JP2013058888A - Amplification device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an amplification device that keeps distortion compensation performance intact by suppressing the execution of wrong delay adjustments.SOLUTION: The amplification device for amplifying an input signal in an amplifier 2 includes: a delay section 3 for delaying the input signal; a distortion compensation control section 4 for creating correction information for compensating for a distortion generated during the amplification in the amplifier 2 on the basis of the delayed input signal and a feedback signal that is an output of the amplifier 2 fed back; a distortion compensation section 1 for applying a distortion compensation process based on the correction information to the input signal; a delay adjustment section 5 for adjusting the delay of the delay section 3 so as to reduce a degree of shift in signal waveform between the delayed input signal and the feedback signal; and a burst signal detection section 6 for detecting that the input signal includes a waveform interval having a predetermined low frequency component, and excluding each signal in the interval from the adjustment in the delay adjustment section 5.

Description

  The present invention relates to an amplifying apparatus used in a base station apparatus for mobile communication, and more particularly to an amplifying apparatus having a function of compensating for distortion generated in an amplifying circuit in amplification of a transmission signal.

  In a base station apparatus of a mobile communication system, a signal to be transmitted is input to an amplifying apparatus and amplified. In addition, in the amplifying apparatus, nonlinear distortion is generated according to the level of the input signal and the like, so that the distortion is compensated by, for example, a predistortion method.

  In the predistortion type amplifying apparatus with a distortion compensation function, for example, a distortion component generated due to the memory effect of the amplifier is compensated using a temporal difference of the result of raising the input signal to an even power. As an example, the function that multiplies the input signal by an even power, the function that delays the signal of the even power result, the function that detects the difference between the signal of the even power result and the delayed signal, and the signal of the detection result and the input signal are multiplied. And a function of multiplying the signal of the multiplication result by the distortion compensation coefficient and a function of adding the input signal and the signal of the multiplication result (see, for example, Patent Document 1).

FIG. 2 shows a configuration example of a conventional amplifying apparatus.
The amplifying apparatus of this example includes a distortion compensation unit 11, an amplifier 12, a delay unit 13, a distortion compensation control unit 14, and a delay adjustment unit 15.
The delay unit 13 delays an input signal (for example, a transmission signal).
The distortion compensation control unit 14 obtains a feedback signal obtained by feeding back the input signal delayed by the delay unit 13 and the output of the amplifier 12, and creates correction information for compensating for nonlinear distortion generated in amplification by the amplifier 12. The distortion compensation unit 11 is set.
The distortion compensator 11 performs distortion compensation processing on the input signal based on the correction information set by the distortion compensation controller 14, and outputs the input signal after distortion compensation to the amplifier 12.
The amplifier 12 amplifies the distortion-compensated input signal input from the distortion compensation unit 11 and outputs the amplified signal.
The delay adjustment unit 15 uses the delay unit 13 so that an error value indicating the degree of deviation of the waveform of each signal is reduced with respect to the feedback signal obtained by feeding back the input signal delayed by the delay unit 13 and the output of the amplifier 12. Adjust the delay amount.

The delay adjustment by the delay adjustment unit 15 will be described more specifically.
The delay adjustment unit 15 sets a delay amount obtained by adding a predetermined adjustment range value (range) (for example, 15 samples) to the currently held delay amount (delay amount at the time of performing the delay adjustment process) in the delay unit 13. After that, the amplitude information of the input signal and the amplitude information of the feedback signal are acquired in a predetermined number of samples (smp) (for example, 1024 samples), and the average amplitude level of the feedback signal is obtained by (Equation 1). Match to the average amplitude level (level correction).

（式１）において、ＦＢ＿Ｒｉ’は、レベル補正後の帰還信号の振幅情報である。
また、ＦＢ＿Ｒｉ，ＦＢ＿Ｒｊは、帰還信号の振幅情報である。
また、Ｔｘ＿Ｒｊは、送信信号の振幅情報である。

In (Expression 1), FB_Ri ′ is amplitude information of the feedback signal after level correction.
FB_Ri and FB_Rj are amplitude information of the feedback signal.
Tx_Rj is amplitude information of the transmission signal.

（式２）において、Ｅｒｒは、誤差値である。
また、ＦＢ＿Ｒｉは、帰還信号の振幅情報である。
また、Ｔｘ＿Ｒｉは、送信信号の振幅情報である。 Subsequent processing uses amplitude information of the feedback signal after level correction.
The delay adjustment unit 15 squares the difference between the amplitude information of each input signal and the amplitude information of the feedback signal according to (Equation 2) and accumulates the error value (represents the degree of deviation of the waveform of each signal). Value).

In (Expression 2), Err is an error value.
FB_Ri is the amplitude information of the feedback signal.
Tx_Ri is amplitude information of the transmission signal.

  Here, the delay adjustment unit 15 calculates an error value for each offset by changing the offset of (Equation 2) from 0 to (range * 2 + 1), and obtains a delay amount that minimizes the error value. Then, when the delay amount with the smallest error value is calculated a plurality of times (for example, four times) and the calculated minimum delay amount is all within ± 1 sample, it is closest to the currently held delay amount. Let the delay amount be the delay amount between the input signal and the feedback signal. If any one of the calculated minimum delay amounts is not within ± 1 sample, the delay adjustment is performed again.

JP 2009-219167 A

Regarding the delay adjustment by the above-described method, the delay amount can be appropriately calculated by performing the delay adjustment using a signal having a waveform having a relatively high frequency component as illustrated in FIG.
On the other hand, when delay adjustment is performed using a signal having a waveform with a relatively low frequency component (for example, a burst signal) as shown in FIG. 4, even if the amplitude information of the transmission signal is shifted by several samples, the error value is reduced. There are cases where the change is poor and the amount of delay is erroneously calculated. When the distortion compensation control unit 14 is operated in a state where the delay amount is incorrect, the distortion compensation control unit 14 cannot create appropriate correction information, and as a result, distortion generated in the amplifier 12 increases.

  The present invention has been made in view of such a conventional situation, and provides an amplifying apparatus that prevents deterioration of distortion compensation performance by suppressing erroneous execution of delay adjustment. Objective.

In order to achieve the above object, in the present invention, an amplifying apparatus is configured as follows.
That is, in an amplifying apparatus that amplifies an input signal by an amplifier, based on a delay unit that delays the input signal, a signal that is delayed by the delay unit, and a signal obtained by feeding back the output of the amplifier, The distortion compensation means for compensating for the distortion generated in amplification by the amplifier, and the error value indicating the degree of deviation of the waveform of each signal is small for the signal delayed by the delay means and the signal obtained by feeding back the output of the amplifier. As described above, the delay adjustment means for adjusting the delay amount by the delay means, the detection means for detecting that the input signal includes a waveform section having a predetermined low frequency component, and the detection means When a section of a waveform having a predetermined low frequency component is detected, the delay adjusting means converts the delayed signal and the fed back signal for the section. A control to control means so as not to use the adjustment by, with a.

Further, as one configuration example, the detection unit includes an error value for a signal obtained by shifting the input signal by a first delay amount and a signal obtained by feeding back the output of the amplifier in a detection processing target section. Calculating an error value for a signal obtained by shifting the input signal by a second delay amount and a signal obtained by feeding back the output of the amplifier, and when the difference between these error values is less than or equal to a threshold value, The section is determined to be a section of a waveform having a predetermined low frequency component.
Here, as a section of a waveform having a predetermined low frequency component, for example, a section of a burst signal is applicable.

  According to the amplifying apparatus of the present invention, since execution of delay adjustment using a waveform portion having a predetermined low frequency component is suppressed, it is possible to prevent deterioration in distortion compensation performance due to erroneous adjustment of the delay amount. Is possible,

It is a figure which shows the structural example of the amplifier which concerns on one Example of this invention. It is a figure which shows the structural example of the conventional amplifier. It is a figure which contrasts and illustrates the transmission signal which has a waveform of a comparatively high frequency component, and its feedback signal. It is a figure which compares and illustrates the transmission signal which has a waveform of a comparatively low frequency component, and its feedback signal. It is a figure which illustrates a mode when the transmission signal of FIG. 3 is shifted 10 samples. It is a figure which illustrates a mode when the transmission signal of FIG. 4 is shifted 10 samples. It is a figure explaining the difference of error value ErrA and error value ErrB. It is a figure explaining a burst signal.

An embodiment of the present invention will be described with reference to the drawings.
FIG. 1 shows a configuration example of an amplifying apparatus according to an embodiment of the present invention.
The amplifying apparatus of this example includes a distortion compensation unit 1, an amplifier 2, a delay unit 3, a distortion compensation control unit 4, a delay adjustment unit 5, and a burst signal detection unit 6.
Note that the distortion compensation unit 1, the amplifier 2, the delay unit 3, the distortion compensation control unit 4, and the delay adjustment unit 5 in the amplification device of this example are the distortion compensation unit 11, the amplifier 12, the delay unit 13 in the amplification device of FIG. Since it is the same as the distortion compensation control unit 14 and the delay adjustment unit 15, description thereof is omitted, and the burst signal detection unit 6 will be mainly described.

Prior to the description of the burst signal detector 6, the background of the present invention will be described.
When an input signal having a waveform of a relatively low frequency component as illustrated in FIG. 4 (a waveform when the delay adjustment is incorrect) is shifted by 10 samples, a waveform as illustrated in FIG. 6 is obtained. An error value (a value indicating the degree of deviation between the waveform of the input signal and the waveform of the feedback signal) calculated using (Equation 2) for each signal in FIG. 6 is obtained for each signal in FIG. ) Is approximately equal to the error value calculated using

  On the other hand, when an input signal having a waveform of a relatively high frequency component as illustrated in FIG. 3 (a waveform when there is no error in delay adjustment) is shifted by 10 samples, a waveform as illustrated in FIG. 5 is obtained. Then, the error value calculated using (Equation 2) for each signal in FIG. 5 is relatively larger than the error value calculated using (Equation 2) for each signal in FIG.

  In this way, the waveform when misadjusting the delay (waveform with a relatively low frequency component) has little change in the error value even if the input signal is shifted, whereas the waveform when not misadjusting the delay (with a relatively high frequency) Focusing on the feature that the error value increases when the input signal is shifted, there is a possibility that the delay adjustment may be mistaken in the amplification device of this example by adding the burst signal detector 6 as described below. The waveform is detected effectively, and the delay adjustment using the waveform is not performed.

The burst signal detection unit 6 first calculates the amplitude information of the input signal (for example, transmission signal) delayed by the delay unit 3 and the amplitude information of the feedback signal obtained by feeding back the output of the amplifier 2 with a predetermined number of samples (for example, 1024). (Sample), and the average amplitude level of the feedback signal is adjusted to the average amplitude level of the input signal (level correction) by (Equation 1).
Subsequent processing uses amplitude information of the feedback signal after level correction.

  The burst signal detection unit 6 uses the error value ErrA when the offset of (Expression 2) is “range” (shifted by the first delay amount) and the offset of (Expression 2) is (range * 2 + 1) (the first). Error value ErrB is calculated. Here, “range” is a predetermined adjustment range value to be added to the delay amount currently held by the delay adjustment unit 5 (the delay amount at the time of performing the delay adjustment process), and for example, 15 samples are used.

Thereafter, the burst signal detection unit 6 determines whether or not (Equation 3) is satisfied for the calculated ErrA and ErrB.

When (Equation 3) is not satisfied (that is, when the difference between the error values is equal to or less than the threshold (Threshold)), the input signal and the feedback signal in the section are detected as signals that may cause delay adjustment. Then, control is performed so as not to be used for adjustment by the delay adjustment unit 5 (in this example, the delay adjustment unit 5 discards it without passing it).
On the other hand, when (Equation 3) is satisfied (that is, when the difference between the error values is larger than the threshold), the input signal and the feedback signal in the section are passed to the delay adjustment unit 5 to perform delay adjustment.

The delay adjustment unit 5 uses the input signal and feedback signal passed from the burst signal detection unit 6 to perform delay adjustment similar to the conventional one.
That is, the delay adjustment unit 5 calculates the error value for each offset by changing the offset of (Equation 2) from 0 to (range * 2 + 1), and obtains a delay amount that minimizes the error value. Then, when the delay amount with the smallest error value is calculated a plurality of times (for example, four times) and the calculated minimum delay amount is all within ± 1 sample, it is closest to the currently held delay amount. Let the delay amount be the delay amount between the input signal and the feedback signal. If any one of the calculated minimum delay amounts is not within ± 1 sample, the delay adjustment is performed again.

  As described above, in this example, the error value between the waveform of the input signal and the waveform of the feedback signal is calculated by varying the shift amount (delay amount) of the input signal, and the frequency is calculated from the magnitude of the difference between the error values. The degree of the component was examined, and if the frequency component had a predetermined low waveform, it was not used for delay adjustment. As a result, it is possible to prevent the delay amount from being adjusted erroneously and to prevent the distortion compensation performance from being degraded due to the erroneous adjustment.

The difference between the error value ErrA and the error value ErrB will be described with reference to FIG.
FIG. 7A illustrates an error amount calculated by (Equation 2) for a waveform having a relatively low frequency component, and FIG. 7B shows an error amount calculated for the waveform having a relatively high frequency component (Equation 2). The error amount calculated by () is illustrated. In the graphs of FIGS. 7A and 7B, the horizontal axis represents the delay amount [sample], and the vertical axis represents the error amount.
Here, assuming that the error value when the delay amount is 0 samples is ErrA and the error value when the delay amount is −10 samples is ErrB, in the example of FIG. 7A, the error value ErrA = 4500 and the error value ErrB. = 9500, and the difference between these error values = 5000. On the other hand, in the example of FIG. 7B, the error value ErrA = 50000 and the error value ErrB = 1500,000, and the difference between these error values = 14.50000. Therefore, in this example, in order to exclude a waveform having a relatively low frequency component according to (Equation 3), for example, Threshold = 100000 is set.
As a waveform of a relatively low frequency component, a signal waveform of 60 kHz generally corresponds.

  A threshold (Threshold) serving as a reference for detecting a section of a waveform to be excluded so as not to be used for delay adjustment (a waveform having a predetermined low frequency component) is calculated and set in advance by a test or the like. An example of such a waveform signal is a burst signal. As illustrated in FIG. 8, the burst signal refers to a signal including an amplitude such that a small level continues for several tens [μs] to a normal signal. In the graph of FIG. 8, the horizontal axis represents time, and the vertical axis represents amplitude.

  If the delay adjustment in operation is not taken into consideration, the delay amount on the apparatus may be adjusted in advance at the time of product manufacture to set the delay amount fixedly. However, such operation cannot cope with a change with time or a change in temperature. Therefore, when it is desired to perform optimization in consideration of changes over time, temperature changes, etc., delay adjustment in operation is required as in this example. Further, according to the amplification device of this example, since automatic adjustment can be performed in operation, adjustment at the time of product shipment is unnecessary, and ST reduction can be expected.

  Here, in the amplification device of this example, a delay unit is configured by the function of the delay unit 3, a distortion compensation unit is configured by the functions of the distortion compensation unit 1 and the distortion compensation control unit 4, and a delay is performed by the function of the delay adjustment unit 5. An adjustment unit is configured, and a detection unit and a control unit are configured by the function of the burst signal detection unit 6.

In addition, the configuration of the system and apparatus according to the present invention is not necessarily limited to the above-described configuration, and various configurations may be used. The present invention can also be provided as, for example, a method or method for executing the processing according to the present invention, a program for realizing such a method or method, or a recording medium for recording the program. It is also possible to provide various systems and devices.
The application field of the present invention is not necessarily limited to the above-described fields, and the present invention can be applied to various fields.
In addition, as various processes performed in the system and apparatus according to the present invention, for example, the processor executes a control program stored in a ROM (Read Only Memory) in hardware resources including a processor and a memory. A controlled configuration may be used, and for example, each functional unit for executing the processing may be configured as an independent hardware circuit.
The present invention can also be understood as a computer-readable recording medium such as a floppy (registered trademark) disk or a CD (Compact Disc) -ROM storing the control program, and the program (itself). The processing according to the present invention can be performed by inputting the program from the recording medium to the computer and causing the processor to execute the program.

  1, 11: Distortion compensation unit, 2, 12: Amplifier, 3, 13: Delay unit, 4, 14: Distortion compensation control unit, 5, 15: Delay adjustment unit, 6: Burst signal detection unit,

Claims (3)

In an amplifying apparatus that amplifies an input signal by an amplifier,
Delay means for delaying the input signal;
Distortion compensation means for compensating for distortion generated in amplification by the amplifier based on a signal delayed by the delay means and a signal obtained by feeding back the output of the amplifier;
Delay adjustment means for adjusting a delay amount by the delay means so that an error value indicating the degree of deviation of the waveform of each signal is reduced for the signal delayed by the delay means and the signal obtained by feeding back the output of the amplifier. When,
Detecting means for detecting that the input signal includes a section of a waveform having a predetermined low frequency component;
When the detection unit detects a waveform section having a predetermined low frequency component, control is performed so that the delayed signal and the feedback signal for the section are not used for adjustment by the delay adjustment unit. Control means to
An amplifying apparatus comprising: The amplification device according to claim 1,
In the detection processing target section, the detection means calculates an error value for a signal obtained by shifting the input signal by a first delay amount and a signal obtained by feeding back the output of the amplifier, and the input signal. An error value is calculated for a signal shifted by a second delay amount and a signal obtained by feeding back the output of the amplifier. When the difference between these error values is less than or equal to a threshold value, the target section has a predetermined frequency component. Judge as the low waveform section,
An amplifying device characterized by that. The amplification device according to claim 1 or 2,
The section of the waveform whose frequency component is a predetermined low is the section of the burst signal.
An amplifying device characterized by that.

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