JPH0685582A - Transmission power detector - Google Patents

Abstract

PURPOSE:To provide the device at low cost by simplifying the configuration. CONSTITUTION:A signal outputted by an amplifier circuit 1 is passed through a power distributor 2 and a low-pass filter 3 and outputted from an antenna 4 as a radio wave. The power distributor 2 outputs one part of the output from the amplifier circuit 1 to a power detection circuit 31. The power detection circuit 31 detects the level of the inputted signal and feeds the detected signal back to the amplifier circuit 1. The amplifier circuit 1 controls the output power so that the output of the power detection circuit 31 can be coincident with a prescribed reference value. The amplifier circuit 1 is provided with a GaAsFET as an amplifying element, and a gate bias signal outputted from a gate bias generation circuit 6 is supplied to the gate. The bias generated by this gate bias generation circuit 6 is supplied to the power detection circuit 31.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transmission power detecting device suitable for use in, for example, a wireless communication device.

[0002]

2. Description of the Related Art FIG. 5 shows an example of the configuration of a conventional transmission power detecting device. In this example, after the input signal is amplified by the amplifier circuit 1, it is output as a radio wave from the antenna 4 via the power distributor 2 and the low pass filter 3. The power distributor 2 outputs a part of the signal output by the amplifier circuit 1 to the power detection circuit 5. The power detection circuit 5 detects the power output from the amplification circuit 1 from this input signal and feeds back the detection result to the amplification circuit 1. The amplifier circuit 1 controls the output power so that the output of the power detection circuit 5 matches a preset reference value.

On the other hand, the gate bias generation circuit 6 generates a gate bias voltage to be supplied to the gate of the GaAs FET included in the amplification circuit 1 and outputs it to the amplification circuit 1.

The power detection circuit 5 is basically constructed as shown in FIG. That is, the signal supplied from the power distributor 2 is rectified by the detection diodes 12 and 13 via the capacitor 11 and smoothed by the capacitor 14. As a result, a detection signal corresponding to the signal supplied from the power distributor 2 is obtained as the terminal voltage of the capacitor 14.

However, the diodes 12 and 13 are
For example, it has the characteristics as shown in FIG. 7, and when the input voltage is relatively small, its output current becomes almost zero. That is, in order for the diodes 12 and 13 to output a current, it is necessary to input a voltage of a certain magnitude or more. This means that the power detection circuit 5 cannot detect this unless the power output from the amplifier circuit 1 is higher than a certain level.

Therefore, the power detection circuit 5 is, for example, as shown in FIG.
It is configured as shown in. In this example, a predetermined reference voltage Vcc is integrated by the resistor 21 and the capacitor 23 and supplied as a bias voltage to the diodes 12 and 13 via the coil 22. By supplying the bias voltage in this manner, the detection current is output from the diode 13 even when the level of the signal input via the capacitor 11 is relatively small. As a result, even when the power output from the amplifier circuit 1 is relatively small, this can be detected.

However, when a bias voltage is applied to the detection diodes 12 and 13 in this way, the bias voltage, and hence the detection voltage, fluctuates due to the temperature characteristics of the PN junction (Schottky junction) of the diode.

Conventionally, in order to cancel this temperature characteristic, a constant current circuit is prepared and the current flowing through the diode 13 is controlled to be constant.

[0009]

Since the conventional device is provided with the constant current circuit as described above, there is a problem that not only the structure becomes complicated but also the cost becomes high.

The present invention has been made in view of such circumstances, and it is an object of the present invention to simplify the structure and realize a low-cost device.

[0011]

A transmission power detection apparatus according to the present invention includes an amplification circuit 1 having a GaAsFET and amplifying an input signal, and a gate bias generation circuit 6 generating a bias voltage supplied to the gate of the GaAsFET. , A power detection circuit 3 which rectifies the output of the amplifier circuit 1 by the detection diodes 12 and 13 and detects the power output from the amplifier circuit 1.
In the transmission power detection device including the power detection circuit 1, the power detection circuit 31 includes a rectifier circuit 60 as a first generation circuit that generates a bias voltage to be supplied to the detection diodes 12 and 13 from the output of the gate bias generation circuit 6. Rectification as a second generation circuit that generates a bias voltage to be supplied to the additional diodes 82 and 83 from the output of the gate bias generation circuit 6 and the additional diodes 82 and 83 that are connected in series with the detection diodes 12 and 13. Circuit 70, outputs of detection diodes 12 and 13 and additional diode 8
Resistor 84 as a combining circuit for combining the outputs of 2,83,
And 85.

The rectifier circuits 60 and 70 are diodes 61, 62, which rectify the output of the gate bias generator circuit 6, respectively.
71, 72 may be included.

[0013]

In the transmission power detecting device having the above structure, the voltage generated by the rectifying circuit 70 is the additional diodes 82 and 83.
Is supplied to. Then, the outputs of the diodes 82 and 83 are combined by the resistor 84 with the voltage output from the detection diodes 12 and 13 via the resistor 85. Therefore, the characteristics of the detection diodes 12 and 13 are set to the additional diode 82,
By making it correspond to the characteristic of 83, the temperature characteristics of the detection diodes 12 and 13 can be compensated.

[0014]

1 is a block diagram showing the configuration of an embodiment of a transmission power detecting apparatus of the present invention, in which parts corresponding to those in FIG. 5 are designated by the same reference numerals. In this embodiment, the signal output from the power distributor 2 is
The detection result is detected by the power detection circuit 31, and the detection result is fed back to the amplification circuit 1.
Further, the output of the gate bias generation circuit 6 is supplied to the power detection circuit 31.
Other configurations are the same as those in FIG.

The amplifier circuit 1 is, as shown in FIG.
It has an sFET (gallium arsenide FET) 42 as an amplifying element. A signal to be output from the antenna 4 is supplied to the gate of the GaAs FET 42 via the capacitor 41. This GaAs FET
42 is efficient and can amplify a high frequency signal. However, the GaAs FET 42 needs to apply a predetermined bias voltage to its gate.
This bias voltage is supplied from the gate bias generation circuit 6.

FIG. 3 shows a configuration example of the gate bias generation circuit 6 and the power detection circuit 31.

The gate bias generation circuit 6 includes a DC power source 5
A voltage obtained by switching the DC voltage output from the circuit 1 by the switching circuit 52 is supplied to the diodes 54 and 55 via the capacitor 53 and half-wave rectified. The rectified output is smoothed by the capacitor 56 and supplied to the gate of the GaAs FET 42 as a bias voltage (negative bias voltage).

On the other hand, the switching voltage output from the switching circuit 52 is supplied to the rectifier circuits 60 and 70 of the power detection circuit 31 via the capacitor 53. The rectifier circuit 60 is composed of diodes 61 and 62 and a capacitor 63. This rectifier circuit 60
Thereby, the switching voltage of the switching circuit 52 is half-wave rectified to generate a positive DC voltage. The positive DC voltage is supplied as a bias voltage to the detection diodes 12 and 13 via the resistor 21 and the coil 22.

On the other hand, the rectifier circuit 70 includes a diode 71,
It is composed of a capacitor 72 and a capacitor 73, and the switching voltage output from the switching circuit 52 is half-wave rectified to generate a negative DC voltage.

The DC voltage is supplied as bias voltage to the additional diodes 82 and 83 via the resistor 81. The additional diodes 82 and 83 are connected in series with the detection diodes 12 and 13. Then, the outputs of the additional diodes 82 and 83 are combined with the outputs of the detecting diodes 12 and 13 via the combining resistors 84 and 85, respectively.
This combined output is fed back to the amplifier circuit 1 as a detection voltage of the power detection circuit 31.

Next, the operation will be described with reference to the waveform chart of FIG. The switching circuit 52 switches the DC voltage output from the DC power supply 51 (see FIG. 4).
(A)). The DC component of this switching voltage is removed by the capacitor 53 (FIG. 4B), and the diode 5
Half-wave rectification is performed by 4, 55 and smoothing by the capacitor 56, and a negative DC voltage (FIG. 4C) is generated. This DC voltage is supplied as a bias voltage to the gate of the GaAs FET 42 as an amplifying element incorporated in the amplifying circuit 1.

A signal input from a circuit (not shown) is supplied to the gate of the GaAs FET 42 via the capacitor 41, amplified, supplied to the antenna 4 via the power distributor 2 and the low-pass filter 3, and the radio wave. Is output to a receiving device (not shown).

A part of the signal output from the amplifier circuit 1 is distributed by the power distributor 2 and input to the power detection circuit 31. In the power detection circuit 31, this input signal is transmitted via the capacitor 11 to the detection diodes 12, 13
After being half-wave rectified by and smoothed by the capacitor 14, it is fed back to the amplifier circuit 1 via the resistor 85.

Next, the bias will be described. The switching voltage output from the switching circuit 52 is supplied to the rectifier circuit 60 via the capacitor 53, half-wave rectified by the diodes 61 and 62, and smoothed by the capacitor 63. The voltage smoothed by the capacitor 63 is
A bias voltage is applied to the diodes 12 and 13 via the resistor 21 and the coil 22. As a result, even when the level of the signal component supplied from the capacitor 11 is small, this is detected by the diodes 12 and 13.

On the other hand, the switching pulse output from the switching circuit 52 is supplied to the rectifying circuit 70 via the capacitor 53, half-wave rectified by the diodes 71 and 72, and smoothed by the capacitor 73. Diode 7
1, 72 are connected in the opposite direction to the diodes 61, 62. As a result, the capacitor 63 is charged with a positive DC voltage, while the capacitor 73 is charged with a negative DC voltage.

The charging voltages charged in the capacitors 63 and 73 can be made to have the same absolute value and different polarities by making the characteristics of the diodes 61, 62 and 71, 72 correspond.

As a result, a bias current flows through the path of the capacitor 63, the resistor 21, the coil 22, the diode 13, the resistor 85, the resistor 84, the diode 83, the resistor 81, and the capacitor 73. Now, resistor 21 and resistor 81, resistor 85
And the resistor 84, and the diode 13 and the diode 83 are selected to have the same characteristics, the impedance of the coil 22 for blocking the AC component is ignored (or the resistor 21 corresponds to the combined component of the coil 22 of the resistor 21). By doing so, the voltage drop across the resistor 21 and the coil 22 and the voltage drop across the resistor 81 are equal, the voltage drop across the diode 13 and the voltage drop across the diode 83 are equal, and the voltage drop across the resistor 85 and the resistor 84. Since the voltage drop becomes equal, the resistance 85
The potential for the bias current at the connection point of
It becomes V. That is, when the output voltage of the amplifier circuit 1 input from the power distributor 2 via the capacitor 11 is 0V, the output voltage at the connection point of the resistors 84 and 85 is also 0V.

When the characteristic of the detection diode 13 changes in response to the temperature change, the characteristic of the diode 83 also changes in response to the temperature change. As a result, the bias voltage component at the connection point between the resistors 84 and 85 is 0.
It remains V.

However, since the bias voltage is applied to the diode 13, when the output voltage of the amplifier circuit 1 is supplied via the capacitor 11, the signal is for detection even if the level of the output voltage is low. Diode 13
Is rectified by the capacitor 14, smoothed by the capacitor 14, and output to the amplifier circuit 1 as a detection voltage from the connection point of the resistors 85 and 84.

The amplifier circuit 1 responds to this detected voltage by
Servo is applied so that the output voltage matches a predetermined reference voltage.

In the above embodiments, the diodes are used as a pair, but the diodes 12, 54, 61, 71 can be omitted.

[0032]

As described above, according to the transmission power detection apparatus of the present invention, an additional diode is connected in series to the detection diode, and the bias voltage supplied to the detection diode and the additional diode is supplied to the gate bias generation circuit. Since it is generated from the output of, the configuration can be simplified and a low-cost device can be realized.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an embodiment of a transmission power detection device of the present invention.

FIG. 2 is a circuit diagram illustrating an internal configuration of an amplifier circuit 1 of FIG.

3 is a circuit diagram showing a configuration example of a gate bias generation circuit 6 and a power detection circuit 31 of FIG.

FIG. 4 is a timing chart explaining the operation of the embodiment of FIG.

FIG. 5 is a block diagram showing a configuration of an example of a conventional transmission power detection device.

6 is a circuit diagram showing a configuration example of a power detection circuit 5 in FIG.

7 is a diagram illustrating characteristics of a diode 13 in FIG.

8 is a circuit diagram showing another configuration example of the power detection circuit 5 of FIG.

[Explanation of symbols]

 1 amplification circuit 2 power distributor 4 antenna 5 power detection circuit 6 gate bias generation circuit 12, 13 detection diode 14 capacitor 21 resistance 22 coil 23 capacitor 31 power detection circuit 42 GaAsFET 51 DC power supply 52 switching circuit 60 rectification circuit 61, 62 Diode 63 Capacitor 70 Rectifier circuit 71,72 Diode 73 Capacitor 82,83 Additional diode 84,85 Resistance

Claims (2)

[Claims] 1. An amplifier circuit having a GaAsFET for amplifying an input signal, a gate bias generating circuit for generating a bias voltage to be supplied to the gate of the GaAsFET, and an output of the amplifier circuit rectified by a detection diode, In a transmission power detection device including a power detection circuit that detects the power output from the amplifier circuit, the power detection circuit generates a bias voltage to be supplied to the detection diode from the output of the gate bias generation circuit. No. 1 generation circuit, an additional diode connected in series with the detection diode, a second generation circuit that generates a bias voltage to be supplied to the additional diode from the output of the gate bias generation circuit, and the detection circuit. Providing a combining circuit for combining the output of the diode and the output of the additional diode Transmission power detecting apparatus according to claim. 2. The transmission power detection device according to claim 1, wherein the first and second generation circuits include a diode that rectifies an output of the gate bias generation circuit.