WO2008053535A1

WO2008053535A1 - Distortion compensating circuit

Info

Publication number: WO2008053535A1
Application number: PCT/JP2006/321770
Authority: WO
Inventors: Shiro Masumoto; Sinzi Ookawa; Tsutomu Hibino
Original assignee: Panasonic Corporation
Priority date: 2006-10-31
Filing date: 2006-10-31
Publication date: 2008-05-08

Abstract

A distortion compensating circuit capable of simultaneously reducing both the affection of a first memory effect occurring in an envelope signal and that of a second memory effect occurring in a burst signal. In this distortion compensating circuit, an envelope memory PD part (103b) refers to a first distortion compensation coefficient stored in a first LUT (105) to compensate the distortion caused by the first memory effect of the envelope signal. A second adapting part (108) compares an input side burst signal detected by an input side burst detecting part (102) with an output side burst signal detected by an output side burst detecting part (111), calculates a distortion component caused by the second memory effect of the output side burst signal occurring due to a temperature variation of a power amplifying part (112), and calculates, based on temperature information from a temperature sensor (109), a second distortion compensation coefficient. A burst memory PD part (104) refers to the second distortion compensation coefficient to compensate the distortion caused by the second memory effect of the burst signal.

Description

Specification

Distortion compensation circuit

Technical field

The present invention relates to a distortion compensation circuit that performs distortion compensation of a transmission signal by a predistortion method.

Background art

[0002] Conventionally, when distortion occurs in the spectrum of a transmission signal transmitted by force such as a cellular phone, an inverse function distortion (inverse distortion) is generated for the distortion component, and the distortion component of the transmission signal is generated. A predistortion type (predistortion type) distortion compensation circuit that compensates for distortion by reverse distortion is known. In addition, the envelope signal generated by modulating the transmission signal does not deteriorate its distortion characteristics due to the memory effect caused by the asymmetric spectrum of the transmission signal caused by the hysteresis phenomenon of the circuit elements (devices) constituting the power amplification device. A distortion compensation circuit taking into account the memory effect is used.

[0003] For example, by detecting the temperature of a device constituting the power amplifying device with a temperature sensor, and changing the predistortion coefficient of the predistortion circuit (predistortion circuit) according to the detected temperature level (that is, Distortion compensation circuits have been disclosed that perform distortion compensation of envelope signals so that the distortion characteristics do not depend on temperature (by changing the inverse strain function in response to device temperature changes) (see, for example, Patent Document 1). ). Also disclosed is a technique for a distortion compensation circuit that includes a memory-less pre-distortion circuit and a memory pre-distortion circuit, and compensates for distortion caused by the memory effect of the envelope signal by the memory pre-distortion circuit ( For example, see Patent Document 2). According to this technology, the table value of the predistortion coefficient for compensating the distortion component of the envelope signal is corrected by the envelope signal one sample before detected by the delay circuit (that is, hysteresis compensation of the envelope signal is performed). By doing so, it is possible to eliminate fluctuations in distortion characteristics due to the memory effect due to the electrical characteristics of the devices constituting the power amplifying device, and to prevent deterioration in distortion compensation due to the memory effect of the envelope signal.

Patent Document 1: JP 2004-336750 A Patent Document 2: JP-A-2005-101908

Disclosure of the invention

Problems to be solved by the invention

[0004] However, a transmission signal of a mobile phone or the like is output as a burst signal in which the amplitude of the envelope signal changes at a predetermined period in accordance with fluctuations in the amount of data to be transmitted, the number of people accommodated, and the like. In the conventional W-CDMA (Wideband Code Division Multiple Access) method, the amplitude of this burst signal fluctuates with a period of about 10 ms. In next-generation communication systems, the amplitude fluctuates at a fast cycle of about 0.5 ms.

[0005] On the other hand, the memory effect includes an electrical memory effect (hereinafter referred to as the first memory effect) in which a hysteresis phenomenon occurs in the envelope signal due to fluctuations in the voltage applied to the device of the power amplifying device. There is a thermal memory effect (hereinafter referred to as the second memory effect) in which a hysteresis phenomenon occurs in the burst signal due to the temperature time constant of the device. The temperature time constant of the device at this time is about 0.1 ms, which is much larger than the electrical time constant of the device! /.

[0006] However, in conventional W-CDMA communication, the device temperature time constant of 0.1 ms is considerably smaller than the burst signal period of 10 ms, so the burst signal is temperature saturated at each period. Almost no influence of excessive characteristics due to. However, in next-generation communication systems such as 3GPP-LTE, the device temperature time constant of 0.1 ms is not negligible for a burst signal period of 0.5 ms. A big influence. In other words, in next-generation communication systems such as 3GPP-LTE, in addition to the first memory effect in which the distortion characteristics of the power amplifying device change depending on the symbol rate of the digitally modulated envelope signal, burst signals are also included. The second memory effect, in which the distortion characteristics of the power amplifier change depending on the signal period, is greatly affected.

[0007] That is, the conventional distortion compensation circuit performs distortion compensation of the envelope signal in consideration of the first memory effect, but appropriate distortion compensation in consideration of the second memory effect for the burst signal. Is not done. In other words, the conventional distortion compensation circuit has a signal period of 0.05. The first memory effect (electrical memory effect) that appears in a high-speed envelope signal of ~ 0.2 sec and the second memory effect (temperature) that appears in a low-speed burst signal with a signal period of about 0.5 ms Since the optimal distortion compensation cannot be performed when the dynamic memory effect occurs simultaneously, there arises a problem that the distortion compensation accuracy in the power amplifying device is deteriorated.

[0008] Further, according to the technique described in Patent Document 1 above, the table of LUT (Look Up Table) is related to at least one of the temperature level or power level of the power amplifying device. Although the predistortion coefficient is changed according to the temperature, distortion compensation for the second memory effect caused by temperature hysteresis is not performed. In other words, the distortion compensation accuracy of the power amplifying device deteriorates because distortion compensation is not performed for two memory effects that occur simultaneously (the first electrical memory effect and the second thermal memory effect). In other words, the distortion compensation table can be adaptively changed with respect to temperature fluctuations, but this distortion compensation table compensates only for the first memory effect in the envelope signal, and the second memory effect. Is not compensated for. Furthermore, in the technique described in Patent Document 2 described above, since only the compensation circuit for the first memory effect of the envelope signal is provided, the first memory effect of the envelope signal and the first signal of the burst signal having greatly different delay times are used. The distortion compensation amount deteriorates for a transmission signal in which the two memory effects of memory effect 2 occur simultaneously.

The object of the present invention has been made in view of such circumstances, and simultaneously reduces the influence of the first memory effect generated in the envelope signal and the influence of the second memory effect generated in the burst signal. Thus, it is to provide a predistortion type distortion compensation circuit capable of performing optimum distortion compensation, and a power amplifying apparatus using the distortion compensation circuit.

Means for solving the problem

A distortion compensation circuit according to the present invention is a distortion compensation circuit that performs distortion compensation of a transmission signal by a predistortion method, and is configured to reduce distortion caused by an electrical memory effect generated in an envelope signal that is a modulation signal of the transmission signal. An envelope memory predistortion unit for compensation and a burst memory predistortion unit for compensating for distortion caused by the thermal memory effect generated in the burst signal obtained by the envelope of the envelope signal are adopted. The invention's effect

[0011] According to the distortion compensation circuit of the present invention, the envelope memory PD (Pre-Distortion) unit is provided to compensate for the distortion caused by the first memory effect of the envelope signal, and the burst memory PD unit is provided. Envelope force of the envelope signal extracted from the input and output of the power amplification device When a burst signal is detected and a distortion component is generated in the burst signal due to the second memory effect, the burst memory PD unit Compensates for signal distortion. Furthermore, when it is determined that the second memory effect has occurred in the burst signal based on the temperature information of the temperature sensor force, the burst memory PD unit performs distortion compensation by the second memory effect of the burst signal. ing.

[0012] In this way, two memory effects with greatly different delay times (that is, the first memory effect of the envelope signal and the second memory effect of the burst signal) are adaptively processed by the individual PD units! Therefore, the calculation time of the envelope memory PD section and the burst memory PD section can be reduced. As a result, it is possible to increase the speed and efficiency of the distortion compensation circuit in the power amplifying device and improve the distortion compensation accuracy. Brief Description of Drawings

[0013] FIG. 1 is a waveform diagram showing a time transition of a general transmission power waveform in a power amplifying apparatus, and a temperature characteristic diagram of a device.

FIG. 2 is a block diagram showing a configuration of a distortion compensation circuit according to Embodiment 1 of the present invention.

FIG. 3 is a first block diagram showing the function of the burst memory PD section and the configuration of its peripheral elements in the distortion compensation circuit shown in FIG.

FIG. 4 is a second block diagram showing the function of the burst memory PD section and the configuration of its peripheral elements in the distortion compensation circuit shown in FIG.

FIG. 5 is a block diagram showing a configuration of a distortion compensation circuit according to Embodiment 2 of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

The distortion compensation circuit of the present invention is an envelope signal memory compensation circuit (that is, an envelope memory PD section) that compensates for distortion caused by the first memory effect of the envelope signal, as in the prior art. It has. Furthermore, the input side and output side of the power amplifier Envelope force of the envelope signal extracted from the input burst detector and output burst detector for detecting the burst signal, a temperature sensor for detecting the temperature of the power amplifier device, the input burst detector and the output burst Based on the burst signal detected by the detector and the temperature information of the device detected by the temperature sensor, the burst signal memory compensation circuit (that is, compensation for distortion caused by the second memory effect of the burst signal) And burst memory PD section)!

With such a configuration, when the second memory effect occurs in the burst signal, the envelope memory PD section compensates for distortion generated due to the first memory effect of the envelope signal. Aside from the second memory effect caused by the burst signal detected by the input burst detector and the output burst detector based on the temperature information of the device detected by the PD memory temperature sensor, To compensate for distortion that occurs. As a result, it is possible to reduce the amount of computation and the computation time of the entire distortion compensation circuit, thereby realizing high-speed distortion correction processing and high efficiency, and further improving the distortion compensation accuracy of the transmission signal. it can.

Next, some specific embodiments of the distortion compensation circuit according to the present invention will be described in detail. In the drawings used in the following embodiments, the same components are denoted by the same reference numerals, and redundant description is omitted.

Fig. 1 is a waveform diagram showing the temporal transition of a typical transmission power waveform in a power amplifier and a temperature characteristic diagram of the device. The horizontal axis represents time, the vertical axis represents the device temperature and the burst signal amplitude. Show. As shown in Fig. 1, the transmission power waveform shows the burst signal S as the peak value of the envelope signal S, which is the modulated wave of the transmission signal, fluctuates in a predetermined cycle.

e b is formed. Therefore, the amplitude of the burst signal S has a predetermined period (0.5 ms in FIG. 1).

b

(Period).

[0018] In this way, the device temperature fluctuates each time the burst signal amplitude fluctuates, the device temperature rises when the burst signal amplitude is large, and the device temperature increases when the burst signal amplitude is small. The temperature falls. The temperature time constant of the device at this time is about 0.lms. [0019] At this time, the temperature of the device is fixed with respect to the period of amplitude fluctuation of burst signal S 0.5ms

b

Since the number 0.1 ms is a relatively large value, the amplitude fluctuation of the burst signal S

b

Greatly affects the degree of transient characteristics. Because of this, the amplitude of the burst signal s is large

b

The second memory effect due to device temperature fluctuations appears greatly. Therefore, in the present invention, a burst memory PD section that also has a burst signal memory compensation circuit power is provided to compensate for distortion characteristics degradation due to the second memory effect caused by temperature fluctuations of the device. As a result, the burst signal S is a rectangular wave with the memory effect removed as shown in FIG.

b

It becomes a shape.

FIG. 2 is a block diagram showing a configuration of the distortion compensation circuit according to Embodiment 1 of the present invention. In FIG. 2, this distortion compensation circuit includes an input envelope detector 101, an input burst detector 102, an envelope memoryless PD 103a, an envelope memory PD 103b, a burst memory PD 104, a first LUT105, second LUT106, first adaptive processing unit 107, second adaptive processing unit 108, temperature sensor 109, output side envelope detection unit 110, output side burst detection unit 111, and power amplification unit 112 is provided. In the following description, the envelope signal and burst signal on the input side of the power amplifier 112 are combined with the envelope signal and burst signal on the input side, and the envelope signal and burst signal on the output side of the power amplifier 112 are converted. The output side envelope signal and the output side burst signal are called.

[0021] The input-side envelope detection unit 101 detects the envelope of a modulation signal (that is, the input-side envelope signal before being distorted by the power amplification unit 112) input to a mobile phone or the like, thereby To the first detection processing unit 107 and the first detection processing unit The input burst detector 102 detects the input burst signal from the envelope of the input envelope signal detected by the input envelope detector 101 and outputs it to the second adaptive processor 108.

[0022] The memoryless PD unit 103a for envelope performs distortion compensation when an electrical memory effect (that is, the first memory effect) does not occur in the output-side envelope signal. The envelope memory PD 103b performs distortion compensation when an electrical memory effect (first memory effect) occurs in the output envelope signal. The burst memory PD unit 104 compensates for distortion when a thermal memory effect (that is, the second memory effect) occurs in the output burst signal. Make compensation.

[0023] The first LUT 105 stores a first distortion compensation coefficient (first inverse function of distortion) for performing optimum distortion compensation corresponding to the first memory effect generated in the output-side envelope signal. This is the first table. The second LUT 106 stores a second distortion compensation coefficient (second inverse function of distortion) for optimal distortion compensation corresponding to the second memory effect generated in the output burst signal. It is a table.

[0024] The first adaptive processing unit 107 calculates the envelope of the input envelope signal detected by the input envelope detector 101 and the envelope of the output envelope signal detected by the output envelope detector 110. In comparison, a distortion component due to the first memory effect of the output-side envelope signal generated by the power amplifying unit 112 is calculated, and a first distortion compensation coefficient (first distortion inverse) is used to optimally compensate for the distortion component. Function) and output to the first LUT105.

[0025] The second adaptive processing unit 108 includes an input side burst signal sampled and detected by the input burst detection unit 102 and an output side burst detection unit 111. Compared with the output-side burst signal sampled and detected, the distortion component due to the second memory effect of the output-side burst signal caused by the temperature fluctuation of the power amplifier 112 is calculated, and based on the temperature information from the temperature sensor 109 The second distortion compensation coefficient (second inverse function of distortion) for optimally compensating the distortion component is calculated and output to the second LUT 106.

The temperature sensor 109 detects the temperature of a device (not shown) in the power amplification unit 112 and outputs temperature information of the power amplification unit 112 to the second adaptive processing unit 108. The output-side envelope detection unit 110 detects the envelope of a signal that is output in force, such as a mobile phone (that is, the output-side envelope signal distorted by the power amplification unit 112), and the output-side burst detection unit 111 and the first envelope detection unit 110 To the adaptive processing unit 107. The output-side burst detector 111 samples and detects the envelope signal of the envelope signal detected by the output-side envelope detector 110 and outputs the burst signal to the second adaptive processor 108. The power amplifier 112 amplifies the input signal and outputs it.

Next, the operation of the distortion compensation circuit shown in FIG. 2 will be described. Input-side envelope detector 101 Input-side envelope obtained by detecting the envelope of the modulation signal input to the power amplifier 112 The bellows signal is output to the first adaptive processing unit 107, and the output-side envelope signal obtained by the output-side envelope detection unit 110 detecting the envelope of the modulation signal output from the power amplification unit 112 is output. Output to the first adaptive processing unit 107.

[0028] Then, the first adaptive processing unit 107 compares the input envelope signal detected by the input envelope detector 101 with the output envelope signal detected by the output envelope detector 110. Thus, the distortion component due to the first memory effect of the output side envelope signal generated by the power amplifier 112 is calculated, the first distortion compensation coefficient for optimally compensating the distortion component is calculated, and the first distortion compensation coefficient is calculated. Store in LUT105.

[0029] Thus, the memoryless PD unit 103a for envelopes is optimal from the first LUT 105 when there is no electrical memory effect (that is, the first memory effect) in the output-side envelope signal. Obtain the first distortion compensation coefficient and perform distortion compensation on the output envelope signal. In addition, the envelope memory PD 103b is configured so that the first memory generated in the output envelope signal from the first LUT 105 when the electrical memory effect (first memory effect) is generated in the output envelope signal. The first distortion compensation coefficient corresponding to the effect is acquired, and optimal distortion compensation is performed for the output envelope signal.

[0030] Furthermore, the input burst detector 102 samples and detects the envelope force of the input envelope signal detected by the input envelope detector 101, and outputs it to the second adaptive processor 108. At the same time, the output-side burst detection unit 111 detects the output-side burst signal from the envelope of the output-side envelope signal detected by the output-side envelope detection unit 110 and outputs it to the second adaptive processing unit 108.

[0031] Then, the second adaptive processing unit 108 compares the input burst signal sampled and detected by the input burst detector 102 with the output burst signal sampled and detected by the output burst detector 111. A distortion component due to the second memory effect of the output-side burst signal generated by the temperature fluctuation of the amplification unit 112 is calculated, and a second component for optimally compensating the distortion component based on the temperature information from the temperature sensor 109 is calculated. The distortion compensation coefficient is calculated and stored in the second LUT 106.

Accordingly, the burst memory PD unit 104 outputs the output from the second LUT 106 when a thermal memory effect (that is, the second memory effect) occurs in the output burst signal. The second distortion compensation coefficient corresponding to the second memory effect generated in the side burst signal is obtained, and optimal distortion compensation is performed for the output burst signal.

As described above, the distortion compensation circuit of the present invention performs distortion compensation by the first memory effect in the output-side envelope signal and distortion compensation by the second memory effect in the output-side burst signal by using individual PD units ( That is, it is performed by the envelope memory PD section 103b which is an envelope signal memory compensation circuit and the burst memory PD section 104) which is a burst signal memory compensation circuit. At this time, the burst memory PD section 104 properly performs distortion compensation by the second memory effect in the output burst signal based on the temperature information of the power amplification section 112 acquired from the temperature sensor 109.

Here, the internal configuration of burst memory PD section 104 applied to the present invention will be described. FIG. 3 is a first block diagram showing the function of burst memory PD section 104 and the configuration of its peripheral elements in the distortion compensation circuit shown in FIG. In other words, the function of the distortion component can be expressed by an orthogonal function of the I signal and the Q signal in the same way as the transmission signal. Therefore, as shown in FIG. 3, the complex arithmetic unit 121 of the burst memory PD unit 104 uses the second distortion compensation coefficient for optimally compensating for the distortion component due to the second memory effect as the I signal. Is obtained from the second LUT 106 as the orthogonal function (A + jB) of the Q signal and this orthogonal function (A + jB) is multiplied by the orthogonal function (C + jD) of the transmission signal. This makes it possible to properly compensate for distortion caused by the second memory effect.

FIG. 4 is a second block diagram showing the function of burst memory PD section 104 and the configuration of its peripheral elements in the distortion compensation circuit shown in FIG. That is, distortion compensation can be performed by correcting the phase and amplitude of the transmission signal. Therefore, as shown in FIG. 4, the burst memory PD unit 104 includes a variable phase unit 122 and a variable attenuation unit 123. The variable phase unit 122 adjusts the phase of the transmission signal, and the variable attenuation unit 123 adjusts the transmission signal. By adjusting the amplitude, the distortion compensation due to the second memory effect can be properly performed.

[0036] As described above, the distortion compensation circuit of the present invention is a new burst signal memory compensation circuit (envelope memory PD unit 103b) in addition to the conventional envelope signal memory compensation circuit (envelope memory PD unit 103b). By providing the burst memory PD section 104), the first electrical memory effect and the second thermal memory effect, which differ greatly in delay time, can be individually adapted. It becomes possible to do. As a result, the calculation time of the entire distortion compensation circuit can be shortened, and the table values of the first LUT 105 storing the first distortion compensation coefficient and the second LUT 106 storing the second distortion compensation coefficient can be reduced. Can be simple. As a result, it is possible to realize high-speed arithmetic processing and high efficiency in the distortion compensation circuit. Furthermore, since the envelope compensation force burst signal of the envelope signal can be easily detected in the distortion compensation circuit of the present invention, the detection circuit for detecting the burst signal is not likely to be complicated.

FIG. 5 is a block diagram showing a configuration of a distortion compensation circuit according to Embodiment 2 of the present invention. The distortion compensation circuit of the second embodiment shown in FIG. 5 differs from the distortion compensation circuit of the first embodiment shown in FIG. 2 in that the second adaptive processing unit 108 is deleted and a pattern determination unit 113 is added. The storage unit 114 is newly added.

[0038] The non-turn determining unit 113 includes the input burst signal detected by the input burst detector 102, the output burst signal sampled by the output burst detector 111, and the temperature information obtained from the temperature sensor 109. Based on the above, the second memory effect pattern generated in the output burst signal is determined, and the memory effect pattern is output to the storage unit 114. The storage unit 114 preliminarily stores the second memory effect generated in the burst signal on the output side, and based on the memory effect pattern information acquired from the pattern determination unit 113, the optimum distortion compensation coefficient V is obtained. And rewrite the table value of the second LUT 106 using this distortion compensation coefficient.

Next, the operation of the distortion compensation circuit according to the second embodiment shown in FIG. 5 will be described, but the description overlapping with that in the first embodiment will be omitted. Each time the amplitude or burst period of the burst signal on the output side changes, the storage unit 114 calls a memory effect pattern stored in advance and optimizes it based on the memory effect pattern information obtained from the pattern determination unit 113. The second distortion compensation coefficient is selected and the table value of the second LUT 106 is rewritten. As a result, the burst memory PD unit 104 obtains the second distortion compensation coefficient corresponding to the second memory effect from the second LUT 10 6 and performs optimal distortion compensation on the output burst signal. . In this way, the burst memory PD unit 104 uses the second distortion compensation coefficient stored in the pre-arranged storage unit 114, so that the second distortion compensation coefficient adaptive process is performed. Since the calculation can be omitted, the calculation time of the second distortion compensation coefficient can be further shortened compared to the distortion compensation circuit of the first embodiment.

Industrial applicability

[0041] According to the distortion compensation circuit of the present invention, the distortion caused by the first memory effect generated in the envelope signal and the distortion caused by the second memory effect generated in the burst signal are individually compensated for at high speed and with high accuracy. Therefore, it can be effectively used for a power amplifying apparatus such as a mobile phone in a next generation communication system.

Claims

The scope of the claims

[1] A distortion compensation circuit that performs distortion compensation of a transmission signal by a predistortion method, and that compensates for distortion caused by an electrical memory effect generated in an envelope signal that is a modulation signal of the transmission signal. And

A distortion compensation circuit comprising: a burst memory predistortion unit that compensates for distortion caused by a thermal memory effect generated in a burst signal obtained by an envelope of the envelope signal.

[2] The envelope memory predistortion unit compensates for distortion caused by an electrical memory effect generated in the envelope signal using the first distortion compensation coefficient stored in the first table,

The distortion according to claim 1, wherein the burst memory predistortion unit compensates for distortion caused by a thermal memory effect generated in the burst signal using a second distortion compensation coefficient stored in a second table. Compensation circuit.

[3] Furthermore, a temperature sensor for detecting the temperature of the power amplification unit that amplifies the power of the transmission signal is provided,

2. The distortion compensation circuit according to claim 1, wherein distortion due to a thermal memory effect generated in the burst signal is compensated based on temperature information detected by the temperature sensor.

[4] Furthermore, a temperature sensor that detects the temperature of a power amplification unit that amplifies the power of the transmission signal;

A burst detection unit for detecting the burst signal by an envelope of the envelope signal;

A pattern determination unit that determines a pattern of the thermal memory effect based on a burst signal detected by the burst detection unit and temperature information detected by the temperature sensor; and the thermal memory determined by the pattern determination unit A storage unit for storing an effect pattern,

The memory predistortion force for the burst Each time the amplitude or period of the burst signal changes by a predetermined amount, the pattern of the thermal memory effect stored in the storage unit 3. The distortion compensation circuit according to claim 2, wherein a second distortion compensation coefficient corresponding to a signal is selected as the second table force, and distortion caused by a thermal memory effect occurring in the burst signal is compensated.