JP2001326541A - Device for changing amplitude and phase - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an amplitude and phase changing device that realizes distortion compensation, etc., with high accuracy by realizing control of the amplitude and phase of a signal with high accuracy. SOLUTION: When a predistortion circuit 3, for instance, changes the amplitude and phase of a transmission signal, a distributing means 21 distributes the transmission signal into a plurality of parts (two), phase shifting means 22 and 23 change the phases of the respective distributed signals, a synthesizing means 24 combines these distributed signals whose phases are changed to acquire a synthetic signal having an amplitude variation and a phase variation corresponding to the phase variations of the respective distributed signals by the means 22 and 24. Thus, distortion generated in an amplifier 4 can be compensated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an amplitude / phase changing device for changing the amplitude and phase of a signal, and a predistortion type distortion compensating device for changing the amplitude and phase of a signal to compensate for distortion generated in an amplifier. In particular, the present invention relates to a technique capable of adjusting an amplitude and a phase only by adjusting a phase of a signal.

[0002]

2. Description of the Related Art For example, portable telephone systems and PHS (Pers
2. Description of the Related Art In a wireless base station device or the like provided in a mobile communication system such as an onal handy phone system, a signal (transmission signal) to be wirelessly transmitted is amplified by an amplifier (for example, a power amplifier (P
A: Power Amplifier)), but there is a problem of deterioration of the transmission spectrum due to the nonlinearity of the amplifier. Such degradation of the transmission spectrum may be caused, for example, by the fact that the power leaked to the frequency band adjacent to the original frequency band of the transmission signal (adjacent channel leakage power) is generated by the amplifier, for example, the signal components of the transmission signal The distortion is generated due to mutual modulation and distortion (intermodulation distortion) occurring in the amplifier.

FIG. 8 shows the amplitude and phase of a signal.
An example of the input / output characteristics of the nonlinear amplifier is shown. The horizontal axis of the graph shown in FIG. 7 indicates the amplitude (input amplitude) of the signal input to the amplifier, and the vertical axis indicates the amplitude (output amplitude) and phase (output phase) of the signal output from the amplifier. .
As shown in the figure, the output amplitude is ideally increased in proportion to the input amplitude as shown in the "ideal characteristic" in the figure. As shown in “AM-AM Conversion”, there is a saturation characteristic of output amplitude known as AM-AM conversion. Therefore, when the input amplitude is sufficiently smaller than the "saturation point" in the figure, the input / output amplitude characteristic becomes a straight line, but the output amplitude becomes saturated as the input amplitude approaches the "saturation point". ,
As the input amplitude further increases, the deviation from the “ideal characteristic” increases as the output amplitude increases.

Similarly, as for the output phase, it is ideal that the output phase does not change irrespective of the input amplitude. However, in actuality, as shown in "AM-PM conversion" in FIG. There is a change in output phase with input amplitude known as PM conversion. For this reason, when the input amplitude is sufficiently smaller than the “saturation point” in the figure, the shift between the input phase and the output phase becomes zero, but the input amplitude becomes “saturation point”.
, The output phase starts to rotate, and when the input amplitude further increases, the rotation amount (change amount) of the output phase increases as the output amplitude increases. Due to such signal distortion due to the output amplitude saturation characteristic and the output phase rotation characteristic, the above-described degradation of the transmission spectrum is caused.

[0005] As an example of a method for improving such deterioration of the transmission spectrum, a pre-distortion method for compensating for nonlinearity of an amplifier by previously deforming a signal input to the amplifier at a stage preceding the amplifier is known. . In this predistortion method, distortion having characteristics opposite to amplitude and phase with respect to distortion generated in an amplifier (characteristics of suppressing each other when summed up) is given to a signal to be amplified. The characteristics of the signal output from the amplifier are set to ideal characteristics.

Specifically, for an amplifier having input / output characteristics as shown in FIG. 8, for example, the input / output amplitude as shown in "AM-AM distortion compensation characteristics" in FIG. Compensating for the non-linearity of the amplifier by generating distortion in the signal before amplification having characteristics and input / output phase characteristics as shown in "AM-PM distortion compensation characteristics" in FIG. Can be. As in the case of FIG. 8, the horizontal axis of the graph shown in FIG. 9 indicates the input amplitude, and the vertical axis indicates the output amplitude and the output phase.

Next, FIG. 10 shows an example of a distortion compensating amplifier provided with a predistortion type distortion compensating circuit according to a conventional example. This distortion compensating amplifier is provided in a radio transmitting apparatus such as a base station apparatus. Have been. In this distortion compensation amplifier, the amplitude and phase of a transmission signal are controlled by a predistortion circuit 43 using a variable attenuator (ATT) 61 and a variable phase shifter 62 to perform distortion compensation.

An operation example of the distortion compensation amplifier shown in FIG. That is, in this distortion compensation amplifier, for example, a signal (transmission signal) in a radio frequency band to be transmitted is input from an input terminal R, and the transmission signal is divided into two by a distributor 41, and one of the divided signals is used for time difference adjustment. And outputs the other distributed signal to the power detector 46 via the delay line 42 of FIG. The power detector 46 detects the power level (envelope level) of the envelope (envelope) of the input distribution signal, and the A / D converter 4
7 converts the detected envelope level into digital data (envelope data) and outputs it to the control circuit 52.

The storage circuit 51 stores a distortion compensation value table. In this distortion compensation value table, a distortion compensation value relating to amplitude is set as an attenuation value corresponding to each value of envelope data (envelope level indicated by). The stored distortion compensation value is stored as a phase shift value corresponding to each value of the envelope data. Then, the control circuit 52 reads out the attenuation value and the phase shift value corresponding to the value of the inputted envelope data from the storage circuit 51, and sends the control value (ATT control value) for realizing the attenuation value to the D / A converter 49. The control value is output to the variable attenuator 61 via the D / A converter 50 and to the variable attenuator 61 via the D / A converter 50.

The D / A converter 49 converts the ATT control value from a digital value to an analog value and outputs it to the variable attenuator 61, whereby the amount of attenuation of the variable attenuator 61 is controlled and the variable attenuator 61 is controlled. Reference numeral 61 attenuates the transmission signal (the one distribution signal) by an attenuation amount corresponding to the analog value and outputs the signal to the variable phase shifter 62. Similarly, the D / A converter 50 converts the phase shift control value from a digital value to an analog value and outputs it to the variable phase shifter 62, whereby the phase shift amount of the variable phase shifter 62 (phase change amount) ) Is controlled, and the variable phase shifter 62 changes the phase of the transmission signal by the phase shift amount corresponding to the analog value and outputs the same to the amplifier 44.

Here, the characteristics of the amplitude change given to the transmission signal by the variable attenuator 61 provided in the pre-distortion circuit 43 and the characteristics of the phase change given to the transmission signal by the variable phase shifter 62 will be described later. In this manner, the adjustment is performed so as to have the inverse characteristic as shown in FIG. 9 with respect to the AM-AM conversion or AM-PM conversion of the amplifier 44.

The amplifier 44 outputs the input transmission signal to the distributor 45, and the distributor 45 converts the amplified transmission signal into two.
The signal is distributed and a part of the transmission signal is output to the distortion detection circuit 48, and the remaining part is supplied from the output terminal T to the transmission antenna. Here, for example, when the input amplitude of the amplifier 44 is large, distortion of the amplitude and phase occurs in the amplifier 44, but when the distortion compensation by the predistortion circuit 43 is appropriately performed, the output from the amplifier 44 is The distortion contained in the signal is suppressed to a small level (ideally, to zero), whereby the degradation of the spectrum of the transmission signal output from the amplifier 44 can be reduced.

The distortion detection circuit 48 detects the level of distortion generated in the transmission spectrum due to nonlinear distortion or the like generated by the amplifier 44 and notifies the control circuit 52 of the level. Here, the distortion detection circuit 48 can be configured using, for example, a band-pass filter that extracts only the adjacent frequency band of the transmission signal. That is, as an example, the level of a signal that has passed through such a band-pass filter is determined. It is detected as the level of distortion. The control circuit 52 updates the attenuation value and the phase shift value stored in the distortion compensation value table of the storage circuit 51 so that the notified distortion level becomes, for example, the minimum.
Appropriate distortion compensation is realized.

Next, an example of a method of updating the phase shift value stored in the distortion compensation value table will be described with reference to FIG. Here, an example of a method of updating the phase shift value is shown as a representative of the phase shift value, but a similar update method can be applied to the attenuation value stored in the distortion compensation table. The horizontal axis of the graph shown in the figure is the amplitude of the transmission signal (input amplitude)
The vertical axis indicates the phase (output phase) of the transmission signal. Here, the amplitude on the horizontal axis uniquely corresponds to, for example, the envelope level of the transmission signal, and corresponds to the address value of the distortion compensation value table.

First, assuming that the amplifier 44 has perfect linear characteristics, the curve showing the output phase characteristic (output phase characteristic curve) becomes constant without depending on the input amplitude. A phase shift value according to the linear characteristic (that is, a constant value independent of the input amplitude) is set as an “initial value” of the phase shift value as shown in FIG.

Next, the output phase characteristic curve is corrected from the above-mentioned "initial value" to the plus side or the minus side so that the amount of distortion detected by the distortion detecting circuit 48 is reduced, so that the corrected Are sequentially updated as the latest value with the phase shift value according to the output phase characteristic curve. Here, such an update is performed, for example, in order to improve reliability, the average value of the result of measuring the level of the distortion detected by the distortion detector 48 for a certain period (for example, a period of about 100 μs or more) or the like. Is performed so as to reduce the distortion amount.

As described above, by shifting the latest value of the phase shift value to the + side or the − side, the direction in which the level of the distortion detected by the distortion detecting circuit 48 decreases is selected and stored in the distortion compensation value table. By successively updating the phase shift values, the distortion compensation that finally stores the phase shift value that can minimize the phase distortion generated in the amplifier 44 (ideally, to zero) can be achieved. You can get a value table.

In FIG. 1, an example of an output phase shift characteristic curve when corrected to the + side is shown as a "distortion compensation value table 1", and an output phase shift characteristic when corrected to the-side. An example of the curve is shown as “distortion compensation value table 2”, and “AM−” is similar to that shown in FIG.
Further, correcting the output phase characteristic curve so as to reduce the distortion level is equivalent to bringing the curve closer to the above-mentioned "AM-PM distortion compensation characteristic". Specifically, a curve approximating the “AM-PM distortion compensation characteristic” is obtained as an output phase characteristic curve.

According to the configuration of the pre-distortion type distortion compensating circuit as described above, for example, it is possible to directly compensate for a transmission signal in a radio frequency band or to simultaneously compensate for a plurality of carrier signals, for example. Compared to a distortion compensation configuration using a feed-forward method that requires two amplifiers (a main amplifier for amplifying a transmission signal and an auxiliary amplifier for amplifying a distortion signal), the efficiency of the amplifier can be improved (for example, (transmission power / power consumption). ) Can be improved.

However, in the conventional pre-distortion type distortion compensating circuit as shown in FIG. 10, the following description will be made due to the use of the variable attenuator (in this case, the variable attenuator 61). Such a problem has occurred.
That is, as a variable attenuator used in a pre-distortion type distortion compensation circuit, in order to realize a required distortion characteristic that can suppress distortion due to adjacent channel leakage power or intermodulation generated in an amplifier, for example, 3
It is necessary to have a device capable of performing control following the envelope of a transmission signal with an accuracy of about 0.1 dB in a control range of about dB to 5 dB. However, in practice, generally used variable attenuators are generally designed on the assumption that they are used in a rather wide dynamic range (for example, several tens of dB), and the high precision as described above is used. In practice, it is very difficult to realize a variable attenuator capable of performing various controls.

In the variable attenuator, the amount of attenuation is changed to 0.5 degree (°) / dB to several degrees / d.
There is a problem that the phase rotation of B is generated in the signal. The numerical value of 0.5 degree (°) / dB to several degrees / dB is, for example, the width of the AM-PM conversion compensated by the subsequent variable phase shifter (the variable phase shifter 62 in FIG. 10). This is a value that cannot be ignored compared to about 10 degrees (accuracy is within 1 degree, for example). In such a conventional configuration, it is necessary for the variable phase shifter to perform the phase control in consideration of the phase distortion generated in the variable attenuator in accordance with the control of the attenuation of the variable attenuator. Therefore, generation of the distortion compensation value table for the phase shift value is very complicated and difficult.

For reference, an example of a conventional configuration for controlling the amplitude and phase of a signal like the pre-distortion circuit 43 shown in FIG. 10 will be introduced below. For example, in a "vector modulation type phase shifter" described in Japanese Patent Application Laid-Open No. 5-199002, an input signal is distributed by a hybrid coupler into a signal shifted by 0 ° and a signal shifted by 90 ° to adjust two vectors. Attenuator attenuates each of these two distribution signals and controls their respective phases, and combines the output signals from the two vector adjusters with a combiner to control the amplitude and phase of the input signal. The obtained synthesized signal is obtained.

In a "phase shift circuit" described in, for example, JP-A-6-244604, an input signal is divided by a distributor, and the phases of the divided signals are divided by transmission lines each having a predetermined electrical length. By controlling and alternately switching the plurality of divided signals and outputting the divided signals to the combiner, a combined signal whose phase is controlled with respect to the input signal is obtained.

In a "phase shifter" described in, for example, JP-A-11-17464, an input signal is divided into two by a power divider, and each of the two divided signals is divided by two variable attenuators. Is attenuated, and these two attenuated signals are combined by a directional coupler at mutually different phases, thereby obtaining a combined signal in which the phase of the input signal is controlled with a phase shift amount corresponding to the attenuation amount of the variable attenuator. Is done. This publication also discloses a configuration example of the above-described distortion compensation circuit using the feedforward method.

In a "vector combining type phase modulator" described in, for example, Japanese Patent Application Laid-Open No. 5-1528851, an input signal is divided into two in-phase signals by a power divider, and the distribution signal is divided for each divided signal. The signal is divided into an in-phase signal and an in-phase signal by a power divider, one is amplified by a variable gain amplifier, and the other is amplified by a fixed gain amplifier, and these two amplified signals are combined by a power combiner. By combining the two combined signals obtained for the distribution signal with a phase difference of 90 ° by the power combiner, a combined signal in which only the phase is controlled without changing the amplitude of the input signal is obtained.

[0026]

As described in the above conventional example, in the conventional pre-distortion type distortion compensating circuit,
For example, since a variable attenuator and a variable phase shifter were provided to adjust the amplitude and phase of a signal by each, it was difficult to realize high-precision adjustment as described above. .

The present invention has been made in order to solve such a conventional problem, and is suitable for use in, for example, distortion compensation by a predistortion method as described above. It is an object of the present invention to provide an amplitude and phase changing device that causes the amplitude and phase to be changed. It is another object of the present invention to provide a pre-distortion type distortion compensator capable of controlling the amplitude and phase with high accuracy when compensating for distortion generated in an amplifier. In the present invention, it is possible to change the amplitude and phase of a signal using a novel and highly useful configuration.

[0028]

In order to achieve the above object, an amplitude and phase changing apparatus according to the present invention changes the amplitude and phase of a signal as follows. That is, the distributing means distributes the signal into a plurality of signals, the phase shifting means changes the phase of each of the divided signals, and the synthesizing means synthesizes the plurality of divided signals whose phases have been changed, and A composite signal having an amplitude change amount and a phase change amount according to the phase change amount of the distribution signal is obtained.

The present invention utilizes the fact that, when the distribution signals are changed in phase and synthesized, the amplitude and phase of the synthesized signal change in accordance with the phase change amount of each distribution signal. Therefore, for example, it is possible to obtain a composite signal in which both the amplitude and the phase are controlled only by controlling the phase of each distribution signal. Also, for example, since only the phase control of the signal needs to be performed, high-precision amplitude control is performed. And phase control can be realized.

The predistortion type distortion compensator according to the present invention compensates for distortion generated in an amplifier for amplifying a signal as follows. That is, the level detection means detects a signal level corresponding to the level of the signal input to the amplifier, the distribution means divides the signal input to the amplifier into a plurality, and the phase shift means detects the signal level based on the detection result of the level detection means. And a synthesizing means for synthesizing the plurality of distribution signals whose phases have been changed, and an amplitude change amount and a phase change amount corresponding to the phase change amount of each distribution signal by the phase shift means. Obtain a composite signal having a quantity.

In such a configuration, the predistortion type distortion compensator according to the present invention adjusts the phase change amount of each divided signal by the phase shift means to suppress the amplitude change amount and the distortion generated in the amplifier. A synthesized signal having a phase change amount is obtained by the synthesizing means, and the synthesized signal is output to the amplifier.

In the present invention, when an amplitude change or a phase change that suppresses the distortion generated in the amplifier is applied to the signal input to the amplifier, such an amplitude change and a phase change and the distortion generated in the amplifier are generated. This is based on the fact that the distortion contained in the signal output from the amplifier is reduced by suppressing each other. Further, in the present invention, in response to the magnitude of the amplitude distortion and phase distortion generated in the amplifier depending on the level of the signal input to the amplifier,
The configuration is such that the phase of each distribution signal is changed based on the detection result of the signal level.

Therefore, for example, it is possible to obtain a composite signal in which both the amplitude and the phase are controlled by merely controlling the phase of each distribution signal, and it is also necessary to perform only the phase control of the signal. It is possible to realize an accurate amplitude control and phase control. Then, by such high-precision amplitude control and phase control, a synthesized signal having an amplitude change amount and a phase change amount that suppresses distortion generated in the amplifier based on the signal level detection result is obtained, and the synthesized signal is obtained. Is output to the amplifier, so that highly accurate distortion compensation by the predistortion method can be realized.

Here, the signal level detected by the level detecting means may be any signal level that can predict the magnitude of the amplitude distortion or phase distortion generated in the amplifier, for example. The power value and the signal amplitude value can be detected as a signal level.
Similarly, the “signal level corresponding to the level of the signal input to the amplifier” may be any signal that can predict the magnitude of amplitude distortion or phase distortion generated in the amplifier, for example. For example, not only the mode of detecting the level of the signal immediately before input to the amplifier, but also the mode of fake detection of the level of the signal input to the amplifier by detecting the level of one of the distribution signals, for example. It can also be used.

The method of "adjusting the amount of phase change of each distribution signal by the phase shifting means" is not particularly limited. For example, by detecting the magnitude of distortion included in the signal output from the amplifier, A method of constantly adjusting the amount of phase change of each divided signal by the phase shift means so as to reduce the distortion can be used, and as another example, the phase change of each divided signal is While the adjusted phase change amount is stored using a method of constantly adjusting the amount, a method of using the stored phase change amount as it is when the required accuracy of distortion suppression is obtained can be used. . In addition, as another example, the amount of phase change of each distribution signal used corresponding to various values of the signal level detected by the level detection unit is obtained in advance by an experiment or the like,
It is also possible to adjust and set in advance the phase change amount of each distribution signal by the phase shifting means so as to match the obtained phase change amount.

As a mode for suppressing the distortion generated in the amplifier, for example, it is preferable to cancel the distortion generated in the amplifier to zero. However, in the present invention, not only such a mode but also, for example, a practical Other modes may be used as long as the distortion can be reduced to the extent effective above. That is, the "suppressing distortion" mode referred to in the present invention includes not only the mode in which the distortion is reduced to zero, but also the mode in which the distortion is reduced to a practically effective level.

[0037]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment according to the present invention will be described with reference to the drawings. Hereinafter, an embodiment of the pre-distortion type distortion compensating apparatus according to the present invention will be described, and also an embodiment of the amplitude / phase changing apparatus according to the present invention will be described. First, a first embodiment according to the present invention will be described with reference to the drawings. FIG. 1 shows an example of a distortion compensating amplifier including a pre-distortion type distortion compensating circuit which is an embodiment of a pre-distortion type distortion compensating apparatus according to the present invention. Wireless transmission device.

As shown in the drawing, the distortion compensating amplifier of the present embodiment includes a distributor 1 on the input side, a delay line 2, a predistortion circuit 3, an amplifier 4, and a distributor 5 on the output side.
, A power detector 6, an A / D converter 7, a distortion detection circuit 8, two D / A converters 9, 10, and a storage circuit 11.
And a control circuit 12. Further, the pre-distortion circuit 3 of the present example includes a distributor 21 and two variable phase shifters (a first variable phase shifter 22 and a second variable phase shifter 23).
And a synthesizer 24. In the distortion compensation amplifier of this example, a signal (transmission signal) in a radio frequency band to be transmitted is input from an input terminal P, and after the transmission signal is distortion-compensated and amplified, the amplified transmission signal is output to an output terminal Q. To the transmitting antenna.

Hereinafter, a configuration example and an operation example of each of the above-described processing units 1 to 12 will be described. The splitter 1 is composed of, for example, a power splitter, splits a transmission signal input from the input terminal P into two signals, outputs one split signal to the delay line 2, and outputs the other split signal. Is output to the power detector 6.

The delay line 2 has a function of delaying the transmission signal (the one distribution signal) input from the distributor 1 for a predetermined time and outputting the transmission signal to the distributor 21 of the predistortion circuit 3. Here, as the predetermined time, for example, a value for adjusting a time difference between the timing of the signal processing by the pre-distortion circuit 3 and the timing of the control processing by the control circuit 12 and the like described later is set. It is ensured that the signal portion to be detected is processed by the pre-distortion circuit 3 at the timing when the pre-distortion circuit 3 is controlled by the control circuit 12 based on the signal level detected by the power detector 6. Is set. Although the signal is delayed using the delay line 2 in this example, other signal delay means may be used as long as the signal can be delayed.

The pre-distortion circuit 3 includes a delay line 2
AM of the subsequent amplifier 4 for the transmission signal input from the
-Amplitude change and AM-PM corresponding to inverse characteristics of AM conversion
It has a function of giving a phase change corresponding to the inverse characteristic of the conversion and outputting the transmission signal whose amplitude and phase have been changed in this way to the amplifier 4. A more detailed configuration example and operation example of the pre-distortion circuit 3 will be described later.

The amplifier 4 is composed of, for example, a power amplifier. The amplifier 4 amplifies a transmission signal output from the synthesizer 24 of the predistortion circuit 3 (a synthesized signal described later by the synthesizer 24) and outputs the amplified signal to the distributor 5. It has the function to do. Here, for example, when the input amplitude of the amplifier 4 is large, distortion of the amplitude and phase occurs in the amplifier 4, but when the distortion compensation by the predistortion circuit 3 is appropriately performed, the output from the amplifier 4 is output. The distortion contained in the signal is kept small (preferably to zero),
The degradation of the spectrum of the transmission signal output from the amplifier 4 can be reduced.

The distributor 5 is composed of, for example, a power distributor, and divides a transmission signal (amplified transmission signal) input from the amplifier 4 into two signals and distorts a part of the transmission signal. It has a function of outputting to the detection circuit 8 and supplying the remaining portion from the output terminal Q to the transmitting antenna. The transmission signal supplied to the transmission antenna is wirelessly transmitted from the transmission antenna to a wireless communication device that is a transmission partner.

The power detector 6 detects the power level (envelope level) of the envelope (envelope) of the signal (the other distributed signal) input from the distributor 1, and detects the detected envelope level (analog value). It has a function of outputting to the A / D converter 7. The A / D converter 7 is
It has a function of converting the envelope level input from the power detector 6 into digital data (envelope data) and outputting it to the control circuit 12. Here, the envelope data is data indicating the power level detected by the power detector 6 described above.

The distortion detection circuit 8 generates a distortion component generated by the amplifier 4 or the like from the signal (part of the transmission signal) input from the distributor 5 (that is, the distortion provided by the pre-distortion circuit 3 and the distortion generated by the amplifier 4). And a function of detecting the level (for example, power value or amplitude value) of the distortion component and outputting a signal indicating the detection result to the control circuit 12. Here, the distortion detection circuit 8 can be configured by using, for example, a band-pass filter that extracts only the adjacent frequency band of the transmission signal. That is, as an example, the level of a signal that has passed through such a band-pass filter is determined. It is detected as the level of distortion.

The D / A converter 9 has a control circuit 12 which will be described later.
Has a function of converting a first control value, which is input as a digital value from, into an analog value and outputting the analog value to the first variable phase shifter 22 of the predistortion circuit 3. Similarly, D / A
The converter 10 has a function of converting a second control value input as a digital value from the control circuit 12 described later into an analog value and outputting the analog value to the second variable phase shifter 23 of the predistortion circuit 3.

Here, in the present embodiment, as will be described later, both the amplitude and the phase of the transmission signal are controlled by controlling the phase shift amount (phase change amount) of the two variable phase shifters 22 and 23. The phase shift amount of each of the variable phase shifters 22 and 23 is controlled to a phase shift amount according to the envelope level detected by the power detector 6.

In response to this, the storage circuit 11 stores a phase shift value table. The phase shift value table stores a first variable corresponding to the envelope data (envelope level indicated by the above). The phase shift value to be set in the phase shifter 22 is stored as the first phase shift value and the second
A phase shift value to be set in the variable phase shifter 23 is stored as a second phase shift value. Note that the storage circuit 11 is configured by, for example, a memory that stores information. In this example, the value of the above-described envelope data is used as an address, and a first area corresponding to the value is stored in a storage area corresponding to the address.
The phase shift value and the second phase shift value are stored.

The control circuit 12 reads out the first phase shift value and the second phase shift value corresponding to the envelope data input from the A / D converter 7 from the storage circuit 11 and realizes the first phase shift value. A control value (first control value) is output to the first variable phase shifter 22 via the D / A converter 9 and the second variable
It has a function of outputting a control value (second control value) for realizing the phase shift value to the second variable phase shifter 23 via the D / A converter 10.

Further, the control circuit 12 sets the distortion level notified from the distortion detection circuit 8 to, for example, the minimum level.
It has a function of updating the first phase shift value and the second phase shift value stored in the phase shift value table of the storage circuit 11, thereby realizing appropriate distortion compensation. The method of updating the first phase shift value and the second phase shift value stored in the phase shift value table is not particularly limited, and as an example, an update similar to that shown in FIG. Ways can be used.
In addition, such an update is performed, for example, by improving the average value of the results of measuring the level of the distortion detected by the distortion detector 8 for a certain period (for example, a period of about 100 μs or more) in order to improve reliability. The distortion is preferably performed so as to reduce the amount of distortion.

In this example, by updating such a phase shift value table, the pre-distortion circuit 3
The characteristics of the amplitude change amount and the phase change amount given to the transmission signal due to
The conversion is adjusted so as to have, for example, the inverse characteristic shown in FIG.

Next, a configuration example and an operation example of each of the processing units 21 to 24 provided in the predistortion circuit 3 will be described. The splitter 21 is composed of, for example, a power splitter. The splitter 21 splits a transmission signal input from the delay line 2 into two signals, for example, and splits one of the split signals into the first variable phase shifter 2.
2 and a function of outputting the other distribution signal to the second variable phase shifter 23.

The first variable phase shifter 22 receives the one distribution signal from the distributor 21 and receives the D / A converter 9
And the function of changing the phase of the distribution signal by the amount of phase change indicated by the first control value, and outputting the distribution signal after the change to the combiner 24. ing. Similarly, the second variable phase shifter 23 receives the other distribution signal from the distributor 21 and
The second control value is input from the A converter 10, the phase of the distribution signal is changed by a phase change amount indicated by the second control value, and the changed distribution signal is output to the combiner 24. Has a function.

The combiner 24 is composed of, for example, a power combiner, and outputs the phase-changed distributed signal input from the first variable phase shifter 22 and the phase-changed signal input from the second variable phase shifter 23. And a function of outputting the synthesized signal to the amplifier 4. Here, the amplitude and the phase of the synthesized signal are different from the amplitude and the phase of the transmission signal before being input to the pre-distortion circuit 3 according to the amount of phase change by the variable phase shifters 22 and 23 described above. Can only be changed.

This will be specifically described below. FIG. 2 illustrates an example of a signal output from the first variable phase shifter 22 (“phase shifter 1 output”) and a signal output from the second variable phase shifter 23 on a plane using polar coordinates. An example of the signal (“phase shifter 2 output”), and when these two output signals are combined by the combiner 24 (in the example of FIG. 3, the vector combination is shown), the signal is output from the combiner 24. An example of the combined signal (“phase shifter combined output”) is shown in FIG.

In the example shown in the figure, it is assumed that the amount of phase change by the first variable phase shifter 22 is θ1 and the amount of phase change by the second variable phase shifter 22 is θ2. , Θ2, the amplitude of the combined signal is, for example, in the range of 0 to 2 times the amplitude of the transmission signal before distribution by the distributor 21 (hereinafter referred to as the transmission signal before distortion compensation). For example, the phase of the combined signal can be arbitrarily changed in the range of 0 ° to 360 ° with respect to the phase of the transmission signal before distortion compensation. is there.

As an example, FIG. 3 shows that θ1 = −
An example of the amplitude change amount of the combined signal with respect to the transmission signal before distortion compensation when θ1 is changed in the range of 0 ° to 40 ° as θ2 is shown. Here, the horizontal axis of the graph shown in FIG. 7 indicates the value of θ1 (= −θ2) (° (deg)), and the vertical axis indicates the amplitude value of the synthesized signal when θ1 = 0 as a reference (0 dB). 5 shows the amplitude value (dB) of the combined signal when this is done.

In this case, as shown in FIG.
By changing (= -θ2) in the phase range of 40 ° (0 ° to 40 °), the attenuation of the combined signal can be reduced to about 2.3 dB.
In the amplitude range (0 dB to about 2.3 dB), and the amplitude change amount per unit phase change is (about 0.1 dB).
(dB / 1 °) or less. Then, for example, by limiting the variable phase shift range of each of the variable phase shifters 22 and 23 to a predetermined range, it is easy to suppress the accuracy of the phase change amount by each of the variable phase shifters 22 and 23 to within 1 °. Since it can be realized, it is possible to control the amplitude value of the composite signal with an accuracy of about 0.1 dB by controlling the amount of phase change of each of the variable phase shifters 22 and 23 in steps of 1 °.

FIGS. 4 to 6 show the first variable phase shifter 2.
2 and the phase change amount θ2 by the second variable phase shifter 23.
Is changed in the range of −40 ° to 0 °, an example of the amplitude characteristic and an example of the phase characteristic of the combined signal output from the combiner 24 are shown. Note that the amplitude characteristics show the amplitude change characteristics (gain characteristics) when the amplitude value of the combined signal when θ1 = 40 ° and θ2 = −40 ° is the reference (0 dB). .

FIG. 4A, FIG. 5A and FIG.
The vertical axis of the graph in (a) represents the amplitude change (dB) and phase change (° (de) of the combined signal with respect to the transmission signal before distortion compensation.
g)), and in particular, in FIG. 4A, a scale (dB) relating to the amplitude change amount is shown on the left axis.
In FIGS. 5A and 6A, the scale (° (deg)) relating to the phase change amount is shown on the left axis.

FIG. 4B, FIG. 5B and FIG.
The vertical axis of the graph in (b) indicates the amount of phase change (° (deg)) by each of the variable phase shifters 22 and 23. Also, the horizontal axis of the graph in FIGS. 4 (a), 5 (a) and 6 (a) and the horizontal axis of the graphs in FIGS. 4 (b), 5 (b) and 6 (b) Indicate a value corresponding to the envelope level detected by the power detector 6 (a value corresponding to the input amplitude of the amplifier 4), and the value corresponds to, for example, the phase shift stored in the storage circuit 11 as described above. It uniquely corresponds to the address value in the value table.

Specifically, in the examples of FIGS. 4A and 4B,
The phase change amounts θ1 and θ2 by the respective variable phase shifters 22 and 23 are controlled by setting θ1 = −θ2. In this case, the phase gain of the synthesized signal is fixed (for example, 0 °), and the amplitude gain of the synthesized signal is approximately 2.3dB range (0dB to about 2.3dB)
Can be changed. 5 (a) and 5 (b)
In the example, the second variable phase shifter 23 is fixed at θ1 = 40 °.
In this case, the amplitude gain of the synthesized signal is substantially constant (for example, approximately 0 dB), and the phase of the synthesized signal is in the range of about 20 ° (0 ° to about 20 °).
°).

FIGS. 6A and 6B show the case where θ1 and θ2 are controlled by imitating the inverse characteristics of the AM-AM conversion characteristics and the AM-PM conversion characteristics of the actual amplifier 4. In this case, the phase change amount θ1 by the variable phase shifters 22 and 23 is set to a value as shown in FIG.
By controlling θ2, as shown in FIG. 9A, for example, a curve similar to the AM-AM distortion compensation characteristic curve shown in FIG. 9 is realized as the characteristic curve of the amplitude gain of the composite signal. And the characteristic curve of the amount of phase change of the synthesized signal is, for example, the AM curve shown in FIG.
-A curve similar to the curve of the PM distortion compensation characteristic can be realized.

As described above, in this example, the phase of the two variable phase shifters 22 and 23 is determined using the first and second phase shift values according to the level of the transmission signal to be amplified by the amplifier 4. By controlling the amount of change, a desired amplitude change and phase change can be given to the composite signal, whereby the distortion compensation characteristic corresponding to the AM-AM conversion characteristic and the AM-PM conversion characteristic of the amplifier 4 used is obtained. Is provided to the transmission signal.

In the present embodiment, as a preferred embodiment, the phase shift control range of a plurality of (two in this embodiment) variable phase shifters 22 and 23 is set as the phase shift control range of each of the variable phase shifters 22 and 23. A range in which a part or end of the range (boundary value of the range) overlaps (in this example, θ1 = 0 ° to 40 °, θ2 =
(−40 ° to 0 °), but other setting methods may be used.

As described above, in the distortion compensation amplifier of this embodiment,
When amplifying and outputting the signal in the radio frequency band transmitted by the radio transmitting apparatus by the amplifier 4,
Since the predistortion circuit 3 provided at an earlier stage performs amplitude adjustment and phase adjustment for compensating for distortion generated in the amplifier 4 on the transmission signal, the distortion included in the transmission signal output from the amplifier 4 is reduced. It can be small (preferably zero).

At this time, in the pre-distortion type distortion compensating circuit of the present example comprising the above-described pre-distortion circuit 3 and the respective processing units 1, 5 to 12 constituting the control system,
For example, it is possible to obtain a synthesized signal in which both the amplitude and the phase of the transmission signal are controlled by merely controlling the amount of phase change by each of the variable phase shifters 22 and 23. For example, if only the phase control of the signal is performed Since it is good, it is possible to realize high-precision amplitude control and phase control, and in particular, it is possible to obtain an effect of improving the accuracy of amplitude control, for example, higher than in the past.

By such high-precision amplitude control and phase control, as described above, the synthesis having the amplitude change amount and the phase change amount for suppressing the distortion generated in the amplifier 4 based on the detection result of the signal level. Signal can be obtained,
By outputting the synthesized signal thus obtained to the amplifier 4, highly accurate distortion compensation by the predistortion method can be realized.

As described above, in the distortion compensation amplifier of this embodiment, not only the phase control of the transmission signal but also the amplitude control can be performed only by the control of the variable phase shifters 22 and 23. It is possible to improve the accuracy of the control, for example, as compared with the related art. Further, when distortion compensation is performed by the pre-distortion method as in this example, for example, a highly efficient distortion compensation amplifier (having a large transmission power to power consumption ratio) can be realized. Note that, for example, a commercially available phase shifter can be used as the variable phase shifters 22 and 23, thereby realizing highly accurate distortion compensation.

Here, in this embodiment, the function of the power detector 6 detecting the signal level corresponding to the level of the transmission signal input to the amplifier 4 constitutes the level detecting means according to the present invention. Further, in this example, the distributor 21 divides the transmission signal input to the amplifier 4 into a plurality of (two in this example) signals at a stage preceding the amplifier 4, so that the distribution means according to the present invention is configured. Have been.

In this embodiment, the first variable phase shifter 22 and the second variable phase shifter 23 are controlled according to the control of the control circuit 12 and the like based on the detection result of the power detector 6, for example.
The function of changing the phase of each distribution signal distributed by the distributor 21 constitutes a phase shift means according to the present invention. Further, in this example, the combiner 24 combines the plurality of distribution signals whose phases have been changed by the respective variable phase shifters 22 and 23, so that the phase change of the respective distribution signals by the respective variable phase shifters 22 and 23 is performed. The function of acquiring a synthesized signal having an amplitude change amount and a phase change amount according to the amount constitutes a synthesizing unit according to the present invention.

With such a configuration, for example, the amplitude and phase changing device according to the present invention can change the amplitude and phase of the signal. Further, with such a configuration, for example, in the pre-distortion type distortion compensating apparatus according to the present invention, the amplitude change amount and the phase change amount that suppress the distortion generated in the amplifier by adjusting the phase change amount of each distribution signal by the phase shift unit are adjusted. By obtaining a synthesized signal having a change amount by the synthesizing unit and outputting the synthesized signal to the amplifier, it is possible to compensate for distortion generated in the amplifier that amplifies the signal.

Next, a second embodiment according to the present invention will be described with reference to FIG. FIG. 1 shows an example of a distortion compensating amplifier including a pre-distortion type distortion compensating circuit which is an embodiment of a pre-distortion type distortion compensating device according to the present invention. Wireless transmission device.

As shown in the figure, the distortion compensating amplifier of this embodiment has, for example, an input terminal P similar to that shown in FIG. 1 of the first embodiment, a distributor 1 on the input side, a delay Line 2,
A pre-distortion circuit 3, an amplifier 4, a distributor 5 on the output side, and an output terminal Q provided with a distributor 21 and two variable phase shifters 22, 23 and a combiner 24 are provided. A control system having a configuration different from that of the first embodiment is provided. In this example, for convenience of explanation, components 1 to 5, 21 to 24, P, and Q similar to those shown in FIG. 1 of the first embodiment are the same as those used in FIG. , And detailed description of these similar components will be omitted.

The above-described control system of the present embodiment includes the power detector 3
1, an A / D converter 32, a distortion detection circuit 33, two D / A converters 34 and 35, and two storage circuits 36 and 37.
, A distortion compensation algorithm circuit 38, and the two distributors 1 and 5 described above. In the following, components 31 to 31 that perform operations similar to those of the first embodiment will be described.
Detailed description of 35 is omitted.

That is, the power detector 31 has a function of detecting the envelope level of the signal in the radio frequency band input from the distributor 1, and the A / D converter 32 digitizes the envelope level, The envelope data obtained by the digitization is stored in two storage circuits 3
6 and 37. The distortion detection circuit 33 has a function of detecting the level of distortion included in the signal input from the distributor 5 and outputting the detection result to the distortion compensation algorithm circuit 38.

The D / A converter 34 has a function of converting a first control value output as an analog value from a storage circuit 36 described later into a digital value and outputting the digital value to the first variable phase shifter 22. Similarly, the D / A converter 35 has a function of converting a second control value output as an analog value from a storage circuit 37 described later into a digital value and outputting the digital value to the second variable phase shifter 23. I have.

In this embodiment, the same number of storage circuits 36 and 37 as the number of variable phase shifters 22 and 23 (two in this embodiment) are provided for each variable phase shifter 22 and 23. Thus, the phase shift values to be set for each of the variable phase shifters 22 and 23 are stored in separate storage circuits 36 and 37, respectively.

Specifically, one storage circuit 36 stores the first
A phase shift value table for controlling the variable phase shifter 22 is stored. The phase shift value table stores a first variable phase shifter corresponding to the envelope data (envelope level indicated by the above). A control value for realizing a phase shift value to be set to 22 is stored as a first control value. Specifically, the storage circuit 36 stores the first control value corresponding to the value in the storage area corresponding to the address using the value of the envelope data as an address.
When envelope data is input from the D converter 32, the first control value stored at the address position corresponding to the value of the envelope data is read out and the D / A converter 34 is read.
It has the function of outputting to

Similarly, the other storage circuit 37 stores a phase shift value table for controlling the second variable phase shifter 23, and the phase shift value table stores the above-mentioned envelope data (shown by the envelope data). A control value for realizing a phase shift value to be set in the second variable phase shifter 23 is stored as a second control value in association with the corresponding envelope level. Specifically, the storage circuit 37 stores the second control value corresponding to the value in the storage area corresponding to the address using the value of the envelope data as an address, and
When the envelope data is input from the converter 32, the second control value stored in the address position corresponding to the value of the envelope data is read out and output to the D / A converter 35.

Further, the distortion compensation algorithm circuit 38 uses, for example, a predetermined algorithm so that the level of the distortion detected by the distortion detection circuit 33 (in this example, for example, an average value) is minimized, for example. Each storage circuit 3
6, 37 stored in the phase shift value table stored in
It has a function of updating the control value and the second control value. The method of updating the control value by the algorithm is not particularly limited. In short, the control value for realizing the phase shift value that reduces the distortion level is stored in each of the storage circuits 36 and 37.
What is necessary is just to be set to.

As described above, also in the distortion compensating amplifier of this embodiment, for example, the same effect as that of the distortion compensating amplifier shown in the first embodiment can be obtained.
Since the control value stored in each of the storage circuits 36 and 37 is directly read out from the envelope data using the value of the envelope data output from the / D converter 32 as an address, for example, a distortion compensation algorithm circuit 38 can only spend processing power on updating the phase shift value table based on the level of distortion,
For example, higher-speed sampling processing and the like can be performed as compared with the configuration of the control system as shown in the first embodiment.

Here, the configurations of the amplitude phase shifter according to the present invention and the predistortion type distortion compensator according to the present invention are not necessarily limited to those described in the above embodiments, but various configurations may be used. You may. As an example, in the above-described embodiment, the configuration has been described in which the signal is divided into two, and the amplitude and phase of the combined signal are adjusted by changing the phase of the two divided signals and combining them. May be used to adjust the amplitude and phase of the combined signal by distributing the signals to three or more and changing the phases of the three or more divided signals and combining them.

The amplitude / phase change apparatus according to the present invention and the signal amplitude and signal phase change processing performed by the predistortion type distortion compensator according to the present invention include:
For example, in a hardware resource including a processor, a memory, and the like, the processor may be configured to be controlled by executing a control program stored in a ROM. It can also be configured as an independent hardware circuit. Further, the present invention can be understood as a computer-readable recording medium such as a floppy disk or a CD-ROM storing the above control program,
The processing according to the present invention can be performed by inputting the control program from the recording medium to the computer and causing the computer to execute the control program.

The field of application of the amplitude / phase changing apparatus according to the present invention is not particularly limited, and can be applied to, for example, various apparatuses for adjusting the amplitude and phase of a signal. The present invention can be applied to devices other than the pre-distortion type distortion compensating device as shown in the above embodiment. Similarly, the field of application of the predistortion-type distortion compensating device according to the present invention is not particularly limited, and can be applied to, for example, various devices that perform compensation for distortion generated in an amplifier. The present invention can also be applied to devices other than the wireless transmission device such as the base station device and the mobile station device as shown in the above embodiments.

[0086]

As described above, according to the amplitude / phase changing apparatus according to the present invention, when changing the amplitude and phase of a signal, the signal is divided into a plurality of signals, and the phase of each of the divided signals is changed. Are combined to obtain a combined signal having an amplitude change amount and a phase change amount corresponding to the phase change amount of each distribution signal, for example, the phase of each distribution signal , It is possible to obtain a synthesized signal in which both the amplitude and the phase are controlled, and it is possible to realize high-precision amplitude control and phase control, for example, since only the phase control of the signal needs to be performed. it can.

Further, in the pre-distortion type distortion compensator according to the present invention, when compensating for the distortion generated in the amplifier for amplifying the signal, the signal level corresponding to the level of the signal input to the amplifier is detected, and the signal is supplied to the amplifier. The input signal is divided into a plurality of signals, the phase of each of the divided signals is changed based on the result of the level detection, the plurality of divided signals whose phases are changed are combined, and the phase change amount of each divided signal is calculated. In this configuration, the amplitude change amount and the phase that suppress the distortion generated in the amplifier by adjusting the phase change amount of each distribution signal by acquiring the synthesized signal having the amplitude change amount and the phase change amount according to Since the synthesized signal having the amount of change is obtained and the synthesized signal is output to the amplifier, for example, high-precision amplitude control or phase control can be performed similarly to the above-described amplitude-phase changing device. It can be realized, which makes it possible to realize highly accurate distortion compensation.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating an example of a distortion compensation amplifier according to a first embodiment of the present invention.

FIG. 2 is a diagram for explaining an example of amplitude and phase control using two phase shifters.

FIG. 3 is a diagram illustrating an example of an amplitude change amount of a composite signal with respect to a phase change amount of two phase shifters;

FIG. 4 is a diagram illustrating an example of an amplitude change amount and a phase change amount of a composite signal with respect to a phase change amount of two phase shifters.

FIG. 5 is a diagram illustrating an example of an amplitude change amount and a phase change amount of a composite signal with respect to a phase change amount of two phase shifters;

FIG. 6 is a diagram illustrating an example of an amplitude change amount and a phase change amount of a composite signal with respect to a phase change amount of two phase shifters.

FIG. 7 is a diagram illustrating an example of a distortion compensation amplifier according to a second embodiment of the present invention.

FIG. 8 is a diagram illustrating an example of input / output characteristics of a nonlinear amplifier.

FIG. 9 is a diagram illustrating an example of a pre-distortion distortion compensation characteristic that provides an inverse characteristic of the input / output characteristic of the nonlinear amplifier.

FIG. 10 is a diagram illustrating an example of a distortion compensation amplifier according to a conventional example.

FIG. 11 is a diagram for explaining an example of a method of updating a phase shift value stored in a distortion compensation value table.

[Explanation of symbols]

1, 5, 21 · · · divider, 2 · · delay line, 3 · · pre-distortion circuit, 4 · · amplifier, 6, 31 · · ·
Power detector, 7, 32 A / D converter, 8, 33
..Distortion detection circuit, 9, 10, 34, 35 D / A converter, 11, 36, 37 storage circuit 12, control circuit 22, 23 variable phase shifter 24 Synthesizer,
38 ··· Distortion compensation algorithm circuit, P ··· Input terminal,
Q ... output terminal,

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5J090 AA01 AA41 CA21 FA19 GN03 GN05 GN06 KA00 KA15 KA16 KA23 KA34 MA11 SA14 TA01 TA02 5J091 AA01 AA41 CA21 FA19 KA00 KA15 KA16 KA23 KA34 MA11 SA14 TA01 TA02

Claims (2)

[Claims] 1. An amplitude and phase changing apparatus for changing the amplitude and phase of a signal, comprising: a distribution means for distributing a signal into a plurality of signals; a phase shift means for changing the phase of each of the divided signals; Combining means for combining a plurality of distributed signals and obtaining a combined signal having an amplitude change amount and a phase change amount according to the phase change amount of each of the divided signals by the phase shift means. Amplitude and phase change device. 2. A pre-distortion type distortion compensator for compensating for distortion generated in an amplifier for amplifying a signal, comprising: a level detecting means for detecting a signal level corresponding to a level of a signal input to the amplifier; Means for distributing the divided signals into a plurality of signals, phase shifting means for changing the phase of each of the divided signals based on the detection result of the level detecting means, and synthesizing the plurality of divided signals having changed phases. Synthesizing means for obtaining a synthesized signal having an amplitude change amount and a phase change amount according to the phase change amount of each distribution signal by the phase shift means, and adjusting the phase change amount of each distribution signal by the phase shift means. A combined signal having an amplitude change amount and a phase change amount for suppressing distortion generated in the amplifier by the combining means, and outputting the combined signal to the amplifier. Li-distortion system distortion compensation device.