JPH04314205A - Power amplifier - Google Patents

Abstract

PURPOSE:To sequentially compensate a gain by accurately detecting the gain fluctuation of a power amplifier caused due to change in ambient temperature with respect to an optional attenuation setting value in the power amplifier. CONSTITUTION:A DC component extracted from a part of an input signal is converted into a digital signal an A/D converter 18, a signal resulting from calculating a stepping variable attenuator control signal sent from an attenuation value setting circuit 5 by an arithmetic processing circuit 20 is used as a reference signal and it is compared with a DC component extracted from a part of the output signal of a high output amplifier section 7 by an error amplifier 27. The attenuation of a voltage controlled variable attenuator 6 is controlled by an error voltage attended with gain fluctuation.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power amplifying device for high frequency signals (several MHz to several + GHz) used in satellite communications and other applications.

0002

2. Description of the Related Art Conventionally, there has been a device of this type as shown in FIG. In the figure, 1 is a signal input terminal, 2 is a small signal amplification section, 3 is a step type variable attenuation section, 4 is an attenuation value setting signal input terminal, 5 is an attenuation value setting circuit, 6 is a voltage controlled variable attenuator, and 7 is a A high output amplifier section, 8 is a gain compensation circuit, 9 is an error amplifier, 10 is a resistor, 11 is a thermistor, 12 is a DC voltage application terminal, and 13 is a signal output terminal.

Next, the operation will be explained. The signal to be amplified applied to the signal input terminal 1 is linearly amplified to an appropriate level in a small signal amplification section 2, and then is passed to a step type variable attenuation section 3 consisting of one or more step type variable attenuators. Sent. The step type variable attenuation section 3 can attenuate the input signal level using a 1/0 binary control signal from the attenuation value setting circuit 5, and can attenuate the input signal level according to changes in the input signal level read from the attenuation value setting signal input terminal 4. It operates according to the attenuation value setting information and sets the attenuation amount from 0 to 15 dB in 1 dB increments. In this example, 0/1dB, 0/2dB, 0/4dB,
This is a case of four step variable attenuators of 0/8 dB. Furthermore, the output signal of the step type variable attenuator 3 is input to the voltage controlled variable attenuator 6. In the gain compensation circuit 8, a divided voltage of the DC voltage applied to the DC voltage application terminal 12 is extracted from the connection point between the resistor 10 and thermistor 11, and
It is input to the inverting input terminal of the error amplifier 9, and as the ambient temperature changes, the resistance value of the thermistor 11 changes and the output of the error amplifier 9 changes accordingly. In the case of a microwave band, the voltage-controlled variable attenuator 6 is composed of, for example, a PIN diode, and attenuates the input signal according to temperature changes by taking in the output of the error amplifier 9 as a forward bias voltage of the diode. be able to. The output of the voltage controlled variable attenuator 6 is further power-amplified to a desired level in a high-output amplification section 7, and then outputted from a signal output terminal 13. As mentioned above, the conventional device changes the settings of the step type variable attenuator as the input signal level changes to obtain a constant output power. By mounting a thermistor with a temperature coefficient that cancels out gain fluctuations in the variable attenuator 3 and the high-output amplifier 7, the gain of the entire device is kept constant.

0004

[Problem to be Solved by the Invention] Conventional power amplifiers are configured as described above, but the amount of gain variation in each part of the device caused by changes in ambient temperature is calculated in advance by prediction or actual measurement, and this is compensated for. Adjustment time is required because the thermistor value is determined through several temperature tests, and the amount of gain variation varies depending on the setting value in the step type variable attenuation section 3, so the optimum gain variation can be achieved for all set attenuation values. The problem was that compensation could not be provided.

The present invention was made in order to solve the above-mentioned problems, and it is an object of the present invention to accurately detect the gain fluctuation of the device caused by changes in ambient temperature at an arbitrary attenuation setting value, and to perform successive gain compensation. The purpose is to obtain a power amplification device that can

[0006]

[Means for Solving the Problems] A power amplifier according to the present invention converts a DC component extracted from a part of an input signal into an
An arithmetic processing circuit is provided that takes in the D/D-converted signal and a part of the step-type attenuator control signal sent from the attenuation value setting circuit, and performs high-output amplification using the D/A-converted value of the output as a reference signal. An error amplifier performs a comparison with a DC component extracted from a part of the unit output, and the attenuation amount of the voltage-controlled variable attenuator is controlled using the error voltage caused by the gain fluctuation.

[0007] Furthermore, an A/D converter is provided to convert the output signal of the second envelope detector into a digital signal, and the output signal level detection value is input into the arithmetic processing circuit and extracted from a part of the input signal. A signal obtained by A/D converting the DC component,
Arithmetic processing is performed together with a part of the step type attenuator control signal sent from the attenuation value setting circuit.

[0008]

[Operation] In the power amplifying device according to the present invention, the output level that changes as the ambient temperature changes is compared with the reference signal, and the difference is output as an error signal to increase or decrease the amount of attenuation of the voltage-controlled variable attenuator.

Furthermore, an error signal for controlling the amount of attenuation of the voltage-controlled variable attenuator is generated by the arithmetic processing circuit.

0010

[Example] Example 1. An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, numerals 1 to 7 and 13 are exactly the same as those in the conventional example. 14 is an input coupler, 1
5 is a gain compensation circuit, 16 is a first envelope detector, 17 is a first low-pass filter, 18 is an A/D converter, 19 is a timing signal generation circuit, 20 is an arithmetic processing circuit, and 21 is a D/A Converter, 22 is an output coupler, 23 is a first resistor, 24 is a second resistor, 25 is a second envelope detector, 26 is a second low-pass filter, and 27 is an error amplifier. FIG. 2 shows an example of output waveforms to supplement the explanation of this embodiment, in which a and a' are input coupler output waveforms, b and b' are first envelope detector output waveforms, and c and c' are output waveforms of the first envelope detector. 1 low-pass filter output waveform, d and d' are D/A converter output waveforms, e and e' are voltage conversion waveforms of the output coupler output waveform by the first and second resistors, f and f' are the 2 envelope detector output waveform, g and g' are the second
This is the low-pass filter output waveform.

In the power amplifier configured as described above, the signal to be amplified applied to the signal input terminal 1 is linearly amplified to an appropriate level by the small signal amplification section 2 via the input coupler 14. , is sent to a step-type variable attenuator 3 consisting of one or more step-type variable attenuators. Similar to the conventional example, the step type variable attenuation section 3 controls the attenuation amount from 0 to 15 dB using the 1/0 binary control signal from the attenuation value setting circuit 5, which operates according to the attenuation value setting information read from the attenuation value setting signal input terminal 4. Set in 1dB increments,
The signal level input from the small signal amplification section 2 is attenuated. The output signal of the step-type variable attenuator 3 passes through the voltage-controlled variable attenuator 6, is power amplified to a desired level by the high-output amplifier 7, and is further outputted from the output terminal 13 via the output coupler 22.

First, gain compensation when the input signal level to the present device is the maximum (input signal level is 0 dB) will be explained. Gain compensation is performed by the gain compensation circuit 15. First, the peak value of a part of the input signal (waveform a in FIG. 2) taken out by the input coupler 14 is detected by the first envelope detector 16 (waveform a in FIG. 2). 2 waveform b), after the ripple component is removed by the first low-pass filter 17 (Fig. 2 waveform c) A/
The D converter 18 converts the signal from the timing signal generation circuit 19 into a digital signal at each timing, and sends it to the arithmetic processing circuit 20 . This example shows the case of a 6-bit A/D converter, and the conversion value when the input signal level is maximum is 1.
, 1, 1, 1, 1, 1 (0V, 0, 0, 0,
0, 0, 0). Further, a part of the step type variable attenuation section 3 control signal is transmitted from the attenuation value setting circuit 5 to the arithmetic processing circuit 20.
is being sent to. The arithmetic processing circuit 20 subtracts the input value from the attenuation value setting circuit 5 from the maximum value 1, 1, 1, 1, and performs an operation to convert the power decibel value into a voltage true value. Next, the signal from the A/D converter 18 is multiplied, and the calculation result is sent to the D/A converter 21.

When the input signal level is maximum, the signal from the attenuation value setting circuit 5 is 1, 1, 1, 1, so the result of the above subtraction and power decibel value/voltage true value conversion is 1 ((lo
g-1 ((15-15)/10)1/2 = 1,15 is a decimal value of binary 1, 1, 1, 1). The result of multiplication with the signal from the A/D converter 18 is 64 (1×6
4=64,64 is 1 in binary 1, 1, 1, 1, 1, 1
decimal value + 1).

The above calculation result is sent as a binary signal to the D/A converter 21, where it is converted into an analog voltage value and sent as a reference voltage to the inverting input terminal of the error amplifier 26 (waveform d in FIG. 2). On the other hand, a part of the high output amplifier 7 output signal taken out by the output coupler 22 is transferred to the first resistor 23.
After resistance voltage division is performed by the second resistor 24 (waveform e in FIG. 2), a peak value is detected by the second envelope detector 24 (waveform f in FIG. 2), and the second low-pass filter 26 After the ripple component is removed (waveform g in Figure 2), the error amplifier 27
input to the non-inverting input terminal of Here, the first resistor 2
3 and the second resistor 24 are set to be equal to the reference voltage applied to the inverting input terminal of the error amplifier 27 at room temperature, so no error voltage is generated in the error amplifier 27. No (Figure 2 waveform d
and g have the same value).

Now, due to changes in ambient temperature, the small signal amplification section 2,
When the gain in the high-output amplification section 7 or the amount of attenuation in the step-type variable attenuation section 3 increases or decreases, the output signal level of the high-output amplification section changes, and the waveform e in FIG. 2 becomes, for example, e'. Accordingly, the output waveform of the second envelope detector 24 changes to waveform f' in FIG. 2, and the output waveform of the second low-pass filter 26 changes to waveform g' in FIG. 2, so an error voltage is generated in the error amplifier 27. (Error voltage d-g'V). The voltage control terminal of the voltage controlled variable attenuator 6 is connected to the output of the error amplifier 27, forming a control loop in which the amount of attenuation changes according to the error voltage, so that a constant gain is always maintained.

Next, the input signal level to this device is -6 dB.
The case of gain compensation when . Signal extracted by the input coupler 14, first envelope detector 16
The waveforms of the signals detected in and after ripple components are removed by the first low-pass filter 17 are waveforms a′ in FIG.
, b', c'. The voltage value of the waveform c' in FIG. 2 is 1/2 of the maximum value, and the converted voltage values at the A/D converter 18 are 0, 1, 1, 1, 1, 1. When the input signal level is -6 dB, the attenuation amount setting value in the step type variable attenuation section 3 is 9 dB, and the control signal from the attenuation value setting circuit 5 is 1, 0, 0, 1 (binary value of 9). .

The result of subtraction and power decibel value/voltage true value conversion in the arithmetic processing circuit 20 is 2 ((log-1(
(15-9)/10)1/2=2). The result of multiplication with the signal from the A/D converter 18 is 64. (2×
32=64, 32 is binary 0, 1, 1, 1, 1, 1,
decimal value + 1).

As described above, even when the input signal level is -6 dB, the calculation result in the arithmetic processing circuit 20 is the same as when the input signal level is the maximum. The calculation result is sent as a binary signal to the D/A converter 21 in the same way as when the input signal level is at its maximum, where it is converted to an analog voltage value and sent as a reference voltage to the inverting input terminal of the error amplifier 27 (Fig. 2 waveform d
´). The subsequent operation is the same as when the input signal level is maximum, and a constant gain is always maintained by a loop that controls the amount of attenuation of the voltage-controlled variable attenuator 6 according to the error voltage from the error amplifier 27 generated due to ambient temperature fluctuations. ing.

In this embodiment, the case where the input signal level is the maximum and the case where the input signal level is -6 dB has been explained, but the variable range of the step type variable attenuation section 3 is 15 dB, so it is possible to operate up to the input signal level of -15 dB. be. If the step type variable attenuation section 3 is set according to the input signal level as described above for other input signal levels,
The calculation result in the calculation processing circuit 20 is constant (64 in this example)
Therefore, the gain in the small signal amplification section 2 and the high output amplification section 7 or the attenuation amount in the step type variable attenuation section 3 is compensated for due to ambient temperature fluctuation under the set conditions. Further, by increasing the number of stages of the step type variable attenuator constituting the step type variable attenuation section 3, the same control as described above can be performed over a wide input signal level range. In addition, the first part in this explanation
low-pass filter 17 and second low-pass filter 2
The frequency characteristics of No. 6 may not be the same because they are determined in consideration of the ripple removal rate in each filtered signal and the response speed of the control loop due to temperature fluctuations.

Example 2. In the first embodiment, the error voltage that controls the attenuation amount of the voltage-controlled variable attenuator 6 is supplied to the error amplifier 27.
The difference in analog voltage value between the inverting input terminal and the non-inverting input terminal of A similar operation can be expected even if a voltage is generated and converted back to an analog signal using a D/A converter.

In the second embodiment shown in FIG. 3, the output signal of the first low-pass filter 17 is converted into a digital signal by the A/D converter 18 as in the first embodiment, but the output signal of the second low-pass filter 26 is converted into a digital signal. The output signal is also converted into a digital signal by the second A/D converter 28 and input to the arithmetic processing circuit 20. In the arithmetic processing circuit 20, the same calculation as in the first embodiment is first performed, and the calculation result is used as a reference voltage, and from the ratio of the signal value with the second A/D converter 28, a small signal due to a change in ambient temperature is determined. Part 2, the gain fluctuation in the high-output amplification part 7 and the amount of attenuation value fluctuation in the step type variable attenuation part 3 are calculated, and the voltage is controlled variable using the signal converted to an analog error voltage by the D/A converter 21. The amount of attenuation of the attenuator 6 is controlled.

Example 3. In the first and second embodiments described above, the envelope detector is used to detect the output signal levels of the input coupler 14 and output coupler 22, but
Any device capable of detecting the level, such as a square-law detector, may be used and does not go beyond the scope of the present invention.

[0023]

[Effects of the Invention] Since the present invention is constructed as described above, it produces the following effects.

The automatic gain control loop generates an error voltage according to the gain fluctuation of the device due to changes in ambient temperature and controls the attenuation amount of the voltage-controlled variable attenuator, so the temperature compensation element ( This eliminates the need to select the optimum value for the thermistor (thermistor), reducing personnel and equipment costs.

In the automatic gain control loop, the reference voltage value of the error amplifier is always constant regardless of the set attenuation value of the step type variable attenuator. It is possible to accurately track the fluctuations in gain and attenuation at the time, and perform gain compensation.

[0026] Furthermore, by performing the function of generating an error voltage in the error amplifier through arithmetic processing, the error amplifier, the first,
The second resistor is not required, and the test time required in the first embodiment, such as adjusting the voltage division ratio of the first and second resistors, inverting the error amplifier, and adjusting the initial level between the non-inverting input terminals, can be further reduced.

[Brief explanation of drawings]

FIG. 1 is a circuit block diagram showing a first embodiment of the present invention.

FIG. 2 is a signal waveform diagram supplementing the explanation of the operation of the first embodiment of the present invention.

FIG. 3 is a circuit block diagram showing a second embodiment of the invention.

FIG. 4 is a circuit block diagram showing a conventional power amplifier device.

[Explanation of symbols]

1 Signal input terminal 2 Small signal amplification section 3. Step type variable attenuation section 4 Attenuation value setting signal input terminal 5 Attenuation value setting circuit 6 Voltage controlled variable attenuator 7 High output amplification section 13 Signal output terminal 14 Input coupler 15 Gain compensation circuit 16 First envelope detector 17 First low-pass filter 18 A/D converter 19 Timing signal generation circuit 20 Arithmetic processing circuit 21 D/A converter 22 Output coupler 23 First resistor 24 Second resistor 25 Second envelope detector 26 Second low pass filter 27 Error amplifier 28 Second A/D converter

Claims (2)

[Claims] Claim 1: A small signal amplification section consisting of one or more small signal amplifiers, an attenuation value setting circuit operated by an attenuation value setting signal, and one or more small signal amplifiers controlled by the attenuation value setting circuit output signal. It consists of a step-type variable attenuation section consisting of step-type variable attenuators, a voltage-controlled variable attenuator whose attenuation amount can be changed depending on the applied voltage, and a high-output amplification section consisting of one or more high-output amplifiers. In a power amplifier device, an input coupler extracts a part of an input signal, a first level detector detects the output signal level of the input coupler, and removes an alternating current component of the output signal of the first level detector. A first low-pass filter that converts the output of the first low-pass filter into a digital value at each timing from the timing signal generation circuit.
A/D converter, an arithmetic processing circuit that inputs the output signal of this A/D converter and a part of the output signal of the attenuation value setting circuit and processes the arithmetic operation at each timing from the timing signal generation circuit, and this arithmetic processing circuit. A D/A converter that converts the output signal of the circuit into an analog value, an output coupler that takes out a part of the output signal of the high output amplification section, and the output signal of this output coupler is divided by a plurality of resistors, a second level detector that detects the voltage-divided level; a second low-pass filter that removes the alternating current component of the output signal of the second level detector; and a non-inverting input of the output of the second low-pass filter. A power amplification device comprising: an error amplifier which inputs the output of the D/A converter into an inverting input terminal and controls the amount of attenuation of the voltage-controlled variable attenuator based on the output voltage thereof. 2. A small signal amplification section consisting of one or more small signal amplifiers, an attenuation value setting circuit operated by an attenuation value setting signal, and one or more small signal amplifiers controlled by the attenuation value setting circuit output signal. It consists of a step-type variable attenuation section consisting of step-type variable attenuators, a voltage-controlled variable attenuator whose attenuation amount can be changed depending on the applied voltage, and a high-output amplification section consisting of one or more high-output amplifiers. In a power amplifier device, an input coupler extracts a part of an input signal, a first level detector detects the output signal level of the input coupler, and removes an alternating current component of the output signal of the first level detector. a first low-pass filter that extracts a part of the output signal of the high-output amplification section, a second level detector that detects the output signal level of this output coupler, and this second level detector. a second low-pass filter that removes an alternating current component of the output signal; and first and second filters that convert the output signals of the first and second low-pass filters into digital values at each timing from the timing signal generation circuit. A/D converter, the output signals of the first and second A/D converters, and the output signal of the attenuation value setting circuit are input, and the calculation is performed at each timing from the timing signal generation circuit. A processing circuit, and a D/A converter for converting the error voltage output from the arithmetic processing circuit into an analog signal and controlling the attenuation amount of the voltage-controlled variable attenuator using the analog signal. Characteristic power amplification device.