JPS61135239A - Echo canceller - Google Patents
Echo cancellerInfo
- Publication number
- JPS61135239A JPS61135239A JP25802784A JP25802784A JPS61135239A JP S61135239 A JPS61135239 A JP S61135239A JP 25802784 A JP25802784 A JP 25802784A JP 25802784 A JP25802784 A JP 25802784A JP S61135239 A JPS61135239 A JP S61135239A
- Authority
- JP
- Japan
- Prior art keywords
- signal
- echo
- input signal
- narrowband
- receiving side
- 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
Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B3/00—Line transmission systems
- H04B3/02—Details
- H04B3/20—Reducing echo effects or singing; Opening or closing transmitting path; Conditioning for transmission in one direction or the other
- H04B3/23—Reducing echo effects or singing; Opening or closing transmitting path; Conditioning for transmission in one direction or the other using a replica of transmitted signal in the time domain, e.g. echo cancellers
- H04B3/238—Reducing echo effects or singing; Opening or closing transmitting path; Conditioning for transmission in one direction or the other using a replica of transmitted signal in the time domain, e.g. echo cancellers using initial training sequence
Landscapes
- Engineering & Computer Science (AREA)
- Computer Networks & Wireless Communication (AREA)
- Signal Processing (AREA)
- 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
本発明は長距離電話回線等で発生するエコー信号を消去
し、通話品質の向上を図るために用いられるエコーキャ
ンセラに関するものである。DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an echo canceller used to eliminate echo signals generated in long-distance telephone lines and the like to improve call quality.
従来の技術
近年、長距離電話回線あるいは遠隔地点を結ぶ通信会議
システム等で発生するエコー信号を消去し、通話品質の
向上を図るエコーキャンセラが開Proc、ICASS
P 83.PP、466−469 、Apri1198
3)に記載されているようなエコーキャンセラが開発さ
れている〇
以下図面を参照しながら上述した従来のエコーキャンセ
ラの一例について説明する。Conventional technology In recent years, echo cancellers have been developed to improve call quality by eliminating echo signals generated in long-distance telephone lines or teleconferencing systems that connect remote points.Proc, ICASS
P 83. PP, 466-469, Apri1198
An echo canceller as described in 3) has been developed. An example of the conventional echo canceller described above will be described below with reference to the drawings.
第6図は従来のエコーキャンセラの構成図である。第6
図において、23は受信側入力信号端子、24は受信側
出力信号端子、26は送信側入力信号端子、26は送信
側出力信号端子、27は受信側入力信号と送信側出力信
号とに基いて送信側入力信号に含まれるエコー信号の推
定値(擬似エコー信号)を作成するための可変係数トラ
ンスバーサルフィルタから成る適応フィルタ、28は前
記送信側入力信号から前記擬似エコー信号を差し引くこ
とによりエコー信号の消去された前記送信側出力信号を
作成する減算器、29はエコーキャンセラ、30は前記
受信側入力信号から前記送信側入力信号へのエコー信号
を発生させるエコー経路である。FIG. 6 is a block diagram of a conventional echo canceller. 6th
In the figure, 23 is a receiving side input signal terminal, 24 is a receiving side output signal terminal, 26 is a transmitting side input signal terminal, 26 is a transmitting side output signal terminal, and 27 is a terminal based on the receiving side input signal and the transmitting side output signal. An adaptive filter 28 includes a variable coefficient transversal filter for creating an estimated value (pseudo echo signal) of an echo signal contained in the input signal on the transmitting side; 29 is an echo canceller, and 30 is an echo path that generates an echo signal from the receiving side input signal to the transmitting side input signal.
以上のように構成されたエコーキャンセラについて、以
下その動作について説明する。The operation of the echo canceller configured as described above will be described below.
なお、以下の説明では、エコーキャンセラ内部の信号は
時間に関してサンプリングされた離散的時間信号として
取扱うが、そのために必要なアナログディジタル変換器
及びディジタルアナログ変換器については周知のことで
あり、以下の説明では省略する。In the following explanation, the signal inside the echo canceler will be treated as a time-sampled discrete time signal, but the analog-to-digital converter and digital-to-analog converter necessary for this purpose are well known, and will not be explained below. I will omit it here.
エコーキャンセラ29では、適応フィルタ2アをもちい
て、時刻jにおける受信側入力信号Xjと送信側出力信
号J とに基いてエコー経路30のインパルス応答(
適応フィルタのフィルタ係数にあたる)h、(t=o、
1.・・・−、N−1、Nはインパルス応答のサンプル
数)の推定を行ない、推定されたインパルス応答り、(
△は推定値を表わす記号である)と前記受信側入力信号
とを第(1)式に示すようにたたみ込む(前記フィルタ
係数で受信側入力信号をフィルタリングする)ことによ
って送信側入力信号Zl に含まれる擬似エコー信号
11を作成する。The echo canceller 29 uses the adaptive filter 2a to calculate the impulse response (
corresponding to the filter coefficients of the adaptive filter)h, (t=o,
1. ...-, N-1, N is the number of impulse response samples), and the estimated impulse response is (
△ is a symbol representing an estimated value) and the receiving side input signal as shown in equation (1) (filtering the receiving side input signal with the filter coefficient), the transmitting side input signal Zl is obtained. A pseudo echo signal 11 to be included is created.
次に減算器28をもちいて第(2)式【示すように前記
送信側入力信号から前記擬似エコー信号を差し引くこと
によりエコー信号の消去された送信側出力信号を作成す
る。Next, the subtracter 28 is used to subtract the pseudo echo signal from the transmitter input signal as shown in equation (2) to create a transmitter output signal from which the echo signal has been eliminated.
ei=”j −yj ”“°゛゛゛′°゛゛゛
律)適応フィルタ係数のフィル゛り係数の推定は、前記
送信側入力信号が前記受信側入力信号のみによって生じ
ている時に行ない、たとえば第(3)式に示す学習同定
法のアルゴリズムにしたがってサンプル周期毎にフィル
タ係数を修正することによって行なう。ei=”j −yj ””°゛゛゛′°゛゛゛゛゛゛゛゛゛゛゛゛゛゛゛゛゛゛゛゛゛゛゛゛゛゛゛゛゛゛゛゛) This is done by modifying the filter coefficients at each sampling period according to the algorithm of the learning identification method shown in the equation.
・・・・・・・・・・・・・・・(3)ただし、αは0
〈αく2なる定数である。・・・・・・・・・・・・・・・(3) However, α is 0
<α is a constant equal to 2.
以上のように長距離電話口#あるいは通信会議システム
にエコーキャンセラをもちいることによってエコー信号
の消去された自然な通話を行なうことが可能となる。As described above, by using an echo canceller in a long-distance telephone port number or a communication conference system, it becomes possible to conduct a natural telephone conversation in which echo signals are eliminated.
発明が解決しようとする問題点
しかしながら上記のような構成のエコーキャンセラでは
、受信側入力信号がモデム信号のような狭帯域信号の場
合、長時間エコー経路の推定を続けると動作が不安定と
なり、エコー消去量の大巾な劣化を招くという問題点を
有していた。Problems to be Solved by the Invention However, in the echo canceller configured as described above, if the receiving side input signal is a narrowband signal such as a modem signal, the operation becomes unstable if the echo path estimation continues for a long time. This has the problem of causing a significant deterioration in the amount of echo cancellation.
すなわち、エコーキャンセラ29は適応フィルタ27を
もちいてエコー経路30のインパルス応答の推定を行な
うものであるが、推定を行なうだめの受信側入力信号が
狭帯域信号の場合、受信側入力信号の周波数帯域外では
エコー経路の推定ができないため、正しいインパルス応
答の推定を行なうことができない。実際、文献二山本、
来山。That is, the echo canceller 29 uses the adaptive filter 27 to estimate the impulse response of the echo path 30. However, if the input signal on the receiving side to be estimated is a narrowband signal, the frequency band of the input signal on the receiving side Since the echo path cannot be estimated outside, the impulse response cannot be estimated correctly. In fact, the literature Niyamamoto,
Coming to Mt.
田材、千原、桜井、″高速カルマンフィルタを用いたエ
コーキャンセラのアルゴリズムとその特性“。Tazai, Chihara, Sakurai, ``Echo canceller algorithm and its characteristics using a fast Kalman filter''.
’rl 子連(iir 学会論文誌(”) + ””
、’ 6 ’−By A 4゜PP、318−325.
1978によれば、受信側入力信号が音声信号の場合、
エコー経路の推定は主として、相関性が少なく広帯域な
無声音期間になされることが報告されている。'rl Ziren (iir academic journal (") + ""
, ' 6 '-By A 4°PP, 318-325.
According to 1978, when the receiving side input signal is an audio signal,
It has been reported that echo path estimation is mainly performed during unvoiced speech periods with little correlation and wide band.
また、エコーキャンセラをハードウェアで実現する際の
有限のレジスタ長、またエコー経路への雑音の混入等に
よってエコー経路の推定時に演算誤差を生ずる。したが
って受信側入力信号が狭帯域信号の場合、長時間エコー
経路の推定を続けると、前記演算誤差が徐々に累積して
、動作が不安定となり、エコー消去量の大巾な劣化を招
くという問題点があった。In addition, a calculation error occurs when estimating the echo path due to the finite register length when implementing the echo canceller in hardware, the introduction of noise into the echo path, and the like. Therefore, if the input signal on the receiving side is a narrowband signal, if the echo path estimation is continued for a long time, the calculation errors will gradually accumulate, making the operation unstable and causing a significant deterioration in the amount of echo cancellation. There was a point.
本発明は前記問題点に鑑み、音声信号のみならずモデム
信号のような狭帯域信号に対しても安定に動作するエコ
ーキャンセラを提供するものである。In view of the above problems, the present invention provides an echo canceller that operates stably not only for voice signals but also for narrowband signals such as modem signals.
問題点を解決するための手段
前記問題点を解決“するために本発明のエコーキャンセ
ラは、受信側入力信号と送信側出力信号とに基いて擬似
エコー信号を作成する適応フィルタと、送信側入力信号
から前記擬似エコー信号を差し引くことにより前記送信
側出力信号を作成する減算器と、前記受信側入力信号の
狭帯域性を測定し前記狭帯域性に基いて前記適応フィル
タの係数の修正を禁止する狭帯域信号検出器とから構成
されている。Means for Solving the Problems In order to solve the above-mentioned problems, the echo canceller of the present invention includes an adaptive filter that creates a pseudo echo signal based on a receiving side input signal and a transmitting side output signal, and a transmitting side input signal. a subtractor that creates the transmitter output signal by subtracting the pseudo echo signal from a signal; and a subtractor that measures the narrowband nature of the receiver input signal and prohibits modification of the coefficients of the adaptive filter based on the narrowband nature. It consists of a narrowband signal detector.
作 用
本発明のエコーキャンセラは上記した構成によって、受
信側入力信号が狭帯域信号の場合には、狭帯域信号検出
器がその狭帯域性を検出し、適応フィルタの係数の修正
を禁止することによって、エコー経路の推定を停止させ
るので、前述した演算誤差が累積することなく安定に動
作する。したがって本発明のエコーキャンセラは音声信
号のみならずモデム信号のような狭帯域信号を長時間入
力しても常に安定に動作することができる。The echo canceller of the present invention has the above-described configuration, so that when the input signal on the receiving side is a narrowband signal, the narrowband signal detector detects the narrowband nature of the signal and prohibits modification of the coefficients of the adaptive filter. As a result, the estimation of the echo path is stopped, so that the calculation error described above does not accumulate and the operation is stable. Therefore, the echo canceller of the present invention can always operate stably even when not only audio signals but also narrowband signals such as modem signals are input for a long time.
実施例
以下本発明の一実施例のエコーキャンセラについて図面
を参照しながら説明する。Embodiment Hereinafter, an echo canceler according to an embodiment of the present invention will be described with reference to the drawings.
第1図は本発明の一実施例におけるエコーキャンセラの
構成図を示すものである。第1図において1は受信側入
力信号端子、2は受信側出力信号端子、3は送信側入力
信号端子、4は送信側出力信号端子、6は受信側入力信
号と送信側出力信号とに基いて擬似エコー信号を作成す
るだめの可変トランスバーサルフィルタから成る適応フ
ィルタ、6は送信側入力信号から前記擬似エコー信号を
差し引くことによりエコー信号の消去された前−記送信
側出力信号を作成する減算器、7は前記受信側入力信号
の狭帯域性を測定し、前記狭帯域性に基いて前記適応フ
ィルタの係数の修正を禁止する狭帯域信号検出器、8は
エコーキャンセラ、9は前記受信側入力信号から前記送
信側入力信号へのエコー信号を発生させるエコー経路で
ある。FIG. 1 shows a configuration diagram of an echo canceller in an embodiment of the present invention. In FIG. 1, 1 is a receiving side input signal terminal, 2 is a receiving side output signal terminal, 3 is a transmitting side input signal terminal, 4 is a transmitting side output signal terminal, and 6 is based on a receiving side input signal and a transmitting side output signal. 6 is an adaptive filter consisting of a variable transversal filter for creating a pseudo-echo signal by subtracting the pseudo-echo signal from the transmitting-side input signal; 7 is a narrowband signal detector that measures the narrowband nature of the input signal on the receiving side and prohibits modification of the coefficients of the adaptive filter based on the narrowband nature; 8 is an echo canceller; 9 is the receiving side; An echo path that generates an echo signal from an input signal to the transmitter input signal.
以上のように構成されたエコーキャンセラについて、以
下その動作を説明する。The operation of the echo canceller configured as above will be described below.
まず、エコー経路9の推定インパルス応答をそのフィル
タ係数として記憶している適応フィルタ6をもちいて受
信側入力信号をフィルタリングすることにより擬似エコ
ー信号を作成する。First, a pseudo echo signal is created by filtering the receiving side input signal using the adaptive filter 6 which stores the estimated impulse response of the echo path 9 as its filter coefficient.
次に減算器6をもちいて送信側入力信号から前記擬似エ
コー信号を差し引くことにより送信側出力信号を作成す
る。Next, a subtracter 6 is used to subtract the pseudo echo signal from the transmitter input signal to create a transmitter output signal.
狭帯域信号検出器7では前記受信側入力信号の狭帯域性
を測定し、前記狭帯域性に基いて狭帯域信号と判定され
た時は、適応フィルタ5のフィルタ係数の修正を禁止す
る信号(以下フィルタ係数修正禁止信号と呼ぶ)を出力
する。The narrowband signal detector 7 measures the narrowband nature of the input signal on the receiving side, and when it is determined to be a narrowband signal based on the narrowband nature, a signal ( Hereinafter referred to as a filter coefficient modification prohibition signal) is output.
適応フィルタ6のフィルタ係数の推定は、狭帯域信号検
出器7がら前記フィルタ係数修正禁止信号が出力されて
いない時で前記送信側入力信号が前記受信側入力信号の
エコー信号のみによって生じている時に行ない、たとえ
ば前述した学習同定法のアルゴリズムにしたがって、フ
ィルタ係数を逐次修正することにより行なう。The filter coefficients of the adaptive filter 6 are estimated when the narrowband signal detector 7 does not output the filter coefficient modification prohibition signal and when the input signal on the transmitting side is generated only by the echo signal of the input signal on the receiving side. For example, this is done by successively modifying the filter coefficients according to the algorithm of the learning identification method described above.
以下本発明の特徴である狭帯域信号検出器7についてさ
らに詳細な説明を行なう。The narrowband signal detector 7, which is a feature of the present invention, will be explained in more detail below.
第2図は狭帯域信号検出器7の第1の実施例における内
部構成図を示すものである。第2図において10は受信
側入力信号端子、111から11nは受信側入力信号を
複数個(n個)の周波数帯域の帯域信号に分割するため
の帯域通過フィルタ、121から12nは前記帯域信号
からその短時間エネルギを算出するための短時間エネル
ギ算出器、13は前記n個の帯域信号の短時間エネルギ
に基いてその狭帯域性を測定し、狭帯域信号と判定され
場合には適応フィルタ5にフィルタ係数修正禁止信号を
出力する狭帯域性判定器、14はフィルタ係数修正禁止
信号出力端子である。FIG. 2 shows an internal configuration diagram of the first embodiment of the narrowband signal detector 7. As shown in FIG. In FIG. 2, 10 is an input signal terminal on the receiving side, 111 to 11n are band pass filters for dividing the input signal on the receiving side into band signals of a plurality of (n) frequency bands, and 121 to 12n are input signal terminals for the band signals. A short-time energy calculator 13 for calculating the short-time energy measures the narrowband nature of the n band signals based on the short-time energy, and if it is determined to be a narrowband signal, an adaptive filter 5 14 is a filter coefficient modification inhibition signal output terminal.
以上のように構成された狭帯域信号検出器について以下
その動作を説明する。The operation of the narrowband signal detector configured as above will be explained below.
受信側入力信号端子10より受信側入力信号が入力され
ると、第3図に示すような周波数特性を有するn個の帯
域通過フィルタ111から11nによってn個の帯域信
号が得られる。次に短時間エネルギ算出器121から1
2nをもちいて各帯域信号の短時間エネルギの算出を行
ない、狭帯域性判定器13に出力する。When a receiving side input signal is input from the receiving side input signal terminal 10, n band signals are obtained by n band pass filters 111 to 11n having frequency characteristics as shown in FIG. Next, the short-time energy calculator 121 to 1
2n is used to calculate the short-time energy of each band signal and output it to the narrowband determiner 13.
受信側入力信号が狭帯域信号の場合、たとえば第4図に
示すような短時間エネルギの分布図が得られる。When the input signal on the receiving side is a narrowband signal, a short-time energy distribution diagram as shown in FIG. 4, for example, is obtained.
狭帯域性判定器13では前記帯域信号の短時間エネルギ
の総和を算出して全短時間エネルギを求めるとともに前
記全エネルギに対する前記帯域信号の短時間エネルギの
比を求め、前記比の値が所定の閾値を越える場合は、特
定の周波数帯域にエネルギが集中している狭帯域信号と
判定してフィルタ係数修正禁止信号をフィルタ係数修正
禁止信号14に出力する。The narrowband determination unit 13 calculates the total short-time energy of the band signal to obtain the total short-time energy, and also calculates the ratio of the short-time energy of the band signal to the total energy, and determines whether the value of the ratio is a predetermined value. If the threshold is exceeded, it is determined that the signal is a narrowband signal with energy concentrated in a specific frequency band, and a filter coefficient modification prohibition signal is output as the filter coefficient modification prohibition signal 14.
以上のように本実施例によれば、受信側入力信号の周波
数軸上の短時間エネルギ分布から前記受信側入力信号の
狭帯域性を測定し前記狭帯域性に基いて適応フィルタの
係数の修正を禁止する狭帯域信号検出器を設けることに
より、受信側入力信号として狭帯域信号を長時間入力し
てもエコー経路推定時の演算誤差が累積することなく安
定に動作スるエコーキャンセラを提供することができる
。As described above, according to this embodiment, the narrowband characteristic of the receiving side input signal is measured from the short-time energy distribution on the frequency axis of the receiving side input signal, and the coefficients of the adaptive filter are corrected based on the narrowband characteristic. To provide an echo canceller that operates stably without accumulating calculation errors during echo path estimation even if a narrowband signal is input as a receiving side input signal for a long time by providing a narrowband signal detector that prohibits echo path estimation. be able to.
第5図は狭帯域信号検出器の第2の実施例における内部
構成図を示すものである。第5図において15は受信側
入力信号端子、16は受信側入力信号の零交差回数を算
出する零交差回数算出器、17は前記零交差回数を記憶
するためのメモリ、18は前記メモリ17に記憶されて
いる零交差回数の最大値を検出するための最大値検出器
、19は前記メモリに記憶されている零交差回数の最小
値を検出するだめの最小値検出器、20は前記零交差回
数の最大値と最小値との差を求めるための減算器、21
は前記零交差回数の最大値と最小値の差に基いて前記受
信側入力信号の狭帯域性を判定し狭帯域信号と判定され
た時には適応フィルタにフィルタ係数修正禁止信号を出
力する狭帯域性判定器、22はフィルタ係数修正禁止信
号出力端子である。FIG. 5 shows an internal configuration diagram of a second embodiment of the narrowband signal detector. In FIG. 5, 15 is a receiving side input signal terminal, 16 is a zero crossing frequency calculator for calculating the zero crossing frequency of the receiving side input signal, 17 is a memory for storing the zero crossing frequency, and 18 is a memory 17. a maximum value detector 19 for detecting the maximum value of the number of zero crossings stored in the memory; 19 a minimum value detector for detecting the minimum value of the number of zero crossings stored in the memory; 20 the zero crossing Subtractor for determining the difference between the maximum value and the minimum value of the number of times, 21
determines the narrowband nature of the input signal on the receiving side based on the difference between the maximum value and the minimum value of the number of zero crossings, and outputs a filter coefficient modification prohibition signal to the adaptive filter when it is determined to be a narrowband signal. The determiner 22 is a filter coefficient modification inhibition signal output terminal.
以上のように構成された狭帯域信号検出器について以下
その動作を説明する。The operation of the narrowband signal detector configured as above will be explained below.
受信側入力信号端子15より受信側入力信号が入力され
ると、零交差回数算出器16では所定の時間(以下この
時間をフレームと呼ぶ)の零交差回数を算出し、所定の
フレーム数の最新の零交差回数を記憶するためのメモリ
17に書き込む。次に最大値検出器18及び最小値検出
器19をもちいてメモリ17に記憶されている内容を読
み出し、それぞれ零交差回数の最大値及び最小値を検出
する。次いで減算器2oをもちいて前記零交差回数の最
大値と最小値の差を求める。狭帯域性判定器21では前
記零交差回数の最大値と最小値の差が所定の閾値上り小
さい場合には、すなわち零交差回数が所定の時間所定の
範囲内の値で継続した場合、受信側入力信号が狭帯域信
号であると判定してフィルタ係数修正禁止信号をフィル
タ係数修正禁止信号出力端子22に出力する。When the receiving side input signal is input from the receiving side input signal terminal 15, the zero crossing number calculator 16 calculates the number of zero crossings in a predetermined time (hereinafter referred to as a frame), and calculates the number of zero crossings in a predetermined time (hereinafter referred to as a frame), and is written into the memory 17 for storing the number of zero crossings. Next, the contents stored in the memory 17 are read using the maximum value detector 18 and the minimum value detector 19, and the maximum value and minimum value of the number of zero crossings are respectively detected. Next, the subtracter 2o is used to find the difference between the maximum and minimum values of the number of zero crossings. If the difference between the maximum value and the minimum value of the number of zero crossings is smaller than a predetermined threshold value, that is, if the number of zero crossings continues within a predetermined range for a predetermined period of time, the narrowband determination unit 21 determines whether the receiving side It determines that the input signal is a narrowband signal and outputs a filter coefficient modification inhibition signal to the filter coefficient modification inhibition signal output terminal 22.
以上のように本実施例によれば、受信側入力信号の零交
差回数という時間軸上のパラメータから前記受信側入力
信号の狭帯域性を測定し前記狭帯域性に基いて適応フィ
ルタの係数の修正を禁止する狭帯域検出器を設けること
により、受信側入力信号として狭帯域信号を長時間入力
してもエコー経路推定時の演算誤差が累積することなく
安定に動作するエコーキャンセラを提供することができ
る。また、第2の実施例では、算出の容易な零交差回数
というパラメータをもちいて狭帯域性の判定を行なうの
で、第1の実施例と比較してノ1−ドウエア量及び演算
量が少なくてよいという特徴を有する。As described above, according to this embodiment, the narrowband characteristic of the receiving side input signal is measured from the parameter on the time axis such as the number of zero crossings of the receiving side input signal, and the coefficients of the adaptive filter are determined based on the narrowband characteristic. To provide an echo canceller that operates stably without accumulating calculation errors during echo path estimation even if a narrowband signal is input as a receiving side input signal for a long time by providing a narrowband detector that prohibits modification. I can do it. In addition, in the second embodiment, since the narrowband property is determined using the easily calculated parameter of the number of zero crossings, the amount of hardware and calculations are smaller than in the first embodiment. It has the characteristic of being good.
発明の効果
以上のように本発明のエコーキャンセラは、周波数軸上
もしくは時間軸上で受信側入力信号の狭帯域性を測定し
前記狭帯域性に基いて適応フィルタの係数の修正を禁止
する狭帯域検出器を設けることにより、音声信号のみな
らず狭帯域信号に対しても安定に動作することができ、
その適用範囲を拡張することができる。Effects of the Invention As described above, the echo canceller of the present invention measures the narrowband nature of the input signal on the receiving side on the frequency axis or the time axis, and prohibits modification of the coefficients of the adaptive filter based on the narrowband nature. By providing a band detector, it can operate stably not only for audio signals but also for narrowband signals.
Its scope of application can be expanded.
第1図は本発明の第1の実施例におけるエコーキャンセ
ラの構成図、第2図は同第1の実施例の狭帯域信号検出
器の内部構成図、第3図は同帯域通過フィルタの周波数
特性を示す図、第4図は狭帯域信号を入力信号とした時
の帯域信号の短時間エネルギ分布図、第6図は同第2の
実施例の狭帯域信号検出器の内部構成図、第6図は従来
のエコーキャンセラの構成図である。
1・・・・・・受信側入力信号端子、2・・・・・・受
信側出力信号端子、3・・・・・・送信側入力信号端子
、4・・・・・・送信側出力信号端子、6・・・・・・
適応フィルタ、6・・・・・・減算器、7・・・・・・
狭帯域信号検出器、8・・・・・・エコーキャンセラ、
9・・・・・・エコー経路、1o・−・・・・受信側入
力信号端子、111〜11n・・・・・・帯域通過フィ
ルタ、121〜12n・・・・・・短時間エネルギ算出
器、13・・・・・・狭帯域性判定器、14・・・・・
・フィルタ係数修正禁止信号出力端子、15・・・・・
・受信側入力信号端子、16・・・・・・零交差回数算
出器、17・・・・・・メモリ、18・・・・・・最大
値検出器、19・・・・・・最小値検出器、20・・・
・・・減算器、21・・・・・・狭帯域性判定器、22
・・・・・・フィルタ係数修正禁止信号出力端子。
代理人の氏名 弁理士 中 尾 敏 男 ほか1名wJ
1図
第2図FIG. 1 is a configuration diagram of an echo canceller in a first embodiment of the present invention, FIG. 2 is an internal configuration diagram of a narrowband signal detector in the first embodiment, and FIG. 3 is a frequency diagram of the bandpass filter. 4 is a diagram showing the short-time energy distribution of a band signal when a narrow band signal is used as an input signal. FIG. 6 is an internal configuration diagram of the narrow band signal detector of the second embodiment. FIG. 6 is a block diagram of a conventional echo canceller. 1... Receiving side input signal terminal, 2... Receiving side output signal terminal, 3...... Transmitting side input signal terminal, 4...... Transmitting side output signal Terminal, 6...
Adaptive filter, 6... Subtractor, 7...
Narrowband signal detector, 8...Echo canceller,
9...Echo path, 1o...Receiving side input signal terminal, 111-11n...Band pass filter, 121-12n...Short-time energy calculator , 13... Narrowband determiner, 14...
・Filter coefficient modification inhibition signal output terminal, 15...
- Receiving side input signal terminal, 16... Zero crossing frequency calculator, 17... Memory, 18... Maximum value detector, 19... Minimum value Detector, 20...
. . . Subtractor, 21 . . . Narrowband determination device, 22
...Filter coefficient modification inhibition signal output terminal. Name of agent: Patent attorney Toshio Nakao and one other person wJ
Figure 1 Figure 2
Claims (3)
エコー信号を作成する適応フィルタと、送信側入力信号
から前記擬似エコー信号を差し引くことにより前記送信
側出力信号を作成する減算器と、前記受信側入力信号の
狭帯域性を測定し前記狭帯域性に基いて前記適応フィル
タの係数の修正を禁止する狭帯域信号検出器とから構成
されていることを特徴とするエコーキャンセラ。(1) An adaptive filter that creates a pseudo-echo signal based on a receiving-side input signal and a transmitting-side output signal; and a subtracter that creates the transmitting-side output signal by subtracting the pseudo-echo signal from the transmitting-side input signal. and a narrowband signal detector that measures the narrowband nature of the input signal on the receiving side and prohibits modification of the coefficients of the adaptive filter based on the narrowband nature.
波数帯域の帯域信号に分割し、前記帯域信号に基いて前
記受信側入力信号の狭帯域性を測定し、前記狭帯域性に
基いて適応フィルタの係数の修正を禁止することを特徴
とする特許請求の範囲第1項記載のエコーキャンセラ。(2) The narrowband signal detector divides the receiving side input signal into band signals of a plurality of frequency bands, measures the narrowband nature of the receiving side input signal based on the band signal, and measures the narrowband nature of the receiving side input signal. 2. The echo canceller according to claim 1, wherein modification of the coefficients of the adaptive filter is prohibited based on the echo canceller.
数を測定し、前記零交差回数に基いて前記受信側入力信
号の狭帯域性を測定し、前記狭帯域性に基いて適応フィ
ルタの係数の修正を禁止することを特徴とする特許請求
の範囲第1項記載のエコーキャンセラ。(3) The narrowband signal detector measures the number of zero crossings of the receiving side input signal, measures the narrowband nature of the receiving side input signal based on the number of zero crossings, and adapts based on the narrowband nature. 2. The echo canceller according to claim 1, wherein modification of filter coefficients is prohibited.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP25802784A JPS61135239A (en) | 1984-12-06 | 1984-12-06 | Echo canceller |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP25802784A JPS61135239A (en) | 1984-12-06 | 1984-12-06 | Echo canceller |
Publications (1)
Publication Number | Publication Date |
---|---|
JPS61135239A true JPS61135239A (en) | 1986-06-23 |
Family
ID=17314511
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
JP25802784A Pending JPS61135239A (en) | 1984-12-06 | 1984-12-06 | Echo canceller |
Country Status (1)
Country | Link |
---|---|
JP (1) | JPS61135239A (en) |
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