JPH0758648A - Radio transmitter - Google Patents

Abstract

PURPOSE:To cope with a wide-range audio signal level without damaging a natural feeling by setting of the extent of attenuation by changing the extent of attenuation in a variable attenuator from the just preceding extent of attenuation in an attenuation extent controller by a prescribed extent corresponding to the discriminated level range at the time of judging that the automatic level control voltage is within a prescribed range. CONSTITUTION:The transmission power level is detected by an output level detecting circuit 7, and the voltage from the circuit 7 is rectified and smoothed in accordance with this level, and this voltage is compared with the reference voltage outputted from a reference voltage supply circuit 10. As the result, a voltage exceeding the reference voltage is outputted as the automatic level control voltage from an automatic level control voltage generating circuit 9 and is supplied as a gain control voltage to a variable gain amplifying circuit 5 to control the gain of the circuit 5, thus controlling the transmission power level to a prescribed level or lower. Further, the automatic gain control voltage is subjected to A/D conversion by a converter 11, and the automatic level control voltage is sent to a variable attenuation extent control circuit 12 to control the extent of attenuation in a variable attenuation circuit 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radio transmitter for controlling a transmission output level of a carrier wave suppression / amplitude modulation radio wave modulated by a voice signal to a predetermined output level or lower, and more specifically to a radio transmitter. The present invention relates to a wireless transmitter that automatically controls the audio signal level to be output.

[0002]

2. Description of the Related Art Suppressing a carrier wave modulated by an audio signal
A radio transmitter including a conventional automatic level control (ALC) circuit that controls the transmission output level of an amplitude-modulated radio wave to a predetermined output level or less and transmits the voice is output from a microphone 1 as shown in FIG. 6, for example. Signal amplification circuit 2
Is amplified and then attenuated by the variable attenuation circuit 3A whose attenuation amount is manually controlled, and the audio signal attenuated by the variable attenuation circuit 3A is supplied to the modulator 4 as a modulation signal to amplitude-modulate the carrier wave by the audio signal, In addition, the carrier wave is suppressed and transmitted as a carrier wave suppression / amplitude modulation output, the carrier wave suppression / amplitude modulation output is amplified by the variable gain amplifier circuit 5, and the carrier wave suppression / amplitude modulation output is amplified by the variable gain amplifier circuit 5 and output amplified. The circuit 6 is configured to be amplified, supplied to the antenna 8 via the output level detection circuit 7 formed of, for example, a directional coupler, and transmitted from the antenna 8.

The conventional radio transmitter further detects the transmission power level by the output level detection circuit 7, rectifies and smoothes the voltage output from the output level detection circuit 7 corresponding to the detected transmission power level, The smoothed voltage is compared with the reference voltage output from the reference voltage source circuit 10, and the voltage exceeding the reference voltage is output from the automatic level control voltage generation circuit 9 as the automatic level control voltage to change the automatic level control voltage. It is supplied to the gain amplifier 5 as a gain control voltage to control the transmission power level to a predetermined level or lower.
The LC is performed to keep the output power level at or below a predetermined peak power value with respect to changes in the total gain due to temperature drift and frequency characteristics, and changes in sound pressure during transmission.

[0004]

However, in the case of the above-mentioned conventional wireless transmitter, even if ALC is performed, the input level changes due to the sensitivity of the microphone used and the individual difference of the speaker. There was a problem that it could not follow. Also, if you force it to follow, the surrounding noise from when loudly speaking to when not speaking will also be transmitted at a constant output power level or less, so the receiver seems to have significantly impaired natural feeling. There was a problem of feeling it. Furthermore, if the signal is forcibly followed, the signal applied to the modulator and other circuits will change greatly from high level to low level, and distortion due to saturation at each stage will also become a problem, and in order to solve this distortion the circuit will be complicated. There was also the problem that it would be a problem.

For this reason, a gain adjusting circuit for the microphone, a variable attenuating circuit 3A, etc. are provided to vary the modulation signal level from the outside, and the level of the automatic level control voltage is used as an index for adjusting the level of the modulation signal. The microphone gain and the variable attenuation circuit 3 are displayed on the display unit 15 and the speaker refers to the display on the display unit 15.
Since the attenuation amount due to A is adjusted, there is a problem that the operation becomes troublesome.

The present invention solves the above problems, automatically controls the modulation signal level, and can cope with a wide range of voice signal levels without impairing the natural feeling of the receiver. The purpose is to provide a machine.

[0007]

The wireless transmitter of the present invention comprises:
A radio that detects the transmission output level of a carrier wave suppression / amplitude modulation radio wave modulated by an audio signal, generates an automatic level control voltage, and controls the transmission output level below a predetermined level based on the automatic level control voltage to transmit. In the transmitter, a variable attenuating means for attenuating the amplified audio signal and sending it to the modulator, and an automatic level control voltage in a direction of increasing or decreasing beyond a proper level range are divided into a plurality of level ranges over a predetermined period. When it is determined by the automatic level control voltage determining means and the automatic level control voltage determining means that the automatic level control voltage exists in any of the level ranges, it is determined that the automatic level control voltage exists. A damping amount control that changes the damping amount in the variable damping means from the previous damping amount by a predetermined amount corresponding to the level range. Characterized by comprising a means.

The radio transmitter according to the present invention is characterized in that the predetermined period in the automatic level control voltage determining means is different depending on the level range.

[0009]

The radio transmitter of the present invention detects the transmission output level of the carrier wave suppression / amplitude modulation radio wave modulated by the voice signal to generate the automatic level control voltage, and based on the automatic level control voltage, the transmission output level. In a wireless transmitter that controls and transmits the signal to a predetermined level or less, the automatic level control voltage exists in any range divided into a plurality of level ranges over a predetermined period in the direction of increasing or decreasing beyond the appropriate level range. Whether or not it is determined by the automatic level control voltage determining means, and when it is determined that the automatic level control voltage exists in any of the ranges, only a predetermined amount corresponding to the level range determined to exist, The attenuation amount in the variable attenuation means is changed from the previous attenuation amount by the attenuation amount control means. Therefore, by setting the range, the time, and the changed attenuation amount, it is possible to cope with a wide audio signal level without deteriorating the natural feeling.

[0010]

EXAMPLES The present invention will be described below with reference to examples. Figure 1
FIG. 3 is a block diagram showing the configuration of an embodiment of the present invention.

The audio signal output from the microphone 1 is amplified by the voltage amplification circuit 2 and then attenuated by the variable attenuation circuit 3 whose attenuation amount is controlled by the attenuation amount control circuit 14 to be described later, and then attenuated by the variable attenuation circuit 3. A voice signal is supplied to the modulator 4 as a modulation signal, the carrier wave is amplitude-modulated by the voice signal, the carrier wave is suppressed, and the carrier wave suppression / amplitude modulation output is sent out. 5, the carrier suppression / amplitude modulation output amplified by the variable gain amplifier circuit 5 is amplified by the output amplifier circuit 6, and is supplied to the antenna 8 via the output level detection circuit 7 composed of a directional coupler. It is configured to transmit from 8.

The output power level is detected by the output level detection circuit 7, the voltage output from the output level detection circuit 7 is rectified and smoothed corresponding to the detected power level, and the smoothed voltage is used as a reference voltage. Compared with the reference voltage output from the source circuit 10, a voltage exceeding the reference voltage is output from the automatic level control voltage generation circuit 9 as an automatic level control voltage, and the automatic level control voltage is supplied to the variable gain amplifier 5 as a gain control voltage. ALC for controlling the gain of the variable gain control amplifier to control the transmission power level below a predetermined level.

Further, the automatic level control voltage is supplied to the A / D converter 11 to be converted into digital data, and the automatic level control voltage converted to digital data is supplied to the variable attenuation control circuit 12 composed of a microcomputer. Then, the amount of attenuation in the variable attenuation circuit 3 is controlled based on the automatic level control voltage.

Here, the attenuation control circuit 14 is functionally arranged so that the automatic level control voltage converted into digital data output from the A / D converter 11 increases or decreases beyond the appropriate level range. The automatic level control voltage determination circuit 13 for determining which range the automatic level control voltage is divided into a plurality of level ranges over a predetermined period, and the automatic level control voltage determination circuit 13 determines the automatic level control voltage as described above. When it is determined to exist in any of the level ranges, an attenuation amount control circuit for changing the attenuation amount in the variable attenuation circuit 3 from the previous attenuation amount by a predetermined amount corresponding to the level range determined to exist. 1
4 and. The automatic level control voltage determination circuit 13 constitutes an automatic level control voltage determination means, and the attenuation amount control circuit 14 constitutes an attenuation amount control means.

In the radio transmitter according to the present embodiment having the above-described structure, the microphone 1, the voltage amplification circuit 2, the variable attenuation circuit 3, the modulator 4, the variable gain amplification circuit 5, the output amplification circuit 6, and the output level detection are performed. The operation of the circuit 7, the automatic level control voltage generation circuit 9, and the reference voltage source circuit 10 is performed by the ALC circuit except that the attenuation amount in the variable attenuation circuit 3 is controlled by the output of the attenuation amount control circuit 14. Is kept below a predetermined peak power value as in the case of a wireless transmitter having a conventional ALC circuit, and a description thereof will be omitted.

In addition to the above, the wireless transmitter according to the present embodiment has the automatic level control voltage converted into digital data by the A / D converter 11 and is variable based on the automatic level control voltage converted into digital data. Under the control of the attenuation amount control circuit 12, the attenuation amount in the variable attenuation circuit 3 is selectively changed.

The operation of the variable attenuation control circuit 12 will be described below with reference to the ALC characteristic diagram shown in FIG. 2 and the flow charts shown in FIGS.

FIG. 2 is an ALC characteristic diagram showing the ALC operation, showing the relationship between the audio signal input level, the automatic level control voltage, and the transmission output power level.

The variable attenuation control circuit 12 includes a timer, a program memory, and a data memory having a work area,
In this embodiment, as shown in FIG. 2, the range of the automatic level control voltage is such that the range (VALC <a) in which the level of the automatic level control voltage is less than a is the input underrange, and the range of the input underrange or more and less than b. The range (a ≤ VALC <b) is set as the proper input range, and the range (b ≤ VALC <
c) is defined as a range close to input excess, and a range close to input excess or above is classified as an input excess range (c ≦ VALC), and each range data is stored in the data memory.

When the program is started, the automatic level control voltage converted into digital data is stored in the data memory as VALC (step S1). Step S
After 1, it is checked whether VALC is within the input under-range (VALC <a) (step S2). When it is determined that it is within the input under-range, it is checked whether the timer is counting time. (Step S3). When it is determined that the timer is not counting time, the timer starts counting (step S4). If it is determined that the input is within the input underrange, the timer time period is set to 5 seconds.

When it is determined in step S3 that the timer is measuring time, it is checked whether the timer has finished measuring time (step S5), and when it is determined that the timer has finished measuring, The attenuation amount in the variable attenuation circuit 3 can be reduced by 3 dB from the current attenuation amount (step S6). That is, within the input under-range, VAL
If the presence of C continues for 5 seconds, the attenuation amount of the variable attenuation circuit 3 is reduced by 3 dB from the current attenuation amount. Here, the variable attenuation circuit 3 is composed of, for example, an electronic volume,
By executing step S6, the position of bit 1 registered in the shift register of four stages is shifted to the left by one stage, and controlled by the output of the stage of the shift register which has become bit 1 which constitutes the electronic volume. The on / off of the transistor is changed and the attenuation is 3 dB from the current attenuation.
Be lowered.

When it is determined in step S1 that the input is not too small, when step S4 is executed, when it is not determined that the timer has finished counting in step S5, or when the attenuation amount is changed in step S6, It is checked whether VALC is within the proper range (a≤VALC <b) (step S7). When it is determined in step S7 that VALC is within the proper range, the timer is reset (step S8).
If it is determined in step S7 that VALC is not within the proper range, or if step S8 is executed, VALC is in a range close to input excess (b ≦ VALC <
It is checked whether it is within c) (step S).
9).

Here, the step S8 is executed after the step S7 and the attenuation amount of the variable attenuation circuit 3 is not changed. In this case, since the VALC is within the proper range, the attenuation amount is The current attenuation amount is maintained as appropriate.

When it is determined in step S9 that VALC is in the range close to the excessive value, it is checked whether or not the timer is counting time (step S10). When it is determined that the timer is not counting time, the timer starts counting (step S11). If it is determined that the time period is within the excessively large range, the time period of the timer is set to 3 seconds.

When it is determined in step S10 that the timer is measuring time, it is checked whether the timer has finished measuring time (step S1).
2) If it is determined that the timer has finished counting, the attenuation amount in the variable attenuation circuit 3 can be increased by 3 dB from the current attenuation amount (step S13). That is, when VALC is kept within a range close to the input excess for 3 seconds, the attenuation amount of the variable attenuation circuit 3 is increased by 3 dB from the current attenuation amount. Here, by executing step S13, the position of bit 1 registered in the shift register of four stages is shifted to the right by one stage, and according to the output of the stage of the shift register which has become bit 1 constituting the electronic volume. The controlled transistor is turned on / off to increase the attenuation by 3 dB from the current attenuation.

When it is determined in step S9 that the state is not close to excessive input, when step S11 is executed, when it is not determined that the timer has finished counting in step S12, or when the attenuation amount is changed in step S13 Indicates that VALC is in an excessive range (c ≦ VAL
It is checked whether it is within C) (step S1).
4).

When it is determined in step S14 that VALC is within the excessive range, it is checked whether or not the timer is measuring time (step S15). When it is determined that the timer is not counting, the timer starts counting (step S16). If it is determined that the time is within the excessive range, the timer time period is set to 100 msec.

When it is determined in step S15 that the timer is measuring time, it is checked whether the timer has finished measuring time (step S1).
7) If it is determined that the timer has finished counting, the attenuation amount in the variable attenuation circuit 3 can be increased by 3 dB from the current attenuation amount (step S18). That is, if VALC is kept within the input excessive range for 100 msec, the attenuation amount of the variable attenuation circuit 3 is 3 dB from the current attenuation amount.
Can be increased. Here, by executing step S18, the position of bit 1 registered in the shift register of four stages is shifted to the right by one stage, and controlled by the output of the stage of the shift register that has become bit 1 that constitutes the electronic volume. The amount of attenuation can be increased by 3 dB from the current amount of attenuation by changing the on / off state of the transistor.

When it is determined in step S14 that the input is not excessive, when step S16 is executed, when it is not determined in step S17 that the timer has finished counting, or when the attenuation amount is changed in step S18, The following program is executed. During the next execution of the program, when the timer has timed, the steps subsequent to the timer timed are executed.

As described above, according to the wireless transmitter of the present embodiment, when the input audio signal level is too low, the ALC
When the circuit outputs a small automatic level control voltage and the automatic level control voltage enters the input under-range and remains in that state for 5 seconds, the attenuation amount in the variable attenuation circuit 3 is reduced by 3 dB from the current attenuation amount. If the input audio signal level is too high, the ALC circuit outputs a large automatic level control voltage, and if the automatic level control voltage falls within the range close to the excessive input and the state continues for 3 seconds, the variable attenuation circuit The attenuation at 3 is increased by 3 dB from the current attenuation.

When the input audio signal level is an excessive input level, a larger automatic level control voltage is output by the ALC circuit, and if the automatic level control voltage is within the input excessive range and the state continues for 100 msec, The amount of attenuation in the variable attenuation circuit 3 is 3 dB from the current amount of attenuation.
Can be increased. Thus, the input voice signal level is
When the stable transmission power level control cannot be expected by the ALC circuit due to entering into the excessive range, the range close to the excessive range, or the excessive range, the ALC circuit performs the stable ALC operation by controlling to the optimum modulation input level.

Although the output level detection circuit 7 detects the voltage corresponding to the transmission power level in the above description, the output voltage or output current of the output amplifier may be detected.

Further, the variable attenuator circuit 3, the modulator 4, and the variable gain amplifier circuit 5 are replaced by a digital signal processor to perform ALC operation in a narrow range by fast attack and slow release as before, and further exceed that range. In the case of the input audio signal level, in addition to the above-described conventional fast attack and slow release, by controlling the average value-processed slow attack and slow release, the same effect as that of the present embodiment can be obtained. .

[0034]

As described above, according to the present invention, the automatic level control voltage is divided into a plurality of level ranges over a predetermined period in a direction of increasing or decreasing beyond the appropriate level range. If the automatic level control voltage determining means determines whether the automatic level control voltage exists in any of the above ranges, and the automatic level control voltage exists in any of the ranges, the level range is determined to be present. Since the attenuation amount in the variable attenuation means is changed from the immediately previous attenuation amount by the attenuation amount control means by the predetermined amount thus set, the range, the time and the attenuation amount to be changed are naturally set. There is an effect that a wide range of audio signal levels can be dealt with without impairing the feeling.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a wireless transmitter according to an embodiment of the present invention.

FIG. 2 is an ALC in a wireless transmitter according to an embodiment of the present invention.
FIG. 9 is a characteristic diagram for explaining the operation.

FIG. 3 is a flowchart for explaining the operation of the wireless transmitter according to the embodiment of the present invention.

FIG. 4 is a flowchart for explaining the operation of the wireless transmitter according to the embodiment of the present invention.

FIG. 5 is a flowchart for explaining the operation of the wireless transmitter according to the embodiment of the present invention.

FIG. 6 is a block diagram showing a configuration of a conventional wireless transmitter.

[Explanation of symbols]

 1 Microphone 2 Voltage amplification circuit 3 Variable attenuation circuit 4 Modulator 5 Variable gain amplification circuit 6 Output amplification circuit 7 Output level detection circuit 9 Automatic level control voltage generation circuit 10 Reference voltage source circuit 12 Variable attenuation control circuit 13 Automatic level control voltage Judgment circuit 14 Attenuation control circuit

Claims (2)

[Claims] 1. Suppressing a carrier wave modulated by an audio signal
In a wireless transmitter that detects the transmission output level of amplitude-modulated radio waves, generates an automatic level control voltage, and controls the transmission output level below a predetermined level based on the automatic level control voltage to transmit, an amplified audio signal Attenuating and transmitting it to the modulator, and in which range the automatic level control voltage in the direction of increasing or decreasing beyond the appropriate level range is divided into a plurality of level ranges over a predetermined period. When the automatic level control voltage determining means determines whether the automatic level control voltage exists in any of the level ranges, the automatic level control voltage determining means determines a predetermined range corresponding to the level range determined to exist. And a damping amount control means for changing the damping amount in the variable damping means from the preceding damping amount by a predetermined amount. Transmitter. 2. The wireless transmitter according to claim 1, wherein the predetermined period in the automatic level control voltage determination means is different depending on the level range.