JPH04245729A - Single tone detector - Google Patents

Abstract

PURPOSE:To attain the rapid an fixed timed detection of a single tone and to enable output in a sound section in the single tone, in soundless section in the single tone, in a sound section in other than the single tone, and in a soundless section in other than the single tone. CONSTITUTION:A sound detector 9 detects a sound part of an inputted digital signal. A counter 11 counts up a sound part to be the updating section of a single tone detecting result based upon the detection result of the detector 9 and applies an updating signal to a holding circuit 6. A counter 10 counts up the sound part to be the detection time of the single tone based upon the updating signal or the detection result of the detector 9 and applies a detection signal to a maximum value detecting part 5.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of Industrial Application The present invention is applied to a single tone detector of a high-efficiency terminal equipment. In particular, high-efficiency terminal equipment (DCME, Di
digital circuit multiple
The present invention relates to a single tone detector for detecting a single tone consisting of a single period of a voice modem signal identifier manufactured by ION Equipment.

0002

2. Description of the Related Art FIG. 2 is a block diagram of a conventional single tone detector.

Conventionally, a single tone detector includes an input terminal 1, a period detection circuit 2, a period deviation detection circuit 3, an absolute value detection circuit 4, a maximum value detection circuit 5, a holding circuit 6, and a counter, as shown in FIG. 21, a determination circuit 7 and an output terminal 8.

The input digital signal is input to a period detection circuit 2. The period detection circuit 2 detects the period based on zero crossings of the input digital signal. This detected period is input to the period deviation detection circuit 3 and the maximum value detection circuit 5, and the period deviation detection circuit 3 calculates the deviation from the period one period before and outputs it to the absolute value detection circuit 4. The absolute value detection circuit 4 calculates the absolute value of this periodic deviation and outputs it to the maximum value detection circuit 5.

[0005] The counter 21 is a counter that counts the detection period, and outputs it to the maximum value detection circuit 5 and the holding circuit 6. The maximum value detection circuit 5 detects the maximum value of the absolute value of the period deviation within the detection interval by the counter 21 and the period when the absolute value of the period deviation becomes the maximum.

The holding circuit 6 stores the maximum value of the absolute value of the periodic deviation which is the output value of the maximum value detection circuit 5 one detection period before the detection period by the counter 21, and the maximum absolute value of the periodic deviation when the absolute value of the periodic deviation becomes the maximum. The period is held and output to the determination circuit 7.

If the input digital signal is an arbitrary single tone having a single period, the absolute value of the period deviation will be approximately zero because the period is constant. In audio band data and audio signals, the absolute value of the period deviation within the detection interval has a value of several percent with respect to the period, and this value takes a different value for each period. Therefore, a threshold value for the period deviation with respect to the period is set in consideration of the case where the input digital signal includes background noise, and when the period deviation is less than the threshold value, the judgment circuit 7 determines that the input digital signal is simple. It is determined that it is an arbitrary single tone consisting of one period, and if the period deviation is greater than the threshold value, it is determined that it is not a single tone and is output to the output terminal 8. By repeating this operation, the single tone detection signal is updated.

[0009]

[Problems to be Solved by the Invention] However, since such a conventional single tone detection circuit does not have a sound detector, the relationship between the start of a sound part and the detection section is uncertain. If a signal is input during the detection period, the single tone signal cannot be detected even though it is a single tone signal, and the single tone signal can only be detected at the end of the next detection period. There was a problem that the detection time increased and the detection time was not constant. Also,
There was a problem in that the detailed state of the input signal could not be detected, such as a sound section for a single tone, a silent section for a single tone, a sound section for a non-single tone, and a silent section for a non-single tone.

[0010] In satellite communications and submarine cable communications, the line capacity that can be used is limited, and the bit unit cost of the line is expensive. Therefore, by using 4-bit ADPCM (Adaptive Differential Pulse Code Modulation) to communicate the normal audio signal using 8-bit PCM, it is possible to secure twice as many audio lines. This is the conventional ADPC
It is possible with M's technology, but this 4-bit ADPCM does not have a noticeable quality for conversational voices, but
If the modem signal is higher than bit/s, an error will occur during signal transmission. Therefore, it is necessary to distinguish between the voice signal and the modem signal, and 5-bit ADPCM is applied to the modem signal.

[0011] The required characteristics of this voice modem signal discriminator include IESS-50, which is the Intelsat standard.
1 and the CCITT standard G.1. 763 There is
Single tone is not a modem signal, but a 4-bit AD signal.
Since sufficient quality can be obtained with PCM, it is recommended to identify single tones and transmit them with 4-bit ADPCM.

[0012] As described above, this single tone detector is suitable for use in high-efficiency terminal equipment (
DCME) voice modem signal identifier.

[0013] The above-mentioned IESS-501 and G. With G.763, there is a limit to the required detection time, and detection results must be produced within 200ms. Furthermore, as the detection time becomes longer, the time during which 5-bit ADPCM is applied becomes longer, and the efficiency of the line deteriorates. The problem with making the time constant is that when this voice modem signal discriminator is actually used, it will be easier to design it if it is known in advance how many detection results will be output after a signal is input.

[0014] The present invention solves the above problems.
A single tone detector that can perform high-speed and fixed-time single tone detection, and can also output the states of a sound section with a single tone, a silent section with a single tone, a sound section with a non-single tone, and a silent section with a non-single tone. The purpose is to provide

[0015]

[Means for Solving the Problems] The present invention includes a period detection circuit that detects the period of an input digital signal, and a frequency deviation between the currently detected period and the previously detected period from this period detection circuit. A period deviation detection circuit calculates the absolute value of the calculated period deviation, an absolute value detection circuit calculates the absolute value of the calculated period deviation, and detects a single tone based on the input detection signal, the period detected this time, and the absolute value of the calculated period deviation. A maximum value detection circuit that detects the maximum absolute value of the period deviation in the detection interval and the maximum absolute value period when the absolute value of the period deviation becomes maximum, and the detection results of this maximum value detection circuit are held and input. A single tone that includes a holding circuit that updates its contents using an update signal, and a judgment circuit that judges whether or not the corresponding digital signal is a predetermined digital signal consisting of a single period based on the contents of this holding circuit. In the detector, there is a sound detector that detects the sound part of the input digital signal, and based on the detection result of this sound detector, the sound part that is an update section of the single tone detection result is counted and the update signal is calculated. and a second counter that counts the sound part that is the detection time of a single tone based on this update signal or the detection result of the sound presence detector and provides a detection signal. shall be.

Further, in the present invention, the determination circuit may include means for determining that the tone is a single tone when the maximum value of the periodic deviation is less than a predetermined threshold value.

Further, in the present invention, the first counter starts counting when the input digital signal changes from a silent part to a sound part based on the detection result of the sound detector, and including means for providing the update signal at intervals of a specified period of time added to the detection time width on medium-periodical basis;
The second counter starts counting when the input digital signal changes from a silent part to a sound part or when the update signal is input based on the detection result of the sound detector, and during the sound period. Means for providing a detection signal during the detection time can be included.

[0018]

[Operation] The sound detector detects the sound part of the input digital signal. The first counter counts the sound portion, which is an update section of the single tone detection result, based on the detection result of the sound detector, and provides an update signal to the holding circuit. The second counter counts the sound portion corresponding to the single tone detection time based on this update signal or the detection result of the sound presence detector, and provides a detection signal to the maximum value detection circuit.

Further, the determination circuit can determine that the tone is a single tone when the maximum value of the periodic deviation is less than a predetermined threshold value.

Further, the first counter starts counting when the input digital signal changes from a silent part to a sound part based on the detection result of the sound detector, and periodically changes the detection time width during the sound period. An update signal is given to the holding circuit every time the predetermined time is added to the second counter, and the second counter outputs the update signal when the input digital signal changes from a silent part to a sound part based on the detection result of the sound detector. It can start counting when input and provide a detection signal during the detection time during the sound period. As described above, single tone detection can be performed at high speed and at a constant time, and also output states of a sound section for a single tone, a silent section for a single tone, a sound section for other than a single tone, and a silent section for other than a single tone.

[0021]

Embodiments Examples of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram of a single tone detector according to an embodiment of the present invention. In FIG. 1, the single tone detector includes an input terminal 1 for inputting a digital signal, a period detection circuit 2 for detecting the period of the input digital signal, and a currently detected period and a previously detected period from the period detection circuit 2. A period deviation detection circuit 3 calculates the frequency deviation from the period detected, an absolute value detection circuit 4 calculates the absolute value of the calculated period deviation, an input detection signal, the period detected this time, and the period detected above. a maximum value detection circuit 5 for detecting the maximum absolute value of the period deviation in the single tone detection section based on the absolute value of the period deviation and the maximum absolute value period when the absolute value of the period deviation becomes maximum; A holding circuit 6 holds the detection result of the detection circuit 5 and updates its contents by an input update signal, and determines whether the corresponding digital signal is a predetermined digital signal having a single period based on the contents of the holding circuit 6. a determination circuit 7 that determines whether
and an output terminal 8 for outputting the single tone detection signal of the determination circuit 7.

The features of the present invention include a sound detector 9 that detects a sound part of an input digital signal, and an update interval of a single tone detection result based on the detection result of the sound detector 9. A counter 11 is used as a first counter to count the sound parts that correspond to the detection time of a single tone and generate a detection signal based on this update signal or the detection result of the sound detector 9. The present invention is provided with a counter 10 as a second counter that provides a second counter, and an output terminal 12 that outputs the detection result of the sound detector 9.

Further, the determination circuit 7 includes means for determining that the tone is a single tone when the maximum value of the periodic deviation is less than a predetermined threshold value.

Further, the counter 11 starts counting when the input digital signal changes from a silent part to a sound part based on the detection result of the sound detector 9, and periodically changes the detection time width during the sound period. The counter 10 includes means for supplying the update signal at intervals of a predetermined time period, and the counter 10 outputs the update signal when the input digital signal changes from a silent part to a sound part based on the detection result of the sound detector 9, or means for starting a count upon input and providing a detection signal for a detection time during a sound period.

The operation of such a configuration will be explained. The input digital signal is input to the period detection circuit 2. The period detection circuit 2 detects the period based on zero crossings of the input digital signal. This detected period is input to the period deviation detection circuit 3 and the maximum value detection circuit 5,
The period deviation detection circuit 3 calculates the deviation from the period one period before, and outputs it to the absolute value detection circuit 4. The absolute value detection circuit 4 calculates the absolute value of this period deviation and outputs the calculation result to the maximum value detection circuit 5.

The sound detector 9 detects the sound part of the input digital signal and sends the detection result to the counter 10 and the counter 11.
and output to the output terminal 12.

The counter 10 is a counter that counts the detection time, and starts counting when the sound detector 9 changes from a silent part to a sound part and every time the update time which is the output of the counter 11 is reached. During the detection period, the detection signal is output to the maximum value detection circuit 5 during the detection time. The counter 11 is a counter that counts the update time, and starts counting when a silent part changes to a sound part, and periodically sends an update signal every time the detection time width is added to a specified time during the sound part. is output to the holding circuit 6 and the counter 10.

The maximum value detection circuit 5 detects the maximum value of the absolute value of the period deviation and the period when the absolute value of the period deviation becomes the maximum within the detection time by the counter 10. Until the update signal from the counter 11 is input, the holding circuit 6 maintains the maximum absolute value of the period deviation, which is the output value of the maximum value detection circuit 5 before the previous update signal, and the absolute value of the period deviation. The period at which this occurs is held and output to the determination circuit 7.

When an input digital signal is actually input, the sound time of the signal and the sound time detected by the sound presence detector 9 may differ somewhat due to characteristics such as the response delay time of the sound presence detector 9. Sometimes.

Therefore, when a sound part changes to a silent part, the sound detector 9 may still output the sound part even though the actual input digital signal is already a silent part, but the counter Since the output of 11 is set to be a specified time longer than the detection time, an update signal is not output to the holding circuit 6 even if a silent part is included within the detection time.

If the input digital signal is an arbitrary single tone having a single period, the absolute value of the period deviation will be approximately zero because the period is constant. In audio band data and audio signals, the absolute value of the period deviation within the detection time has a value of several percent with respect to the period, and this value takes a different value for each period. Therefore, a threshold value for the period deviation with respect to the period is set in consideration of the case where the input digital signal includes background noise, and the judgment circuit 7 determines whether the input digital signal is single if the period deviation is less than the threshold value. It is determined that it is an arbitrary single tone consisting of a period of
If the periodic deviation is greater than the threshold value, it is determined that the tone is not a single tone, and is output to the output terminal 8. By repeating this operation, the single tone detection signal is updated.

[0031]

As explained above, the present invention is capable of speeding up and fixed-time single tone detection, and detecting a sound section for a single tone, a silent section for a single tone, and a sound section for non-single tones. It has the excellent effect of outputting silent sections other than single tones.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a single tone detector according to an embodiment of the present invention.

FIG. 2 is a block diagram of a conventional single tone detector.

[Explanation of symbols]

1 Input terminal 2 Period detection circuit 3 Period deviation detection circuit 4 Absolute value detection circuit 5 Maximum value detection circuit 6 Holding circuit 7 Judgment circuit 8, 12 Output terminal 9 Sound detector 10, 11, 21 counter

Claims (3)

[Claims] Claim 1: A period detection circuit that detects the period of an input digital signal; a period deviation detection circuit that calculates a frequency deviation between the currently detected period and the previously detected period from the period detection circuit; An absolute value detection circuit that calculates the absolute value of the calculated periodic deviation, an input detection signal,
Based on the period currently detected above and the absolute value of the period deviation calculated above, detect the maximum absolute value of the period deviation in the single tone detection interval and the maximum absolute value period when the absolute value of the period deviation becomes maximum. a maximum value detection circuit that holds the detection result of this maximum value detection circuit and updates its contents with an input update signal, and a corresponding digital signal that has a single period based on the contents of this holding circuit. A single tone detector including a determination circuit that determines whether or not it is a predetermined digital signal,
a sound detector that detects the sound part of the input digital signal; and a first sound detector that counts the sound part that is an update section of the single tone detection result based on the detection result of the sound detector and provides the update signal. and a second counter that counts the sound portion that is the detection time of the single tone based on this update signal or the detection result of the sound presence detector and provides a detection signal. Detector. 2. The single tone detector according to claim 1, wherein said determining circuit includes means for determining that a single tone is present when the maximum value of said periodic deviation is less than a predetermined threshold. 3. The first counter starts counting when the input digital signal changes from a silent part to a sound part based on the detection result of the sound detector, and periodically counts during the sound period. The second counter includes means for providing the update signal at intervals of a detection time width plus a specified time, and the second counter is configured to change the input digital signal from a silent part to a sound part based on the detection result of the sound detector. 2. A single tone detector as claimed in claim 1, including means for starting counting when a change occurs or upon inputting said update signal and for providing a detection signal for a detection time during a sound interval.