JPH0583145A - Variable output amplifier circuit - Google Patents

Abstract

PURPOSE:To prevent thermal destruction of a power amplifier due to a temperature rise at the-consecutive abnormal transmission of a large transmission power through the use of a temperature sensor. CONSTITUTION:A level of a transmission signal inputted to an input terminal 5 is adjusted by a variable attenuator 1, and the power is amplified at a power amplifier 2 up to a transmission power and the result is outputted to an output terminal 6. An adjustment signal inputted externally to an adjustment signal terminal 7 adjusts the variable attenuator 1 and a bias for an output stage amplifier element of the power amplifier 2 interlockingly. A temperature sensor 4 is provided in the vicinity of the power amplifier 2 to detect a temperature of the power amplifier 2. The detection signal is inputted to an adjustment device 3 and when the temperature rises up to a temperature predicting a thermal destruction of the power amplifier 2, the attenuation of the variable attenuator 1 is increased and the bias of the output stage amplifier element of the power amplifier 2 is adjusted shallow and the output level is decreased up to a safe level.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a variable output amplifier circuit, and more particularly, to a variable output amplifier circuit for obtaining its transmission power in a microwave communication device.

[0002]

2. Description of the Related Art In a microwave communication device, the transmission power is made variable in order to ensure the quality of the line, and when the deep fading occurs, on the contrary, when the radio wave propagation is good, the transmission power is increased or decreased. To improve the transmission efficiency.

Conventionally, as a variable output amplifier circuit for obtaining this kind of transmission power, a power amplifier, a variable attenuator provided on the input side of this power amplifier for varying the output level of the power amplifier, The power amplifier and the variable attenuator are linked to each other to adjust the output level. If the output level is low, the amount of attenuation of the variable attenuator is increased, and in conjunction with this, the adjustment circuit adjusts the bias of the output stage amplification element of the power amplifier to be shallow. On the contrary, when it is necessary to increase the output level, the amount of attenuation of the variable attenuator is decreased, and in conjunction with this, the bias of the output stage amplification element of the power amplifier is adjusted to be deeper.

When the bias of the output stage amplifying element of the power amplifier is deepened, the power consumption increases and the temperature rise increases, but heat dissipation measures against this increase are designed in the following manner. It is considered that the time required to increase the transmission power due to the occurrence of deep fading is at most several hours per year, and considering the cost conditions, the time to output the large transmission power is short and the heat dissipation design is relaxed. Has become.

[0005]

As described above, in the conventional example, the heat radiation is designed so that a large transmission power is generated stochastically in a short time, so there is usually no problem. When deviating from (probabilistically 0
However, there is a risk that the power amplifier may be thermally damaged due to temperature rise if a large transmission power is sustained due to equipment failure or maintenance error.

[0006]

A variable output amplifier circuit according to the present invention comprises a power amplifier for varying a bias of an output stage amplifier element according to an output level, and an output level provided on an input side of the power amplifier. A variable attenuator for varying,
An adjustment circuit that adjusts the output level by interlocking the bias of the power amplifier and the attenuation amount of the variable attenuator by an external signal, and detects the temperature of the power amplifier and inputs the detection signal to the adjustment circuit. The temperature sensor adjusts the output level in priority to the external signal.

Further, the variable attenuator may use a variable gain amplifier, and the temperature sensor may detect the temperature of a power board for supplying power to the power amplifier.

[0008]

Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing the configuration of this embodiment. The transmission signal input to the input terminal 5 is the variable attenuator 1
The level is adjusted by, the power is amplified by the power amplifier 2 up to the transmission power, and output to the output terminal 6. The adjustment signal externally input to the adjustment signal terminal 7 adjusts the attenuation amount of the variable attenuator 1 and the bias of the output stage amplification element of the power amplifier 2 in association with each other.

That is, when the radio wave propagation is good, the attenuation amount of the variable attenuator 1 is large due to this adjustment signal, and the power amplifier 2
The bias of the output stage amplifying element is adjusted to be shallow, and the output level becomes small. Further, when deep fading occurs, the amount of attenuation of the variable attenuator 1 is small, the bias of the output stage amplifying element of the power amplifier 2 is deeply adjusted, and its output level becomes large.

The temperature sensor 4 is provided near the power amplifier 2 and detects the temperature of the power amplifier 2. This detection signal is input to the regulator 3, and when the temperature rises to a temperature at which thermal damage of the power amplifier 2 is predicted, the regulator 3 increases the amount of attenuation of the variable attenuator 1 by the detection signal and the power amplifier 2
Adjust the bias of the output stage amplification element to a shallow level to lower the output level to a safe level. This adjustment is prioritized over that by a normal adjustment signal, and its temperature operating point has a hysteresis characteristic for stabilizing the operation. or,
This forcible adjustment does not last a long time and therefore does not cause any serious problems in practical use.

The variable attenuator 1 may be a variable gain amplifier when a gain is required, and the temperature sensor supplies power to the power amplifier 2 instead of near the power amplifier 2 for convenience of installation. If it is convenient near the board (not shown), it may be located there.

[0012]

As described above, according to the present invention, the temperature rise of the power amplifier is detected, and when the temperature is abnormally high, the output level is lowered to adjust the temperature to lower the temperature. Therefore, the heat damage of the power amplifier can be prevented. There is an effect.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an example.

[Explanation of symbols]

 1 Variable attenuator 2 Power amplifier 3 Regulator 4 Temperature sensor

Claims (3)

[Claims] 1. A power amplifier for varying a bias of an output stage amplifying element according to an output level, a variable attenuator provided on an input side of the power amplifier for varying the output level, and an external signal for the attenuator. An adjusting circuit that adjusts the output level by interlocking the bias of the power amplifier and the attenuation amount of the variable attenuator, and detecting the temperature of the power amplifier and inputting the detection signal to the adjusting circuit, the external signal. And a temperature sensor that adjusts the output level in the direction of lowering the output level. 2. The variable output amplifier circuit according to claim 1, wherein the variable attenuator uses a variable gain amplifier. 3. The variable output amplifier circuit according to claim 1, wherein the temperature sensor detects a temperature of an external power board that supplies power to the power amplifier.