JPH06276033A - Power amplifier - Google Patents

Abstract

PURPOSE:To reduce an increase in phase distortion due to variance in AM-PM characteristics as to the power amplifier constituted by adding a linear compensating circuit to an amplifying circuit which has nonlinear input/output characteristics and high power efficiency. CONSTITUTION:The power amplifier, equipped with an amplifying means 11 which has linear input/output characteristics and amplifies the electric power of an input signal to a specific output power level to obtain an output signal, an amplitude variation extracting means 13 which extracts an amplitude variation component included in the input signal at a level proportional to the gain of the amplifying means 11, an amplitude variation component detecting means 15 which detects the amplitude variation component of the signal by detecting the envelope of its output signal, and a linear compensating means 17 which feeds the difference between those amplitude variation components negatively back to the amplifying means 11 to linearly compensate the input/output characteristics, is equipped with a control means 19 which intermits the feedback path of the negative feedback according to the variation rate of phase characteristics of the output signal to the input signal level within the variation range of the difference negatively fed back by the linear compensating means 17.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power amplifier configured by adding a circuit for linearly compensating the input / output characteristic to an amplifier circuit having a nonlinear input / output characteristic and high power efficiency.

[0002]

2. Description of the Related Art In a portable mobile station device of a digital mobile communication system, it is required to keep driving power low in parallel with downsizing and weight saving of the device. Further, in the digital mobile communication system, since the amplitude phase modulation method is adopted for the purpose of effectively using the radio frequency, the transmission power is switched and stabilized as in the conventional analog type mobile communication system. In addition, it is required to compensate for distortion generated in the transmitted wave signal during the control process. Therefore, in the above-mentioned portable mobile station apparatus, by performing linear compensation on a non-linear amplification circuit having high power efficiency to configure a power amplifier, power consumption can be reduced and distortion can be compensated at the same time.

FIG. 3 is a diagram showing a configuration example of a conventional power amplifier. In the figure, the output of the power amplifier 31 is connected to the output of the modulator 33 that modulates the carrier signal according to the baseband signal obtained from the transmission information via the waveform generation circuit 32. Gives a transmitted wave signal.

In the power amplifier 31, the output of the modulator 33 is connected to the input of the saturation amplification circuit 34, and the output thereof gives the above-mentioned transmission wave signal to the input of the coupler 35 and the subsequent stage.
The output of the combiner 35 is connected to the anode of the diode 36, and its cathode is connected to the inverting input of the differential amplifier 37. The transmission power control signal is given to one input of the envelope generation circuit 38, and the first output thereof is the differential amplifier 37.
Connected to the non-inverting input of. The output of the differential amplifier 37 is connected to one input of the adder 39, and the other output is connected to the other output of the envelope generation circuit 38. The output of the adder 39 is connected to the input of the drain voltage control circuit 40, and its output is Ga which is the amplification element of the saturation amplification circuit 34.
Connected to the drain terminal of As FET.

In the power amplifier having such a configuration, the saturation amplifier circuit 34 amplifies the power level of the modulated wave signal supplied from the modulator 33 and outputs the above-mentioned transmission wave signal, and the diode 36 causes the transmission wave signal to be transmitted. The signal is captured via the coupler 35 and envelope detection is performed.

The envelope generation circuit 38 compensates for the above-mentioned instantaneous values I and Q of the baseband signal and the transmission power level indicated by the transmission power control signal for the error caused by the non-linearity of the diode 36 at the power level. Depending on the coefficient k including minutes

[0007]

[Equation 1]

The arithmetic operation given by the equation (1) is performed to obtain the instantaneous value e which the envelope of the transmission wave signal modulated by the transmission information should take. The differential amplifier 37 has such an instantaneous value e.
And the instantaneous value of the detection output signal obtained by the envelope detection described above, the distortion component included in the detection output signal due to the nonlinearity of the saturation amplification circuit 34 is obtained. The adder 39 adds the above-mentioned error component to the instantaneous value e of the envelope curve to generate a feedback signal.

The drain voltage control circuit 40 stores in advance the value of the drain voltage to be applied in order to linearly compensate the input / output characteristics of the saturation amplification circuit 34 in correspondence with all possible values of such a feedback signal. , The stored value of the drain voltage is sequentially read according to the value of the feedback signal described above, and is applied to the drain terminal.

That is, in the saturation amplification circuit 34, the nonlinear input / output characteristic is linearly compensated by negatively feeding back the instantaneous value of the envelope of the transmission wave signal obtained at its output, so that, for example, the saturation amplification circuit 34 GaAs FE which is an amplification element
Input signal level at each value of the drain voltage V _D of T - phase characteristic of the output signal (. Hereinafter referred to as "AM-PM characteristic") when is indicated by a solid line in FIG. 4 (a), above the drain voltage The phase of the output signal obtained according to the drain voltage given from the control circuit 40 changes gently with a small value with respect to the change of the input signal level as shown by the dotted line in FIG. 4 (a). Therefore, at the output of the power amplifier 31, a low-distortion transmission wave signal is obtained at the power level set according to the transmission power control signal.

[0011]

By the way, in such a conventional power amplifier, the amplification element of the saturation amplification circuit 34 has a flat AM as shown by the solid line in FIG. In the case of having the −PM characteristic, the characteristic is deteriorated by the negative feedback described above as shown by the dotted line in FIG. 7B and is obtained at the output end, so that the phase distortion included in the transmitted wave signal is increased. Moreover, such phase distortion can be ignored because the transmission information is not included in the amplitude component of the transmission wave signal in the conventional analog mobile communication system using the angle modulation method. In the existing digital mobile communication system, it causes deterioration of transmission quality and cannot be ignored.

It is an object of the present invention to provide a power amplifier capable of reducing the increase in phase distortion caused by the variation in the AM-PM characteristic of the amplification element.

[0013]

FIG. 1 is a block diagram showing the principle of the present invention. The present invention has an amplifying means 11 having a non-linear input / output characteristic, which amplifies the power of an input signal to a predetermined output power level to obtain an output signal, and an amplitude fluctuation accompanying the modulation of the input signal by transmission information. Amplitude fluctuation amount extraction means 13 for extracting the component at a level proportional to the gain of the amplification means 11.
And an amplitude variation detecting means 15 for detecting the amplitude variation of the output signal by envelope detection, and the amplitude variation extracted by the amplitude variation extracting means 13 and the amplitude variation detecting means 15. In the power amplifier including the linear compensation means 17 which linearly compensates the input / output characteristic by negatively feeding back the difference from the amplitude fluctuation amount to the amplification means 11, amplification in the variable range of the difference negatively fed back by the linear compensation means 17. The control means 19 for connecting / disconnecting the feedback path of the negative feedback according to the rate of change of the phase characteristic of the input signal level-output signal of the means 11.
It is characterized by having.

[0014]

In the present invention, the linear compensating means 17 is the amplifying means 1.
In order to linearly compensate the non-linear input / output characteristic of No. 1, the difference of the amplitude variation between the input signal and the output signal of the amplifying means is negatively fed back. However, when the change rate of the phase characteristic of the input signal level-output signal unique to the amplifying means 11 is smaller than a predetermined value in the variable range of the negatively fed back difference, the control means 19 has the above-mentioned negative value. Disconnect the return route of return.

That is, when the rate of change in the phase characteristics of the input signal level and the output signal is sufficiently small, the control means 19 deteriorates such favorable characteristics due to the negative feedback performed by the linear compensation means 17. Therefore, it is possible to realize a power amplifier with a standardized circuit configuration that absorbs variations in the characteristics of the amplification means 11 and has good linearity in the input / output characteristics.

[0016]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 2 is a diagram showing an embodiment of the present invention.

In the figure, parts having the same functions and configurations as those shown in FIG. 3 are designated by the same reference numerals, and the description thereof will be omitted here. In the present embodiment, the characteristic feature of the present invention is that the output of the adder 39 is connected to one contact of one end of the switch 21 and the common contact thereof is connected to the input of the drain voltage control circuit 40, and the other end of the switch 21 is connected. A semi-fixed resistor 22 that divides the DC power supply voltage E at the contact of
The voltage dividing terminal is connected and the control terminal of the switch 21 is connected to the setting terminal 23.

Regarding the correspondence relationship between this embodiment and the block diagram shown in FIG. 1, the saturation amplification circuit 34 is the amplification means 1
1, the envelope generation circuit 38 corresponds to the amplitude variation extraction means 13, and the diode 36 corresponds to the amplitude variation detection means 1.
5, the differential amplifier 37, the adder 39 and the drain voltage control circuit 40 correspond to the linear compensation means 17, and the switch 21, the semi-fixed resistor 22 and the setting terminal 23 correspond to the control means 19.

The operation of this embodiment will be described below. In the present embodiment, the connection of the setting terminal 23 that determines which of the output of the adder 39 and the voltage dividing terminal of the semi-fixed resistor 22 is connected to the input of the drain voltage control circuit 40 in the switch 21, Since the setting and setting of the voltage division ratio of the semi-fixed resistor 22 are performed manually during the adjustment, the adjustment procedure will be described below.

In such adjustment, first, the setting terminal 23
To the drain voltage control circuit 40 through the switch 21 by applying a predetermined DC voltage corresponding to the high (low) level to the output signal of the adder 39. Furthermore, while monitoring the level of the spurious component of the transmitted wave signal using a spectrum analyzer or other measuring device, a predetermined adjustment is made to the antenna system which gives the transmitted wave signal and the preceding stage from the modulator 33 so that the level is minimized. To do.

However, even if such adjustment is performed, if the above-mentioned spurious component is greatly deteriorated in response to the switching of the transmission power level, the DC voltage applied to the setting terminal 23 is switched to the low (high) level. Thus, the voltage dividing terminal of the semi-fixed resistor 22 is connected to the input of the drain voltage control circuit 40 via the switch 21. Furthermore, while monitoring the level of the spurious component of the transmission wave signal, the voltage dividing point of the semi-fixed resistor 22 is set at the point where the level is minimum.

As described above, according to this embodiment, the AM-PM characteristic peculiar to the amplification element of the saturation amplification circuit 34 is, for example,
If the variation improves by negative feedback as shown in Fig. 4 (a), a negative feedback path similar to the conventional example is formed,
On the contrary, as shown in Fig. 4 (b), when it deteriorates due to such negative feedback, the amount of feedback in the negative feedback path is made constant regardless of the transmission power level that is set to be switched. The distortion component of the transmission wave signal obtained at the output end of the circuit 34 is suppressed to a small value by adapting to the above-mentioned variation in the AM-PM characteristic of the amplification element.

In this embodiment, the switch 21 is arranged in front of the drain voltage control circuit 40 and the saturation amplification circuit 3 is provided.
However, the present invention is not limited to such a method, and equivalent switching means may be arranged at the output end of the drain voltage control circuit 40, for example.

Further, in the present embodiment, the contact of the switch 21 is semi-fixedly set based on the spurious level of the transmitted wave signal observed at the time of adjustment, but the present invention is not limited to such a method. For example, AM− of the saturation amplification circuit 34
A method may be used in which the PM characteristic is measured in advance and semi-fixed setting is performed based on the result of the measurement, or the transmission power level is sequentially switched according to a transmission power control signal for switching setting.

Further, in the present embodiment, the saturation amplification circuit 34
Although a negative feedback path via the drain voltage control circuit 40 is formed in order to linearly compensate the input / output characteristics of the above, the present invention is not limited to the negative feedback path having such a configuration, and the saturation amplification circuit 34
It suffices to form a negative feedback path adapted to the circuit system and the characteristics of the amplifying element.

Further, in this embodiment, the amplitude variation of the transmission wave signal to be obtained at the output of the saturation amplification circuit 34 is calculated based on the instantaneous values of the two orthogonal baseband signals output from the waveform generation circuit 32. However, the present invention is not limited to such a method. For example, the amplitude variation of the modulated wave signal output from the modulator 33 is measured, and the content of the transmission power control signal is added to the measurement result. A method of performing weighting or other processing according to the above may be used.

Further, in the present embodiment, the amplitude variation included in the transmission wave signal is detected by the envelope detection performed by the diode 36, but the present invention is not limited to such a method, and for example, a predetermined value is used. A transistor or other semiconductor set to the operating point of may be used.

Further, in the present embodiment, the GaAs FET is used as the amplifying element of the saturation amplifying circuit 34, but the present invention is
The present invention is not limited to the saturation amplification circuit having such a configuration, and any circuit system and amplification can be used as long as the transmission wave signal can be obtained at a desired power level and the input / output characteristics can be linearly compensated with a predetermined accuracy from the outside. Elements may be used.

Further, in the present embodiment, the saturation amplification circuit 34
The signal to be amplified is a modulated wave of amplitude phase modulation performed by the modulator 33, but the present invention is not limited to an input signal obtained by such a quadrature modulation method, and for example, a multi-valued AS
Any power amplifier can be applied as long as it is a K-modulation method and amplifies a signal obtained by modulating the amplitude of a carrier wave according to transmission information.

[0030]

As described above, according to the present invention, when the rate of change in the phase characteristic of the input signal level-output signal peculiar to the amplifying means is sufficiently small within the variable range of the feedback amount negatively fed back to the amplifying means. By cutting off the feedback path of the negative feedback described above, it is possible to prevent such good characteristics from being deteriorated by the negative feedback.

That is, since the variation in the characteristic of the amplifying means is absorbed by using the circuit having the standardized structure and the power amplifier having the excellent linearity of the input / output characteristic is realized, the power consumption is limited and the linearity is reduced. In the required wireless equipment, the characteristics are made uniform and the performance is improved.

[Brief description of drawings]

FIG. 1 is a principle block diagram of the present invention.

FIG. 2 is a diagram showing an embodiment of the present invention.

FIG. 3 is a diagram showing a configuration example of a conventional power amplifier.

FIG. 4 is a diagram illustrating a problem of a conventional power amplifier.

[Explanation of symbols]

 11 Amplification Means 13 Amplitude Fluctuation Extraction Means 15 Amplitude Fluctuation Detection Means 17 Linear Compensation Means 19 Control Means 21 Switches 22 Semi-Fixed Resistors 23 Setting Terminals 31 Power Amplifiers 32 Waveform Generation Circuits 33 Modulators 34 Saturation Amplification Circuits 35 Couplers 36 Diode 37 Differential Amplifier 38 Envelope Generating Circuit 39 Adder 40 Drain Voltage Control Circuit

Claims (1)

[Claims] 1. An amplification means (11) having a non-linear input / output characteristic and amplifying the power of an input signal to a predetermined output power level to obtain an output signal, and the input signal being modulated by transmission information. Amplitude variation extraction means (13) for extracting the amplitude variation associated with the gain at a level proportional to the gain of the amplification means (11), and amplitude for detecting the amplitude variation of the output signal by envelope detection. A variation detecting means (15), a difference between the amplitude variation extracted by the amplitude variation extracting means (13) and the amplitude variation detected by the amplitude variation detecting means (15), and the amplifying means ( 11) which is negatively fed back to the linear compensating means (17) for linearly compensating the input / output characteristic, wherein the amplifying means () in the variable range of the difference negatively fed back by the linear compensating means (17) 1 input signal level) - in accordance with the change of the phase characteristics of the output signal, the negative feedback of a feedback path power characterized by comprising an intermittent control means (19) amplifier.