JPH05315873A - Transmission power control circuit and transmission power amplifier with alc circuit - Google Patents

Abstract

PURPOSE:To prevent an output level of a transmission power control circuit from not being kept constant due to a frequency characteristic of an output level detection RF detector. CONSTITUTION:An output level at an output terminal 5 is kept constant even when an RF signal level inputted to an input terminal 1 is changed in the transmission power amplification factor with an ALC (automatic output level control) circuit. A conventional ALC circuit includes a reference voltage generator 7 generating a reference voltage, a 1st RF detection circuit comprising a coupler 4 and a diode 9 and a comparison amplifier 8, and also includes a 2nd RF detection circuit comprising a coupler 2 and a diode 6, outputting a detection voltage Vd and having the same frequency characteristic as that of the 1st RF detection circuit and an adder 10 adding the detection voltage Vd to the reference voltage as a new reference voltage Va.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transmission power control circuit for controlling the transmission output level of a transmission power amplification device and the like, and a transmission power amplification device with an automatic output level control (ALC) circuit to which this circuit is applied. The present invention relates to the improvement of the frequency characteristics of the above-mentioned circuit and device using the RF detector having the above as an output level detector.

[0002]

2. Description of the Related Art A conventional transmission power control circuit of this type and a transmission power amplifier with an ALC circuit to which this circuit is applied will be described with reference to the block diagram of FIG.

The radio frequency (RF) signal supplied from the input terminal 1 to the signal input terminal 31 of the transmission power amplifier 3 whose transmission power level is to be controlled is amplified by this amplifier 3 and goes through the signal output terminal 33 to the output terminal 5. Is output to. In addition,
The gain of the amplifier 3 is controlled by the control voltage applied to the control terminal 32. The RF detector 19 detects the RF signal according to the RF signal level (RF output level) at the output terminal 33 of the transmission power amplifier 3 and converts it into a DC voltage (detection voltage). The comparison amplifier 8 compares the reference voltage applied from the reference voltage generator 7 with the detection voltage from the RF detector 19, and if the detection voltage is lower than the reference voltage, a control voltage higher than the reference voltage is transmitted to the transmission power amplifier. Control end 32 of 3
If the detected voltage is higher than the reference voltage, a control voltage lower than the reference voltage is applied to the control terminal 32. That is, if the RF output level is lower than the output level corresponding to the reference voltage, the detected voltage is low, and a higher control voltage is applied to the control terminal 32. Then, the RF output level rises, the detection voltage rises accordingly, and the control terminal 32
The control voltage applied to the IC becomes low and the RF output level decreases. While repeating this, output terminal 5 (signal output terminal 3
The RF output level in 3) stabilizes at the output level corresponding to the reference voltage. Automatic output level control (AL
C) By the loop, if the reference voltage is determined, the output level of the transmission power amplifier 3 is kept constant.

[0004]

However, in the above-described conventional transmission power control circuit and transmission power control device with ALC, the output level of the transmitted power control circuit whose transmission power should be controlled to be constant, for example, the transmission power amplifier. Since the output level is controlled according to the detection voltage output from the RF detector, the flat frequency characteristic is promised only when the RF detector has the flat frequency characteristic. If R
If the F-detector has a frequency characteristic, the detection voltage generated from the RF detector differs depending on the input frequency to this device, so that the output level of the transmitted power control circuit cannot be kept constant. As described above, the conventional transmission power control circuit and the transmission power control device with ALC have a problem that the output level cannot be kept constant due to the frequency characteristic of the RF detector.

[0005]

The transmission power control circuit of the present invention generates a control voltage in response to a reference voltage generator for generating a reference voltage and a first detection voltage and the reference voltage. A transmission power control circuit comprising: a comparison amplifier supplied for controlling an output level of a transmitted power control circuit; and a first RF detector that detects an output level of the transmitted power control circuit to generate the first detected voltage. A second RF detector having substantially the same frequency characteristic as that of the first RF detector for detecting the input level of the transmitted power control circuit to generate a second detected voltage, and adding the reference voltage and the second detected voltage to each other. The reference voltage, which is one of the comparison inputs of the comparison amplifier, is replaced with the addition voltage.

The transmission power control apparatus can be applied to a transmission power amplification apparatus with ALC.

[0007]

The present invention will be described below with reference to the drawings.

FIG. 1 is a circuit diagram of an embodiment of the present invention.
This transmission power amplification device to which the transmission power control circuit according to the present invention is applied has a transmission power amplifier 3, a reference voltage amplifier 7 and a comparison amplifier 8 as in the conventional example shown in FIG.
RF signal is input from the input terminal 1 and RF is output from the output terminal 5.
Output a signal. In addition, the coupler 4 and the detection diode constitute the RF detector (first RF detector) 19. That is, the coupler 4 makes the signal output terminal 33 of the amplifier 3
Outputs a large part of the signal from the output terminal 7 to the output terminal 7 and supplies a part of the above signal to the diode 9, which diode 9 outputs R signal at the signal output terminal 33 from the RF signal.
A detection voltage Vc corresponding to the F output level is generated. In addition,
The comparison amplifier 8 comprises an operational amplifier A1 and a feedback resistor R4, and a resistor R5 is connected between the output end of the diode 9 and the first input end of the operational amplifier A1 on the resistor R4 connection side. ..

In addition to the conventional example shown in FIG. 2, this power amplifying device has a second structure including a coupler 2 and a detection diode 6.
It includes an RF detector and an adder 10 including an operational amplifier A2 and a feedback resistor R3. The coupler 2 outputs most of the RF signal input to the input terminal 1 to the signal input terminal 31 of the amplifier 3 and supplies a part of this signal to the diode 6, and the diode 6 inputs from this part of the RF signal. A detection voltage Vd corresponding to the RF signal input level at the terminal 1 is generated. The couplers 4 and 2 and the detection diodes 9 and 6 have almost the same performance. However, an RF signal attenuator (not shown) is included between the coupler 4 and the diode 9 in order to make the RF signal level to the diodes 9 and 6 the same, and the diodes 9 and 6 are included.
The detection voltages Vc and Vd from the above are substantially the same.
The adder 10 adds the reference voltage from the reference voltage generator 7 and the detection voltage Vd from the diode 6 to one of the input terminals and adds the added voltage Va to the output terminal of the second input of the comparison amplifier 8. Supply to the edge. A series circuit of resistors R1 and R2 is connected between the diode 6 and the reference voltage generator 7 so that the diode 6 and the reference voltage generator 7 are not adversely affected. The midpoint of R2 is connected to the input of adder 10.

The output level control operation of this transmission power amplifier will be further described with reference to FIG. 1. When a constant reference voltage is applied from the reference voltage generator 7 to the adder 10, an added voltage Va equal to this reference voltage is applied. Is input to the comparison amplifier 8. From the input terminal 1, for example, a constant level RF signal having a frequency of 800 MHz is supplied to the signal input terminal 31 of the transmission power amplifier 3.
Control voltage Vb is applied to the control terminal 32 of the transmission power amplifier 3, and a transmission output is obtained from the output terminal 5. At this time, the detection voltage Vc from the diode 9 is input to the comparison amplifier 8, whereby the control voltage Vb is lowered and the transmission output level at the output terminal 10 becomes constant.

Next, the operation of correcting the frequency characteristic of the transmission power amplifier 9 itself when the frequency is set to 850 MHz will be described. The frequency characteristic of the transmission power amplifier 9 means that the same reference voltage is applied from the reference voltage generator 7 at the time of both RF signals of 800 MHz and 850 MHz, and the same RF signal level is applied to the input terminal 1.
The transmission output levels are different. In the device of FIG.
Regardless of whether the RF signal frequency is 800 MHz or 850 MHz, the control voltage Vb is made different depending on the frequency so that the signal level at the signal output terminal 33 of the transmission power amplifier 3, that is, the detection voltage Vc, is made different, and the frequency of the transmission power amplifier 3 itself. The characteristics are corrected. As a result, the same output level can be obtained if the reference voltages are the same regardless of whether the input RF signal frequency is 800 MHz or 850 MHz.

Further, the correction operation of the frequency characteristics of the diodes 9 and 6 which are the detection elements of the RF detector will be described. For example, the diode 9 has a frequency of 800
A detection voltage Vc1 of A (V) is generated from the RF signal of MHz and level +30 dBm, and (A-
1) When the detection voltage Vc2 of (V) is generated, the frequency 850
The detection voltage Vc2 of MHz becomes 1 (V) lower than the detection voltage Vc1 of frequency 800 MHz. Therefore, the frequency 80
When the control voltage Vb from the comparison amplifier 8 is set to Vb1 so that the normal +30 dBm output is obtained at 0 MHz, the control voltage Vb2 at the frequency of 850 MHz is the control voltage Vb1.
At a frequency of 850 MHz, an output of (+ 30 + α) dBm is produced at the output terminal 33. Therefore, in the embodiment of FIG. 1, a diode having the same frequency characteristic as the diode 1 is used as the diode 6, and the detected voltage Vd is added to the reference voltage and input to the adder 6 to change the added voltage Va.

Therefore, at the frequency of 850 MHz, even if the detection voltage Vc from the diode 9 decreases, the detection voltage Vd from the diode 6 also decreases, so that the addition voltage Va from the adder 6 becomes a lower voltage than at 800 MHz. .. Therefore, the control voltage Vb to the control terminal 32 of the amplifier 3 changes, and the frequency characteristic of the diode 9 is corrected.
That is, even if the frequency of the RF signal input to this device changes, the reference voltage from the reference voltage generator 7 is constant, but the addition voltage Va is controlled by the change in the detection voltage Vd from the diode 6, The frequency characteristic of 9 is canceled by the frequency characteristic of the diode 6. Therefore, the frequency characteristic of the entire transmission power amplifier can be corrected, and a constant transmission output level can be maintained.

Even if a variable attenuator whose output level is controlled by a control signal is used instead of the transmission power amplifier 3 as the transmission power control circuit, the transmission power control circuit applied to this embodiment is effective. It goes without saying that he works for.

[0015]

As described above, according to the present invention, not only the frequency characteristic of the transmitted power control circuit itself such as the transmission power amplifier but also the frequency characteristic of the output RF detector for detecting the output level is detected by the input RF detection. Since it is corrected by the detection voltage generated by the detector, there is an effect that transmission power with a constant output level can always be obtained regardless of the frequency.

[Brief description of drawings]

FIG. 1 is a circuit diagram of an embodiment of the present invention.

FIG. 2 is a block diagram of a conventional example.

[Explanation of symbols]

 1 Input Terminal 2, 4 Coupler 3 Transmission Power Amplifier 5 Output Terminal 6, 9 Diode 7 Reference Voltage Generator 8 Comparison Amplifier 10 Adder 19 RF Detector 31 Signal Input Terminal 32 Control Terminal 33 Signal Output Terminal A1, A2 Operational Amplifier R1 ~ R5 resistor

Claims (3)

[Claims] 1. A reference voltage generator for generating a reference voltage,
A comparator amplifier for generating a control voltage in response to the first detected voltage and the reference voltage and supplying the control voltage for controlling the output level of the transmitted power control circuit, and an output level of the transmitted power control circuit are detected. To generate the first detection voltage
A transmission power control circuit having an F detector, the second RF detector having substantially the same frequency characteristic as that of the first RF detector for detecting the input level of the transmitted power control circuit to generate a second detection voltage, and the reference. And a second adder for adding a voltage to the second detected voltage to generate an added voltage, wherein the reference voltage, which is one of the comparison inputs of the comparison amplifier, is replaced with the added voltage. Power control circuit. 2. The transmission power control circuit according to claim 1, wherein the transmission power control circuit is a transmission power amplifier whose output level is controlled by the control voltage applied to a control terminal. 3. A transmission power amplifier whose output level is controlled by a control voltage applied to a control terminal, a reference voltage generator for generating a reference voltage, and a first detection voltage and the reference voltage in response to the first detection voltage and the reference voltage. A transmission power amplification apparatus with an ALC circuit, comprising: a comparison amplifier that generates a control voltage; and a first RF detector that detects the output level of the transmission power control circuit to generate the first detection voltage. Second RF detector having substantially the same frequency characteristic as that of the first RF detector for detecting the input level of 1 to generate the second detected voltage, and an adder for adding the reference voltage and the second detected voltage to generate an added voltage The AL, further comprising: and the reference voltage, which is one of the comparison inputs of the comparator amplifier, is replaced with the added voltage.
Transmission power amplifier with C circuit.