JP2001345645A - Power amplifier - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power amplifier in which spurious radiation exceeding a predetermined level is prevented and an inappropriate control leading to breakdown of an element is blocked by realizing high speed adaptive control of a strain compensation system, even when the characteristics of the amplifier are varied abruptly at the time power is applied, for example. SOLUTION: Variation in the characteristics of a main amplifier 4 due to the ambient temperature and the time elapsed after turned on are measured previously and stored in a lookup table 15. Optimal control of a vector regulator 3 is performed at high speed based on data from a temperature sensor 13 and a timer 14.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power amplifier suitable for a communication device for performing wireless or wired transmission by a linear modulation method.

[0002]

2. Description of the Related Art FIG. 4 shows an example of a conventional power amplifier constituting a power amplifier of a communication apparatus. Such a configuration is disclosed in, for example, "Ultra Low Distortion Multi-Frequency Common Amplifier for Mobile Communications" by IEICE RC90-4, Toshio Nojima and Shoichi Narahashi. In FIG. 4, reference numeral 1 denotes an input terminal, and a modulated signal input from the input terminal 1 is branched into two paths by a directional coupler 2. One of the branched signals is amplified to a level required for transmission by the main amplifier 4 via the vector adjustment unit 3, but the output signal includes a distortion component due to non-linearity of the main amplifier other than the main signal. included.

[0003] The other of the split signals is a delay element (DLY) 8 for providing the same delay as the delay amount in the main amplifier 4.
Is input to the subtractor 9 via the. The amplitude and phase of the signal are adjusted by the vector adjuster 3, and the output level of the delay element 8 is matched with the level of the main signal included in the output of the main amplifier 4 via the directional coupler 5. By taking the difference between these two signals at 9, only the distortion component appears at the output of the subtractor 9.

[0004] The distortion component is passed through a vector adjuster 10 so as to adjust the distortion component contained in the signal transmitted through the directional coupler 5 and the delay element 6 so that the distortion component becomes a signal of the opposite phase, that is, an inverse vector. . By adding the inverse vector of the distortion component to the signal that has passed through the directional coupler 5 and the delay element 6 in the directional coupler 7, it is intended to compensate for the nonlinearity generated in the main amplifier 4. .

[0005] As an adjustment method, at the time of startup, for example, two adjacent unmodulated waves or the like are input to the input terminal 1 as a test signal, and while monitoring the output of the subtractor 9 and the signal of the output terminal 12, the vector Although a method of adjusting the adjusters 3 and 10 can be adopted, this method cannot follow a characteristic change due to a temperature change or the like after the start of actual data transmission.

Therefore, in the conventional example of the power amplifier having the configuration shown in FIG. 4, a method is employed in which a pilot signal is inserted from the input terminal 1 near the transmission band to perform adaptive control. FIG.
Shows a signal spectrum after the pilot signal P is inserted. As shown in FIG. 7, the output of the main amplifier 4 includes a main signal M, a distortion component D, and a pilot signal P. The adjustment in this case is performed as follows.

First, the output of the subtractor 9 is supplied to the directional coupler 21.
, And the signal M in the band at the output of the main amplifier 4 is detected. The total power of this detected signal is minimized, ie
The vector control unit 3 including the variable attenuator 301 and the variable phase shifter 302 is controlled by the control unit (CONT) 23 so that the total power in the band at the output of the subtractor 9 is minimized.

Further, a pilot signal component of the signal output from the directional coupler 17 is extracted by the detector 18, and the variable attenuator 101 and the variable attenuator 101 are adjusted so that the signal level of the extracted pilot signal P is minimized. The controller 19 controls the vector adjuster 10 including the phase shifter 102. Thus, the distortion component generated in the main amplifier 4 is adaptively compensated.

FIG. 6 shows an example of another conventional power amplifier constituting a power amplifier of a communication device. Such a configuration is disclosed in, for example, JP-A-2000-004124.

In FIG. 6, a system from an input terminal 1 to an output terminal 12 via a directional coupler 2, a vector adjuster 3, a main amplifier 4, a directional coupler 5, a delay element 6, and a directional coupler 7 is shown. The operation of the system from the directional coupler 2 to the output terminal 12 via the delay element 8, subtractor 9, vector adjuster 10, error amplifier 11 and directional coupler 7 is shown in FIG. , But different in the following points.

That is, in this conventional example, characteristic changes of the main amplifier 4 and the error amplifier 11 with respect to the ambient temperature are measured in advance, and look-up tables (TBL) 15 and 16 storing these are provided. Vector adjuster 3 so that the distortion compensation operation is optimal for
Are controlled, or the variable attenuator 101 and the variable phase shifter 102 which configure the vector adjuster 10 are controlled.

[0012]

In a device such as a high-output transistor, which consumes a large amount of power, when the power is turned on, the temperature inside the device rises more rapidly than the change in the ambient temperature, and the device characteristics itself also changes rapidly. In any of the conventional examples described above, adaptive control cannot follow when the characteristics of the amplifier change rapidly, such as when the power is turned on. For this reason, it takes time for the spurious component or the adjacent channel leakage power to become equal to or less than a prescribed value that can be transmitted.

In particular, when the amplitude and phase of the main amplifier are not optimally controlled, the level of the signal input to the error amplifier becomes excessive, and there is a possibility that the element may be deteriorated or the element may be destroyed. .

An object of the present invention is to provide a power amplifier having a distortion compensation system capable of performing adaptive control at high speed.

[0015]

In order to achieve the above object, a power amplifier according to the present invention is provided with a temperature sensor and a timer, based on an ambient temperature and an elapsed time since power-on.
It is characterized in that the distortion compensation system is adapted to be adaptively controlled.

As a result, adaptive control of the distortion compensation system in the power amplifier can be performed at high speed, unnecessary radiation exceeding a specified value is prevented, and occurrence of an inappropriate control state such as element destruction is prevented. be able to.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, preferred embodiments of a power amplifier according to the present invention will be described in detail using specific examples with reference to the accompanying drawings.

<Embodiment 1> FIG. 1 is a block diagram showing an embodiment of a power amplifier according to the present invention. In FIG. 1, the same components as those of the conventional example shown in FIGS. 4 and 6 are denoted by the same reference numerals. The same applies to the following embodiments.

The input terminal 1 is connected to a vector adjuster 3 and a delay element 8 via a directional coupler 2. The vector adjuster 3 is connected to the output terminal 12 via the main amplifier 4, the directional coupler 5, the delay element 6, and the directional coupler 7. The directional coupler 5 is further connected to a subtractor 9. Here, the vector adjuster 3 includes a variable attenuator 301 and a variable phase shifter 302.

On the other hand, the delay element 8 is connected to the directional coupler 7 via a subtractor 9, a vector adjuster 10, and an error amplifier 11. Here, the vector adjuster 10 includes a variable attenuator 101 and a variable phase shifter 102. Further, a temperature sensor (THM) 13 and a timer (TMR) 14
Are connected to the vector adjuster 3 via a first look-up table (TBL) 15. The first lookup table 15 stores a control value (for example, a voltage value for controlling the phase and amplitude of the vector adjuster 3) determined by the ambient temperature and the elapsed time from the start of power-on, in advance, as reference value data. This is a storage device that is stored as (control data) and outputs corresponding reference value data according to the temperature and time given from the temperature sensor 13 and the timer 14.

Hereinafter, the operation of the power amplifier of the present embodiment configured as described above will be described. The signal handled in this embodiment is, for example, a π / 4 shift QP
A high frequency signal modulated by SK (Quadrature Phase Shift Keying) is used (the same applies to the following embodiments).

The signal input to the input terminal 1 is split by the directional coupler 2, one of which is input to the main amplifier 4 via the vector adjuster 3, and the other is input to the delay element 8. In the main amplifier 4, the input signal is amplified so as to have a specified transmission power at the output terminal 12. Here, intermodulation distortion occurs due to the non-linearity of the main amplifier 4. The output of the main amplifier 4 is split by the directional coupler 5, one of which is input to the delay element 6 and the other is input to the arithmetic unit 9.

The subtractor 9 subtracts the signal input through the delay element 8 from the signal having the distortion component input through the directional coupler 5 to extract the distortion component. In the directional coupler 7, the extracted distortion components are combined with the distortion components included in the output of the main amplifier 4 passing through the delay element 6 at the same level and in opposite phases, thereby canceling the distortion components. The vector adjuster 10 and the error amplifier 11
Is controlled.

Since the error amplifier 11 is required to have linearity, a signal input to the error amplifier 11 has power sufficiently lower than the saturation power of the error amplifier itself, that is, at least 1/1.
It is necessary that the power of 00 to 1/1000 be small. In order to reduce the power handled by the error amplifier 11, it is necessary to make the amplitude and phase relationship of the main signal between the signal including the distortion and the undistorted signal in the subtractor 9 a relationship of the same amplitude and opposite phase. Yes, the vector adjuster 3 adjusts the signal level and phase.

Here, the operation of the main amplifier 4 when the power is turned on will be considered. After the power is turned on, a bias current flows through the amplifying element such as a transistor, so that the temperature of the amplifying element increases, and accordingly, the surrounding temperature starts to increase. Due to this temperature rise, the characteristics of components such as a resistor and a capacitor used around the amplifying element and its surroundings change according to the temperature coefficient. The characteristic changes of these components are
Since the amplitude and phase of the signal are affected, the amplitude and phase of the output signal continue to change after the power is turned on until the temperature rise approaches the saturation point.

In view of this, the amount of change in phase and amplitude with respect to the ambient temperature of the main amplifier 4 due to the time after the power is turned on is measured in advance, and the respective attenuation corresponding to each temperature and each time to correct the measured amount of change. The control values of the amount and the phase shift amount are tabulated and stored in the first lookup table 15. The temperature at the time of turning on the power is sensed by the temperature sensor 13, the elapsed time from the turning on of the power is measured by the timer 14, and the optimal attenuation amount and phase amount are stored in the first lookup table 15 from the values of both. The variable attenuator 301 and the variable phase shifter 302 which constitute the vector adjuster 3 are selected from the calculated values.

Thus, it is possible to obtain a power amplifier having a non-linearity compensation function.

<Embodiment 2> FIG. 2 is a block diagram showing another embodiment of the power amplifier according to the present invention. In FIG. 2, an input terminal 1 is connected to a vector adjuster 3 and a delay element 8 via a directional coupler 2. The vector adjuster 3 is connected to the output terminal 12 via the main amplifier 4, the directional coupler 5, the delay element 6, and the directional coupler 7. The directional coupler 5 is further connected to a subtractor 9. Here, the vector adjuster 3 includes a variable attenuator 301 and a variable phase shifter 302.

On the other hand, the delay element 8 is connected to the directional coupler 7 via a subtractor 9, a vector adjuster 10, and an error amplifier 11. Here, the vector adjuster 10 includes a variable attenuator 101 and a variable phase shifter 102. Further, the temperature sensor 13 and the timer 14 are connected to the vector adjuster 3 via the first look-up table 15, and further connected to the vector adjuster 10 via the second look-up table 16. As described above, the second embodiment differs from the configuration of the first embodiment shown in FIG. 1 in that the second lookup table is provided.

Hereinafter, the operation of the power amplifier of this embodiment will be described. A system from the input terminal 1 to the output terminal 12 via the directional coupler 2, the vector adjuster 3, the main amplifier 4, the directional coupler 5, the delay element 6, and the directional coupler 7;
The operation of the system from the directional coupler 2 to the output terminal 12 via the delay element 8, the subtractor 9, the vector adjuster 10, the error amplifier 11, and the directional coupler 7 is the same as that of the first embodiment. Therefore, the detailed description is omitted.

In the same way that the output phase amplitude characteristic of the main amplifier 4 changes due to a sudden temperature change at the time of power-on, the level of the output signal of the error amplifier 11 also changes due to a sudden temperature change at the time of power-on. Amplitude and phase change. Therefore, in the present embodiment, the output phase amplitude characteristic of the error amplifier 11 based on the ambient temperature and the elapsed time from the time when the power is turned on is measured in advance, and the control data for correcting the phase amplitude characteristic corresponding thereto is tabulated. Then, it is stored in the second look-up table 16, and the vector adjuster 10 connected to the error amplifier 11 is further controlled based on this value.

<Embodiment 3> FIG. 3 is a block diagram showing still another embodiment of the power amplifier according to the present invention. In FIG. 3, an input terminal 1 is connected to a vector adjuster 3 and a delay element 8 via a directional coupler 2. The vector adjuster 3 includes a main amplifier 4, a directional coupler 5, a delay element 6,
It is connected to the output terminal 12 via the directional coupler 7 and the directional coupler 17. The directional coupler 5 further includes a subtractor 9
Connected to. The directional coupler 17 is a detector (DET) 1
8. The controller (CONT) 19 is connected to the vector adjuster 10 via the switch 20. Here, the vector adjuster 3 includes a variable attenuator 301 and a variable phase shifter 302.

On the other hand, the delay element 8 includes a subtractor 9, a directional coupler 21, a vector adjuster 10, and an error amplifier 11
Is connected to the directional coupler 7. Here, the vector adjuster 10 includes a variable attenuator 101 and a variable phase shifter 102.
Consists of The directional coupler 21 is connected to the vector adjuster 3 via a detector 22, a control unit 23, and a switch 24.
Connected to.

The temperature sensor 13 and the timer 14 are connected to the vector adjuster 3 via a first look-up table 15 and a switch 24, and further via a second look-up table 16 and a switch 20. Connected to the vector adjuster 10. As described above, this embodiment is different from the configuration of the second embodiment shown in FIG. 2 in that the switches 20 and 24 are further provided.

Hereinafter, the operation of the power amplifier according to this embodiment will be described. A system from the input terminal 1 to the output terminal 12 via the directional coupler 2, the vector adjuster 3, the main amplifier 4, the directional coupler 5, the delay element 6, and the directional coupler 7;
The operation of the system from the directional coupler 2 to the output terminal 12 via the delay element 8, the subtractor 9, the directional coupler 21, the vector adjuster 10, the error amplifier 11, and the directional coupler 7 is as follows.
Since this is the same as in the first embodiment, a detailed description thereof will be omitted.

The initial operation when the power is turned on is the same as that of the second embodiment shown in FIG. That is, based on the output phase amplitude characteristics of the main amplifier 4 and the error amplifier 11 measured in advance, the temperature at power-on and the elapsed time after power-on are
It controls the vector adjuster 3 and other vector adjusters 10.

After that, after the temperature rise of the amplifiers 4 and 11 is saturated, the switch 24 is set to the control unit 23 and the switch 20 is set in order to cope with a characteristic change of a relatively long cycle such as a minute change in ambient temperature and a change with time. To the control unit 19 side.

Regarding the vector adjuster 3 on the main amplifier 4 side, a point at which the main signal level at the output of the subtractor 9 becomes minimum may be found. That is, the entire power within the band of the output of the subtractor 9 is detected by the detector 22, and the control unit 23 controls the variable attenuator 301 and the variable phase shifter 302 so that the detected power value is minimized.

The vector adjuster 10 on the side of the error amplifier 11
Detects the distortion power in the directional coupler 17 with the detector 18, and controls the variable attenuator 101 and the variable phase shifter 102 by the control unit 19 so that the distortion power is minimized.

<Embodiment 4> Next, an application example of the power amplifier according to the present invention will be described with reference to FIG. FIG. 5 is a block diagram of a transmitter of a wireless communication device to which the power amplifier of the present invention is applied.

The audio / video input terminal 25 is connected to a format converter 28 via an analog / digital (A / D) converter 27, and the digital data input terminal 26 is connected to the format converter 28. The format converter 28 is connected to an antenna 33 via a modulator (MOD) 29, a frequency converter 30 and an amplifier 32, and the frequency converter 30 is connected to a local oscillator 31.

Hereinafter, the operation of the transmitter configured as described above will be described. The analog signal input from the audio / image input terminal 25 is converted into a digital signal by the A / D converter 27 and input to the format converter 28. From the digital data input terminal 26, a digital signal is directly input from a device such as a computer or a facsimile. These digital signals are converted into a predetermined communication format by a format converter 28, and mapping and waveform shaping are performed by a modulator 29. The frequency conversion unit 30 performs frequency conversion to a predetermined transmission frequency using a signal from the local oscillator 31. The output of the frequency conversion unit 30 is amplified to a specified output by the power amplifier 32, and a radio wave is transmitted from the transmitting antenna.

Here, assuming that the modulation method is a linear modulation method such as π / 4 QPSK or QAM (Quadrature Amplitude Modulation), the power amplifier 32 has the following characteristics from the viewpoints of securing transmission quality and preventing generation of unnecessary radiation. While high linearity is required, high efficiency and low power consumption are simultaneously required. Therefore, the power amplifier of any one of the above-described embodiments having a nonlinearity compensation function capable of performing compensation control so as to minimize distortion power may be used as the power amplifier 32 of the transmitter of the present embodiment. .

[0044]

As is apparent from the above-described embodiment, the power amplifier of the present invention has a temperature sensor and a timer, and configures the power amplifier based on the ambient temperature and the time elapsed since the power was turned on. Since the main amplifier and / or the phase and amplitude of the output are controlled, optimal control can be performed at high speed even when the characteristics of the amplifier suddenly change, such as when power is turned on. In addition, it is possible to provide a stable power amplifier that prevents deterioration and destruction of characteristics of the error amplifier due to excessive input.

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment of a power amplifier according to the present invention.

FIG. 2 is a block diagram showing another embodiment of the power amplifier according to the present invention.

FIG. 3 is a block diagram showing still another embodiment of the power amplifier according to the present invention.

FIG. 4 is a block diagram illustrating an example of a conventional power amplifier.

FIG. 5 is a block diagram of a transmitter showing an example of application of the power amplifier according to the present invention.

FIG. 6 is a block diagram showing another example of a conventional power amplifier.

FIG. 7 is a signal spectrum diagram after a pilot signal is inserted into the power amplifier shown in FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Input terminal, 2 ... Directional coupler, 3 ... First vector adjuster, 4 ... Main amplifier, 5,7 ... Directional coupler, 6,8
... delay element (DLY), 9 ... subtractor, 10 ... second vector adjuster, 11 ... error amplifier, 12 ... output terminal, 13 ...
Temperature sensor (THM), 14 timer (TMR), 15 first look-up table (TBL), 16 second look-up table, 17, 21 directional coupler, 18,
22: detector (DET), 19, 23 ... control unit (CON
T), 20, 24 switch, 25 analog signal input terminal, 26 digital signal input terminal, 27 analog / digital (A / D) converter, 28 format converter, 29 modulator (MOD), 30 ... frequency conversion unit, 31
... local oscillator, 32 ... power amplifier, 33 ... transmission antenna, 101, 301 ... variable attenuator (ATT), 102, 3
02: variable phase shifter, D: distortion component, M: main signal, P: pilot signal.

 ──────────────────────────────────────────────────の Continued on the front page (72) Inventor Hiroki Sato 32nd Miyukicho, Kodaira-shi, Tokyo Inside the Koganei Plant of Hitachi Electronics Co., Ltd. (72) Inventor Takuya 32nd Miyukicho, Kodaira-shi, Tokyo Koganei Plant of Hitachi Electronics Co., Ltd. (72) Inventor Hiroshi Kishida 1-280 Higashi-Koigabo, Kokubunji-shi, Tokyo F-term in Hitachi Central Research Laboratory, Ltd. HA26 HA38 HA43 HN03 HN06 HN08 HN13 HN14 HN15 HN20 KA15 KA16 KA23 KA25 KA26 KA55 MA14 SA14 TA01 TA03 5J091 AA01 AA21 AA41 AA51 CA02 CA21 CA27 CA48 CA57 CA85 FA08 FA18 FA19 FA20 KA08 KA08 HA01 KA08 5J092 AA01 AA21 AA41 AA51 CA02 CA21 CA27 CA48 CA57 CA85 FA08 FA18 FA19 FA20 FR02 FR07 HA2 6 HA38 HA43 KA15 KA16 KA23 KA25 KA26 KA55 MA14 SA14 TA01 TA03

Claims (5)

[Claims] 1. A main amplifier for amplifying a signal to a specified transmission power, extraction means for extracting a distortion component generated in the main amplifier by subtracting a signal before amplification from the main amplifier, and an extracted distortion component A power amplifier having an error amplifier for amplifying the output power, an adjusting means for adjusting the phase and amplitude of the extracted distortion component, and a means for suppressing the distortion component by subtracting the error amplifier output from the main amplifier output. Temperature detecting means for detecting the ambient temperature of the amplifier; time measuring means for measuring an elapsed time after power-on; and pre-stored in accordance with the temperature detected by the temperature detecting means and the time measured by the time measuring means. To correct the phase and amplitude of the main amplifier
And a first storage device that outputs the control data of (a), wherein the first control data is used to control the phase and amplitude of the signal input to the main amplifier. 2. The power amplifier according to claim 1, wherein a phase and an amplitude of a power amplifier output stored in advance are corrected according to the temperature detected by said temperature detecting means and the time measured by said time measuring means. A second storage device for outputting second control data for controlling the phase and the amplitude of the distortion component extracted by the extracting means using the second control data. . 3. The power amplifier according to claim 1, wherein a part of the distortion component extracted by the extraction unit is input, and a first detector that detects a power level of the distortion component; A first control unit that controls a phase and an amplitude of the signal input to the main amplifier based on a detection output of the first detector; and a phase and amplitude of the signal input to the main amplifier,
First switching means for switching between control by the first control unit and control by the first control data output from the first storage device; and detecting a power level of a distortion component of final output power. A second detector; a second control unit that controls the phase and amplitude of the distortion component extracted by the extraction unit based on a detection output of the second detector; Phase and amplitude,
A second switching unit for switching between control by the second control unit and control by the second control data output from the second storage device, wherein after the temperature rise is saturated, By switching the first switching means and the second switching means, the first control unit controls the phase and amplitude of the signal input to the main amplifier, and the second control unit A power amplifier, wherein a phase and an amplitude of the distortion component extracted by the extraction means are controlled. 4. The power amplifier according to claim 3, wherein when the time measured by the time measuring means is equal to or longer than a predetermined time, the first switching means and the second switching means are switched. The first control unit controls the phase and amplitude of the signal input to the main amplifier, and the second control unit controls the phase and amplitude of the distortion component extracted by the extraction unit. Characteristic power amplifier. 5. A transmitter using the power amplifier according to any one of claims 1 to 4.