JP2000252755A - Linearizer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a linearizer with low distortion by compensating the phase and gain characteristics of a high-output amplifier even if there is temperature variation by providing a thermistor for coping with temperature variations of the phase and gain characteristics of the high-output amplifier. SOLUTION: This linearizer is connected to the high-output amplifier to have the opposite characteristics from the phase and gain characteristics of the high-output amplifier and equipped with a diode 5 and a resistor 4 for bias supply which are connected in parallel to a signal path where an input signal is supplied to an input terminal and outputted from an output terminal and the thermistor 9 which is connected in parallel to the signal path and connected in series with the diode 5 and varies in resistance value with temperature. For example, this thermistor 9 in use increases in resistance value as the temperature drops and decreases in resistance value as the temperature rises. As the temperature rises, the delay of the phase becomes large and an increase in the gain becomes large.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-power amplifier used for mobile communication equipment, satellite communication equipment and the like.
The present invention relates to a linearizer that compensates for low distortion of the phase and the gain with high accuracy according to a temperature change.

[0002]

2. Description of the Related Art With respect to a conventional linearizer, a GaAs FET is used as a high-output amplifier for a satellite communication device or the like. In general, a high-output amplifier of this type has a reduced gain and an advanced phase as the input signal increases. It is known to have properties. For this reason, the characteristic is opposite to the characteristic of this type of high-power amplifier, that is, the gain increases with an increase in the input signal,
In order to obtain a phase delay characteristic, a conventional linearizer utilizing the nonlinear characteristic of a forward-biased diode is known. On the other hand, as described in JP-A-63-86603, as a conventional linearizer, as a linearizer for a traveling-wave tube amplifier, a Schottky diode is used to increase the amplitude as the input signal increases. There is known a device that attempts to obtain linearity in a drive region approaching a saturation region of an amplifier.

[0003]

However, in the prior art, since each element constituting the linearizer has almost no temperature characteristic, the phase and the gain of the conventional linearizer hardly change with a temperature change. There is a problem that a sufficiently low distortion cannot be realized for a high-output amplifier used for a satellite communication device or the like. SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and provides a thermistor for responding to a temperature change in the phase and gain characteristics of a high-power amplifier. It is an object of the present invention to provide a novel linearizer capable of realizing low distortion by compensating characteristics.

[0004]

A linearizer according to a first aspect of the present invention is a linearizer connected to the high power amplifier so as to have characteristics opposite to the phase and gain characteristics of the high power amplifier, An input signal is supplied to an input terminal, and a diode and a bias supply resistor are connected in parallel to a signal path output from an output terminal, and are connected in parallel to the signal path, and are connected in series to the diode. And a thermistor whose resistance changes according to the temperature.

According to a second aspect of the present invention, there is provided a linearizer according to the first aspect, further comprising a fixed resistor connected in series or parallel to the thermistor.

A linearizer according to a third aspect of the present invention is the linearizer according to the first aspect, wherein the first fixed resistor connected in parallel to the thermistor;
And a second fixed resistor connected in series to a parallel circuit of the fixed resistors.

A linearizer according to a fourth aspect of the present invention is the linearizer according to any one of the first to third aspects, wherein the diode is a Schottky diode, and is connected in series to the capacitor connected in parallel to the Schottky diode and the thermistor. It has a connected inductor.

A linearizer according to a fifth aspect of the present invention is the linearizer according to the first aspect, wherein the diode, the bias supply resistor, and the thermistor are incorporated in an electronic device body.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of a linearizer according to the present invention will be described with reference to the drawings. FIG.
FIG. 2 is a circuit configuration diagram of a linearizer according to the present invention. FIG.
, A high-frequency input signal is supplied to an input terminal RF IN and a high-frequency output signal is formed from an output terminal RF OUT to form a signal path. In the figure, reference numerals 1 and 2 denote DC blocking capacitors provided in the signal path, and reference numeral 3 denotes a noise cut capacitor having one end connected to the bias voltage Vd and the other end grounded. 4 is the bias voltage Vd and the capacitor 1
A bias supply resistor 5 provided between the first and second connection points A is a Schottky diode connected in parallel to the signal path. Reference numeral 7 denotes a capacitor connected in parallel to the Schottky diode 5, and reference numeral 8 denotes an inductor having one end connected to the Schottky diode 5 and the other end grounded. 9 is a thermistor connected in parallel to the signal path and connected in series to the Schottky diode 5.

The thermistor 9 may be configured as shown in FIG. 2A shows a case where the thermistor 10 and the fixed resistor 11 are connected in series, FIG. 2B shows a case where the thermistor 12 and the fixed resistor 13 are connected in parallel, and FIG. Fixed resistor 1 in parallel circuit
6 is a circuit diagram in which 6 are connected in series. The linearizer as shown in FIG. 1 has a high-output amplifier whose output terminal RF OUT is not shown, for example, GaAs used for satellite communication equipment or the like.
Connected to FET.

Generally, the phase and gain (amplitude) characteristics of a high-output amplifier are such that the gain decreases as the input signal increases and the phase advances. In the linearizer shown in FIG. 1, a fixed resistor (not shown) is used instead of the thermistor 9.
Is used, the phase and gain characteristics of the linearizer are determined by the fixed resistor, the capacitor 7, and the inductor 8
Can be changed by changing the values of For example, when the resistance value of the fixed resistor is increased, the phase / gain characteristics of the linearizer are as shown in FIGS. 3A and 3B. That is, when the resistance value of the fixed resistor is increased as shown by arrows in FIGS.
As the input signal increases, the phase lag becomes smaller as compared with the case where the resistance value is small as shown by the arrow in FIG. 3A, and the gain increase increases as shown by the arrow in FIG. 3B. The value is smaller than when the value is small. Further, since the bias voltage Vd is also a parameter element that determines the phase / gain characteristics of the linearizer, the phase / gain characteristics of the linearizer can be changed by changing the bias voltage Vd. Accordingly, by appropriately setting the resistance value of the fixed resistor of the linearizer to be opposite to the phase-gain characteristics of the high-output amplifier, low distortion of the phase-gain characteristics of the high-output amplifier can be realized.

However, since the phase / gain characteristics of a high-output amplifier generally depend on temperature, the phase-gain characteristics of a high-output amplifier cannot be sufficiently reduced unless the linearizer also has temperature dependence. FIG. 4A is a phase / gain characteristic diagram generally showing the temperature dependence of a high-output amplifier. FIG.
In (a), Tl is a low temperature (−40 ° C. to −30 °).
C), Tm is room temperature (25 ° C), Th is high temperature (50 ° C)
5 shows the phase / gain characteristics at 60 ° C.). This figure 4
As can be seen from (a), when the input signal increases, the gain decreases as the temperature rises, and the phase has the characteristic of progressing as the temperature rises. For this reason, the linearizer is also shown in FIG.
A temperature characteristic is provided by using a thermistor 9 as shown in FIG.

Here, it is assumed that the thermistor 9 shown in FIG. 1 has a characteristic that the resistance value increases when the temperature decreases, and the resistance value decreases when the temperature increases.
When the temperature decreases, that is, when the temperature changes from Tm to Tl, the resistance value increases, so that the phase delay decreases from the position shown in FIG. 3A and the gain increases from the position shown in FIG. Becomes smaller. On the other hand, when the temperature rises,
That is, when the temperature changes from Tm to Th, the resistance value decreases, so that the phase delay is larger than in FIGS.
The increase in gain is large. Therefore, by using such a thermistor 9, the phase / gain characteristics of the linearizer can be changed over a low temperature Tl, a normal temperature Tm, and a high temperature Th, as shown in FIG.
The characteristics as shown in FIG. Therefore,
The phase / gain characteristics of the high power amplifier can be effectively made as shown in FIG.

According to FIGS. 3 (a) and 3 (b), when the resistance value decreases, the phase delay and the gain increase increase, and when the resistance value increases, the phase delay and the gain increase decrease.
On the other hand, FIGS. 5A and 5B are capacitance-phase and gain characteristic diagrams showing how the phase and gain of the linearizer change with respect to the input signal when the capacitance of the capacitor 7 shown in FIG. 1 is increased. FIGS. 6A and 6B are inductance phase and gain characteristic diagrams showing how the phase and gain of the linearizer change with respect to the input signal when the inductance of the inductor 8 shown in FIG. 1 is increased. FIGS. 7A and 7B are bias voltage-phase and gain characteristic diagrams showing how the phase and gain of the linearizer change with respect to the input signal when the bias voltage Vd shown in FIG. 1 is increased. For example, as shown in FIG.
As d increases, the phase lag decreases, and FIG.
The larger the inductance, the smaller the phase delay. Therefore, by using the thermistor 9, the phase / gain characteristics of the linearizer can be made closer to the characteristics shown in FIG. 4B, and the capacitance, inductance, and bias voltage Vd can be further adjusted to achieve higher accuracy. The characteristic (c) can be obtained.

Further, in order to obtain a highly accurate linearizer,
As shown in FIGS. 2A, 2B, and 2C, the fixed resistor 11 is connected in series to the thermistor 10, the fixed resistor 13 is connected in parallel to the thermistor 12, or the fixed resistor 15 is connected to the thermistor 14. Fixed resistor 1 in parallel circuit connected in parallel
6 can be used in place of the thermistor 9 shown in FIG. In this case, it is used when low distortion of the high power amplifier is required with high accuracy. In other words, when it is difficult to sufficiently respond to the temperature-dependent changes in the phase and gain characteristics of the high-output amplifier with the resistance value of the thermistor 9 and its temperature change rate shown in FIG. 1, FIG. By using the fixed resistors 11, 13, 15, and 16 having such a connection configuration, the resistance value of the thermistor 9 and the temperature change rate thereof are finely adjusted.

Such a linearizer is mainly placed in the preceding stage in the case of a single high-power amplifier, and is placed in an optimal location where low distortion can be realized in the case of a multi-stage high-power amplifier. It is built in various electronic devices, for example, mobile communication devices and satellite communication devices, by reducing the size of the configuration and the like.

[0017]

As described above, according to the present invention, by providing a thermistor for responding to the temperature change of the phase and the gain in the high power amplifier, the distortion of the phase and the gain characteristic of the high power amplifier can be reduced even by the temperature change. High accuracy can be compensated.

[0018]

[Brief description of the drawings]

FIG. 1 is a circuit configuration diagram of a linearizer according to the present invention.

FIG. 2 is a circuit diagram of a thermistor used in the linearizer according to the present invention.

FIG. 3 is a phase and gain characteristic diagram of the linearizer according to the present invention.

FIG. 4 is a phase / gain characteristic diagram showing the temperature dependence of the high-output amplifier according to the present invention, a phase-gain characteristic diagram showing the temperature dependence of the linearizer, and an effective phase-gain characteristic diagram of the high-output amplifier. It is.

FIG. 5 is a graph showing capacitance-phase and gain characteristics with respect to an input signal when the capacitance of the capacitor 7 shown in FIG. 1 is increased.

6 is an inductance phase and gain characteristic diagram for an input signal when the inductance of the inductor 8 shown in FIG. 1 is increased.

7 is a bias voltage-phase and gain characteristic diagram for an input signal when the bias voltage Vd shown in FIG. 1 is increased.

[Explanation of symbols]

5: Schottky diode, 7: Capacitor, 8: Inductor, 9, 10, 12, 14 ... Thermistor, 11,
13, 15, 16 ... fixed resistor

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5J090 AA01 AA41 CA02 CA21 CA25 CA26 CA27 CA32 CN01 FN05 HA09 HA19 HA24 HA25 HA29 HA33 HA43 HN13 HN20 HN23 SA14 TA02

Claims (5)

[Claims] 1. A linearizer connected to a high-power amplifier so as to have characteristics opposite to the phase and gain characteristics of the high-power amplifier, wherein an input signal is supplied to an input terminal and output from the output terminal. And a bias supply resistor connected in parallel to the signal path, and a thermistor connected in parallel to the signal path and connected in series to the diode and having a resistance value that changes in accordance with a temperature change. Features a linearizer. 2. The linearizer according to claim 1, further comprising a fixed resistor connected to the thermistor in series or in parallel. 3. A semiconductor device comprising: a first fixed resistor connected in parallel to the thermistor; and a second fixed resistor connected in series to a parallel circuit of the thermistor and the first fixed resistor. The linearizer according to claim 1, wherein: 4. The Schottky diode according to claim 1, further comprising a capacitor connected in parallel with the Schottky diode, and an inductor connected in series with the thermistor. The linearizer described in Crab. 5. The linearizer according to claim 1, wherein the diode, the bias supply resistor, and the thermistor are incorporated in an electronic device main body.