JPH0522061A - Output power detection circuit - Google Patents

Abstract

PURPOSE:To output a detected voltage in proportion to output power within fixed error by impressing bias from a constant voltage circuit, which is equipped with a Zener diode having a positive temperature characteristic, to a half wave rectifier circuit. CONSTITUTION:An output power detection circuit 10 is equipped with a GaAs monolithic chip connected while providing a diode D1, resistor Ra and resistor Rb, and a half wave rectifier is composed of the diode D1 and capacitor C1. A voltage Va at the anode of a Zener diode ZD impresses a bias voltage Vb through resistors R1, R2, Ra and Rb to the diode D1, and a power amplifier 12 outputs high frequency power. This high frequency power is passed through a capacitor C2 and directional couplers L1 and L2 and turned to an output voltage Pout on one hand. On the other hand, it is impressed to the diode D1, receives half wave rectification and is extracted from an output terminal 16 as a DC output power signal Vdet in proportion to the output power of a power amplifier 14.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an output power detection circuit, and more specifically to an output power control circuit provided in an automatic output control circuit for maintaining a transmission power at a set value in a mobile telephone such as an automobile telephone or a portable telephone. The present invention relates to a detection circuit.

[0002]

2. Description of the Related Art A technique of this kind is an automatic output control circuit (AOC) with temperature compensation for a high dynamic range high frequency signal power amplifier described in US Pat. No. 4,523,155.
This automatic output control circuit is a circuit for maintaining the output level of the output power of the power amplifier from 9 milliwatts to 5 watts, that is, in seven steps over the dynamic range of 27db, within an error of 1.5db. The output of the power amplifier is proportional to the drive current supplied from the previous stage current amplifier. The half-wave rectifier to which the output of the power amplifier is input outputs an output power signal having a magnitude proportional to the output of the power amplifier. This half-wave rectifier has a diode connected through a resistor and a power source supplied through another resistor,
Temperature compensation and bias voltage are provided to maintain the linearity of the output power signal. The output power signal output from the half-wave rectifier is amplified by the amplifier whose amplification factor is selected by the level control signal and input to the comparator. The comparator is
The difference between the amplified output power signal and the reference voltage corresponding to the predetermined output of the power amplifier is output to the current amplifier, and the drive current output to the power amplifier by the current amplifier is changed, whereby the output of the power amplifier is changed to the predetermined value. The automatic output control is performed to fix the output level of.

[0003]

As described above, the conventional automatic output control circuit detects the output power signal proportional to the output power by connecting the temperature compensation circuit including the diode and the resistor to the half-wave rectifier. The output of the power amplifier is automatically controlled to a set value based on the difference between the output power signal and the reference signal.

It is an object of the present invention to provide an output power detection circuit which maintains a good proportional relationship between output power and an output power signal regardless of a normal diode configuration.

[0005]

In the output power detection circuit according to the present invention, a constant voltage circuit composed of a constant voltage diode and a resistor is connected to a half-wave rectifier circuit of an automatic output control circuit.

More specifically, the output power detection circuit according to the present invention has a half-wave rectifier circuit to which the high frequency output of the power amplifier is input, and the half wave rectifier circuit is proportional to the dynamic range of the output power of the high frequency output. Output the detected voltage,
Further, the output power detection circuit has a constant voltage circuit including a Zener diode connected between the reference potential and the power supply via a resistor, and the output of the constant voltage circuit is connected to the half wave rectifier circuit to form a half wave rectifier. A bias voltage is applied to the circuit, which causes the half-wave rectifier circuit to output a detection output under a predetermined temperature condition while maintaining a proportional relationship with the output power.

[0007]

According to the present invention, the high frequency output of the power amplifier is input to the half-wave rectifier circuit, and the output power detection circuit outputs a detection voltage proportional to the dynamic range of the output power. The constant voltage circuit provides a proper bias voltage to the half-wave rectifier, which allows it to operate under certain temperature conditions, such as -30 ° C to +85 ° C.
The error of the output power displayed by the detection voltage in the range of C is ± 1db
Can be set to.

[0008]

Embodiments of the output power detection circuit according to the present invention will now be described in detail with reference to the accompanying drawings. The output power detection circuit of this embodiment is advantageously applied to mobile phones such as car phones and mobile phones. Such a mobile phone is provided with an automatic output control circuit (AOC) for fixing the transmission power to a set value. A power amplifier that outputs transmission power has a wide dynamic range of, for example, about 30 db, and the output of the amplifier is fixed to one of a plurality of set values within this range by an output automatic control circuit. The automatic output control circuit has an output power detection circuit that outputs an output power signal that is proportional to the output power.The latter detects the difference between the output power signal and the reference voltage and always sets the output of the power amplifier to the set value. The output is automatically controlled to be substantially fixed. The output power accuracy is very high, for example in temperature conditions (-30 ° C to +85
The error of the setting output in ° C) is specified within ± 1db.

FIG. 1 is a circuit diagram showing an embodiment of an output power detection circuit according to the present invention. The output power detection circuit 10 in this embodiment has a diode D1, and a GaAs monolithic chip 12 including resistors Ra and Rb connected as shown, with diode D1 and capacitor C1 being a half-wave rectifier. Make up. The output power detection circuit 10 also has a Zener diode ZD and resistors R0 to R2.
Has an anode 18 to which is applied, the cathode 19 of which is connected to a reference potential, eg earth, as shown. The voltage VA at the anode of the Zener diode ZD depends on the resistors R1, R2, Rb and
Bias voltage Vb is applied to diode D1 of the half-wave rectifier through Ra.
give. The power amplifier 12 outputs high frequency power. This high frequency power becomes the output voltage Pout through the capacitor C2 and the directional couplers L1 and L2 on the one hand, and is applied to the diode D1 and half-wave rectified on the other hand, and the DC output power signal proportional to the output power of the power amplifier 14. Output terminal as Vdet
Taken out from 16.

FIG. 3 shows the temperature characteristics of the Zener voltages VA and VB of the Zener diode ZD in (A) and (B), respectively. FIG. 4 shows the temperature coefficients of the Zener voltages VA and VB of FIG. Zener voltage VB is 1V or more and has a positive temperature coefficient.

FIG. 5 shows the characteristics of the high frequency power Pout of the power amplifier 12 versus the detection voltage (output power signal) Vdet when the bias voltage Vb is used as a parameter at room temperature of 25 ° C. in the output power detection circuit 10 of FIG. Show. From this figure, the bias voltage
It can be seen that the detected voltage and power are proportional to each other at 0.6 V or higher, and the optimum bias voltage Vb can be set to 0.6 V or higher.

FIG. 2 shows the temperature characteristic of the detection voltage of the output power detection circuit 10 of FIG. 1, and the proportional relationship between the detection voltage and the output power at the optimum bias voltage is the temperature condition (-30 ° C to + 85 ° C).
The output power in C) is within the specified value ± 1db, which complies with the conditions in the output automatic control circuit.

FIG. 6 shows a detection circuit included in the above-mentioned US patent as a conventional example. The output power detection circuit 20 is a GaAs monolithic circuit including diodes D2 and D3 and resistors Rc and Rd.
It is composed of a chip 22. The voltage Vd is applied to the diode D2.
Bias voltage Vb (0.6V) is applied from d through resistors Rc, Rb and diode D3. The detection circuit including the diode D2 and the capacitor C3 detects the high frequency power input from the power amplifier 14 and outputs the output power signal Vdet.

The temperature characteristic of the detected voltage is excellent as shown in FIG. 7 with a voltage deviation of 0.10 / high frequency output deviation of 0.5db. The cause is that the detection diode D2 has a positive temperature coefficient as shown in FIG. 8 and the bias diode D3 has a value as shown in FIG.
It has a negative temperature coefficient of 0.10% / ° C, and the linear detection characteristics as shown in Fig. 7 may be obtained by the complementary effect of these positive and negative temperature coefficients.

In the prior art US Pat. No. 4,523,155, a high-frequency input is detected and output by a well-known half-wave rectifier circuit, and a diode having a negative temperature coefficient is used in the bias circuit of the half-wave rectifier circuit to obtain a straight line under temperature conditions. The detection characteristics are secured. However, in this embodiment, the linearity of the detection is obtained by applying an appropriate bias voltage with the Zener diode. Therefore, the structure of the bias circuit of this embodiment is different from that of the conventional example.

[0016]

As described above, according to the present invention, the temperature condition of -3
It is possible to configure an output power detection circuit in which the error of the output power displayed by the detection voltage is substantially within ± 1db at 0 ° C to +85 ° C. Therefore, if the present invention is applied to the automatic output control circuit that compares the detected voltage and the reference voltage and fixes the output power of the power amplifier at a predetermined value, a highly accurate automatic output control circuit can be configured.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of an output power detection circuit according to the present invention.

FIG. 2 is a temperature characteristic diagram of a detection voltage in the embodiment shown in FIG.

FIG. 3 is a temperature characteristic diagram of a Zener voltage of a Zener diode.

FIG. 4 is a characteristic diagram of the temperature coefficient of the Zener voltage shown in FIG.

FIG. 5 is a characteristic diagram of output power and detection voltage with a bias voltage as a parameter.

FIG. 6 is a circuit diagram showing an example of a conventional output power detection circuit.

7 is a temperature characteristic diagram of the detection voltage of the conventional example shown in FIG.

FIG. 8 is a detection voltage temperature characteristic diagram of the detection diode of the conventional example.

FIG. 9 is a voltage-temperature characteristic diagram of the biasing diode of the conventional example.

[Explanation of symbols]

10,20 Output power detection circuit 14 Power amplifier C1, C2 capacitors D1 to D3 diodes R- resistance ZD Zener diode

Claims (2)

[Claims] 1. A half-wave rectifier circuit to which a high-frequency output of a power amplifier is input, and the half-wave rectifier circuit outputs an output power detection circuit that outputs a detection voltage proportional to a dynamic range of output power of the high-frequency output. In, the detection circuit has a constant voltage circuit including a Zener diode connected via a resistor between the reference potential and the power supply, the output of the constant voltage circuit is connected to the half-wave rectifier circuit, A bias voltage is applied to the half-wave rectifier circuit, whereby the half-wave rectifier circuit outputs the detection output while maintaining a proportional relationship with the output power under a predetermined temperature condition. . 2. The output power detection circuit according to claim 1, wherein the temperature condition is set to −30 ° C. to + 85 ° C.
An output power detection circuit, wherein the error of the output power displayed by the output voltage of the half-wave rectifier circuit is substantially within ± 1db.