JP2007060014A - Feedforward distortion compensation amplifier - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem of a conventional feedforward distortion compensation amplifier wherein balancing of loop is collapsed by abrupt fall in level to cause variation in total gain because control of a distortion extraction loop and a distortion removal loop is stopped when the level of an input signal is low, and then to provide a feedforward distortion compensation amplifier in which stabilized amplification operation is performed while compensating distortion and suppressing variation in gain even if the input level is low. <P>SOLUTION: When the input level is lower than a preset specific level, a control section 11 in the feedforward distortion compensation amplifier shifts the control values of phase and amplitude of vector regulator 2/vector regulator 6 beyond a predetermined range and acquires a detection level from detector 10/detector 12. When the detection value is invariant even when the control value is shifted beyond a predetermined range, a decision is made that the detection level has converged at the optimal value, and the control is stopped, and then the control value is held. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a feedforward distortion compensation amplifier, and more particularly, to a feedforward distortion compensation amplifier that can perform stable operation while suppressing feed fluctuation while performing feedforward distortion compensation even when the input level is low.

A general feedforward distortion compensation amplifier will be described with reference to FIG. FIG. 5 is a configuration block diagram of a general feedforward distortion compensation amplifier.
As shown in FIG. 5, the general feedforward distortion compensation amplifier includes a directional coupler 1, a vector adjuster 2, a main amplifier 3, a directional coupler 4, a delay line 5, and a vector adjuster. 6, an auxiliary amplifier 7, a delay line 8, a directional coupler 9, a detector 10, a control unit 11 ′, and a detector 12.

  In general, a distortion compensation amplifier divides an input signal and amplifies one input signal for feedforward function, and an amplified input signal including a distortion component due to amplification and an unamplified input signal of the other Are combined in reverse phase, and the distortion detection loop that outputs the distortion component signal, and the amplified input signal including the distortion component and the distortion component signal are combined in reverse phase to remove the distortion component, and as a result And a distortion removal loop that outputs an amplified input signal that does not include a distortion component.

  In FIG. 5, a portion constituted by the directional coupler 1, the vector adjuster 2, the main amplifier 3, the directional coupler 4 and the delay line 5 is a distortion detection loop, and the directional coupler 4 and the vector adjuster 6, a portion constituted by the auxiliary amplifier 7, the delay line 8, and the directional coupler 9 is a distortion elimination loop.

Each component will be described.
The directional coupler 1 branches an input high-frequency signal into two and outputs it to the vector adjuster 2 and the delay line 5.
The vector adjuster 2 adjusts the phase shift of the input signal and the attenuation process (vector adjustment) of the amplitude of the input signal according to the control from the control unit 11 ′ (described later) (with the control value (adjustment amount) given from the control unit 11 ′). For example, it is composed of a variable phase shifter and a variable attenuator.

  The main amplifier 3 amplifies an input high frequency signal. Normally, in the main amplifier 3, during amplification, a distortion component having a frequency in the vicinity of the fundamental frequency component is generated with respect to the fundamental frequency component that is the original frequency of the input signal.

The delay line 5 delays the signal output from the directional coupler 1 and outputs the delayed signal to the directional coupler 4, and is for synchronizing with the signal output from the main amplifier 3.
The directional coupler 4 outputs the amplified input signal from the main amplifier 3 to the delay line 8 as it is, the input signal including the distortion component output from the main amplifier 3, and the distortion output from the delay line 5. An input signal that does not include a component is synthesized with an opposite phase, and a distortion component signal that is a synthesis result is output to the vector adjuster 6.

The vector adjuster 6 performs phase shift and amplitude attenuation processing adjustment of the distortion component signal in accordance with control from the control unit 11 ′, and includes a variable phase shifter and a variable attenuator.
The auxiliary amplifier 7 amplifies the distortion component signal.
The delay line 8 delays the input signal including the distortion component output from the directional coupler 4 and outputs it to the directional coupler 9 in order to match the delay of the distortion component signal due to amplification in the auxiliary amplifier 7. is there.
The directional coupler 9 synthesizes an input signal including a distortion component and an amplified distortion component signal with opposite phases to obtain an amplifier output signal.

The detector 10 detects a distortion component signal output from the directional coupler 4 and outputs a distortion component level.
The detector 12 detects the residual distortion level in the output signal output from the directional coupler 9.

  The control unit 11 ′ outputs a control signal for controlling the amount of phase and amplitude adjustment in the vector adjuster 2 and the vector adjuster 6, and based on the distortion component level output from the detector 10, the power The amount of adjustment of the vector adjuster 2 is optimized so that the level becomes the minimum value, and the amount of adjustment of the vector adjuster 6 is optimized so that the residual distortion level from the detector 12 is minimized. is there.

  In the above configuration example, the distortion detection method for detecting the residual distortion component in the distortion removal loop is used, but there is also a pilot method using a pilot signal.

Next, the operation of a general feedforward distortion compensation amplifier having the above configuration will be described with reference to FIG.
The input signal is branched by the directional coupler 1 and output to the vector adjuster 2 and the delay line 5. The input signal input to the vector adjuster 2 is adjusted in phase and amplitude and amplified by the main amplifier 3 at a predetermined amplification factor. At this time, a distortion component is generated in the vicinity of the fundamental frequency component, and both are input to the directional coupler 4.

  On the other hand, the input signal branched by the directional coupler 1 and input to the delay line 5 is delayed by a time corresponding to the delay generated in the path of the main amplifier 3 and output to the directional coupler 4. This signal does not include distortion components.

  In the directional coupler 4, the amplified signal from the main amplifier 3 is output as it is to the delay line 8, and the amplified input signal including distortion from the main amplifier 3 and the distortion from the delay line 5 are also output. And an input signal that does not include the signal are synthesized with an opposite phase. Here, the fundamental frequency component is canceled, and as a result, the distortion component in the amplified input signal is output to the vector adjuster 6 and the detector 10.

  The detector 10 detects the distortion component signal and outputs the detection level to the control unit 11 ′. The control unit 11 ′ performs vector adjustment based on the detection level of the distortion component signal so that the detection level is minimized. The adjustment amount of the device 2 is optimized, and the distortion detection loop is optimized.

The distortion component signal input to the vector adjuster 6 is adjusted in phase and amplitude, amplified by the auxiliary amplifier 7 and output to the directional coupler 9.
In the directional coupler 9, the delayed amplified input signal including the distortion from the delay line 8 and the amplified distortion component signal from the auxiliary amplifier 7 are synthesized in antiphase, and the distortion component is obtained. An offset output signal is output.

The output signal is input to the detector 12, and the residual distortion level is output to the control unit 11 '.
Based on the residual distortion level, the control unit 11 ′ controls the adjustment amount in the vector adjuster 6 so as to minimize the residual distortion level, and optimizes the adjustment amount in the distortion removal loop.
In this way, the operation of a general feedforward amplifier is performed.

  By the way, in the conventional feedforward distortion compensation amplifier, when the level of the input signal is a low level lower than a predetermined level (hereinafter referred to as “specified level”), accurate distortion extraction is difficult. Since the adjustment amount fluctuates greatly around the optimum value, there are some which stop the control in the control unit 11 ′. That is, control of the phase and amplitude of the vector adjuster 2 in the control unit 11 ′ is stopped, and control of the vector adjuster 6 is also stopped in the distortion detection method.

As a conventional technique of the feedforward type distortion compensation amplifier, Japanese Patent Laid-Open No. 2003-87065 published on March 20, 2003, “Power Amplifier” (Applicant: Hitachi Kokusai Electric Co., Ltd., Inventor: Fumi Tomaru) Person).
This prior art changes the amplitude change amount and phase change amount of the vector adjuster according to the power level of the residual distortion, and maintains the state of the vector adjuster when the distortion compensation operation becomes stable. Accordingly, a feedforward type distortion compensation amplifier capable of continuously performing highly accurate and highly stable distortion compensation is provided.

JP 2003-87065 A (page 3-4)

  However, in the conventional feedforward amplifier, when the level of the input signal is lower than the specified level, the control of the phase value and the amplitude value in the vector adjuster of the distortion detection loop and the distortion removal loop is stopped. When this occurs, the control stops at the optimum value immediately before the level drops, the loop is unbalanced, the gain of the entire feedforward amplifier fluctuates, and stable amplification cannot be performed. there were.

  The present invention has been made in view of the above circumstances, and enables a distortion detection loop and a distortion removal loop to be controlled even when the level of an input signal is low, and to perform a stable amplification operation with little gain fluctuation. An object of the present invention is to provide a feedforward amplifier capable of performing the following.

  The present invention for solving the problems of the above conventional example includes a first vector adjuster for adjusting the phase and amplitude of an input signal, a main amplifier for amplifying the output of the first vector adjuster, A first directional coupler that detects the distortion component of the input signal by synthesizing the output and the input signal in opposite phases; and a first detector that detects the detected distortion component and outputs a distortion component level. A second vector adjuster for adjusting the phase and amplitude of the output of the first directional coupler, an auxiliary amplifier for amplifying the output of the second vector adjuster, and the output of the first directional coupler; A second directional coupler that combines the outputs of the auxiliary amplifiers in antiphase to remove distortion components; and a second detector that detects the output of the second directional coupler and outputs a residual distortion level. , Control and store the adjustment amount in the first vector adjuster based on the distortion component level Both of the feedforward distortion compensation amplifiers include a control unit that controls an adjustment amount in the second vector adjuster based on the residual distortion level, and the control unit has a distortion component level or an input signal input level. When the level falls below a predetermined level set in advance, the adjustment amount of the first vector adjuster is changed from the adjustment amount at the time when the level falls below the predetermined level by a predetermined amount or more. Store and acquire the distortion component level, and if the difference between the acquired distortion component level and the distortion component level at the time when the distortion component level falls below the preset second amount, the adjustment of the first vector adjuster The second detector is a detector having a dynamic range for detecting noise output from the main amplifier when there is no input signal. There.

  According to the present invention, when the control unit reduces the distortion component level or the input level of the input signal below the predetermined level set in advance, the adjustment amount of the first vector adjuster is set to the predetermined level. The adjustment amount at the time when the value falls below the first amount is stored in a variable manner, the distortion component level is acquired, and the difference between the acquired distortion component level and the distortion component level at the time when the adjustment value falls below If it is less than the set second amount, the control unit stops the process of controlling and storing the adjustment amount of the first vector adjuster, and the second detector is the main amplifier when there is no input signal. Since it is a feedforward distortion compensation amplifier having a dynamic range for detecting the noise output from the feedforward, while performing feedforward distortion compensation of the distortion detection loop and the distortion removal loop to a lower input level than conventional, Suppressing variation in the resultant, there is an effect that it is possible to perform a stable distortion compensation and amplification.

Embodiments of the present invention will be described with reference to the drawings.
The feedforward distortion compensation amplifier according to the present invention acquires the distortion component detection value by moving the phase and amplitude control values over a certain range in the distortion detection loop when the input level becomes low power below a certain level. If the detected value does not change, it is determined that the signal has converged, and the lowest input level at which convergence can be confirmed is obtained. If the input level is less than the lowest input level, the phase and amplitude The control is stopped, and even if the level of the input signal is low, the loop control can be continued until the level is as low as detectable, and a stable amplification operation can be performed. .

  In addition, the feedforward distortion compensation amplifier of the present invention detects the distortion component detection value by moving the phase and amplitude control values over a certain range in the distortion removal loop when the input level becomes low power below a certain level. If the detected value does not change, it is determined that the signal has converged. Regardless of the input level, periodic loop control is performed without stopping control, and the balance of the loop is lost. Therefore, a stable amplification operation can be performed.

FIG. 1 is a configuration block diagram of a feedforward distortion compensating amplifier according to an embodiment of the present invention. In addition, the same code | symbol is attached | subjected and demonstrated about the part which has the structure similar to FIG.
The configuration of the feedforward amplifier (this device) of the present embodiment is almost the same as that of the general feedforward amplifier shown in FIG. 5, and includes a directional coupler 1, a vector adjuster 2, a main amplifier 3, and The directional coupler 4, the delay line 5, the vector adjuster 6, the auxiliary amplifier 7, the delay line 8, the directional coupler 9, the detector 10, the control unit 11, and the detector 12 And an input level detection unit 13. The input level detection unit 13 is not shown in FIG. 5 and is not essential, but may be provided in a general feedforward distortion compensation amplifier to detect the signal level of the input signal ( For example, a detector).

This apparatus is partially different from a general feedforward distortion compensation amplifier in the processing contents in the control unit 11, but the configuration and operation of other parts are the same as the general feedforward distortion compensation shown in FIG. Since it is the same as that of an amplifier, description is abbreviate | omitted here.
However, in the present apparatus, the noise of the main amplifier 3 can be detected by using a detector having a wide dynamic range as the detector 12 for detecting the residual distortion level.

  The control unit 11 controls the distortion detection loop and the distortion removal loop, and includes a CPU that performs processing, a memory that stores programs and various setting values (not shown), and a distortion detection loop control unit. And a distortion removal loop detection means. Each processing means is realized by a processing program corresponding to each means stored in advance in the memory being read and activated by the operation of the CPU. Further, the control unit 11 stores a detection level of the detector 10 or a specified level of the input level.

The distortion detection loop control means of the control unit 11 performs distortion using a perturbation method based on the distortion component level from the detector 10 at a certain time interval (for example, every 30 seconds, every minute, etc.), as in the past. The control value (adjustment amount) of the phase and amplitude of the vector adjuster 2 in the detection loop is controlled. As a feature of the distortion detection loop control means of this apparatus, the detection value or input level of the detector 10 is specified. Even when the input level is low and the control level is low, the control is continued and the detection level of the distortion component signal from the detector 10 is monitored, and the phase and / or amplitude control values change by a certain amount or more. Even when the detection level of the distortion component signal does not vary, it is determined that the control value has converged to the optimum value. That is, in this apparatus, the “first amount” in the claims corresponds to the above “constant amount” or the “variable amount within a certain range” described later, and the “second amount” described in the claims is 0. It corresponds to a certain case.
Further, the distortion detection loop control means of the control unit 11 performs control periodically, and also controls the vector adjuster 2 when the distortion component level from the detector 10 exceeds the reference value, as in the prior art. To do.

  Further, as a feature of the distortion detection loop control means of this apparatus, the minimum input level Pmin for which the optimum value can be obtained by the above method is stored in advance, and the input level from the input level detection unit 13 is less than Pmin. In this case, the control is stopped.

  In addition, the distortion removal loop control means of the control unit 11 controls the phase and amplitude of the vector adjuster 6 in the distortion removal loop at regular time intervals as in the prior art. As a feature of the control means, the residual distortion level from the detector 12 is monitored by moving the control value of the phase and / or amplitude even when the input level is less than the specified level and the control is stopped conventionally. When the residual strain level does not vary, it is determined that the control value has converged to the optimum value.

  Further, as a feature of the present apparatus, the distortion removal loop control means continues periodically without stopping the control regardless of the input level. This is because the noise in the main amplifier 3 can be detected by widening the dynamic range of the detector 12, and a meaningful signal can be obtained from the detector 12 even when the input level is not input.

Next, a method for controlling the distortion detection loop in this apparatus will be described with reference to FIG. FIG. 2 is a schematic explanatory diagram showing an example of the range of the control value of the distortion detection loop of the present apparatus.
Usually, when the input level from the input level detection means 13 is small, the level of the distortion component signal from the detector 10 itself is small and the change is poor.

  Even when the change in the distortion component level from the detector 10 is small and it is difficult to find the optimum point, the distortion component signal from the detector 10 is changed by changing the control value (either one or both) of the phase and amplitude. It is possible to vary the level. In the example of FIG. 2, the phase control value is PH1 and the phase control value is AT1, and the distortion detection loop control means of the present apparatus does not change the signal from the detector 10 even if the control value is changed beyond a certain range. When the level does not change, it is determined that the value has converged to the optimum value.

  For example, in this amplifier, both the phase and amplitude control values are controlled by 8 bits (256 steps from 0 to 255), and the adjustment amount corresponding to the control value is variable in the range of about 140 degrees and the amplitude is about 6 dB. To be adjusted. Here, both the amplitude and phase control values have a certain range of fluctuation amount of 50 steps or more. This corresponds to about 20% of the variable range of the control amount. That is, it is assumed that one or both of the amplitude control value and the phase control value is converged to the optimum value when there is no change in the distortion component signal level from the detector 10 even when the amplitude control value or the phase control value is varied by 50 stages or more. Is. Here, although there are 50 stages, it is desirable to set an optimal fixed range according to the characteristics of the device and the input signal, and the optimal fixed range may be obtained experimentally.

The example of FIG. 2 shows an example of a range in which the distortion detection loop of the present apparatus can be regarded as being in an equilibrium state when the input is as low as a prescribed level.
The horizontal axis is the phase control value PH1 given to the vector adjuster 2, the vertical axis is the amplitude control value AT1, and the detection level of the detector 10 remains the minimum and does not change in the range indicated by the oblique lines. Is shown. In other words, the optimal control value that truly balances the loop is assumed to exist near the center of this range, but it is so small that it cannot detect the deviation of the loop, and there is no particular problem, so it can be regarded as converged within this range. It is.

  As described above, since the control value that can be regarded as converged has a certain range, the amount of variation is set to, for example, 50 levels. As shown in FIG. 2, since the phase shift is more severe than the amplitude, the variation amount may be set separately for the amplitude and the phase. Further, the fluctuation amount is set to be larger than 1/2 of the width of the hatched area in FIG. 2 as the specified level is set to be larger than Pmin (that is, the hatched area further expands as it approaches Pmin). Good.

  As described above, in this apparatus, even when the input level is small, the control value of either one or both of the phase and amplitude control values in the vector adjuster 2 of the distortion detection loop is changed by a certain range or more. If the signal level does not change even if the control value is fluctuated over a certain range, the control value is converged to the optimum value. Since the determination has been made so far, the control is stopped as it is when the input level is low. However, the distortion detection loop can be controlled even at a lower input level, and the fluctuation of the gain can be prevented.

  Further, in this apparatus, the minimum power level Pmin at which the optimum value is obtained by the above method is obtained in advance and set in the control unit 11, and the input level input from the input level detection unit 13 is set in the control unit 11. If it is lower than Pmin stored in the control, the control is stopped.

  When obtaining the minimum power level Pmin, for example, there is a method to obtain it experimentally. The input level is gradually lowered from an input level of about a specified level, and it is checked whether or not it converges to an optimum value. The input level immediately before disappearing is set in the control unit 11 as Pmin.

  In other words, this device controls the distortion detection loop by providing a two-stage threshold value for the input level, and sets the “specified level” as the same value as the conventional one. “Pmin” is set as a lower value, and the input level detected by the input level detector 13 is compared with the magnitudes of the two types of threshold values, and appropriate control is performed according to the magnitude. It is a thing.

Specifically, the control unit 11 stops the control if the input level is less than Pmin, and controls the phase and / or amplitude of the vector adjuster 2 if the input level is greater than Pmin and less than the specified level. The detected value from the detector 10 is monitored by changing the value over a certain range, and if the detected value does not change, the control value is held as if it converged to the optimum value.
Thus, the control is not stopped to the lowest possible level, and the balance of the loop is maintained.

Next, a control method of the distortion removal loop in this apparatus will be described with reference to FIG. FIG. 3 is a schematic explanatory diagram showing an example of the amplitude and phase control values of the distortion removal loop and the detection level change from the detector 12 when there is no input in this apparatus.
FIG. 3 shows the detection level from the detector 12 corresponding to each control value, where AT2 is the amplitude control value and PH2 is the phase control value when there is no input. As can be seen from FIG. 3, the combination of the control values of AT2 and PH2 at which the detection level is the lowest is not a single point but is spread over a certain range. Even if the control value is varied within this range, the detection from the detector 12 is performed. You can see that there is no change in the level.
The present application uses this fact to converge the control value in a range where the detection level is minimum even when there is no input or at a low input level.

  Then, similarly to the above-described distortion detection loop control unit, the distortion removal loop control unit of the control unit 11 causes one or both of the amplitude and the phase to exceed a certain range when the input level is less than the specified level. If the detection level of the detector 12 does not change even if it is varied, it is considered that the signal has converged to the optimum value. The fixed range in which the control value is varied in the distortion removal loop control may be 50 steps as in the distortion detection loop, or may be different values.

  Further, in this apparatus, the dynamic range of the detector 12 is widened to detect the noise of the main amplifier 3, and the loop control is performed periodically without stopping the control regardless of the input level. Even when there is no input, the distortion removal loop can be controlled, and the balance between the distortion detection loop and the distortion removal loop can be prevented from being lost at the same time, thereby preventing the gain fluctuation from increasing.

Next, processing of distortion detection (and distortion removal) loop adaptive control of the control unit 11 of the present apparatus will be described with reference to FIG. FIG. 4 is a flowchart showing processing in adaptive control of the distortion detection (and distortion removal) loop of the control unit 11 of the present invention.
The adaptive control is basically performed by repeating the step of acquiring the detection value of the detector 10 or 12 and the step of updating the control value (adjustment amount) based on the detection value. In the repetition, the characteristic control of the present invention is included as processing when the input level is low. In FIG. 4, the perturbation method is assumed as a method for updating the control value, which will be described in order.

  Further, since the magnitude of the input level and the magnitude of the detection value of the detector 10 tend to be the same, the prescribed level may be prescribed for the detection value of the detector 10. FIG. 4 shows processing in which the specified level is specified for the detection value of the detector 10.

  When activated, the control unit 11 first acquires the detection values of the detectors 10 and 12, and also acquires the input level detected by the input level detection unit 13 (S100). The control unit 11 of this apparatus stores the acquired latest detection value and the previous detection value inside, but the acquisition of the detection value is performed in the update process of the adjustment amount in the process S110 described later in addition to the process S101. Above all, it has come to be acquired.

Next, the control unit 11 compares the acquired input level with Pmin (S102), and when the input level is less than Pmin (in the case of No), the process proceeds to S108.
When the input level is equal to or higher than Pmin in the process S102 (in the case of Yes), the control unit 11 compares the detected value with a specified level stored in the control unit 11 in advance (S104), and the detected value is When it is less than the specified level (in the case of No), that is, when the input level is lower than a certain level, the process branches to S120. Note that the specified level is set to a value that is approximately the same as the reference value (ACP _TH ) of the detection value used in step S108, which will be described later, and is slightly larger than the lowest limit input level Pmin at which convergence can be detected. .

If the input level is equal to or higher than the specified level in step S104 (Yes), the input level is sufficiently high.
In this case, the control unit 11 sets the “specified level flag” to “true (eg,“ 1 ”)” (S106). The “specified level flag” is a flag indicating that the level of the detected value is higher than a predetermined specified level, and is held in a work area inside the control unit 11.

Then, the control unit 11 compares the detection value (ACP; adjacent channel power: adjacent channel leakage power) of the detector 10 with the reference value (ACP _TH ), and determines whether a certain time has elapsed (S108). If the detected value is larger or the fixed time has not elapsed, a weight is applied, and the control unit 11 repeats S108.

The determination as to whether or not a certain time has elapsed can be made based on, for example, the presence or absence of a timer interrupt.
As a result, it is possible to avoid unnecessary updating of the control value in the converged state and to increase the accuracy by increasing the detection value acquisition time (average time). In determining the convergence state, in addition to comparing the detection value (ACP) of the detector 10 with the reference value (ACP _TH ), comparison of the ACPR normalized with the input level of the ACP and its reference value (ACPR _TH ) You may use together.

In process S108, after a predetermined time has elapsed or when the ACP level becomes larger than the reference value, the control unit 11 updates the control value (adjustment amount) (S110).
This process is the same as in the prior art, but will be described briefly.
In the perturbation method, when there are a plurality of control objects, they are updated one by one, for example, cyclically. Specifically, an update control value indicating which control value of AT1 and PH1 shown in FIG. 2 just before (including AH2 and PH2 shown in FIG. 3 when the distortion removal loop is updated together) is updated. Information, each past perturbation amount most recently given to AT1 and PH1 (AH2, PH2), and a previous detection value detected by the detector 10 (and 12) last time are stored.

  Then, the current detection value (detection value of the detector 10 if AT1 or PH1 is updated), which is the result of the previous update, is compared with the previous corresponding detection value stored, and if the current detection value is detected. When the value is smaller, the previous update is valid and the current detection value is stored as the previous detection value. Conversely, when the current detection value is larger than the previous detection value, in order to discard the previous update, the past perturbation amount of the control value is subtracted from the control value indicated by the update control value information. At least the sign of the past perturbation amount is inverted. Finally, the updated control value information is updated to the next control value in the order of circulation, and the past perturbation amount is added to the control value to obtain a new control value. This process is repeated until it converges to the optimum value, and the control value (adjustment amount) is updated with the converged optimum value.

Next, processing after branching in S104, which is a feature of the present embodiment, will be described.
When the detected value is less than the specified level in the process S104 (in the case of No), the control unit 11 sets the “specified level flag” indicating that the input level is sufficiently high to “true (for example,“ 1 ”)”. It is judged whether it is (S120).

When the specified level flag is “true” in the process 120, the control unit 11 holds the current control value (the control value updated in the immediately preceding process S110) as it is (S122).
Then, the control unit 11 sets the specified level flag to “false” (S124), proceeds to processing S110, and updates the adjustment amount.

  In addition, when the specified level flag is not “true” in the processing S120 (in the case of No), the detected value is continuously lower than the specified level, and the detected level is a level sufficiently lower than the detection limit. I understand that. This means that there is almost no difference between the previous detection value and the current detection value. That is, the determination that the specified level flag is “false” in the process S120 can be determined that there is no change in the detected value. The process of FIG. 4 shows a case where the “second amount” described in the claims is zero.

  Therefore, the control unit 11 compares the previous control value with the current control value, and determines whether or not there is a difference of ± 50 steps or more (S126). The “± 50 stage” of the process S126 corresponds to the “first amount” recited in the claims. If there is no deviation of ± 50 steps or more (in the case of No), the detected value is low but there is a possibility that it has not converged to the optimum value, so that the process proceeds to step S110 and the adjustment amount is updated again. I do.

  If the difference between the previous control value and the current control value is greater than or equal to ± 50 in step S126 (Yes), the control unit 11 does not update the adjustment amount and keeps the previous control value. In step S108, the adjustment amount is not updated until the ACP exceeds the reference value or a certain amount of time has elapsed. If the control value difference is greater than or equal to ± 50 in process S126, it is determined again whether or not the detected value has changed (or the difference is less than a certain amount) after process S126. If not, the process may be shifted to S110.

As described above, in this apparatus, in the case of a low input level, even when the control value is fluctuated by a certain amount (in this case ± 50 steps) or more, the control value is not fluctuated (less than a certain amount). By determining that it has converged, it is possible to determine the convergence state by adjusting the control value even in a low input level state that has not sufficiently converged in the conventional process S110. The adaptive control of the control unit 11 is stopped until time elapses.
In this way, the distortion detection (and distortion removal) loop adaptive control process of the present apparatus is performed.

  In addition, while proceeding from S122 to S112, the control amount stored at the time of S122 and the control amount stored in the previous process S132 so that the control amount is near the center of the shaded area in FIG. You may insert the process which uses the thing of taking the average of as a new control amount.

  According to the feedforward amplifier according to the embodiment of the present invention, the adaptive control of the distortion detection loop is stopped when the detection level of the detector 10 does not change even when the control value is moved beyond a certain range, so that the detection is stopped. The loop can be kept balanced at the lower limit of the detection limit of the device 10. As a result, the adaptive control is stopped without the conventional distortion detection loop being balanced, and as a result, the distortion removal loop also deviates from the optimum state and balances, and then the distortion detection when the input level increases and the equilibrium state of the removal loop. This solves the problem that the convergence to the delay is delayed and the gain fluctuates accordingly, and has an effect of performing a stable amplification operation.

  The present invention is suitable for a feedforward distortion compensation amplifier that performs feedforward control even when the input level is low, suppresses fluctuations in gain, and can perform stable operation.

It is a block diagram of the configuration of the feedforward distortion compensation amplifier according to the embodiment of the present invention. It is the model explanatory drawing which showed an example of the range of the control value of the distortion detection loop of this apparatus. FIG. 4 is a schematic explanatory diagram illustrating an example of a change in amplitude and phase control values of a distortion removal loop and a detection level from the detector 12 when there is no input in the present apparatus. It is a flowchart figure which shows the process in the distortion detection loop control means of the control part 11 of this invention. It is a block diagram of a general feedforward distortion compensation amplifier.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Directional coupler, 2 ... Vector regulator, 3 ... Main amplifier, 4 ... Directional coupler, 5 ... Delay line, 6 ... Vector regulator, 7 ... Auxiliary amplifier, 8 ... Delay line, 9 ... Directionality Combiner, 10 ... detector, 11 ... control unit, 12 ... detector, 13 ... input level detection unit

Claims (1)

A first vector adjuster for adjusting the phase and amplitude of the input signal;
A main amplifier for amplifying the output of the first vector adjuster;
A first directional coupler that synthesizes the output of the main amplifier and the input signal in opposite phases to detect a distortion component of the input signal;
A first detector for detecting the detected distortion component and outputting a distortion component level;
A second vector adjuster for adjusting the phase and amplitude of the output of the first directional coupler;
An auxiliary amplifier for amplifying the output of the second vector adjuster;
A second directional coupler that removes distortion components by combining the output of the first directional coupler and the output of the auxiliary amplifier in opposite phases;
A second detector for detecting the output of the second directional coupler and outputting a residual distortion level;
A control unit that controls and stores an adjustment amount in the first vector adjuster based on the distortion component level, and controls an adjustment amount in the second vector adjuster based on the residual distortion level;
A feedforward distortion compensation amplifier comprising:
When the distortion component level or the input level of the input signal falls below a predetermined level set in advance, the control unit sets the adjustment amount of the first vector adjuster to the predetermined level. The amount of adjustment is changed from the adjustment amount at the time of lower than the preset first amount and stored, the distortion component level is acquired, and the difference between the acquired distortion component level and the distortion component level at the time of lower is the difference. A controller that controls and stores the adjustment amount of the first vector adjuster if less than a preset second amount;
The feed-forward distortion compensation amplifier, wherein the second detector is a detector having a dynamic range for detecting noise output from the main amplifier when there is no input signal.

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