JPH0335620A - Transmission power control circuit - Google Patents

Abstract

PURPOSE:To improve the efficiency of power consumption for all the stages of transmission levels and to simplify a circuit by controlling the transmission output level of the transmission power control circuit by means of a computer according to a bias voltage. CONSTITUTION:The microcomputer 22 sets and outputs an output control signal 22a so that is goes to the level designated by a control signal 3a. The signal 22a is converted into an analogue signal with a D/A converter 231 and it goes to a transmission power control signal 23a. In the output level designated with the control signal 3a, the micro computer 22 takes out a value corresponding to the output level which is previously held for setting the bias voltage giving an optimum operation point and outputs it as a control signal 22b. The signal 22b is converted into an analogue signal with a D/A converter 232 and it goes to a bias setting signal 23b.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a transmission power control circuit used as a final stage or driver of a transmission stage of a mobile communication radio device.

[Conventional technology]

Figure 2 is a configuration diagram of a mobile device used as a terminal in a car phone system shown in, for example, ``Car Phone JP, 146 (published by the Institute of Electronics and Communication Engineers, February IO, 1985). , 30 is an antenna, 31
32 is a reception unit composed of a reception mixer 32a, an intermediate frequency amplifier 32b, and a demodulator 32c; 33 is a local oscillation unit that outputs a local frequency signal; 34 is a local oscillation unit that outputs a local frequency signal; 35 is a telephone, and 36 is a transmitting unit composed of a modulator 36a, a transmission mixer 36b, and a transmission power control circuit 36c. When operating near a base station, the mobile device reduces its output power to prevent high-level signals from entering the base station's antenna and causing interference.

Furthermore, when the service area is in a weak electric field area, the output power is increased to ensure voice quality. For this purpose, a control circuit is provided to control the output power.

The signal for controlling the output power is output by the control unit 34 that receives an instruction from the base station, for example. Hereinafter, the circuit that amplifies the transmission power and the power control circuit that receives a control signal from the control unit 34 to increase/decrease the output power and turn on/off the transmitter will be referred to as a transmission power control circuit 36c.

FIG. 3 is a circuit diagram showing a conventional transmission power control circuit 36c. In the figure, ■ is an RF power module that amplifies and outputs the transmission signal (TX), and 2 is a circuit that detects the output signal of the RF power module 1. Detection circuit, 3 is control signal 3a
4a is a DC amplifier that amplifies the detection signal output from the detection circuit 2, and 4b is the multiplexer 3.
DC amplifier that amplifies the output of , 4C is multiplexer 3
A DC amplifier 5 for supplying a reference input voltage to the current control differential amplifier 5 is composed of transistors 5a and 5b, and inputs the outputs of the DC amplifiers 4a and 4b for differential amplification;
is a power charge 1ffll transistor which receives the voltage applied to the power supply voltage terminal 7 as an input and outputs a voltage at a predetermined level to the RF power module 1 according to the output of the current control differential amplifier 5.

Further, 10 is a transmission on/off signal, which is applied to the transistors lla and llb.

The emitters of both transistors lla and llb are connected to a negative power supply 13.

FIG. 4 is a circuit configuration diagram showing an example of the circuit configuration of an RF power module l using FETs.

Also, Figure 5 shows a CMO3I with multiplex function.
FIG. 3 is a circuit configuration diagram showing the internal configuration of C, which has three control signal 3a terminals, three output terminals, and six input terminals, but only three input terminals are used here. The operation is to switch the signal input to the input terminal corresponding to the control signal 3a so as to output it to each output terminal.

Next, the operation will be explained. A transmission signal (TX) is input to the RF power module 1, amplified, and output as a transmission output signal (TX 0UT). This transmission output signal is high-frequency detected by the detection circuit 2, further rectified, and sent to the DC amplifier 4a.

On the other hand, the transmission on/off signal lO is transmitted by the transistor 11a,
The transistor 11a is turned on by the on signal of the transmission on/off signal 10, and the emitters of the transistors 5a and 5b have a potential of 15V, and the current control differential amplifier 5 becomes operational. .

Further, the multiplexer 3 selects a combination of the reference input voltages applied to the three input terminals according to the states of the six encoded control signals 3a, and outputs the selected reference input voltages to the three output terminals. This combined output is converted into a six-step output control signal by resistors having different resistance values connected to the output terminal of the multiplexer 3, and is supplied to the inverting input terminal of the DC amplifier 4b. This output control signal is amplified by the DC amplifier 4b and becomes one input of the differential amplifier 5.

The outputs of both DC amplifiers 4a and 4b are differentially amplified by a current control differential amplifier 5 and applied to the output of a power control transistor 6.

Thereby, the power control transistor 6 controls the voltage supplied to the RF power module 1, stabilizes the transmission power, and performs transmission power control in six 4 dB steps from the maximum transmission power.

In the RF power module 1 using the FET shown in FIG. 4, the drain terminal D
The voltages applied to i and D2 are switched in six stages.

FIG. 6 is a characteristic diagram showing the lo Vc, s characteristics of the FET. As shown in this figure, power consumption is generally highest at maximum output power, so the operating point is usually set higher than the pinch-off voltage ■ to maximize power consumption efficiency at this point. There is. However, in this case, the drain current flows as an idle current even when no input is applied to the gate. Furthermore, when power control is performed to reduce transmission power, the ratio of idle current increases, and the efficiency of the RF power module 1 decreases. In other words, even if the efficiency is optimal in one stage of stepwise control, the efficiency will drop significantly in other stages.

[Problem to be solved by the invention]

Conventional transmission power control circuits are configured as described above, so good power consumption efficiency can only be obtained at a specific transmission power, and the operating point can be set higher than the pinch-off voltage. When used, there were problems such as an idle current flowing through the drain, wasting power, and the circuit was complicated.

This invention was made to solve the above problems, and by changing the bias voltage of the RF power module according to the transmission power, the idle current ratio is reduced to the optimum point, and the RF power module's bias voltage is changed according to the transmission power. The purpose is to obtain a transmission power control circuit that can improve efficiency.

[Means to solve the problem]

The transmission power control circuit according to the present invention inputs a control signal specifying the output level of the RF power module and a detection signal corresponding to the output level of the RF power module, and
Outputs an output control signal that controls the output level of the F power module, and also outputs a bias control signal that specifies a bias voltage that makes the efficiency of the RF power module at the output level specified by the control signal exceed a certain value. A microcomputer circuit is provided, and the output control signal output from the microcomputer circuit is
The A converter converts it into an analog signal and supplies it to the RF power module, and the bias control signal output from the microcomputer circuit is level-adjusted by a bias voltage setting means and then supplied to the RF power module. .

[For production]

The microcomputer circuit of the present invention controls the operating point of the RF power module according to the transmission output level, sets the idle current of the RF power module to the optimum point, reduces the power consumption, and reduces the power consumption of the RF power module. improve efficiency.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. 1st
In the figure, 21 is an A/D converter (detection means) that digitally converts the analog detection signal output from the detection circuit.
, 22 is a one-chip microcomputer (microcomputer circuit) that outputs the output control signal 22a and the bias control signal 22b, and 23 is the output control signal 22.
A D/A converter 231 that converts a into an analog transmission power control signal 23a and a D/A converter that converts a bias control signal 22b into an analog bias setting signal 23b.
24 is a DC amplifier that amplifies the transmission power control signal 23a, and 25 is an RF power module by inputting the bias setting signal 23b and the voltage supplied from the negative power supply 13. This is an operational amplifier that controls the gate bias voltage of the circuit. Here, D/A converter 2
32 and the operational amplifier 25 are bias voltage setting means.

R1 is an input resistance of the operational amplifier 25, R2 is a feedback resistance, R3 and R4 are resistances that apply a reference voltage to the non-inverting input terminal of the operational amplifier 25, and C1 is connected in parallel with the resistor R4, which is input from the power supply system. This is a capacitor that bypasses noise. Other parts are designated by the same reference numerals and are the same as or equivalent to those shown in FIG. 3.

Next, the operation will be explained. Microcomputer 22
inputs the control signal 3a for setting the transmission output level and the detection signal output from the A/D converter 21, and adjusts the output so that the transmission output level of the RF power module 1 becomes the level specified by the control signal 3a. The control signal 22a is set and output. This output control signal 22a is transmitted to the D/A converter 2
31, it is converted to an analog signal and transmitted power control '10
This becomes a signal 23a. The signal is then amplified by the DC amplifier 24 and becomes an input signal to the power control transistor 6 that sets the voltage applied to the drain terminals DI and D2. On the other hand, in order to set the bias voltage that provides the optimum operating point at the output level specified by the control signal 3a, the microcomputer 22 uses a specified value from among the values previously stored in the built-in memory. A value corresponding to the output level is extracted and output as a bias-controlled 1ffll signal 22b. This bias control signal 22b is a D/A
It is converted into an analog signal by the converter 232 and becomes the bias setting signal 23b. The operational amplifier 25 sets the bias setting signal 23b to a voltage value that matches the characteristics of the RF power module 1, and outputs the bias setting signal 23b to the gate terminal G2. Give to G3. In this way, the optimum operating point can be set for each stage of output level.

The value of the bias control signal 22b held by the microcomputer 22 is determined as follows. First, find the gate bias voltage that provides the best efficiency at each output stage of the RF power module 1 alone, and write values such that these values become the output value of the operational amplifier 25 into the memory of the microcomputer 22. put. To find the gate bias voltage for optimal efficiency, the train terminals D of the first and middle FETs of the RF power module 1 must be
When the voltages applied to I and D2 reach a predetermined output level, the voltage applied to the gate terminal 02G3 can be changed to find the point at which the current flowing from the power supply voltage terminal 7 is minimum.

Further, the actual transmission output level is controlled as follows. When the control signal 3a is input to the microcomputer 22, the microcomputer 22 retrieves from the memory a reference signal that causes the transmission output level of the RF power module 1 to become the level specified by the control signal 3a. This reference signal is one of the reference signals for each stage set in the preliminary memory according to each stage of the output level. When the transmission on/off signal lO is turned on, the digital value corresponding to the input control signal 3a among the digital values for bias setting set in the memory in advance is output as the bias control signal 22b.

Then, this bias control signal 22b is converted to a predetermined gate bias voltage by the D/A converter 232 and the operational amplifier 25, and the gate terminal G2. Applied to G3.

On the other hand, a value proportional to the transmission output level of the RF power module 1 is input as a detection signal to the microcomputer 22 via the detection circuit 2 and the A/D converter 21.

The microcomputer 22 compares the reference signal retrieved from the memory with the detected signal and outputs the difference as an output control signal 22a. This output control signal 22a is
The transmission output level of the RF power module 1 is adjusted via the D/A converter 231, the DC amplifier 24, and the power control transistor 6. In this way, the control signal 3a
The transmission output level specified by is set, and at the same time, the power consumption efficiency can be set to the optimum value at each stage of the transmission output level.

In the above embodiment, the microcomputer circuit is a one-chip microcomputer 2 with a built-in memory.
2 is shown, but it goes without saying that an external memory may also be used. In this case, it is possible to easily accommodate a memory capacity of 1,000 yen, and it is also possible to replace only the memory portion.

〔Effect of the invention〕

As described above, according to the present invention, the transmission power control circuit is configured to optimally control the bias voltage of the RF power module according to the transmission output level using a microcomputer circuit. This has the effect of improving power consumption efficiency and simplifying the circuit configuration compared to the stage shown in FIG.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing a transmission power control circuit according to an embodiment of the present invention, FIG. 2 is a configuration diagram showing a mobile device used in a car telephone system, and FIG. 3 is a circuit diagram showing a conventional transmission power control circuit. 4 is a circuit configuration diagram showing an example of an RF power module, FIG. 5 is a circuit configuration diagram showing an example of a multiplexer, and FIG. 6 is a circuit configuration diagram showing an example of a multiplexer. - It is a characteristic diagram which shows an example of VCS characteristic. 1 is an RF power module, 2 is a detection circuit (detection means)
, 6 is a power control transistor, 21 is an A/D converter (
(detection means), 22 is a microcomputer, 231 is D
232 is a D/A converter (bias voltage setting means), 24 is a DC amplifier, and 25 is an operational amplifier (bias voltage setting means). In addition, in the figures, the same reference numerals indicate the same or equivalent parts.

Claims (1)

[Claims] An RF power module that amplifies the transmitted signal, and this RF
Detects the power level of the power module's output signal and
A transmission power control circuit comprising a detection means for outputting a detection signal according to a detected value, a control signal specifying the output level of the output signal of the RF power module and the detection signal are input, and the RF power module outputs an output control signal that makes the output level of the RF power module to the output level specified by the control signal, and corresponds to a bias voltage that makes the power consumption efficiency of the RF power module at the specified output level equal to or higher than a certain value. a microcomputer circuit that outputs a bias control signal; a D/A converter that converts the output control signal from digital to analog to output a transmission power control signal that determines the output level of the RF power module; and the bias control circuit. A transmission power control circuit comprising bias voltage setting means for adjusting the level of a signal and applying it to the RF power module.