit, 11 is a pseudo echo path, 12 is an echo cancellation subtracter, 20 is a transmitting side delay circuit, 21' is a receiving side delay circuit, and 30 is a two-way communication detection circuit. FIG. 2 shows an embodiment of the present invention, in which 10 is an input terminal on the receiving side, 400 is an output terminal on the transmitting side, 10 is a pseudo echo path correction circuit, 11 is a first pseudo echo path, and 12 is a first echo. An erasure subtracter, 21 is a transmitting side delay circuit, 21 is a receiving side delay circuit,
30 is a two-way conversation detector, 40 is a second pseudo echo path, 41
is a second echo canceling subtracter; a section 50 consisting of 10, 11, and 12 is a first echo canceling section, and a section 51 consisting of 40 and 41 is a second echo canceling section. FIG. 3 also shows an embodiment of the echo canceling device according to the present invention, in which 10 is an input terminal on the receiving side, 200 is an output terminal on the receiving side,
30 Kawama transmission side input terminal, 400 transmission side output terminal, 10
11 is a pseudo echo path correction circuit, 11 is a first pseudo echo path, 12 is a first echo cancellation subtracter, 2 channels is a transmitting side delay circuit, 30 is a two-way conversation detector, 40' is a second pseudo echo path, 41 is a second echo cancellation subtracter, 42 is a gate circuit, 10, 11
, 12 is the first echo canceller, 40, 41
A portion 51 consisting of is a second echo canceller. Figure 1 Tsutomu Figure 2 Figure 3

Claims (1)

【特許請求の範囲】 １ 疑似反響路を逐次的に合成する適応型疑似反響路を
有する型の反響消去装置であって、送信側信号に時間遅
延を与える遅延回路と送信側信号を前記遅延回路を介し
て入力とする適応型の第一反響消去部と、前記第一反響
消去部の疑似反響路の反響路特性から前記遅延回路の遅
延時間特性を取り除く手段と、送信側信号を直接入力と
する第二反響消去部と、前記遅延回路を通らない送信側
入力信号と受信側信号とを入力とする双方向通話検出器
とを有し、前記双方向通話検出器の出力によって前記第
一反響消去部の修正係数を制御し、前記第一反響消去部
の疑似反響路から、反響路特性を前記第二反響消去部の
疑似反響路に転送するように構成し、前記第二反響消去
部の出力信号を送信側出力信号とするように構成したこ
とを特徴とする反響消去装置。 ２ 特許請求の範囲の第１項に記載の反響消去装置であ
って、第一反響消去部と第二反響消去部の間の反響路特
性の転送を行うゲート回路を有し、双方向通話検出器の
出力により前記ゲート回路を制御するように構成した反
響消去装置。[Scope of Claims] 1. An echo canceling device having an adaptive pseudo-echo path that sequentially synthesizes pseudo-echo paths, comprising: a delay circuit that provides a time delay to a transmitting signal; and a delay circuit that provides a time delay to a transmitting signal; an adaptive first echo canceller that inputs the signal via the first echo canceller; means for removing the delay time characteristic of the delay circuit from the echo path characteristic of the pseudo echo path of the first echo canceller; and a two-way conversation detector that receives the transmitting side input signal and the receiving side input signal that do not pass through the delay circuit, and eliminates the first echo by the output of the two-way conversation detector. The correction coefficient of the canceling unit is controlled, and the echo path characteristics are transferred from the pseudo echo path of the first echo canceling unit to the pseudo echo path of the second echo canceling unit, and the correction coefficient of the second echo canceling unit is An echo canceling device characterized in that the output signal is configured to be a transmitting side output signal. 2. The echo canceling device according to claim 1, comprising a gate circuit for transferring echo path characteristics between the first echo canceling section and the second echo canceling section, and capable of detecting two-way communication. an echo canceling device configured to control the gate circuit according to an output of the echo canceller.