JPH01314035A - Echo canceler - Google Patents
Echo cancelerInfo
- Publication number
- JPH01314035A JPH01314035A JP14467188A JP14467188A JPH01314035A JP H01314035 A JPH01314035 A JP H01314035A JP 14467188 A JP14467188 A JP 14467188A JP 14467188 A JP14467188 A JP 14467188A JP H01314035 A JPH01314035 A JP H01314035A
- Authority
- JP
- Japan
- Prior art keywords
- signal
- echo
- circuit
- output
- path model
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
- 238000005259 measurement Methods 0.000 claims abstract description 16
- 238000001514 detection method Methods 0.000 claims abstract description 11
- 238000012937 correction Methods 0.000 claims abstract description 7
- 230000003044 adaptive effect Effects 0.000 claims description 2
- 238000012986 modification Methods 0.000 description 6
- 230000004048 modification Effects 0.000 description 6
- 238000010586 diagram Methods 0.000 description 4
- 238000004891 communication Methods 0.000 description 3
- 238000002592 echocardiography Methods 0.000 description 3
- 230000005540 biological transmission Effects 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 230000005236 sound signal Effects 0.000 description 1
Landscapes
- Cable Transmission Systems, Equalization Of Radio And Reduction Of Echo (AREA)
Abstract
Description
【発明の詳細な説明】
〔産業上の利用分野〕
本発明は通信回線に使用されるエコーキャンセラに関す
るものである。DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an echo canceller used in communication lines.
近年長距離回線、特に衛星通信の急激な増大により通信
回線に生じるエコーの存在がその回線遅延の大きさ故に
、通話品質上大きな問題となっている。従来、このエコ
ーを制御するためにエコーサブレ乙すが用いられている
が、これはスイッチング動作を基本としているため、語
頭切断やクリック雑音等の障害が発生するという問題が
有り、この問題を解決するためにエコーキャンセラが開
発された。In recent years, due to the rapid increase in long-distance lines, especially satellite communications, the presence of echoes occurring in communication lines has become a serious problem in terms of speech quality due to the large line delay. Conventionally, echo sub-layers have been used to control this echo, but since they are based on switching operations, there are problems such as truncations at the beginning of words and click noises. An echo canceller was developed for this purpose.
エコーキャンセラは、内部にアダプティブフィルタ(エ
コーパスモデル)を持ち、通話信号を基に受話出力から
送話人力までの特性を測定する。The echo canceller has an internal adaptive filter (echo path model) and measures characteristics from the receiving output to the transmitting power based on the speech signal.
そして、エコーパスモデルをこの測定したエコーパス特
性に合わせ、エコーパスモデルに受話信号を通すことに
よりエコー信号に近似した擬似エコーを作り出す。さら
に、実際のエコー信号からこの擬似エコーを差し引くこ
とによりエコーを打ち消す。Then, by matching the echo path model to the measured echo path characteristics and passing the received signal through the echo path model, a pseudo echo that approximates the echo signal is created. Furthermore, the echo is canceled by subtracting this pseudo echo from the actual echo signal.
この従来のエコーキャンセラは具体的には第2図のブロ
ック図に示される。This conventional echo canceller is specifically shown in the block diagram of FIG.
同図において、受話信号入力端子1より入力された受話
信号は、受話信号出力端子2に送られると同時にエコー
パスモデル6と測定回路8に送られる。エコーパス5に
送られた信号は、このエコーパス5を通ってエコーとし
てエコーキャンセラの送話信号入力端子3に入力される
。In the figure, a received signal inputted from a received signal input terminal 1 is sent to a received signal output terminal 2 and simultaneously to an echo path model 6 and a measuring circuit 8. The signal sent to the echo path 5 passes through this echo path 5 and is input as an echo to the transmission signal input terminal 3 of the echo canceller.
一方、エコーパスモデル6に入力された受話信号ハエコ
ーパス5と同一特性を持つエコーパスモデル6を通るこ
とにより、送話信号入力端子3に入力されるエコーと同
一の擬似エコーに変換される。さらに、この擬似エコー
は減算器7により送話信号入力端子3から入力される実
際のエコー信号から差し引かれ、受話信号は減算器7に
よってエコーが打ち消されて送話信号出力端子4から出
力される。On the other hand, by passing the received voice signal input to the echo path model 6 through an echo path model 6 having the same characteristics as the echo path 5, it is converted into a pseudo echo identical to the echo input to the transmitted voice signal input terminal 3. Furthermore, this pseudo echo is subtracted by the subtracter 7 from the actual echo signal input from the transmit signal input terminal 3, and the received signal is output from the transmit signal output terminal 4 after the echo is canceled by the subtracter 7. .
この時、測定回路8は減算器7の出力を監視して、減算
器7の出力が常に零となるようエコーパスモデル6の特
性を制御している。At this time, the measurement circuit 8 monitors the output of the subtracter 7 and controls the characteristics of the echo path model 6 so that the output of the subtracter 7 is always zero.
しかしながら、上述の従来のエコーキャンセラは、入力
信号が白色雑音のように信号の全帯域に広がっていると
きは、エコーパスモデルの推定は正常に行われるが、入
力信号が単一周波数のように特定帯域にしかないときは
満足なエコーパスモデルの推定が行われないという課題
を有していた。However, the conventional echo canceller described above can successfully estimate the echo path model when the input signal is spread over the entire signal band like white noise, but when the input signal is spread over the entire signal band like white noise, the echo path model is estimated correctly. There is a problem in that a satisfactory echo path model cannot be estimated when the echo path model exists only in a specific band.
つまり、エコーキャンセラではエコーパスモデルの推定
を常時行っているため、通話開始時に帯域の広い音声信
号で推定を行った後に帯域の狭いMF信号等で修正を行
なうと、−度正常にできたエコーパスモデルを壊すこと
になってしまってエコーが戻ることになる。In other words, since the echo canceler constantly estimates the echo path model, if it is estimated using a wide-band audio signal at the start of a call and then corrected using a narrow-band MF signal, the echo This will break the path model and cause the echo to return.
これを前述の第2図を参照して説明すると次のようにな
る。つまり、測定回路8は減算器7の出力が常に零とな
るようエコーパスモデル6の特性を制御しているが、こ
の時受話信号に白色雑音や、音声信号のように帯域の広
い信号が入力されればエコーパスモデルは全帯域にわた
り正しい特性を示す。しかし、単一信号のような狭帯域
の信号が入力されると、その帯域しか打ち消さないよう
な特性を持つエコーパス特性となる。したがって、通話
の途中で電話機のブツシュボタンを押したりすると狭帯
域のMFトーンが送られ、エコーパスモデルの特性が乱
れてその後の通話にエコーが戻ることになる。This will be explained as follows with reference to FIG. 2 mentioned above. In other words, the measurement circuit 8 controls the characteristics of the echo path model 6 so that the output of the subtractor 7 is always zero, but at this time, white noise or a wide band signal such as a voice signal is input to the received signal. If so, the echo path model will show correct characteristics over the entire band. However, when a narrow band signal such as a single signal is input, the echo path characteristic is such that it cancels out only that band. Therefore, if the button on the telephone is pressed during a call, a narrowband MF tone is sent, which disrupts the characteristics of the echo path model and causes an echo to return to subsequent calls.
本発明の目的は、帯域の狭いMF信号等が入力されても
エコーパスモデルを壊すことなく、エコーの打ち消しを
行い得るエコーキャンセラを提供することにある。An object of the present invention is to provide an echo canceller that can cancel echoes without destroying the echo path model even if a narrow band MF signal or the like is input.
このために本発明は、受話信号を複数の帯域に分割する
フィルタと、分割された帯域の各信号レベルを測定する
レベル測定回路と、レベル測定回路の出力により信号の
有無を判定する信号検出回路と、信号検出回路の出力に
より入力信号数を測定する計数回路と、計数回路の出力
から入力信号が狭帯域信号か否かを判定する判定回路と
、判定回路の出力を基に測定回路の出力を制御してエコ
ーパスモデルの修正を制御する修正制御回路とを備えた
ものである。To this end, the present invention provides a filter that divides a received signal into a plurality of bands, a level measurement circuit that measures the signal level of each of the divided bands, and a signal detection circuit that determines the presence or absence of a signal based on the output of the level measurement circuit. , a counting circuit that measures the number of input signals based on the output of the signal detection circuit, a judgment circuit that judges whether the input signal is a narrowband signal from the output of the counting circuit, and an output of the measurement circuit based on the output of the judgment circuit. and a modification control circuit that controls modification of the echo path model.
エコーパスモデルの修正は常に広帯域信号で行われる。 Echo path model modifications are always performed on wideband signals.
次に本発明について図面を参照して以下に説明する。 Next, the present invention will be explained below with reference to the drawings.
第1図は本発明の一実施例の回路構成を表すブロック図
であり、第2図と同符号のものは同一のものを表し、そ
の説明は省略する。FIG. 1 is a block diagram showing a circuit configuration of an embodiment of the present invention, and the same reference numerals as in FIG. 2 represent the same components, and the explanation thereof will be omitted.
入力された受話信号は、受話信号入力端子1に接続され
た複数個のフィルタ9により複数の帯域に分割され、フ
ィルタ9に接続されたフィルタ9と同数のレベル測定回
路10により入力受話信号のレベルが測定される。この
測定結果に基づいて、比較器により構成される、レベル
測定回路10と同数の信号検出回路11により入力信号
の有無の情報が作成される。The input reception signal is divided into a plurality of bands by a plurality of filters 9 connected to the reception signal input terminal 1, and the level of the input reception signal is measured by the same number of level measuring circuits 10 as the filters 9 connected to the filter 9. is measured. Based on this measurement result, information on the presence or absence of an input signal is created by the same number of signal detection circuits 11 as level measurement circuits 10, which are composed of comparators.
計数回路12では信号検出回路11からの信号を基に信
号の有る帯域の数が計数され、この計数結果は判定回路
13に送られて信号の有る帯域の数とこの帯域とを基に
入力信号が狭帯域信号か否かが判定される。そして、修
正制御回路14は、判定回路13が入力信号が狭帯域信
号であると判定した時には、測定回路8がエコーパスモ
デル6を修正しないよう制御する。The counting circuit 12 counts the number of bands in which the signal exists based on the signal from the signal detection circuit 11, and this counting result is sent to the determination circuit 13, which determines the input signal based on the number of bands in which the signal exists and this band. It is determined whether or not is a narrowband signal. Then, the modification control circuit 14 controls the measurement circuit 8 not to modify the echo path model 6 when the determination circuit 13 determines that the input signal is a narrowband signal.
このため、本実施例においては、MP信号等の狭帯域の
受話信号が受話信号入力端子lに入力されても、この信
号入力によりエコーパスモデル6は修正されることはな
く、常に、エコーパスモデル6の修正は、修正制御回路
14によって広帯域信号が入力された場合にのみ行われ
る。従って、従来のように一度正常に出来たエコーパス
モデルは壊されることは無い。Therefore, in this embodiment, even if a narrowband reception signal such as an MP signal is input to the reception signal input terminal l, the echo path model 6 is not modified by this signal input, and the echo path model 6 is always Modification of the model 6 is performed only when a broadband signal is input by the modification control circuit 14. Therefore, an echo path model that has been successfully created will not be destroyed as in the conventional method.
以上説明したように本発明は、受話信号を複数の帯域に
分割するフィルタと、分割された帯域の各信号レベルを
測定するレベル測定回路と、レベル測定回路の出力によ
り信号の有無を判定する信号検出回路と、信号検出回路
の出力により入力信号数を測定する計数回路と、計数回
路の出力から入力信号が狭帯域信号か否かを判定する判
定回路と、判定回路の出力を基に測定回路の出力を制御
してエコーパスモデルの修正を制御する修正制御回路と
を備えたことにより、エコーパスモデルの修正は常に広
帯域信号で行われる。このため、帯域の狭いMF倍信号
が入力されてもエコーパスモデルは壊されることはなく
、エコーパスの乱れは確実に防げ、安定したエコーの打
ち消しを行い得るエコーキャンセラを提供できるという
効果を有する。As explained above, the present invention includes a filter that divides a received signal into a plurality of bands, a level measurement circuit that measures the signal level of each of the divided bands, and a signal that determines the presence or absence of a signal based on the output of the level measurement circuit. a detection circuit, a counting circuit that measures the number of input signals based on the output of the signal detection circuit, a determination circuit that determines whether the input signal is a narrowband signal from the output of the counting circuit, and a measurement circuit based on the output of the determination circuit. The correction control circuit controls the output of the echo path model to control the correction of the echo path model, so that the correction of the echo path model is always performed using a wideband signal. Therefore, even if an MF multiplied signal with a narrow band is input, the echo path model is not destroyed, echo path disturbance can be reliably prevented, and an echo canceller capable of stably canceling echoes can be provided.
第1図は本発明の一実施例の回路構成を表すブロック図
、第2図は従来の回路構成を表すブロック図である。
l・・・受話信号入力端子、2・・・受話信号出力端子
、3・・・送話信号入力端子、4・・・送話信号出力端
子、5・・・エコーパス、6・・・エコーパスモデル、
7・・・fli算器、8・・・測定回路、9・・・フィ
ルタ、IO・・・レベル測定回路、11・・・信号検出
回路、12・・・計数回路、13・・・判定回路、14
・・・修正制御回路。FIG. 1 is a block diagram showing a circuit configuration of an embodiment of the present invention, and FIG. 2 is a block diagram showing a conventional circuit configuration. l... Receive signal input terminal, 2... Receive signal output terminal, 3... Transmit signal input terminal, 4... Transmit signal output terminal, 5... Echo path, 6... Echo path model,
7...fli calculator, 8...measuring circuit, 9...filter, IO...level measuring circuit, 11...signal detection circuit, 12...counting circuit, 13...judgment circuit , 14
...Modified control circuit.
Claims (1)
を測定回路により測定し、この測定された特性と同一特
性のアダプティブフィルタで構成されるエコーパスモデ
ルにより擬似エコーを合成し、実際のエコーからこの擬
似エコーを差し引くことによりエコーを打ち消すエコー
キャンセラにおいて、 受話信号を複数の帯域に分割する複数のフィルタと、こ
のフィルタによって分割された各帯域の各信号レベルを
測定するレベル測定回路と、この各レベル測定回路の出
力により入力信号の有無を判定する信号検出回路と、こ
の各信号検出回路の出力により入力信号数を測定する計
数回路と、この計数回路の出力から入力信号が狭帯域信
号か否かを判定する判定回路と、この判定回路の出力を
基に前記測定回路の出力を制御してエコーパスモデルの
修正を制御する修正制御回路を備えたことを特徴とする
エコーキャンセラ。[Claims] The characteristics of the echo path from the output of the received signal to the input of the transmitted signal are measured by a measuring circuit, and a pseudo echo is synthesized using an echo path model composed of an adaptive filter having the same characteristics as the measured characteristics. An echo canceler that cancels echo by subtracting this pseudo echo from the actual echo includes multiple filters that divide the received signal into multiple bands, and a level measurement that measures the signal level of each band divided by the filters. a signal detection circuit that determines the presence or absence of an input signal based on the output of each level measurement circuit; a counting circuit that measures the number of input signals based on the output of each signal detection circuit; An echo characterized by comprising: a determination circuit that determines whether or not the signal is a narrowband signal; and a correction control circuit that controls the output of the measurement circuit based on the output of the determination circuit to control correction of the echo path model. canceller.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP14467188A JPH01314035A (en) | 1988-06-14 | 1988-06-14 | Echo canceler |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP14467188A JPH01314035A (en) | 1988-06-14 | 1988-06-14 | Echo canceler |
Publications (1)
Publication Number | Publication Date |
---|---|
JPH01314035A true JPH01314035A (en) | 1989-12-19 |
Family
ID=15367530
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
JP14467188A Pending JPH01314035A (en) | 1988-06-14 | 1988-06-14 | Echo canceler |
Country Status (1)
Country | Link |
---|---|
JP (1) | JPH01314035A (en) |
-
1988
- 1988-06-14 JP JP14467188A patent/JPH01314035A/en active Pending
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