JPH0787303B2 - High frequency amplifier - Google Patents

Description

TECHNICAL FIELD The present invention relates to a linear amplifier used in a high frequency band and mainly used as a power amplifier.

[Prior Art] In recent years, in wireless communication, a narrow band of a channel has been advanced in order to effectively use a frequency. As the channel bandwidth becomes narrower, the deterioration of the transmission spectrum caused by the non-linearity of the amplifier becomes a problem. In addition, an amplifier with high power efficiency is required in order to keep the power consumption as small as possible in consideration of mounting on a satellite.

A class F amplifier is known as an amplifier with high power efficiency. This sets the bias condition like the class B amplifier,
The load impedance of the amplifier is short-circuited for even harmonics and open for odd harmonics. Although this amplifier has high efficiency, it has a problem that a large amount of distortion is generated.

As a conventional amplifier for solving this problem, Japanese Patent Laid-Open No. 62-27
There is a high-frequency amplifier shown in Japanese Patent No. 4906 and B-539 (p2-209) of the 1989 IEICE Autumn National Conference Proceedings. This amplifier changes the drain voltage in proportion to the envelope level of the input signal, and even an amplifier with large distortion such as class F can be expected to have an amplification characteristic with good linearity, and the envelope of the input signal can be expected. There is a feature that the power supply efficiency can be increased regardless of the change of the line level.

FIG. 5 is a circuit diagram showing a conventional high-frequency amplifier in which the nonlinear characteristic is compensated and the amount of distortion is reduced. In the figure,
(1) is an RF signal input terminal, (2) and (3) are signal series input terminals, (4) is a DC voltage supply terminal, (5) is an RF signal output terminal, (10) is an amplifier, ( 20) is a non-linear control circuit, and (30) is a variable voltage DC / DC converter. Signals I and Q to the input terminals (2) and (3) represent the real part and the imaginary part of a signal sequence obtained by sample-quantizing a complex signal. The non-linear control circuit (20) outputs a drain voltage according to the envelope level of the modulated wave obtained from the I and Q signals based on the data of the input-output characteristics when the drain voltage of the amplifier (10) is changed. Circuit, ROM (Read Only Memory)
Etc. are realized. The variable voltage DC / DC converter (30) is a circuit that converts the output voltage from the non-linear control circuit (20) into a voltage at which the amplifier (10) operates, and operates at high speed by following the temporal change in the envelope. There is a need. In the circuit thus configured, as shown by the solid line in FIG. 6 (a), even if the amplifier (10) is a large distortion amplifier such as class F, the drain voltage is controlled according to the input signal. As a result, the input-output characteristics can be made almost linear, and linear operation can be performed while maintaining high power supply efficiency. Further, the input-output phase characteristic is improved as compared with the amplifier alone.

FIG. 6 (b) shows the spectrum of the output wave. In the figure, A is the spectrum of the class F amplifier alone, and B is the spectrum of the high frequency amplifier of FIG.

It can be seen that the spectrum B of the high frequency amplifier shown in FIG. 5 is greatly improved as compared with the spectrum A of the amplifier alone, and the leakage power to the adjacent channel is reduced.

[Problems to be Solved by the Invention] However, in the conventional high frequency amplifier as shown in FIG.
Although the efficiency of the amplifier is high, the voltage that can control the drain voltage is limited to, for example, 2 V to 8 V, so that the amplitude characteristic of the amplifier can be maintained in a narrow range. That is, there is a problem that the dynamic range is narrow. Therefore, when the input amplitude changes significantly in the width of 20 dB as in the 4-phase phase modulation method (QPSK method), and the input is changed by a variable attenuator for 20 to 30 dB for output control, the input is changed. Linearity cannot be maintained over the entire range of amplitude change.

Further, in the conventional high frequency amplifier as shown in FIG. 5, the amplitude characteristic of the amplifier is almost linear, but the phase characteristic is not flat, so that the deterioration of the spectrum caused by the phase distortion cannot be prevented. Therefore, when it is desired to make the leakage power to the adjacent channel extremely small, this method is insufficient.

The present invention has been made to solve the above problems, and an object thereof is to obtain a wide dynamic range while maintaining high efficiency, and to make leakage power to an adjacent channel extremely small.

[Means for Solving the Problem] A high frequency amplifier according to the present invention includes an amplifier including a transistor and an input and output matching circuit, and an envelope level of the input signal in a region where the amplitude of the input signal is large. A non-linear control circuit that outputs a voltage that changes the drain voltage or the collector voltage of the transistor based on the above, and that keeps the drain voltage or the collector voltage of the transistor constant in a region where the amplitude of the input signal is small, The output of the non-linear control circuit is converted into a voltage at which the amplifier operates, and an amplitude characteristic correcting means including a voltage variable DC / DC converter applied to the amplifier, and an input signal is changed based on its distortion characteristic, It occurs over a region range where the amplitude of the input signal is changed by the amplitude characteristic correcting means and a range other than that. And a compensating circuit for compensating the distortion of the amplitude characteristic and / or the phase characteristic of the amplifier.

[Operation] In the present invention, the amplitude characteristic correcting means changes the drain voltage or the collector voltage of the amplifier in proportion to the envelope level of the input signal to correct the amplitude distortion of the amplifier, and the amplitude characteristic correcting means. Since the compensation circuit compensates for the distortion of the amplitude and / or phase characteristics that occurs over the range of change of the voltage and the range other than that, the linearity of the amplitude characteristics is maintained over a wide range. A wide dynamic range can be obtained while maintaining high efficiency.

[Embodiment] FIG. 1 is a circuit diagram showing an embodiment of the present invention. In the figure, (2) to (4), (10), (20) and (30) are shown in FIG. It is the same as the one. Reference numeral (40) is a distortion compensating circuit, which is a circuit for compensating for characteristic distortion between a range corrected by the non-linear control circuit (20) and the variable voltage DC / DC converter (30) and a range outside the corrected range. Then, the I and Q data input to the input terminals (2) and (3) are changed according to the distortion characteristics. The non-linear control circuit (20) corrects the amplitude distortion of the amplifier (10) by changing the drain voltage according to the envelope level of the input signal in the area where the input amplitude is large. Such an operation is possible, and the drain voltage is fixed in a region where the input amplitude is small outside the range in which the drain voltage can be changed. Therefore, the input-output characteristic of the amplifier is not linear as shown by the solid line in FIG. By compensating for this bent characteristic with the distortion compensating circuit (40), it is possible to obtain a characteristic without distortion over a wide range.

The distortion compensating circuit (40) can also flatten the phase characteristic, and prevent the deterioration of the spectrum caused by the phase distortion.

Since a wide dynamic range can be obtained while maintaining high efficiency in this way, it is effective for QPSK systems and the like.

FIG. 3 is a block diagram showing an example of the distortion compensation circuit.
Is ROM, (60) is digital-to-analog (DA) converter,
(70) is a quadrature modulator. The ROM (50) has an amplifier (1
0) distortion characteristics are written, and I, Q of the input signal
Change the data to compensate for the distortion.

FIG. 4 is a block diagram showing another example of the distortion compensation circuit,
(7) is an input terminal to the distortion compensation circuit, (51) is a RAM (Random)
(52) is an error detection circuit, (53) is an analog / digital (AD) converter, and (54) is a detection circuit. A part of the output of the amplifier (10) is taken out and input to the input terminal (7). The detection circuit (54) detects both or one of the amplitude and phase, the AD converter (53) digitizes the signal, the error detection circuit (52) detects distortion, and the result is RA.
Write to M (51). This circuit can compensate for the temperature characteristics and variations of the amplifier.

As described above, according to the present invention, the drain voltage of the amplifier is controlled according to the envelope level of the input signal, and the distortion is compensated by the distortion compensating circuit. Since the dynamic range can be obtained and the linearity of the characteristic of the amplifier can be obtained, there is an effect that the electric power leaking into the adjacent channel can be made extremely small.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a high frequency amplifier according to an embodiment of the present invention, FIG. 2 is a characteristic diagram showing characteristics of the high frequency amplifier, FIG. 3 is a configuration diagram showing an example of a distortion compensation circuit, and FIG. FIG. 5 is a configuration diagram showing another configuration example of the distortion compensation circuit, FIG. 5 is a circuit diagram showing a conventional high frequency amplifier, and FIG. 6 is a characteristic diagram showing the specification of the conventional high frequency amplifier. In the figure, (2) and (3) are input terminals, (5) is an output terminal, (4) is a voltage supply terminal, (10) is an amplifier, and (20).
Is a non-linear control circuit, (30) is a variable voltage DC / DC converter,
(40) is a distortion compensation circuit. In the drawings, the same reference numerals indicate the same or corresponding parts.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yukio Ikeda 5-1-1, Ofuna, Kamakura-shi, Kanagawa Mitsubishi Electric Corporation Information Electronics Laboratory (72) Inventor Nao Takagi 5-1-1, Ofuna, Kamakura-shi, Kanagawa No. Mitsubishi Electric Corporation Information Electronics Research Laboratory (72) Inventor Shuji Urasaki 5-1-1, Ofuna, Kamakura-shi, Kanagawa Mitsubishi Electric Corporation Information Electronics Research Laboratory

Claims (1)

[Claims] 1. An amplifier including a transistor and an input and output matching circuit, and in a region where the amplitude of the input signal is large, the drain voltage or the collector voltage of the transistor is set based on the envelope level of the input signal. In the region where the voltage to be changed is output and the amplitude of the input signal is small, the non-linear control circuit that keeps the drain voltage or the collector voltage of the transistor constant and the input of the non-linear control circuit that the amplifier operates Amplitude characteristic correcting means including a variable voltage DC / DC converter for converting the voltage into a voltage and applying the voltage to the amplifier, and the input signal changed by the amplitude characteristic correcting means by changing an input signal based on its distortion characteristic. Distortion of the amplitude characteristic and / or the phase characteristic of the above-mentioned amplifier, which occurs over a range where the amplitude of the High-frequency amplifier, characterized in that a compensation circuit for compensating.