JPH04239824A - Tone disabler signal detection system - Google Patents

Abstract

PURPOSE:To prevent mis-detection of a tone disabler signal without much increase in processing quantity of a signal detection section with respect to the system detecting the tone disabler signal. CONSTITUTION:A first band pass filter 2 and a signal power detection section 4 of a tone disabler signal detection section 1 of a tone disabler to stop the operation of an echo canceller when the tone disabler signal is detected depending on a phase inversion number of the tone disabler signal at a receiver side input and a sender side input, a second band pass filter 3 and a signal power detection section 5 detects the tone disabler signal input at the sender side and a selector 6 inputs a band pass filter output whose signal input is detected to the tone disabler signal detection section 1 to discriminate the detection of the tone disabler signal.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a signal detection method,
In particular, the present invention relates to a method of detecting a tone disabler signal for operating a tone disabler for stopping the operation of an echo canceller.

[0002] An echo canceller inserted into a communication line is activated during voice communication, and when performing data communication, the tone disabler is activated by a tone disabler signal from a modem connected to the communication line. This will stop the operation. At this time, the tone disabler signal is CCITT
It consists of a pilot signal of a specific frequency (2100Hz) whose phase is inverted at fixed time intervals (450ms±25ms) as specified in the recommendations (G.165, V.25). On the receiving side, the tone disabler signal is 2100H.
2100Hz through Z band pass filter (BPF)
When applied to a phase-locked circuit (PLL), this signal is detected using the polarity inversion of the PLL control signal that occurs based on the phase inversion of this signal.

[0003] Such a signal detection method for a tone disabler signal correctly detects and determines whether the tone disabler signal is input from either the received signal input (Rin) or the transmitted signal input (Sin). It is desired to obtain.

0004

2. Description of the Related Art FIG. 8 shows the overall configuration of a tone disabler signal determination circuit, in which 11 is a signal power detection section for detecting the level of an input pilot signal, and 12 is a 2100 Hz band-pass filter ( BPF), 13 is a 2100Hz band elimination filter (BE
F), 14 is a 700Hz low-pass filter (LPF)
, 15 is a 700Hz high-pass filter (HPF), 1
6 is a phase locked loop (PLL), 17, 18, 19, 20
are BPF12, BEF13, LPF14, HP respectively
a signal power detection unit that detects the level of the output of F15, 21
2 is a phase reversal detector that detects the polarity reversal of the control signal of the PLL 16; 22 is a timer that counts a predetermined time; 23 is a counter that counts the number of times the polarity reversal is detected by the phase reversal detector;
Reference numeral 4 denotes a determination circuit that determines the detection of a tone disabler signal.

[0005] When an input signal is input, the signal power detection section 11 detects that the signal power is above a certain threshold value. When the level of the input signal decreases, the detection signal of the signal power detection section 11 immediately stops, so the determination circuit 24 stops outputting the signal that has determined that the tone disabler signal has been detected. As a result, when the input signal level drops, the operation of the tone disabler is terminated and the echo canceller is immediately put into operation.

[0006] When a tone disabler signal is applied to the input, the output level of BPF 12 increases. When the 2100 Hz signal power level detected by the signal power detection section 17 does not reach the determination threshold, the pilot signal detection operation is not performed. When the detection result of the signal power detection section 17 is equal to or higher than the threshold, the signal power detection section 18 checks the signal level other than 2100Hz, which is the output of the BEF 13, and when this exceeds a predetermined threshold, the signal level of the pilot signal is No detection operation is performed. The threshold value in this case is selected to be, for example, (2100 Hz level - 5 dB), and when the S/N of the input signal is poor, the tone disabler signal is not detected.

2100H in the signal power detection section 18
When the signal level other than z does not exceed the threshold, timer 2
At step 2, counting for a predetermined time (400 ms) is started. As a result, the phase inversion detector 21 connected to the output of the PLL 16 stops its operation while the timer 22 is counting. When the timer 22 finishes counting, the phase reversal detector 21 begins its operation. When the phase of the 2100 Hz pilot signal is reversed, the polarity of the control signal of the PLL 16 changes, but due to ringing that occurs during the transient state of PLL operation, the control signal undergoes multiple polarity reversals. The phase reversal detector 21 detects a zero cross based on the polarity reversal of the control signal of the PLL 16 and generates a pulse, and upon detection of the first polarity reversal pulse, it generates an output signal and starts the timer 22 again. As a result, the operation of the phase inversion detector 21 is stopped again, and multiple polarity inversions are not detected due to one phase inversion of the pilot signal.

[0008] After that, the same operation is repeated, but
The counter 23 counts the detection results of phase inversion by the phase inversion detector 21, and when two phase inversions are counted, the determination circuit 24 determines the detection of a tone disabler signal and outputs a signal representing the detection result. At this time, when the tone disabler signal is stopped and a data signal (modem signal) is sent, it is necessary to continue the echo canceller's operation stopped state. Therefore, 70 from LPF14
The modem signal is monitored by detecting the signal power level of a frequency of 0 Hz or less by a signal power detector 19, and by detecting the signal power level of a frequency of 700 Hz or more from the HPF 15 by a signal power detector 20. When this is above a certain threshold level, it outputs a signal that determines the detection of a tone disabler signal to stop the echo canceller from operating, and when it is below the threshold level, it determines that the modem signal has stopped. Control is performed to stop the signal for which it has been determined that the tone disabler signal has been detected, and to cancel the stoppage of the echo canceller operation. In this case, the frequency of the modem signal differs depending on the model, so 700H
The signal power level is detected separately for frequencies below z and frequencies above 700 Hz.

[0009] In the echo canceller, the tone disabler must operate and stop its operation regardless of whether the tone disabler signal is input from the receiving side (Rin) or the transmitting side (Sin). On the other hand, since it is not known whether the tone disabler signal is input from the transmitting side or the receiving side, it is necessary to correctly detect the tone disabler signal in either case so that the tone disabler can operate.

To this end, it is desirable to provide independent tone disabler signal detection circuits for the Rin signal and the Sin signal. However, as shown in FIG. 8, tone disabler signal detection requires 21
00Hz bandpass filter and PL for phase inversion detection
It is difficult to provide independent detection circuits for the Rin signal and the Sin signal, since it requires a considerable number of circuits such as L and a large amount of signal processing. Therefore, Rin
Conventionally, a method has been used in which a tone disabler signal is detected by adding a signal of 1 and a signal of sine and then inputting the signal to a signal detection circuit.

FIG. 9 shows a conventional tone disabler signal detection circuit, in which the same parts as in FIG. 8 are designated by the same numbers, and 25 is an adder circuit. Sender side (S
The tone disabler signal input at the receiving side (Rin) and the tone disabler signal input at the receiving side (Rin) are as follows:
After being added in the adder 25 consisting of an OR circuit or the like, the signal component of 2100 Hz is extracted through the BPF 12, and as a result, the counter 23 generates an output indicating detection of the tone disabler signal as described above.

0012

Problem to be Solved by the Invention In the conventional tone disabler signal detection method shown in FIG.
When a tone disabler signal is input from one of the two, there is no problem if the other signal is not input, but
If some signal is input to the other, there is a problem in that false detection occurs due to interference between the two signals.

[0013] The present invention aims to solve the problems of the prior art, and can prevent false detection of tone disabler signals without significantly increasing the processing amount of the signal detection section. , aims to provide a tone disabler signal detection method.

[0014]

[Means for Solving the Problem] The present invention provides tone disabling by the number of inversions of a control signal of a phase synchronization circuit based on phase inversions of a tone disabler signal at a reception signal input and a tone disabler signal at a transmission signal input. In the tone disabler signal detecting section of the tone disabler, which detects the tone disabler signal and stops the operation of the echo canceller when the tone disabler signal is detected, a first bandpass filter extracts the tone disabler signal on the receiving side. , a second bandpass filter that extracts the tone disabler signal on the transmitting side, a first signal power detection section that detects the output power of the first bandpass filter, and a second bandpass filter that detects the output power of the second bandpass filter. Second to detect
a signal power detection section, and a first signal power detection section or a second signal power detection section.
and a selector for inputting the output signal of the first bandpass filter or the second bandpass filter to the tone disabler signal detection section according to the detection signal of the signal power detection section. .

[0015]

[Operation] The tone disabler signal detecting section 1 of the tone disabler for stopping the operation of the echo canceller detects a tone disabler signal at the reception signal input (Rin) and a tone disabler signal at the transmission signal input (Sin). The tone disabler signal is detected when the control signal of the phase synchronization circuit is inverted a predetermined number of times based on the phase inversion.

In the system of the present invention, as shown in the principle configuration in FIG. 1, a first band-pass filter 2 is provided to extract the tone disabler signal on the reception side, 4, the output power of this first bandpass filter is detected. Further, a second bandpass filter 3 is provided to extract a tone disabler signal on the transmission side, and a second signal power detection section 5 detects the output power of the second bandpass filter. Furthermore, a selector 6 is provided to select the output signal of the first bandpass filter 2 or the second bandpass filter 3 according to the detection signal of the first signal power detection section 4 or the second signal power detection section 5. The tone disabler signal is inputted to the tone disabler signal detection section 1. Therefore, in the system of the present invention, when a tone disabler signal is input to either the receiving side or the transmitting side, even if some signal is input to the other side, erroneous detection will not occur due to interference between the two signals. Furthermore, according to the method of the present invention, the amount of processing for tone disabler signal detection can be reduced compared to the conventional method.

[0017]

[Embodiment] FIG. 2 shows an embodiment of the present invention, in which the same parts as in FIG. 9 are designated by the same numbers, and 31
, 32 are 2100Hz bandpass filters (
BPF), 33 and 34 are signal power detection units that detect the output levels of the BPFs 31 and 32, respectively, and 35 is a control unit (
CNT), 36 and 37 are selectors.

In FIG. 2, when a tone disabler signal is input to Rin, the signal power detection section 33 generates a detection signal based on the output of the BPF 31. Also, when there is a tone disabler signal input to Sin, the BPF32
The signal power detection unit 34 generates a detection signal based on the output. The control unit 35 selects selectors 36 and 37 when a detection signal is generated in either of the signal power detection units 33 and 34.
switch to the side where the detection signal is generated. by this,
The PLL 16 operates via the selector 36, and the phase inversion detector 21 detects the phase inversion of the tone disabler signal as described above, and the counter 23 detects the phase inversion of the tone disabler signal.
When the number of phase inversions has been counted, the counter 23 outputs a signal indicating that the tone disabler signal has been detected. At this time, the timer 2
The input to 2 is also switched, and timer 22 is activated by the rising edge of the 2100 Hz signal on either Rin or Sin.

The processing flow in the tone disabler signal detection system of the present invention will be explained below with reference to FIGS. 3 to 6.

FIG. 3 is a flowchart showing the processing of the selector section. First, it is checked whether or not the tone disabler signal detection flag TDF, which indicates that the tone disabler signal is being detected, is 0. If it is 0, the process moves to the selector section. Note that if it is not 0, the process moves to a release flow that cancels subsequent processing.

In the selector section, the Rin signal and the S
Look at the state of the RXSF flag that indicates the selection state of the in signal, and if it is 0 indicating undetermined, set the Rin signal to 2100Hz.
Give it to the main bandpass filter input (XAIN) of
A Sin signal is given to the 2100 Hz subband pass filter input (XCIN). When the Rin signal is a positive value (>0) indicating the Rin signal input, the Rin signal is applied to the main bandpass filter input (XAIN), and when the Sin signal is a negative value (<0), the Sin The signal is applied to the main bandpass filter input (XAIN). Furthermore, the input of XAIN is given to a band elimination filter. Then, it is checked whether the RXSF flag is 0 or not.

FIG. 4 is a flowchart showing the processing of the control section. When the RXSF flag indicating the selection state of the Rin signal and the Sin signal is 0 indicating undetermined, when the main bandpass filter output PWBPM is greater than or equal to the subbandpass filter output PWBPS, the selection on the subbandpass filter side is performed. A timer TS for selecting the main bandpass filter is set to 0, and when the output level of the 2100 Hz bandpass filter is equal to or higher than a predetermined value (-35dBm0), a timer TM for selecting the main bandpass filter is incremented. When timer TM reaches 50ms or more, R
The XSF flag is set to a positive value (for example, 1), the timer PRTMR for masking the PLL is set to 50 ms, and the process ends. Furthermore, when the 2100Hz bandpass filter output level does not reach the predetermined value (-35dBm0), the timer TM is set to 0, the timer PRTMR is set to 50ms, and the process ends.

Main bandpass filter output PWBPM
When the output level of the 2100 Hz band pass filter does not reach the sub band pass filter output PWBPS, the timer TM is set to 0, and when the 2100 Hz band pass filter output level is equal to or higher than a predetermined value (-35 dBm0), the timer TS is incremented. Timer TS is 5
When it is 0ms or more, set the RXSF flag to a negative value (for example, -1), copy the tap coefficient of the subbandpass filter to the main bandpass filter, and change the main bandpass filter output PWBPM to the subbandpass filter output PWBPS. Change the timer PRTMR to 50m
Set to s and exit.

FIG. 5 is a flowchart showing the first half of the processing of the detection section including the PLL, timer, phase inversion detector, and counter. When the 2100Hz bandpass filter output level is above the predetermined value (-35dBm0), the 2100Hz
The output of the Hz band elimination filter is the threshold value (-
Detected number of reversals in PLL without exceeding 5 dB) PRE
When V does not reach 1 and when the output of the 2100 Hz band elimination filter exceeds the threshold, increment timer T2, which counts the total processing time, and increment timer PRTMR. 2100
When the Hz bandpass filter output level is a predetermined value (-35d
Bm0) and when the output of the 2100Hz band elimination filter does not exceed the threshold (-5dB) and the number of detected inversions in the PLL PREV is 1 or more, it is assumed that the tone disabler signal has not been detected, and timer T2 is set to 0. and tone disabler signal detection flag TD
Set F to 0 and set the RXSF flag to 0 indicating undetermined.

FIG. 6 is a flowchart showing the latter half of the processing of the detection section including the PLL, timer, phase inversion detector, and counter. Check whether timer PRTMR is 400ms or more, and if it is 400ms or more, PLL
is operating, increments the number of PLL inversions, sets timer PRTMR to 0, and sets timer T2 to 90.
Check whether it is 0ms or more. Timer PRTMR is 4
When the time does not reach 00ms and when the PLL is not operating, it is immediately checked whether the timer T2 is 900ms or more. When the timer T2 does not reach 900ms, the tone disabler signal is being input, so the flag TD is
Set F to 0. When timer T2 is 900ms or more, check whether timer T2 is 1000ms or more, and if it does not reach 1000ms, check whether the number of PLL phase inversions is 2 or more, and it does not reach 2. when,
Since the tone disabler signal is being input, the flag TDF
Set to 0. When the number of PLL phase inversions is 2 or more, a tone disabler signal has been detected, and timer T is activated.
2 to 0 and flag TDF to 1. On the other hand, timer T
2 is 1000ms or more, the specified time for detection processing has been exceeded, and the RXSF flag and TDF flag are set to 0.
Set the timer T2 to 0, set the detection number of reversals PREV to 0, and set the timer PRTMR to 50 ms.

FIG. 7 shows a comparison of the amount of processing between the conventional method and the method of the present invention. (A) shows the conventional method, in which the operation of the 2100 Hz bandpass filter, the detection of signal power, 900 to 100 for PLL operation, each timer operation, phase reversal detection, and counter operation.
It takes 0ms. On the other hand, in the method of the present invention shown in (B), the operation of the 2100 Hz band pass filter to detect the Rin signal and the operation of the 2100 Hz band pass filter to detect the Sin signal
The operation of the Hz bandpass filter (■), the detection of the signal power for the Rin signal (■), the detection of the signal power for the Sin signal (■), and the operation of the control unit are performed in a period of 50 ms, and during this period, other processing is not performed. After the selector value is determined after this period has elapsed, other 2100 Hz detection processing ■ or ■ for the Rin signal or Sin signal, signal power detection processing ■ or ■ for the Rin signal or Sin signal, and PLL processing are performed. movement and
The operation of each timer, phase reversal detection, and counter operation are performed between 50 ms and 900 to 1000 ms. Therefore, in the method of the present invention, the amount of processing is significantly reduced compared to the conventional method.

[0027]

As explained above, according to the present invention, when detecting a tone disabler signal that operates a tone disabler that stops the operation of an echo canceller,
When a tone disabler signal is input to either the receiving side or the transmitting side, even if some signal is input to the other side, false detection will not occur due to interference. Furthermore, according to the method of the present invention, the amount of processing for tone disabler signal detection can be reduced compared to the conventional method.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the basic configuration of the present invention.

FIG. 2 is a diagram showing an embodiment of the present invention.

FIG. 3 is a flowchart showing processing of a selector unit.

FIG. 4 is a flowchart showing processing by a control unit.

FIG. 5 is a flowchart showing the first half of processing by a detection unit including a PLL, a timer, a phase inversion detector, and a counter.

FIG. 6 is a flowchart showing the second half of processing by a detection unit including a PLL, a timer, a phase inversion detector, and a counter.

FIG. 7 is a diagram showing a comparison of the processing amount between the conventional method and the method of the present invention.

FIG. 8 is a diagram showing the overall configuration of a tone disabler signal determination circuit.

FIG. 9 is a diagram showing a conventional tone disabler signal detection circuit.

[Explanation of symbols]

1 Tone disabler signal detection section 2 First bandpass filter 3 Second bandpass filter 4 First signal power detection section 5 Second signal power detection section 6 Selector

Claims (2)

[Claims] 1. The tone disabler signal is controlled by the number of inversions of the control signal of the phase synchronization circuit based on the respective phase inversions of the tone disabler signal at the reception signal input (Rin) and the tone disabler signal at the transmission signal input (Sin). A first bandpass that extracts a tone disabler signal on the reception side in a tone disabler signal detection section (1) of a tone disabler that detects a signal and stops the operation of an echo canceller when the tone disabler signal is detected. A filter (2), a second bandpass filter (3) that extracts a tone disabler signal on the transmitting side, and a first signal power detection section that detects the output power of the first bandpass filter (2). (4), a second signal power detection section (5) that detects the output power of the second bandpass filter (3), and a second signal power detection section (4) that detects the output power of the first signal power detection section (4) or the second signal power detection section (4); a selector () that inputs the output signal of the first bandpass filter (2) or the second bandpass filter (3) to the tone disabler signal detection unit (1) according to the detection signal of the detection unit (5); 6) A tone disabler signal detection method comprising: 2. The operation of the first and second band pass filters (2, 3), the operation of the first and second signal power detection units (4, 5), and the selector (2) based on these After first performing the operation 6), the tone disabler signal detecting section (1) is activated by inputting the tone disabler signal on the side determined by the selector (6).
2. The tone disabler signal detection method according to claim 1, wherein the tone disabler signal detection method operates as follows.