JPH09172380A - Transmission output control circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To use the title transmission output control circuit for a TDMA system radio transmitter and the like and to stably and highly precisely control a transmission output burst wave for a wide range SOLUTION: Feedback control for controlling the output of a transmission power amplifier 3 with the error voltage (Vcont) of a comparison error amplifier 9 and feed forward control for previously controlling the output level of a variable output drive amplifier 2 so that the input level of the transmission power amplifier 3 is optimized in such a way that the output control characteristic of the transmission power amplifier part 3 always has almost constant control sensitivity are executed. Then, the ramping waveform of the rise and fall of transmission output is controlled and the transmission output level is controlled.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transmission output control circuit for a radio transmitter or the like, and is particularly suitable for a TDMA transmitter or the like which requires stable control with high accuracy over a wide dynamic range.

[0002]

2. Description of the Related Art Conventionally, as a transmission output control circuit of this type, a closed loop system in which a part of a transmission output is detected and a feedback is applied to a power amplifier by the detected output is often used.

As a transmission output control circuit, for example, FIG.
The method shown in FIG. 10 is known. In FIG. 9, the oscillation source 1
To drive the power amplifier 3 (power amplifier system) to obtain a transmission output (TX), a part of which is taken out by the directional coupler 4 and detected by the wave detector 7 to detect the wave detection output (Vdet) and the reference output (Vref). ) Is compared with the comparison error amplifier 9 and feedback (detection system) is applied so that the output of the comparison error amplifier 9 is controlled by the control voltage (Vcont) to control the output of the power amplifier 3. Reference numeral 8 denotes a burst-like reference output waveform.

Further, Japanese Patent Application No. 2-21921 shown in FIG.
5 and the like, a variable attenuator 5 is provided between the directional coupler 4 and the detector 7, and the amount of attenuation of the variable attenuator 5 is changed according to the value of the transmission output to keep the input level of the detector 7 constant. , Enables stable control over a wide dynamic range for the detection system.

[0005]

However, in the first conventional example shown in FIG. 9, when applied to a TDMA transmitter or the like, the dynamic range of control of both the detection system and the power amplifier system is narrow, so the burst is In order to obtain the transmission output of the shape, its rise and fall characteristics are difficult to speed up,
It was also difficult to adjust the output over a wide range. In addition, there is a defect that the stability including the temperature characteristics of the output is lacking when the output is small.

Further, in the configuration of the second conventional example shown in FIG. 10, the dynamic range of the control of the detection system is widened, so that the stability and the reproducibility are improved. Since this is the same as the case of FIG. 9, there is a problem that an overshoot occurs at the rise of the burst output or unnecessary oscillation occurs. Further, the stability of the temperature characteristics of the transmission output was not sufficient.

SUMMARY OF THE INVENTION The present invention solves such a conventional problem. A transmission which can control a high output from a low output to a high output, and obtains a transmission burst output having a high degree of stability and reproducibility. An object is to provide an output control circuit.

[0008]

In order to achieve the above object, the present invention provides a transmission output control circuit, in addition to feedback control for controlling an output of a transmission power amplification section by an error voltage of a comparison error amplifier, in addition to required transmission. The output level of the variable output amplifier is controlled so that the input level of the transmission power amplifier is optimized so that the output control characteristic of the transmission power amplifier always has a substantially constant control sensitivity with respect to the output level. The feedforward control is performed to control the ramping waveform of the rising and falling of the transmission output and the transmission output level.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention described in the claims of the present invention
In addition to the feedback control in which the transmission output control circuit controls the output of the transmission power amplifier by the error voltage of the comparison error amplifier, the output control characteristic of the transmission power amplifier is always substantially constant with respect to the required transmission output level. Feedforward control is performed to control the output level of the variable output amplifier section so that the input level of the transmission power amplification section is optimized so as to have control sensitivity, and ramping waveform control and transmission of the rising and falling of the transmission output are performed. The output level is controlled, and both the power amplifier system and the detection system are controlled by control signals, the former as an open loop and the latter as a closed loop, individually controlled according to the transmission output. As a result, the dynamic range is expanded and the output range is wide, such as when controlling the rising and falling waveforms of the transmit burst waveform. Precision, highly stable control can be Achieved over.

FIG. 1 shows the configuration of an embodiment of the present invention.
In the figure, 1 is an oscillation source of a transmission signal composed of a VCO (voltage controlled oscillator) or the like, 2 is a variable output drive amplifier described in detail later, 3 is a (transmission) power amplifier (power amplifier), 4 is a directional coupler, Reference numeral 5 denotes a variable attenuator (ATT), the degree of attenuation of which is controlled by the control unit 10. 6 is a high frequency amplifier (RFAM
P) and 7 are detectors composed of diodes and the like, 9 is a comparison error amplifier for comparing the reference voltage (Vref) and the output (Vdet) of the detector 7, 10 is a control unit, and a control signal input 11
The variable output drive amplifier 2, ATT5, and reference voltage (Vref) are respectively controlled by. Reference numeral 8 is a burst-like reference waveform.

Next, the operation will be described with reference to FIG. 1 and FIGS. In FIG. 1, a part of the output of the power amplifier 3 is extracted by the directional coupler 4 and input to the ATT 5. AT
The attenuation of T5 is controlled so that the attenuation changes in response to, for example, a 4-bit digital control signal input from the control signal input 11 of the control unit 10. Such a digital control signal is often sent from a base station. A
The output of the TT 5 is input to the detector 7 via the high-frequency amplifier 6. At this time, the attenuation of the ATT 5 and the high frequency amplifier 6
Is controlled so that the input to the detector 7 becomes as constant as possible irrespective of the transmission output (Po). The output (Vdet) of the detector 7 and the reference voltage (Vref) are compared by a comparison error amplifier 9 including a successive comparator and the like, and the output of the power amplifier 3 is controlled by the error voltage (Vcont).
As described above, the directional coupler 4, the variable attenuator 5, the high-frequency amplifier 6, the detector 7, the comparison error amplifier 9, and the power amplifier 3 form a closed loop of a detection system (feedback). The reference voltage (Vref) has a burst shape like the reference waveform 8, and its peak value is given by the control unit 10 as a voltage that changes in accordance with the transmission output Po. The ATT 5 and the high frequency amplifier 6 form a variable amplifier.

FIG. 4 shows an example in which the output control characteristic of the power amplifier 3 is measured by changing the input drive level. For example, when it is desired to lower the output by 10 dB, the control sensitivity is unchanged by setting the drive level corresponding to the curve from (a) to (b). When it is desired to lower the output by 24 dB, the control level is set to the drive level corresponding to the curve (c), and the control sensitivity is kept constant.

Drive levels satisfying such conditions are obtained for each output level, and those values are determined by the power amplifier 3.
In this case, the ramping waveform of the output burst is improved as shown in the example of FIG. Overshoot and unnecessary oscillation are improved, the control sensitivity is basically the same for all power levels, and the operation level of the detection system is constant.

In particular, when the operation level of the detection diode is constant and the detection voltage is used at a maximum value of several volts, the output control is extremely stable, and as shown in FIG. Is extremely small, and there is a great merit that temperature compensation is not required at all output levels.

On the other hand, another factor of the control system is the control sensitivity of the power amplifier system. When the relationship between the control voltage and the output is linear and the slope is constant as shown in FIG. 3, the control sensitivity of the power amplifier is constant irrespective of the output, and the control sensitivity of the detection system matches well even though the control sensitivity of the detection system is constant. With only a closed loop consisting of a power amplifier system, a detection system, and a comparison error amplifier, transmission output control can be performed over a wide dynamic range from low power to high power. However, in general, the relationship between the control voltage and the output of the power amplifier is as shown in FIG.
The curve becomes saturated near the maximum output, and the control sensitivity at each output level, that is, the tangent changes greatly. In particular, as the output is reduced, the control sensitivity sharply increases, which causes the control loop to oscillate. Oscillation of the closed loop can be stopped by slowing the response of the loop, but burst waveform control cannot be performed near the maximum output, and the effect of automatic output control (APC) on power supply voltage fluctuation, input level fluctuation, etc. cannot be expected. .

Next, FIG. 6 shows a concrete example of the configuration of the variable output drive amplifier 2. The configuration shown in the figure is a two-stage cascade-connected amplifier of FETs with a matching circuit interposed between the input and output sides. First and second FETs (FET1, FET2)
Each of the first gates G1 receives an RF signal and is held at a fixed bias, and uses the second gate G2 as a control terminal. The level variable amount per transistor is 15
２０20 dB. For example, a two-stage configuration is used in order to vary the value by 30 dB or more.

FIG. 7 is a diagram showing a gate voltage vs. output level characteristic when a dual gate FET has two stages.

On the other hand, the optimum drive input level for each output level of the power amplifier 3 changes, for example, in the relationship shown in FIG. 8, and this value has a certain tolerance.

The gate bias of the variable output drive amplifier 2 is given in accordance with each output level according to the designation from the control unit 10. As an embodiment, it is given as a 4-bit digital value as the output level information. If
It is possible to configure the DA converter with a simple operational amplifier to form the circuit shown in FIG. Here, the OR circuit is for increasing the drive level particularly at the highest output level.

By providing such a variable output drive amplifier 2 in front of the power amplifier 3 and performing open loop control, the control sensitivity of the power amplifier is kept almost constant, and a stable transmission burst waveform is obtained at all output levels. Control becomes possible.

[0021]

As described above, according to the present invention as set forth in claim 1, in addition to the feedback control in which the transmission output control circuit controls the output of the transmission power amplification section by the error voltage of the comparison error amplifier, the required transmission is performed. The output level of the variable output amplifier is controlled so that the input level of the transmission power amplifier is optimized so that the output control characteristic of the transmission power amplifier always has a substantially constant control sensitivity with respect to the output level. Feed forward control to control the ramping waveform of the rising and falling of the transmission output and the control of the transmission output level so that the control sensitivity of the detection system can be kept constant against changes in the transmission output. In addition to the closed loop control, the variable output level drive amplifier is placed in front of the power amplifier to change the control sensitivity of the power amplifier. By combining two sets of loops of that, it makes it possible to control at a constant control sensitivity transmission output control at all power levels. As a result, not only control over a wide range of transmission output levels, but also high-speed control over a wide dynamic range, such as control of the rising and falling waveforms of a transmission burst waveform, becomes possible.
Further, since the operation level of the detection system is constant, it is extremely stable and has high reproducibility. In particular, it has a small effect on environmental temperature and has a great effect that temperature compensation is unnecessary at all output levels. Further, according to the present invention, unnecessary oscillation generally occurring when the transmission power is small is not generated, and high-speed and stable control can be performed.

[Brief description of the drawings]

FIG. 1 is a block configuration diagram of a transmission output control device according to an embodiment of the present invention.

FIG. 2 is a waveform diagram for explaining characteristics of the transmission output control device according to the embodiment of the present invention.

FIG. 3 is a characteristic diagram for explaining output characteristics with respect to an ideal control voltage of the transmission output control device according to the embodiment of the present invention.

FIG. 4 is a characteristic diagram showing output characteristics with respect to a measured control voltage of the transmission output control device according to the embodiment of the present invention.

FIG. 5 is a characteristic diagram showing an example of temperature characteristics of output of the transmission output control device according to the embodiment of the present invention.

FIG. 6 is a block configuration diagram showing a configuration example of a variable output drive amplifier of the transmission output control device according to the embodiment of the present invention.

FIG. 7 is a characteristic diagram showing the relationship between the output and the gate control voltage of the transmission output control device according to the embodiment of the present invention.

FIG. 8 is a characteristic diagram showing the relationship between the optimum drive level and the transmission output of the transmission output control device according to the embodiment of the present invention.

FIG. 9 is a block diagram showing a configuration example of a conventional transmission output control circuit.

FIG. 10 is a block configuration diagram showing a configuration example of another conventional transmission output control circuit.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Oscillation source 2 Variable output drive amplifier 3 Power amplifier 4 Directional coupler 5 Variable attenuator 6 High frequency amplifier 7 Detector 9 Comparison error amplifier 10 Control unit

Claims (4)

[Claims] 1. A variable output amplifier section driven by a high frequency signal from an oscillation source, a transmission power amplifier section connected in cascade to the variable output amplifier section, and a directivity for extracting a part of the transmission power of the transmission power amplifier section. A combiner, a variable detector for detecting the output of the directional coupler, a comparison error amplifier for comparing the output of the variable detector with a reference waveform having a rising and falling ramping waveform, and a comparison error amplifier. Is provided with a reference waveform having a rising and falling ramping waveform, and the variable output amplifier section is provided with a control section for outputting a control voltage. The transmission power amplification section is provided by the error voltage of the comparison error amplifier. In addition to the feedback control that controls the output of the transmission power, the output control characteristics of the transmission power amplification unit should always have a substantially constant control sensitivity for the required transmission output level.
Feedforward control is performed to control the output level of the variable output amplifier so that the input level of the transmission power amplifier is optimized, and ramping waveform control of rising and falling of the transmission output and transmission output level control are performed. A transmission output control circuit characterized by the above. 2. The transmission output control circuit according to claim 1, wherein the variable detection section has a variable attenuation degree whose attenuation degree is determined by a control signal corresponding to a required transmission power. 3. The transmission power control circuit according to claim 1, wherein the variable detection unit has a high frequency amplifier having a fixed amplification degree. 4. The variable output amplifier section is constituted by a plurality of cascaded FET amplifier circuits, and at least one stage of the FET amplifier circuits is controlled by a control signal corresponding to a required transmission power level. The transmission power control circuit according to claim 1, which is characterized in that.