JP2007124477A - Level detection apparatus and level control apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a level detection apparatus and a level control apparatus in which a power level can be highly accurately controlled without improving a dynamic range of a control signal. <P>SOLUTION: An inputted high frequency signal is amplified to a fixed level by a variable gain amplifier 2, detected by a high frequency detector 4 and compared with a reference voltage 5 by a comparator 6. In the comparator 6, a comparison voltage is generated in accordance with an error of a comparison result and this is negatively fed back as a control voltage of the variable gain amplifier 2, thereby keeping constant an output level of the variable gain amplifier 2. Thus, the control voltage of the variable gain amplifier 2 is changed in accordance with the input high frequency signal, and by reading a control voltage of a control voltage output terminal 3, the level of the high frequency signal can be measured. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a level detection device and a level control device having a variable gain amplifier whose gain changes exponentially with respect to a control voltage for detecting the signal level in a radio transceiver and controlling the signal level. .

  In recent years, in order to accommodate a large number of users with the spread of wireless devices, the transmission signal levels of individual radios rise in a wide range so as not to interfere with the wireless signals of other users. Techniques for accurately controlling the falling characteristics have been proposed.

  Hereinafter, a high-frequency power level control device that performs automatic control of output power, which is disclosed in Patent Document 1, will be described with reference to FIGS. 5 and 6.

  In FIG. 5, 51 is a high frequency signal input terminal, 52 is a high frequency power amplifier, 53 is a high frequency signal output terminal for outputting an amplified high frequency signal, 54 is a power level switching control signal, 55 and 59 are variable attenuators, and 56 is A high-frequency signal detection circuit, 57 is a reference voltage, 58 is a comparison / smoothing that outputs a comparison result obtained by comparing the detection voltage output from the detection circuit 56 with the reference voltage 57, and further applies a low-pass filter characteristic. Circuit.

  Next, the operation of the level control device will be described. The high-frequency signal input from the high-frequency signal input terminal 51 is amplified by the high-frequency power amplifier 52 and output from the high-frequency signal output terminal 53. At the same time, a part of the high-frequency signal is extracted and subjected to processing described later. The output power is controlled and stabilized by applying feedback. The electric power partially extracted from the high frequency signal output terminal 53 is input to the variable attenuator 55, and the amount of attenuation of the variable attenuator 55 is output from the high frequency signal output terminal 53 using the power level switching control signal 54. The amount of attenuation is increased when the power is output, and the amount of attenuation is decreased when small power is output from the high-frequency signal output terminal 53, so that the output level of the variable attenuator 55 is controlled to be constant.

The control characteristic of the variable attenuator 55 may be any characteristic as long as the degree of attenuation changes uniformly according to the set value of the control signal as shown in FIG. The detection circuit 56 detects the output of the variable attenuator 55, and the voltage obtained by the detection is compared with the reference voltage 57 by the comparison / smoothing circuit 58. The error signal of the comparison result is simultaneously smoothed by the comparison / smoothing circuit 58 and negatively fed back to the high frequency power amplifier 52 via the variable attenuator 59. With the above operation, the power output from the high-frequency signal output terminal 53 can be controlled according to the power level switching control signal 54.
JP-A-4-316205

  However, in order to accurately control the output power over a wide range, desired performance is required for the resolution of the variable attenuator. In order to control the output power with the required accuracy even in the control signal setting range with the highest sensitivity when the sensitivity of the attenuation to the power level switching control signal (hereinafter referred to as control sensitivity) varies depending on the set value of the control signal. A high resolution of the control signal is required. At the same time, even if the control sensitivity is low in a part of the control signal setting range, it is required that the full scale of the control signal is high in order to control the output power over a wide range. Therefore, there is a problem that a very high dynamic range is required for the control signal generation circuit that generates the control signal. Further, in order to correct the individual deviation of the variable attenuator, a memory for storing the control signal data necessary for each set value of the attenuation is required, but there is a problem that the capacity of the memory increases.

  The present invention is directed to solving the problems of the prior art, and provides a level detection device and a level control device that can control the power level with high accuracy without increasing the dynamic range of the control signal. Objective.

  In order to achieve the above object, a level detection apparatus according to the present invention includes a variable gain amplifier that receives a high-frequency signal and whose gain changes exponentially with respect to a control voltage that controls the gain, and a variable gain amplifier. A high-frequency detector for detecting the voltage of the amplified high-frequency signal; and a comparator for outputting a comparison voltage obtained by comparing the voltage detected by the high-frequency detector with a reference voltage as a control voltage of the variable gain amplifier, and controlling the variable gain amplifier It is characterized in that the level of a high frequency signal is detected by a voltage.

  Further, the variable gain amplifier of the level detection device has a bipolar transistor that applies a control voltage for controlling the gain between the base and the emitter, and the gain is proportional to the collector current flowing in the bipolar transistor, or the gain is controlled. And a gain is proportional to the current flowing through the diode.

  The level control device according to the present invention also includes a high-frequency amplifier that receives a high-frequency signal and inputs a first control voltage for controlling gain, and a high-frequency signal that is obtained by extracting a part of power from the output of the high-frequency amplifier. A variable gain amplifier whose gain changes exponentially with respect to a second control voltage that is input and controls gain, a high frequency detector that detects a voltage of a high frequency signal amplified by the variable gain amplifier, and a high frequency detector A comparator that outputs a comparison voltage obtained by comparing the detected voltage and the reference voltage as a first control voltage of the high-frequency amplifier, and controls the level of the output signal of the high-frequency amplifier by the second control voltage of the variable gain amplifier. It is characterized by.

  The variable gain amplifier of the level control device has a bipolar transistor that applies a control voltage for controlling the gain between the base and the emitter, and the gain is proportional to the collector current flowing through the bipolar transistor, or the gain is controlled. A diode for applying a control voltage is provided, and the gain is proportional to the current flowing through the diode.

  The level detection device having the above configuration takes out the level of the high frequency signal in the form of the control voltage of the variable gain amplifier, and the control voltage changes linearly with respect to the level of the high frequency signal, so that the dynamic range of the control voltage reading device is low. However, the level control device can detect the level of the high-frequency signal with high accuracy, and the level control device linearly changes the output level of the high-frequency amplifier with respect to the second control voltage applied to the variable gain amplifier. Even when the dynamic range of the control voltage generating device for generating the signal is low, the level of the output signal of the high frequency amplifier can be controlled with high accuracy.

  According to the level detection apparatus of the present invention, the level of the high frequency signal can be extracted in the form of a control voltage of the variable gain amplifier, and the control voltage changes linearly with respect to the level of the high frequency signal. Even if the dynamic range of the voltage reading device is low, the level of the high frequency signal can be detected with high accuracy. Further, according to the level control device of the present invention, the second control voltage applied to the variable gain amplifier can be detected. Since the output level of the high-frequency amplifier changes linearly, the level of the output signal of the high-frequency amplifier can be controlled with high accuracy even if the dynamic range of the device that generates the control voltage for generating the second control voltage is low. There is an effect that can be.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a block diagram showing a schematic configuration of a level detection apparatus according to Embodiment 1 of the present invention. In FIG. 1, 1 is a high frequency signal input terminal to which a high frequency signal to be subjected to level detection is input, 2 is a variable gain amplifier whose gain changes exponentially with respect to a control voltage for controlling gain, A control voltage output terminal for reading the control voltage of the variable gain amplifier 2, 4 is a high frequency detector for detecting a high frequency signal output from the variable gain amplifier 2, 5 is a reference voltage, and 6 is output from the high frequency detector 4. This is a comparator that outputs the result of comparing the detection voltage and the reference voltage 5 as the control voltage of the variable gain amplifier 2.

  Next, the operation of the level detection device will be described. The high frequency signal input from the high frequency signal input terminal 1 to be measured is amplified by the variable gain amplifier 2. The control voltage for controlling the gain of the variable gain amplifier 2 is subjected to negative feedback, which will be described later, so that the output level is always kept constant. Therefore, the control voltage changes corresponding to the high-frequency signal input from the measured high-frequency signal input terminal 1, and the level of the high-frequency signal can be measured by reading the control voltage from the control voltage output terminal 3. .

  The high frequency signal amplified to a certain level by the variable gain amplifier 2 is detected by the high frequency detector 4, and the voltage after detection is compared with the reference voltage 5 by the comparator 6. A comparison voltage is generated at the output of the comparator 6 in accordance with an error in the comparison result, and the output level of the variable gain amplifier 2 is always constant by applying negative feedback using the comparison voltage as a control voltage of the variable gain amplifier 2. Kept.

  The control characteristics of the variable gain amplifier 2 are shown in FIG. Since the gain changes exponentially with respect to the control voltage, the gain expressed on the logarithmic axis changes linearly with respect to the control voltage. A specific example of a circuit of the variable gain amplifier 2 that realizes such control characteristics is shown in FIG. The variable gain amplifier 2 includes a bipolar transistor Q1, field effect transistors M1 to M8, resistors R1 and R2, a bias voltage source VB, and a bias current source IB.

  The high frequency signal is input from the signal input terminal 33 and output from the signal output terminal 34. The gain is controlled by applying a control voltage 31 to the control voltage input terminal 32. The high-frequency signal input from the signal input terminal 33 is converted into a current signal by the field effect transistors M7 and M8, passes through the field effect transistors M3 and M6, is converted into a voltage signal by the resistors R1 and R2, and is output from the signal output terminal 34. The The ratio of the current flowing through the field effect transistors M3 and M4 and the ratio of the current flowing through the field effect transistors M6 and M5 are proportional to the ratio of the current flowing through the field effect transistors M1 and M2.

  The current flowing through the field effect transistor M1 can be controlled by changing the base / emitter voltage of the bipolar transistor Q1 by the control voltage 31. It is a well-known fact that the current flowing through the bipolar transistor Q1 changes exponentially with respect to the base / emitter voltage. Therefore, the current flowing through the field effect transistors M3 and M6 changes exponentially according to the control voltage 31, and as a result, the gain also changes exponentially.

  In FIG. 3, the current that exponentially changes is generated by the bipolar transistor Q1, but it is easy for a person skilled in the art to construct a circuit that similarly generates an exponentially changing current using a diode. It is.

  As described above, according to the first embodiment, the control voltage of the variable gain amplifier 2 changes in response to the high frequency signal input from the high frequency signal input terminal 1 to be measured, and the control voltage is supplied from the control voltage output terminal 3. By reading, the level of the high-frequency signal can be measured. In addition, since the gain of the variable gain amplifier 2 changes exponentially, the level of the high-frequency signal represented by the logarithmic axis and the control voltage have a linear relationship, so that even if the dynamic range of the control voltage reader is low, it is highly accurate. The level of the high frequency signal can be measured.

  For example, when a control voltage is detected using an AD converter, an AD converter with a low resolution can be used. Further, since the level of the high-frequency signal input to the high-frequency detector 4 is constant, the level detection can be performed with high accuracy without depending on the detection characteristics of the high-frequency detector 4.

  FIG. 4 is a block diagram showing a schematic configuration of the level control apparatus according to Embodiment 2 of the present invention. In FIG. 4, 41 is a high frequency signal input terminal, 42 is a high frequency amplifier, 43 is a high frequency signal output terminal for outputting an amplified high frequency signal, variable gain amplifier 2, high frequency detector 4, reference voltage 5, comparator 6 The same functions as those described in FIG. However, the comparison voltage output from the comparator 6 is given as a first control voltage for controlling the gain of the high-frequency amplifier 42. The control voltage for controlling the gain of the variable gain amplifier 2 is input from the control voltage input terminal 44 as the second control voltage.

  Next, the operation of the level control device will be described. The high-frequency signal input from the high-frequency signal input terminal 41 is amplified by the high-frequency amplifier 42 and output from the high-frequency signal output terminal 43. At the same time, a part of the high-frequency signal is extracted and subjected to processing described later. As a result, the output level is controlled and stabilized.

  The high-frequency signal partially extracted from the high-frequency signal output terminal 43 is input to the variable gain amplifier 2, and the gain of the variable gain amplifier 2 is determined using the second control voltage input from the control voltage input terminal 44. When the large amplitude is output from the output terminal 43, the gain is decreased, and when the small amplitude is output from the high frequency signal output terminal 43, the gain is increased, and the output level of the variable gain amplifier 2 is controlled to be constant.

  Further, as shown in FIG. 2, the gain of the variable gain amplifier 2 linearly changes in logarithmic axis according to the set value of the second control voltage. The high frequency detector 4 detects the output of the variable gain amplifier 2, and the voltage obtained by the detection is compared with the reference voltage 5 by the comparator 6. The error signal of the comparison result is negatively fed back as the first control voltage of the high frequency amplifier 42. With the above operation, the level output from the high-frequency signal output terminal 43 can be controlled according to the second control voltage input from the control voltage input terminal 44.

  According to the second embodiment, since the output level of the high-frequency amplifier 42 changes linearly with respect to the second control voltage applied to the variable gain amplifier 2, the control voltage generation device for generating the second control voltage Even if the dynamic range is low, the level of the output signal of the high frequency amplifier 42 can be controlled with high accuracy.

  For example, when a DA converter is used to generate the second control voltage, a DA converter with low resolution can be used. Even if there is a solid deviation in the variable gain amplifier 2, the logarithmic axis display gain of the variable gain amplifier 2 changes linearly with respect to the second control voltage, so control voltage data for correcting the solid deviation is obtained. There is an advantage that it is not necessary to prepare for each set value of the second control voltage, and the memory capacity for storing the control voltage data can be reduced.

  The level detection device according to the present invention can extract the level of the high-frequency signal as the control voltage of the variable gain amplifier, and the control voltage changes linearly with respect to the level of the high-frequency signal. Even if the range is low, the level of the high-frequency signal is detected with high accuracy, and the level control device linearly changes the output level of the high-frequency amplifier with respect to the second control voltage applied to the variable gain amplifier. Even if the dynamic range of the control voltage generator that generates the control voltage 2 is low, the level of the output signal of the high frequency amplifier can be controlled with high precision, the signal level is detected in the radio transceiver, and the signal level It is useful as a device for controlling.

1 is a block diagram showing a schematic configuration of a level detection apparatus according to Embodiment 1 of the present invention. Diagram showing control characteristics of variable gain amplifier Circuit diagram showing a specific example of a variable gain amplifier The block diagram which shows schematic structure of the level control apparatus in Embodiment 2 of this invention. Block diagram showing a schematic configuration of a conventional level control device Diagram showing control characteristics of variable attenuator

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 High frequency signal input terminal 2 Variable gain amplifier 3 Control voltage output terminal 4 High frequency detector 5 Reference voltage 6 Comparator 31 Control voltage 32 Control voltage input terminal 33 Signal input terminal 34 Signal output terminal 41 High frequency signal input terminal 42 High frequency amplifier 43 High-frequency signal output terminal 44 Control voltage input terminal 51 High-frequency signal input terminal 52 High-frequency power amplifier 53 High-frequency signal output terminal 54 Power level switching control signals 55 and 59 Variable attenuator 56 Detection circuit 57 Reference voltage 58 Comparison / smoothing circuit

Claims (6)

  A variable gain amplifier in which a high frequency signal is input and the gain changes exponentially with respect to a control voltage for controlling gain, a high frequency detector for detecting a voltage of a high frequency signal amplified by the variable gain amplifier, and the high frequency A comparator for outputting, as a control voltage of the variable gain amplifier, a comparison voltage obtained by comparing a voltage detected by the detector with a reference voltage, and detecting a level of a high frequency signal by the control voltage of the variable gain amplifier Level detector.   2. The level according to claim 1, wherein the variable gain amplifier has a bipolar transistor that applies a control voltage for controlling a gain between a base and an emitter, and the gain is proportional to a collector current flowing through the bipolar transistor. Detection device.   2. The level detection apparatus according to claim 1, wherein the variable gain amplifier includes a diode for applying a control voltage for controlling a gain, and the gain is proportional to a current flowing through the diode.   A high-frequency amplifier that inputs a high-frequency signal and inputs a first control voltage for controlling the gain; and a second high-frequency signal that is obtained by extracting a part of power from the output of the high-frequency amplifier and that controls the gain. A variable gain amplifier whose gain varies exponentially with respect to a control voltage, a high frequency detector for detecting a voltage of a high frequency signal amplified by the variable gain amplifier, a voltage detected by the high frequency detector, and a reference voltage A comparator that outputs the compared voltage as a first control voltage of the high-frequency amplifier, and the level of the output signal of the high-frequency amplifier is controlled by a second control voltage of the variable gain amplifier. Level control device.   5. The level according to claim 4, wherein the variable gain amplifier includes a bipolar transistor that applies a control voltage for controlling a gain between a base and an emitter, and the gain is proportional to a collector current flowing through the bipolar transistor. Control device.   5. The level control apparatus according to claim 4, wherein the variable gain amplifier includes a diode for applying a control voltage for controlling a gain, and the gain is proportional to a current flowing through the diode.

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