JP2007336110A - Transmitter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a transmitter with improved gain control of an amplifier. <P>SOLUTION: Amplifiers 3 and 5 amplify a signal to be processed, a level detection means 7 detects the level of the signal amplified by the amplifiers 3 and 5, and a gain control means 15 controls the gain of the amplifier 3 so that the output level from the amplifiers 3 and 5 may be a specified level based on the detection results of the level detection means 7. At that time, state detection means 11-13 detect a state wherein the output level from the amplifiers 3 and 5 is anticipated to exceed the specified level on the assumption that the signal to be processed is inputted into the amplifier 3. When the above state is detected by the state detection means 11-13, a gain reduction control means 15 lowers the gain of the amplifier 3 so that the output level from the amplifiers 3 and 5 may be within the specified level when the signal to be processed which corresponds to the above state is inputted into the amplifier 3. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a transmitter, and more particularly to a transmitter with improved gain control of an amplifier.

For example, in various communication apparatuses such as a base station apparatus and a mobile station apparatus of a mobile communication system, a signal to be transmitted is processed by a transmitter and transmitted.
FIG. 3 shows a configuration example of a transmitter that wirelessly transmits a broadband audio signal. In FIG. 3, for convenience of explanation, the same components as those shown in FIG. 1 that are referred to in the embodiments described later are denoted by the same reference numerals, but the intention is not to limit the present invention. No.
An example of the operation | movement performed in the transmitter shown by FIG. 3 is shown.
An audio signal input to the transmitter is modulated by an SSB (Single Side Band) modulation circuit 1, passes through a frequency conversion circuit 2, and is amplified to a specified output by a first amplifier 3. This amplified output is input to the first bandpass filter 4 and unnecessary waves are removed by the first bandpass filter 4, and then input to the second amplifier 5 to be amplified to a specified output. The The amplified output is further input to the second bandpass filter 6 and output after unnecessary waves are removed by the second bandpass filter 6.

Here, in such a circuit, the output level varies depending on the frequency due to the frequency characteristics of the gain and attenuation amount of each block.
In order to prevent this, the output level from the second band pass filter 6 is detected by the detection circuit 7, and the gain of the first amplifier 3 is changed according to the output level based on the detection result.
A part that performs such gain control is an AGC (Automatic Gain Control) circuit, which can output at a constant level in a wide band.

JP-A-8-46529

  However, in the case of a transmitter as shown in FIG. 3, the principle of the AGC circuit is that the output level is detected and then the gain of the amplifier is controlled (control). In this case, a signal of a predetermined level or higher is output until the AGC circuit operates.

With reference to FIG. 4, an example of the operation when there is a sudden change in voice input will be described. 4A shows the waveform of the audio input signal, FIG. 4B shows the waveform of the output signal from the transmitter, and FIG. 4C shows the waveform of the detection output signal. The waveform is shown. The horizontal axis represents time t, and four periods (period 1) to (period 4) are illustrated.
In the (period 1) portion, since there is no voice input, the output of the transmitter is zero. At this time, since the detection voltage is also 0, the gain of the first amplifier 3 is maximized.
In the period (period 2), audio is input, but the output remains 0 because of a delay in each circuit. For this reason, the detection voltage is also 0, and the gain of the first amplifier 3 remains at the maximum.
In the period (period 3), a transmission output is output, but the gain of the first amplifier 3 is maximum, and thus exceeds a specified level ("A" part in FIG. 4). At this time, the detection voltage rises, and thereby the gain of the first amplifier 3 is lowered.
In the period (period 4), since the gain of the first amplifier 3 is reduced, the signal is output at a specified output level.

As described above, in the transmitter as shown in FIG. 3, the output instantaneously exceeds the specified level in response to a sudden change in the voice input, so that the second amplifier 5 outputs a level higher than the specified level. There is a problem that it is necessary to use an amplifier having an ability to perform such a problem, and there is a problem that the cost becomes high.
The present invention has been made to solve such a conventional problem, and an object thereof is to provide a transmitter with improved gain control of an amplifier. Thereby, for example, an inexpensive amplifier can be used as the second amplifier 5.

In order to achieve the above object, the transmitter according to the present invention performs the following processing.
That is, the amplifier amplifies a signal to be processed. Level detection means detects the level of the signal after being amplified by the amplifier. The gain control means controls the gain of the amplifier based on the detection result by the level detection means so that the output level from the amplifier becomes a specified level.
At this time, when the state detection means assumes that the signal to be processed is input to the amplifier, the state detection means assumes a state in which the output level from the amplifier is expected to exceed the specified level (the signal is input to the amplifier. Detect before input). When the state is detected by the state detection unit, the output level from the amplifier is set to the specified level when the signal to be processed corresponding to the state is input to the amplifier. The gain of the amplifier is lowered so that it is within.

  Therefore, when the signal to be processed is amplified by the amplifier, the output level from the amplifier is expected to exceed the specified level when controlling the gain of the amplifier so that the output level from the amplifier becomes the specified level. When the state of the signal to be detected is detected, the gain of the amplifier may be reduced so that the output level from the amplifier does not exceed a specified level before such a signal is input to the amplifier. Therefore, for example, even when the input state of the signal to be processed changes suddenly as shown in FIG. 2, the output level from the amplifier is prevented from exceeding a specified level. Can do. Thus, for example, when an amplifier (amplifier 5 in FIG. 1) is further provided in the subsequent stage of the amplifier (amplifier 3 in FIG. 1) whose gain is to be controlled as shown in FIG. It is possible to use an inexpensive amplifier.

Here, various signals may be used as signals to be processed.
For example, a combination of a plurality of amplifiers may be used as the amplifier. In this case, the gain of one or more amplifiers is controlled.
Various levels such as a voltage level and a power level may be used as the signal level.
Various levels may be used as the specified level. For example, a certain level may be used, or a level having a width (level range) may be used.
In addition, in order to adjust the timing of the gain reduction of the amplifier by the gain reduction control unit performed after the predetermined state is detected by the state detection unit, for example, a timing adjustment unit such as a delay circuit can be used.

Further, various modes may be used as the gain set in the amplifier by the gain reduction control means. For example, a mode in which the gain is decreased by a predetermined value compared to the gain value of the amplifier at the previous time point, or the amplifier For example, a mode in which a predetermined small value such as a minimum value that can be set as the gain is set can be used.
Various timings may be used as timing for starting to reduce the gain of the amplifier by the gain reduction control means. For example, a signal corresponding to the state detected by the state detection means (output from the amplifier) Various timings can be used when or before a signal whose level is expected to exceed a specified level) is input to the amplifier.
In addition, various modes may be used as a period for reducing the gain of the amplifier by the gain reduction control unit. For example, a period corresponding to a period until a predetermined state is not detected by the state detection unit is used. Alternatively, it is possible to use a mode in which the gain of the amplifier is temporarily reduced for a preset period each time a predetermined state is detected by the state detection unit.

  Normally, the signal vibrates in a form such as a sine wave. As an example, when a level having a magnitude of amplitude (positive value) is used as the signal level, as a comparison of the magnitude relationship between the signal level and a specified level (for example, positive value), for example, a signal There is a state where the level of the signal exceeds the specified level, or a state where the signal level is equal to or lower than the specified level (within the specified level). As another example, when a level at each time timing that vibrates positively or negatively is used as a signal level, a specified level having a predetermined level range can be used. As a comparison of the magnitude relationship with the specified level (predetermined level range), for example, when the signal level exceeds the specified level level range or when the signal level is within the specified level level range (within the specified level) There is a certain state.

As one configuration example, the transmitter according to the present invention can be configured as follows.
The state detection means includes a control amplifier that amplifies the signal to be processed,
Control level detection means for detecting the level of the signal after being amplified by the control amplifier;
Control gain control means for controlling the gain of the control amplifier so that the output level from the control amplifier becomes a prescribed control level based on the detection result by the control level detection means;
Assuming that the signal to be processed is input to the amplifier, the level detected by the control level detection means is a predetermined level as a state where the output level from the amplifier is expected to exceed the specified level. And an overlevel detecting means for detecting a state exceeding the threshold level.
The gain reduction control means, when the level detected by the control level detection means is detected by the over-level detection means, a signal corresponding to the level is sent to the amplifier. The gain of the amplifier is reduced so that the output level from the amplifier is within the specified level when input.

Here, various levels may be used as the control regulation level.
In addition, various levels may be used as the control specified level and the threshold level. For example, a fixed level may be used similarly to the specified level, or a level having a width (level Range) may be used.

  As described above, according to the transmitter of the present invention, by improving the gain control of the amplifier, for example, an excessive level signal is output even when the input signal changes from being absent to being present. Therefore, for example, it is possible to use an inexpensive circuit.

Embodiments according to the present invention will be described with reference to the drawings.
FIG. 1 shows a configuration example of an SSB transmitter that is a transmitter according to an embodiment of the present invention. In the transmitter of this example, a broadband audio signal is amplified and output to an antenna (not shown). This output signal is wirelessly transmitted from the antenna.
The transmitter of this example includes an SSB modulation circuit 1, a frequency conversion circuit 2, a first amplifier 3, a first bandpass filter 4, a second amplifier 5, and a second bandpass filter 6. The first detection circuit 7, the third amplifier 11, the second detection circuit 12, the comparator 13, the delay circuit 14, and the AGC control circuit 15 are provided.
In this example, the third amplifier 11 and the second detection circuit 12 constitute an audio AGC circuit.

An example of the operation performed in the transmitter of this example is shown.
A broadband audio signal is input to the transmitter of this example. The input audio signal is modulated by the SSB modulation circuit 1, frequency-converted by the frequency conversion circuit 2, amplified to a specified level by the first amplifier 3, and this amplified signal is unnecessary by the first band-pass filter 4. The wave is removed and further amplified to a specified level by the second amplifier 5, the unnecessary wave of the amplified signal is removed by the second bandpass filter 6, and the signal of these processing results is output from the transmitter. The
In the frequency conversion circuit 2, for example, the signal frequency is up-converted from a baseband band to a radio frequency (RF) band.

A part of the signal output from the second bandpass filter 6 is extracted and detected by the first detection circuit 7, and the detection result is input to the AGC control circuit 15.
The audio signal input to the transmitter is input to the SSB modulation circuit 1 and also input to the third amplifier 11.
The Audio AGC circuit includes a third amplifier 11 and a second detection circuit 12, and changes the gain of the third amplifier 11 according to the level of the amplified signal output from the third amplifier 11. This is a circuit that keeps the output level constant. That is, the audio signal input to the third amplifier 11 is amplified by the third amplifier 11, the signal resulting from the amplification is detected by the second detection circuit 12, and the third signal is detected based on the result of the detection. The gain of the amplifier 11 is controlled.

In addition, the detection result signal from the second detection circuit 12 is input to the comparator 13.
In the comparator 13, the detection voltage of the detection result input from the second detection circuit 12 is compared with, for example, a preset reference voltage, and when the detection voltage exceeds the reference voltage, a high level signal is output. It is output to the delay circuit 14. This high level signal is delayed by the delay circuit 14 and input to the AGC control circuit 15. The delay circuit 14 is provided for adjusting the delay time in the circuit.

The AGC control circuit 15 outputs an AGC voltage for controlling the gain of the first amplifier 3 to the control terminal of the first amplifier 3 based on the detection result input from the first detection circuit 7. If a high level signal is input from the comparator 13 via the delay circuit 14, the AGC voltage for controlling the gain of the first amplifier 3 is temporarily set to a high level (high level). Thus, the gain of the first amplifier 3 is minimized.
Here, in the AGC by the AGC control circuit 15 of this example, the AGC voltage output to the control terminal of the first amplifier 3 is increased as the detection voltage of the detection result by the first detection circuit 7 increases. In the first amplifier 3, a smaller gain is set as the AGC voltage inputted to the control terminal is larger. That is, in this example, the gain of the first amplifier 3 is set to be smaller as the level of the signal output from the transmitter (detection voltage of the first detection circuit 7) is larger, and the output level from the transmitter is thereby reduced. Held constant.

  With reference to FIG. 2, an example of the operation in the case where there is a sudden change in voice input is shown as the operation in the transmitter of this example. FIG. 2A shows the waveform of the audio input signal, FIG. 2B shows the waveform of the output signal from the third amplifier 11 of the Audio AGC circuit, and FIG. 2 shows the waveform of the detection output signal from the second detection circuit 12 of the Audio AGC circuit, FIG. 2D shows the waveform of the output signal from the transmitter, and FIG. Shows the waveform of the output (AGC voltage) signal from the AGC control circuit 15. The horizontal axis represents time t, and four periods (period 1) to (period 4) are illustrated.

In the (period 1) portion, since there is no voice input, the output of the transmitter is zero. At this time, since the detection voltage of the first detection circuit 7 is also 0, the gain of the first amplifier 3 is maximized. In the Audio AGC circuit, since the detection voltage of the second detection circuit 12 is 0, the gain of the third amplifier 11 is maximized.
In the (period 2) portion, an audio signal is input. Here, normally, the audio AGC circuit keeps its output level constant, but suddenly changes from a state where no audio signal is input (that is, 0) to a state where there is an audio signal (that is, not 0). Therefore, a level exceeding the certain level is output, and thereby an over-output state is detected. That is, at this time, the detection output of the Audio AGC circuit becomes a very large voltage and exceeds the reference voltage set in the comparator 3 (for example, in advance), whereby a high level signal is output from the comparator 13.

In the delay circuit 14, a delay time corresponding to the processing delay in the SSB modulation circuit 1 and the frequency conversion circuit 2 or a delay time thereof (in this example, a delay time for realizing (period 2) in FIG. 2) is set in advance. Thus, a high level signal from the comparator 13 is input to the AGC control circuit 15 slightly before the audio signal input to the transmitter is input to the first amplifier 3.
In the period (period 3), first, a high level signal from the comparator 13 is input to the AGC control circuit 15, whereby the gain of the first amplifier 3 is minimized, and is input to the transmitter. Even if the audio signal is amplified by the first amplifier 3, the output from the transmitter can be prevented from exceeding a specified level.
Thereafter, when the output of the Audio AGC circuit is stabilized to a steady output and the detection output becomes less than the reference voltage of the comparator 13, the high level output from the comparator 13 is stopped, and the AGC control circuit 15 Then, the gain of the first amplifier 3 is controlled based on the detection result from the first detection circuit 7. As a result, the output from the AGC control circuit 15 is also stabilized to a steady output, and the output level from the transmitter is also stabilized to a constant level.
In the period (period 4), the output from the AGC control circuit 15 and the output from the transmitter are stable at a steady output, and a transmission signal having a specified output level is output from the transmitter.

As described above, in the transmitter of this example, the output from the transmitter is detected and the gain of the first amplifier 3 is changed by the detected output to maintain the output level constant (in this example, In the first detection circuit 7 and the AGC control circuit 15), when a sudden change in the voice input is detected, such as when the voice input changes from no to yes, the gain of the first amplifier 3 is temporarily set. By dropping the power, the output from the transmitter is protected from being overpowered. In this example, as a method for detecting a sudden change in voice input, an audio AGC circuit is provided, and a method is used for detection based on the detected output.
Therefore, in the transmitter of this example, an AGC circuit without overshoot can be realized. For example, it is possible to prevent the input to the second amplifier 5 from becoming an excessive input. An inexpensive amplifier can be used as the amplifier 5 and the transmitter as a whole can be realized at a low cost.

  Here, in the transmitter of this example, the second amplifier 5 is provided after the first amplifier 3 whose gain is to be controlled, and output by the first detector circuit 7 after the second amplifier 5. The level is detected and the gain of the first amplifier 3 is controlled based on the detection result. For example, when the gain of the second amplifier 5 is constant, the gain of the first amplifier 3 is controlled. Since the magnitude of the output level detected by the first detection circuit 7 changes according to the magnitude of the AGC, the AGC control for the first amplifier 3 is possible.

In the transmitter of this example, a broadband audio signal is used as a signal to be processed, and an amplifier that amplifies the signal to be processed by the first amplifier 3 or the second amplifier 5 is configured. The first amplifier 3 constitutes an amplifier whose gain is to be controlled, the level detection means is constituted by the function of the first detection circuit 7, and the detection result by the first detection circuit 7 Based on this, the gain control means is configured by the function of controlling the gain of the first amplifier 3 via the AGC control circuit 15, and the third amplifier 11, the second detection circuit 12, and the comparator 13 cause excessive output. The state detection means is configured by the function of detecting the input signal state that is expected to be, and the gain of the first amplifier 3 is adjusted via the AGC control circuit 15 based on the output from the comparator 13. Gain reduction control means is constituted by the function of performing control to made. Further, in the transmitter of this example, the timing adjustment means is configured by the function of the delay circuit 14.
Further, in the transmitter of this example, a control amplifier is configured by the third amplifier 11, and a control level detection unit is configured by the function of the second detection circuit 12, and the second detection circuit 12 is configured. The control gain control means is configured by the function of controlling the gain of the third amplifier 11 on the basis of the detection result by, and the function of detecting the input signal state that is expected to be an excessive output by the comparator 13 is excessive. Level detection means is configured.

Here, the configuration of the apparatus (apparatus) and the system according to the present invention is not necessarily limited to those described above, and various configurations may be used. The present invention can also be provided as, for example, a method or method for executing the processing according to the present invention, a program for realizing such a method or method, or a recording medium for recording the program. It is also possible to provide various devices and systems.
The application field of the present invention is not necessarily limited to the above-described fields, and the present invention can be applied to various fields.
In addition, as various processes performed in the apparatus (device) or system according to the present invention, for example, the processor executes a control program stored in a ROM (Read Only Memory) in a hardware resource including a processor and a memory. The configuration controlled by doing so may be used, and for example, each functional means for executing the processing may be configured as an independent hardware circuit.
The present invention can also be understood as a computer-readable recording medium such as a floppy (registered trademark) disk or a CD (Compact Disc) -ROM storing the control program, and the program (itself). The processing according to the present invention can be performed by inputting the program from the recording medium to the computer and causing the processor to execute the program.

It is a figure which shows the structural example of the transmitter which concerns on one Example of this invention. It is a figure which shows an example of a waveform when there exists a fluctuation | variation rapidly in a voice input. It is a figure which shows the structural example of a transmitter. It is a figure which shows an example of a waveform when there exists a fluctuation | variation rapidly in a voice input.

Explanation of symbols

  1 .... SSB modulation circuit, 2 .... Frequency conversion circuit, 3, 5, 11, ... Amplifier, 4, 6 .... Band pass filter, 7, 12 .... Detection circuit, 13 .... Comparator, 14 .... Delay circuit 15. AGC control circuit,

Claims (1)

In the transmitter,
An amplifier for amplifying a signal to be processed;
Level detection means for detecting the level of the signal after being amplified by the amplifier;
Gain control means for controlling the gain of the amplifier so that the output level from the amplifier becomes a specified level based on the detection result by the level detection means;
State detection means for detecting a state in which an output level from the amplifier is expected to exceed the specified level when the signal to be processed is input to the amplifier;
When the state is detected by the state detection means, when the signal to be processed corresponding to the state is input to the amplifier, the output level from the amplifier is within the specified level. Gain reduction control means for reducing the gain of the amplifier;
A transmitter characterized by comprising:

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