JP7196992B2 - Pulse noise judgment device and program - Google Patents

Description

The present invention relates to a pulse noise determination device and program, and more particularly to a pulse noise determination device and program capable of accurately determining pulse noise included in a received signal together with pulse noise.

A receiver is known that converts a received signal into an IF (Intermediate Frequency) band signal and amplifies the converted IF signal of the IF band. A receiver amplifies an IF signal in an amplifier section, and the amplifier section has an IF-AGC (Automatic Gain Control) function for automatically controlling the gain.

Patent Literature 1 describes that the power transition of a received signal over time is obtained by power calculation, and the moving average for each moving average interval is calculated for the obtained received power value sequence by moving average power calculation. there is Further, Patent Literature 1 describes that an interval greater than a noise threshold in the obtained moving average power value series is detected as an impulse noise superimposed interval by impulse noise detection. Further, in Patent Document 1, a series of processes is performed to generate a new received power value sequence by replacing the power value of the impulse noise superimposed section in the received power value sequence with a constant replacement power value by power replacement. is stated. Patent Document 1 does not describe a method for preventing the intelligibility of a received signal from being degraded when a receiver having an IF-AGC function receives pulse noise together with the received signal.

JP 2012-156687 A

A receiver having an IF-AGC function may receive, together with a received signal, pulse noise that occurs, for example, due to the switching operation of a lamp. In such a case, a receiver with an IF-AGC function controls gain to match pulse noise having an amplitude greater than that of the received signal. As a result, the amplitude of the received signal whose amplitude is smaller than the amplitude of the pulse noise is reduced, so that the intelligibility is reduced or the voice cannot be heard. As described above, when a receiver having an IF-AGC function receives pulse noise together with a received signal, there is a problem that the quality of the received signal deteriorates. In order to solve such a problem, it is desirable to have a function for accurately determining pulse noise. SUMMARY OF THE INVENTION An object of the present invention is to provide a pulse noise determination device and a program capable of accurately determining pulse noise included in a received signal when the pulse noise is received together with the received signal .

Therefore, the present disclosure provides
an amplifier that amplifies a signal;
a control unit for setting, in the amplification unit, a gain setting value for AGC operation that keeps the amplitude of the signal after amplification within a predetermined range;
a determination unit that monitors changes in the gain setting value and determines whether the signal contains pulse noise based on whether the change in the gain setting value satisfies a predetermined condition;
The control unit
an absolute value calculator that rectifies the amplified signal;
an integration processing unit that smoothes the rectified signal to obtain a signal value;
a difference calculation unit that calculates a difference value between the signal value and a predetermined reference value;
an attack control unit and a release control unit that control the gain setting value based on the difference value;
The determination unit is
When the period required for the change in the gain setting value is less than the predetermined period threshold in the period in which the signal value exceeds the predetermined reference value, and the amount of change in the gain setting value exceeds the predetermined amount of change threshold, Characterized by determining that pulse noise is included,
A pulse noise determination device is provided.

This disclosure also provides
Rectify the amplified signal amplified by the amplifier,
smoothing the rectified signal as a signal value,
calculating a difference value between the signal value and a predetermined reference value;
setting a gain setting value to the amplifier so that the amplitude of the signal amplified by the amplifier is within a predetermined range based on the difference value;
When the period required for the change in the gain setting value is less than the predetermined period threshold in the period in which the signal value exceeds the predetermined reference value, and the amount of change in the gain setting value exceeds the predetermined amount of change threshold, determining that the signal contains pulse noise;
Provide a program that makes a computer do something.

Advantageous Effects of Invention According to the present invention, it is possible to provide a pulse noise determination device and program capable of accurately determining pulse noise included in a received signal when pulse noise is received along with the received signal.

1 is a block diagram illustrating a receiver according to an embodiment; FIG. 1 is a block diagram illustrating a receiver according to an embodiment; FIG. 4 is a flow chart illustrating the operation of the receiver according to the embodiment; 5 is a graph illustrating an IF signal input to a reception amplifier; 4 is a graph illustrating an AGC voltage set in a reception amplifier; 5 is a graph illustrating an IF signal output from a reception amplifier; 5 is a graph illustrating an IF signal input to a reception amplifier; 4 is a graph illustrating an AGC voltage set in a reception amplifier; 5 is a graph illustrating an IF signal output from a reception amplifier; 1 is a block diagram illustrating a receiver according to an embodiment; FIG.

[Embodiment]
BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described with reference to the drawings.
First, the outline of the receiver according to the embodiment will be explained.

FIG. 1 is a block diagram illustrating a receiver according to an embodiment.

As shown in FIG. 1 , receiver 10 according to the embodiment includes reception amplification section 11 , control section 12 and determination section 13 .

The reception amplifier 11 amplifies the reception signal.

The control section 12 sets the gain setting value in the reception amplification section 11 so that the amplitude of the reception signal after amplification is within a predetermined range. The reception amplifier 11 amplifies the reception signal based on the gain setting value.

The determination unit 13 determines that the received signal contains pulse noise when the period during which the change in the gain control value exceeds the predetermined change amount threshold is less than the predetermined period threshold.

When it is determined that the received signal contains pulse noise, the control section 12 sets the gain setting value immediately before the pulse noise is generated in the reception amplifying section 11 as the gain setting value immediately after the pulse noise is generated.

A function of setting a gain setting value in the reception amplifier 11 so that the amplitude of the received signal amplified by the reception amplifier 11 is within a predetermined range is called an AGC function. AGC for an IF signal in the IF band is called IF-AGC. The receiver 10 has this IF-AGC function.

Here, the IF-AGC function will be explained.

The IF-AGC function controls the AGC voltage set in the reception amplifier in order to keep the amplitude of the signal amplified by the reception amplifier within a predetermined range. When the AGC voltage is increased, the gain of the reception amplifier increases, and the amplitude of the output signal output from the reception amplifier increases. When the AGC voltage is lowered, the gain of the reception amplification section is lowered and the amplitude of the output signal output from the reception amplification section is reduced.

The IF-AGC function rectifies and smoothes part of the output signal, and converts it to a signal value (eg, DC potential) according to the amplitude of the output signal. The signal value is compared with a predetermined reference value, and when the predetermined reference value (reference level) is exceeded, the gain of the receiving amplifier is lowered to control the amplitude of the output signal to be within a predetermined range.

Here, the IF-AGC function when the receiver 10 receives pulse noise will be described.

Pulse noise is a noise signal that has a large amplitude over a short period of time, up to several milliseconds. When this pulse noise is input, a receiver with an IF-AGC function lowers the AGC voltage and the gain of the receiving amplifier in order to keep the pulse noise with an amplitude greater than the reference level within a predetermined range. conduct. This operation is called an attack operation. In the attack operation, in order to keep the amplitude of the pulse noise within a predetermined range, for example, the AGC voltage is lowered over a period of about 2 milliseconds to lower the gain of the receiving amplifier.

On the other hand, after the pulse noise has passed, the pulse noise disappears, so the amplitude of the signal input to the reception amplifier decreases. Therefore, in order to recover (increase) the decreased gain, the receiver increases the AGC voltage to increase the gain of the receiving amplifier. This operation is called release operation. In the release operation, for example, the AGC voltage is increased for about 100 milliseconds to 10 seconds to restore the gain of the receiving amplifier.

Also, when the receiver receives pulse noise along with the received signal (when the received signal contains pulse noise), the gain of the receiving amplifier decreases due to the attack operation each time the pulse noise is input to the receiver. As a result, the amplitude of the intended received signal is reduced, the intelligibility thereof is lowered, or the voice cannot be heard.

Therefore, in the receiver 10 according to the embodiment, when it is determined that the received signal contains pulse noise, the gain setting value immediately before the pulse noise is generated is set as the gain setting value immediately after the pulse noise is generated. set to This makes it possible to alleviate the decrease in the gain of the reception amplifier 11 that accompanies the attack operation.

Next, details of the receiver according to the embodiment will be described.
FIG. 2 is a block diagram illustrating a receiver according to an embodiment;
In FIG. 2, a received signal is converted into an IF signal in the IF band, the IF signal is amplified by the reception amplifier 11, and IF-AGC is performed on the amplified IF signal. . Embodiments are not limited to this. A received signal may be amplified and AGC may be performed on the amplified received signal.

As shown in FIG. 2, the control unit 12 of the receiver 10 includes an absolute value calculation unit 121, an integration processing unit 122, a difference calculation unit 123, a reference value generation unit 124, a release control unit 127, and an attack control unit. It has a section 126 , a switching section 125 and a voltage gain conversion section 128 . The determination section 13 has a pulse noise determination section 131 .

The receiver 10 receives a received signal and converts the received received signal to an IF signal in the IF band. The reception amplifier 11 amplifies the converted IF signal. The absolute value calculator 121 uses, for example, a rectifier circuit to make the amplitude of the IF signal an absolute value. Integration processing section 122 integrates (smoothes) the absolute value of the amplitude of the IF signal, and outputs a signal value corresponding to the amplitude of the IF signal to difference calculation section 123 and attack control section 126 . The difference calculator 123 calculates the difference between the signal value and the reference value generated by the reference value generator 124 . A standard value may be called a reference level.

When the difference exceeds zero, that is, when the signal value exceeds the reference value, the switching unit 125 selects the attack operation by the attack control unit 126, and connects the terminals 1 and 3. As a result, the output voltage of the attack control section 126 is selected as the AGC voltage.

Further, when the difference is zero or less, that is, when the signal value is less than the reference value, the switching section 125 selects the release operation by the release control section 127, so that the terminal 1 and the terminal 2 are connected. As a result, the output voltage of the release control section 127 is selected as the AGC voltage. The AGC voltage corresponds to the gain setting value set in the reception amplifier section 11 .

The determination section 13 has a pulse noise determination section 131 . A pulse noise determination unit 131 monitors changes in the AGC voltage of the IF-AGC and detects whether or not a change in a predetermined condition has occurred. The pulse noise determination unit 131 determines that the IF signal contains pulse noise when it is detected that the AGC voltage has a predetermined change. Further, the pulse noise determination section 131 determines that the IF signal does not contain the pulse noise when it is not detected that the AGC voltage changes in a predetermined manner.

Specifically, the pulse noise determination unit 131 determines that the IF signal contains pulse noise when the following equations (1) and (2) are satisfied.

ただし、Ｔｋはアタック期間であり、Ｔｋｔはアタック期間閾値である。

where Tk is the attack period and Tkt is the attack period threshold.

When the signal value exceeds the reference value, the control section 12 performs an attack operation to reduce the gain of the reception amplification section 11 by reducing the AGC voltage in order to keep the amplitude of the IF signal within a predetermined range. The case where the signal value exceeds the reference value is also referred to as the case where the difference between the signal value and the reference value exceeds zero. The attack period Tk is a period during which the difference between the signal value and the reference value exceeds zero. Also, the attack period Tk may be a period during which the attack control unit 126 performs an attack operation. The attack control unit 126 has an attack period calculation counter 1261 . The attack period calculation counter 1261 measures the attack period Tk by counting each sample during the attack period Tk.

The attack period threshold Tkt is a predetermined value. The attack period threshold may also be referred to as a predetermined period threshold.

ただし、Ｖｇは電圧変化総量であり、Ｖｇｔは電圧平均変動量閾値である。

However, Vg is the voltage change total amount, and Vgt is the voltage average fluctuation amount threshold.

The voltage change total amount Vg is the total amount of change in the AGC voltage during the attack period Tk. The voltage average fluctuation amount threshold Vgt is a threshold for the average fluctuation amount of the AGC voltage. (Voltage change total amount Vg/attack period Tk) is the average variation amount of the AGC voltage per unit time when the attack operation is performed on the pulse noise. The average amount of change in the AGC voltage per unit time is also referred to as the amount of change in the AGC voltage. The voltage average variation threshold may also be referred to as a predetermined variation threshold.

When the attack period Tk is less than the attack period threshold value Tkt and the total amount of change in the AGC voltage during the attack period Tk exceeds the voltage average variation threshold value Vgt, the pulse noise determination unit 131 determines that the received signal includes pulse noise. determined to be Then, the control unit 12 feeds back the AGC voltage which is held and is the AGC voltage immediately before the occurrence of the pulse noise to the reception amplifier unit 11 and sets it.

In this way, based on the characteristic operation of the IF-AGC function due to pulse noise, the determination unit 13 of the receiver 10 detects the pulse noise from the attack period Tk during which the attack operation is performed and the value of the AGC voltage controlled at that time. is included in the received signal.

Receiver 10 may include a plurality of band-limiting filters (not shown) for band-limiting the IF signal. The band-limiting filter may be exclusively selected from a plurality of band-limiting filters, and is selected according to the radio wave format and bandwidth received by the receiver 10 . By passing through the band-limiting filter, the pulse noise has a longer time width than when it does not pass through the band-limiting filter. Also, when pulse noise passes through a band-limiting filter with a bandwidth narrower than a predetermined bandwidth, the time width of the pulse noise becomes longer than when it passes through a band-limiting filter with a predetermined bandwidth. That is, the narrower the bandwidth of the band-limiting filter, the longer the time width of the pulse noise that has passed through the band-limiting filter.

Therefore, the receiver 10 may change the attack duration threshold Tkt based on the type of band-limiting filter used. Also, the receiver 10 may change the attack duration threshold Tkt based on the bandwidth of the band-limiting filter used.

By passing through the band-limiting filter, the pulse noise becomes smaller in amplitude than when it does not pass through the band-limiting filter. Also, when pulse noise passes through a band-limiting filter with a bandwidth narrower than a predetermined bandwidth, its amplitude becomes smaller than when it passes through a band-limiting filter with a predetermined bandwidth. That is, the narrower the bandwidth of the band-limiting filter, the smaller the amplitude of the pulse noise that has passed through the band-limiting filter.

Therefore, the receiver 10 may change the average voltage variation threshold Vgt based on the type of band-limiting filter used. Also, the receiver 10 may change the average voltage fluctuation amount threshold Vgt based on the bandwidth of the band-limiting filter used.

The contents so far can be summarized as follows.
When a receiver having an IF-AGC function receives pulse noise together with a received signal, the attack operation reduces the gain of the reception amplifier each time the pulse noise is input to the receiver. As a result, the target received signal is affected by it, and the intelligibility is lowered, or the voice cannot be heard. Also, at this time, it takes at least 100 milliseconds to recover the gain of, for example, 60 dB by the release operation.

Therefore, when the determination result of the determination unit 13 determines that the received signal contains pulse noise, the control unit 12 of the receiver 10 according to the embodiment controls the AGC immediately before starting the attack operation against the pulse noise. voltage is set in the reception amplifier 11 as an AGC voltage to be set immediately after pulse noise is detected. As a result, suppression of the gain of the reception amplifier 11 during the release operation period after the attack operation can be alleviated, and the silence period of voice can be reduced.

Moreover, the receiver 10 may further include a storage unit 14 that stores the AGC voltage (gain setting value), as shown in FIG. The control unit 12 may read the AGC voltage (past gain setting value) immediately before starting the attack operation from the storage unit 14 and set the past gain setting value to the reception amplification unit 11 . Also, the AGC voltage is updated when the release operation transitions to the attack operation or when the attack operation transitions to the release operation. That is, it is possible to store the gain setting value at the change point of the AGC operation. The control unit 12 can also hold the AGC voltage immediately before the pulse noise is input.

The control section 12 may further include a voltage gain conversion section 128 that converts the AGC voltage output from the attack control section 126 or the release control section 127 to the gain of the reception amplification section 11 into a gain control signal. Voltage gain conversion section 128 outputs the converted gain control signal to reception amplification section 11 . The reception amplifier 11 controls gain using a gain control signal.

Next, operation of the receiver according to the embodiment will be described.
FIG. 3 is a flow chart illustrating the operation of the receiver according to the embodiment.

As shown in FIG. 3, the voltage gain converter 128 converts the AGC voltage into a gain control signal for setting the gain of the reception amplifier 11 (step S101). Voltage gain conversion section 128 outputs the converted gain control signal to reception amplification section 11 .

The reception amplifier 11 amplifies the IF signal based on the gain control signal (step S102).

The absolute value calculator 121 calculates (rectifies) the absolute value of the amplitude of the IF signal (step S103).

The integration processing unit 122 integrates (smoothes) the absolute value of the amplitude of the IF signal and outputs a signal value (step S104).

The difference calculator 123 determines whether the signal value exceeds the reference value (step S105).

When the signal value exceeds the reference value (step S105: Yes), the switching unit 125 connects the terminals 1 and 3 in order to select the attack operation by the attack control unit 126. FIG. The attack control unit 126 performs an attack operation (step S106). The AGC voltage update unit 1262 updates the AGC voltage according to the attack operation (step S106).

The attack control unit 126 cumulatively adds the AGC voltage values during the attack period Tk to calculate the attack period AGC voltage change total amount (step S107).

The attack control unit 126 increments the attack period calculation counter 1261 to obtain the attack period Tk (step S108) .

When the signal value is equal to or less than the reference value (step S105: No), the switching unit 125 connects the terminals 1 and 2 in order to select the release operation by the release control unit 127. FIG. The release control unit 127 confirms whether or not the current release motion is the first release motion after the attack motion (step S109).

If the current release operation is not the first release operation after the attack operation (step S109: No), the AGC voltage update unit 1272 of the release control unit 127 updates the AGC voltage for the release operation (step S110).

The release control unit 127 updates the held AGC voltage held for starting the release operation with the current AGC voltage (step S111).

If the current release operation is the first release operation after the attack operation (step S109: Yes), the AGC voltage update unit 1272 of the release control unit 127 determines whether or not the IF signal contains pulse noise. The unit 131 is instructed to make a determination (step S112).

When the pulse noise determination unit 131 determines that the IF signal contains pulse noise (step S112: Yes), it sets the current AGC voltage to the holding AGC voltage for starting the release operation (step S113).

After step S111, if step S112 is No, or after step S113, the attack control unit 126 clears the attack period calculation counter 1261 (step S114).

The attack control unit 126 clears the attack period AGC voltage change total amount (step S115).

The receiver 10 returns to step S101 after step S115.

Next, effects of the receiver according to the embodiment will be described.

FIG. 4A is a graph illustrating an IF signal that is input to the reception amplifier.
The horizontal axis of FIG. 4A indicates time, and the vertical axis indicates amplitude. Vs shown in FIG. 4A indicates an audio signal, and Pn indicates pulse noise.
FIG. 4B is a graph illustrating AGC voltages to be set in the reception amplifier.
The horizontal axis of FIG. 4B indicates time, and the vertical axis indicates voltage values for setting attenuation.
FIG. 4C is a graph illustrating an IF signal output from the reception amplifier.
The horizontal axis of FIG. 4C indicates time, and the vertical axis indicates amplitude.
4A to 4C are graphs for signal levels at which the IF-AGC function operates only for pulse noise and does not operate for voice signals.

As shown in FIG. 4A, the IF signal includes pulse noise indicated by Pn in addition to the voice signal indicated by Vs.

As shown in FIG. 4B, when the pulse noise shown in FIG. 4A is input to the reception amplifier 11, the attack operation is started. The AGC voltage decreases in voltage value with the attack operation.

As shown in FIG. 4C, when it is determined that the IF signal contains pulse noise, the receiver 10 sets the AGC voltage immediately before the pulse noise to the reception amplifier 11 as the AGC voltage immediately after the pulse noise occurs. do. As a result, the period during which the IF output signal is low due to pulse noise is shortened.

FIG. 5A is a graph exemplifying an IF signal input to the reception amplifier.
The horizontal axis of FIG. 5A indicates time, and the vertical axis indicates amplitude. Vs shown in FIG. 5A indicates an audio signal, and Pn indicates pulse noise.
FIG. 5B is a graph illustrating an AGC voltage to be set in the reception amplifier.
The horizontal axis of FIG. 5B indicates time, and the vertical axis indicates voltage value.
FIG. 5C is a graph illustrating an IF signal output from the reception amplifier.
The horizontal axis of FIG. 5C indicates time, and the vertical axis indicates amplitude.
5A-5C are graphs of the IF-AGC function operating at the signal level of the signal.

As shown in FIG. 5A, the IF signal includes pulse noise indicated by Pn in addition to the voice signal indicated by Vs.

As shown in FIG. 5B, when the pulse noise shown in FIG. 5A is input to the reception amplifier 11, the attack operation is started. The AGC voltage decreases in voltage value with the attack operation. Since the IF-AGC function also operates on audio signals, the AGC voltage value is low when the audio signal is large, and the AGC voltage value is high when the audio signal is small.

As shown in FIG. 5C, when it is determined that the IF signal contains pulse noise, the receiver 10 sets the AGC voltage immediately before the pulse noise to the reception amplifier 11 as the AGC voltage immediately after the pulse noise occurs. do. As a result, the period during which the IF output signal is low due to pulse noise is shortened.

As described above, in the receiver 10 according to the embodiment, it is possible to solve the problem of pulse noise suppression while maintaining the advantage of high-speed response characteristics, and to perform comfortable reception of the target signal.

The receiver 10 according to the embodiment has a function of determining pulse noise in the IF-AGC function and a function of recovering the gain of the reception amplifier 11 that has been reduced by the pulse noise. As a result, deterioration of the intelligibility of the received signal can be suppressed.

As a result, in the embodiment, it is possible to provide a receiver and a program capable of suppressing deterioration of intelligibility of a received signal when pulse noise is received together with the received signal.

In the embodiment, the case where the AGC voltage is used to control the gain of the reception amplifier section 11 has been described as an example, but the present invention is not limited to this.

It should be noted that the present invention is not limited to the above embodiments, and can be modified as appropriate without departing from the scope of the invention.

DESCRIPTION OF SYMBOLS 1, 2, 3... Terminal 10... Receiver 11... Receiving amplifier 12... Control part 121... Absolute value calculation part 122... Integration processing part 123... Difference calculation part 124... Reference value generation part 125... Switching part 126... Attack control Unit 1261 Attack period calculation counter 1262 AGC voltage update unit 127 Release control unit 1272 AGC voltage update unit 128 Voltage gain conversion unit 13 Judgment unit 131 Pulse noise judgment unit 14 Storage unit Tk Attack period Tkt ... attack period threshold Vg ... voltage change total amount Vgt ... voltage average fluctuation amount threshold

Claims (5)

an amplifier that amplifies a signal;
a control unit for setting, in the amplification unit, a gain setting value for AGC operation that keeps the amplitude of the signal after amplification within a predetermined range;
a determination unit that monitors changes in the gain setting value and determines whether the signal contains pulse noise based on whether the change in the gain setting value satisfies a predetermined condition;
The control unit
an absolute value calculator that rectifies the amplified signal;
an integration processing unit that smoothes the rectified signal to obtain a signal value;
a difference calculation unit that calculates a difference value between the signal value and a predetermined reference value;
an attack control unit and a release control unit that control the gain setting value based on the difference value;
The determination unit is
When the period required for the change in the gain setting value is less than the predetermined period threshold in the period in which the signal value exceeds the predetermined reference value, and the amount of change in the gain setting value exceeds the predetermined amount of change threshold, Characterized by determining that pulse noise is included,
Pulse noise judgment device. The control unit includes a switching unit that switches outputs of the attack control unit and the release control unit,
The switching unit is
selecting an attack operation by the attack control unit when the difference value output by the difference calculation unit exceeds zero, selecting the output voltage of the attack control unit as a gain setting value,
2. The pulse noise determination device according to claim 1, wherein when the difference value output by said difference calculation unit is zero or less, the release operation by said release control unit is selected, and the output voltage by said release control unit is selected as the gain setting value. . The determination unit is
The predetermined period threshold is a threshold for an attack period during which the attack control unit performs an attack operation,
3. The pulse noise detection device according to claim 1, wherein said predetermined amount of change threshold is an average amount of change in gain setting value per unit time when said attack control section performs an attack operation. The pulse noise detection device comprises a plurality of filters exclusively used for the signal input to the amplification unit ,
When the control unit sets the gain setting value for the signal that has passed through the filter, the determination unit determines at least one of the predetermined period threshold value and the predetermined change amount threshold value based on the type of the filter. to determine the pulse noise by changing
The pulse noise determination device according to claim 3 . Rectify the amplified signal amplified by the amplifier,
smoothing the rectified signal as a signal value,
calculating a difference value between the signal value and a predetermined reference value;
setting a gain setting value to the amplifier so that the amplitude of the signal amplified by the amplifier is within a predetermined range based on the difference value;
When the period required for the change in the gain setting value is less than the predetermined period threshold in the period in which the signal value exceeds the predetermined reference value, and the amount of change in the gain setting value exceeds the predetermined amount of change threshold, determining that the signal contains pulse noise;
A program that makes a computer do something.

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