JPWO2015118797A1 - Transmitting apparatus and transmitting method - Google Patents

Abstract

According to one embodiment, the transmission device (1) includes a modulation unit (13) that modulates a baseband signal (Ia, Qa) and outputs a high-frequency signal, and a high-output amplifier (14) that amplifies the high-frequency signal. And a distortion compensation unit (11) that performs distortion compensation processing on the baseband signal (I, Q) using a distortion compensation coefficient for compensating for output distortion included in the output signal of the high-power amplifier (14). Among the frequency components included in the baseband signal (Ia, Qa) subjected to distortion compensation processing, a frequency component whose amplitude becomes a predetermined value or more due to resonance generated in the high-power amplifier (14), An attenuating filter (12).

Description

  The present invention relates to a transmission device and a transmission method.

  High-power amplifiers that amplify high-frequency signals are provided in wireless communication devices such as mobile phone base stations and broadcast stations. This high-power amplifier outputs not only a signal (desired wave) obtained by amplifying a high-frequency signal but also intermodulation distortion (interference wave) generated in the high-power amplifier. Therefore, in general, a radio communication apparatus such as a base station provided in a radio communication system that handles relatively high transmission power, for example, power of about several watts to several tens of watts or more, is generated in a high output amplifier. As a distortion compensation method for compensating for the intermodulation distortion, for example, a digital pre-distortion (DPD) method for compensating for the intermodulation distortion at the stage of the digital baseband signal is adopted.

  A wireless communication apparatus adopting an adaptive digital predistortion method feeds back an RF (Radio Frequency) signal, which is an amplified signal of a high-power amplifier, and converts it to a digital signal, and then calculates a distortion compensation coefficient based on the digital signal. calculate. The digital signal input to the high output amplification is subjected to complex multiplication processing using a distortion compensation coefficient to compensate for intermodulation distortion generated in the high output amplifier.

  Techniques related to distortion compensation of a high-power amplifier are disclosed in Patent Document 1 and Patent Document 2. Patent Document 1 discloses a configuration example of a high-power amplifier. Patent Document 2 shows an example of a distortion compensation circuit that compensates for intermodulation distortion included in an output signal of a high-power amplifier.

  In the above wireless communication device, a wideband signal is amplified in order to efficiently use the frequency, reduce the cost, and further increase the communication capacity in response to the traffic increase accompanying the increase in content. The demand for sending is increasing. As the signal bandwidth increases to satisfy this requirement, the frequency bandwidth in which intermodulation distortion occurs is also increased.

  By the way, in the transistor device which is an amplifying element constituting the high-power amplifier, the video frequency band (for example, a band equal to or wider than the frequency band of the baseband signal, specifically, approximately several tens of megahertz to several hundreds of bands). Resonance occurs at a frequency in the range of megahertz and lower than the frequency of the high-frequency signal (specifically, a frequency band including a frequency of around 100 MHz), affecting the intermodulation distortion generated when the high-frequency signal is amplified. Is known to affect.

  For example, Non-Patent Document 1 discloses that resonance occurs in the video frequency band due to a matching circuit and a bias circuit inside a transistor device, thereby degrading DPD distortion compensation characteristics. In the configuration of Non-Patent Document 1, the configuration of the matching circuit and the bias circuit inside the transistor is devised to increase the video resonance frequency, thereby making it difficult for the video frequency band resonance to be excited due to the signal and distortion. The deterioration of compensation characteristics is prevented. Further, for example, Non-Patent Document 2 discloses the frequency dependence of transmission intermodulation distortion due to resonance in a video frequency band in a transistor. According to Non-Patent Document 2 (FIG. 8), the intermodulation distortion component increases near a specific detuning frequency.

JP 2012-186568 A JP-A-01-225231

Hussain H. Ladhani et al, "Improvements in the Instantaneous-Bandwidth Capability of RF Power Transistors using In-Package High-k Capacitors", IEEE MTT-S International Publication, 2011, pp1-4 freescale Semiconductor, Inc., “Technical Data”, [online], [searched January 6, 2014], Internet, <URL: http://www.freescale.com/files/rf_if/doc/data_sheet/MRF7S21080H. pdf>

  Against this background, a component of a predetermined frequency (for example, a video band frequency around 100 MHz; hereinafter referred to as “resonance frequency”) that causes resonance in a high-power amplifier is directly or mainly a high-frequency signal or intermodulation distortion. When a high-frequency signal including a resonance frequency component in the envelope component of the signal is input to the high-power amplifier or output from the high-power amplifier, the DPD distortion compensation characteristic is deteriorated due to the resonance generated at the resonance frequency. In addition, there is a possibility that the reliability of the high-power amplifier is lowered. Other problems and novel features will become apparent from the description of the specification and the accompanying drawings.

  The present invention has been made to solve such a problem, and is included by controlling or suppressing the resonance frequency component included in the output signal of the high-power amplifier or included in the input signal of the high-power amplifier. An object of the present invention is to provide a transmission apparatus and a transmission method capable of further improving the reliability by attenuating the resonance frequency component.

  According to an embodiment, a transmission device compensates for output distortion included in an output signal of the amplifier, a modulation unit that modulates a baseband signal and outputs a high-frequency signal, an amplifier that amplifies the high-frequency signal, and the amplifier A distortion compensator for performing distortion compensation processing on the baseband signal using a distortion compensation coefficient for generating the frequency component included in the baseband signal subjected to the distortion compensation processing. And a first filter that attenuates a frequency component whose amplitude becomes a predetermined value or more due to resonance.

  Further, according to an embodiment, the transmission device includes a modulation unit that modulates a baseband signal and outputs a high-frequency signal, an amplifier that amplifies the high-frequency signal, and a frequency component included in the baseband signal. And a filter for attenuating a frequency component whose amplitude exceeds a predetermined value due to resonance generated by the amplifier.

  Further, according to an embodiment, the transmission device compensates for output distortion included in the output signal of the amplifier, a modulation unit that modulates a baseband signal and outputs a high-frequency signal, an amplifier that amplifies the high-frequency signal, and A distortion compensation unit that performs distortion compensation processing on the baseband signal using a distortion compensation coefficient to attenuate, and a predetermined frequency component among the frequency components included in the baseband signal that has been subjected to distortion compensation processing And a band rejection filter that performs.

  According to one embodiment, the transmission method modulates a baseband signal to output a high frequency signal, amplifies the high frequency signal by an amplifier, and compensates for output distortion included in the output signal of the amplifier. The baseband signal is subjected to a distortion compensation process using the distortion compensation coefficient, and the amplitude of the frequency component included in the baseband signal subjected to the distortion compensation process is increased by resonance generated in the amplifier. A frequency component that exceeds a predetermined value is attenuated.

  According to the one embodiment, the resonance frequency component included in the output signal of the high output amplifier is controlled or suppressed, or the resonance frequency component included in the input signal of the high output amplifier is attenuated. It is possible to provide a transmission device and a transmission method that can further improve the performance.

1 is a block diagram illustrating an outline of a transmission device according to a first exemplary embodiment; FIG. 3 is a diagram illustrating a relationship between an input signal and an output signal of a single high-power amplifier provided in the transmission apparatus according to the first exemplary embodiment. FIG. 5 is a diagram for explaining a distortion compensation method by a distortion compensation unit 11 provided in the transmission apparatus according to the first exemplary embodiment; The difference frequency Δf of the high-frequency signal input to the high-power amplifier 14 provided in the transmission apparatus according to the first embodiment, and the output distortion (third-order distortion) included in the high-frequency wireless signal output from the high-power amplifier 14 It is a figure which shows the relationship. 2 is a block diagram illustrating a specific configuration example of a transmission apparatus according to a first embodiment; FIG. It is a figure for demonstrating the characteristic of each filter 12,15. It is a figure which shows the relationship between the frequency of the input / output signal of the high output amplifier 14, and a power spectrum. It is a figure for demonstrating the determination method of the attenuation amount of the resonant frequency by the filter. It is a figure for demonstrating the determination method of the attenuation amount of the resonant frequency by the filter. FIG. 6 is a block diagram illustrating a specific configuration example of a transmission device according to a second exemplary embodiment; It is a figure for demonstrating the characteristic of each filter 114,115 provided on the feedback path | route. It is a figure for demonstrating the characteristic of each filter 114a, 115 provided on the feedback path | route. It is a figure for demonstrating the characteristic of each filter 114b and 115 provided on the feedback path | route. FIG. 6 is a block diagram illustrating an outline of a transmission apparatus according to a third embodiment; FIG. 6 is a block diagram illustrating a specific configuration example of a transmission device according to a third exemplary embodiment;

  Hereinafter, embodiments will be described with reference to the drawings. Since the drawings are simple, the technical scope of the embodiments should not be narrowly interpreted based on the description of the drawings. Moreover, the same code | symbol is attached | subjected to the same element and the overlapping description is abbreviate | omitted.

  In the following embodiments, when it is necessary for the sake of convenience, the description will be divided into a plurality of sections or embodiments. However, unless otherwise specified, they are not irrelevant to each other. Are partly or entirely modified, application examples, detailed explanations, supplementary explanations, and the like. Further, in the following embodiments, when referring to the number of elements (including the number, numerical value, quantity, range, etc.), especially when clearly indicated and when clearly limited to a specific number in principle, etc. Except, it is not limited to the specific number, and may be more or less than the specific number.

  Further, in the following embodiments, the constituent elements (including operation steps and the like) are not necessarily essential except when clearly indicated and clearly considered essential in principle. Similarly, in the following embodiments, when referring to the shapes, positional relationships, etc. of the components, etc., the shapes are substantially the same unless otherwise specified, or otherwise apparent in principle. And the like are included. The same applies to the above numbers and the like (including the number, numerical value, quantity, range, etc.).

<Embodiment 1>
FIG. 1 is a block diagram illustrating an outline of the transmission apparatus according to the first embodiment. The transmission device according to the present embodiment is used, for example, in a transmission part of a wireless communication device such as a mobile phone base station or a broadcast station. Among the frequency components included in the input signal of the high output amplifier, the high output amplifier A filter is provided that attenuates a frequency component (that is, a resonance frequency component) whose amplitude becomes equal to or greater than a predetermined value due to the generated resonance. As a result, the transmitting apparatus according to the present embodiment can suppress the frequency component that causes resonance in the high-power amplifier, and can therefore improve the reliability. This will be specifically described below.

  Since the resonance frequency component itself is generally separated from the frequency of the desired high-frequency signal, it is almost always removed using a filter or the like before being input to the high-power amplifier. Therefore, in the following, the case where the resonance frequency component itself is input to the high-power amplifier is not described, and a high-frequency signal including the resonance frequency component in the envelope component such as a high-frequency signal or intermodulation distortion is input to the high-power amplifier. Only the case will be described.

  The transmission apparatus 1 according to the present embodiment includes a distortion compensation unit 11, a filter (first filter; band rejection filter) 12, a modulation unit 13, and a high-power amplifier (amplifier) 14.

  The modulation unit 13 modulates baseband signals (baseband signals subjected to distortion compensation processing) Ia and Qa supplied via the filter 12 and outputs a high-frequency signal. Details of the baseband signals Ia and Qa will be described later.

  The high output amplifier 14 amplifies the high frequency signal output from the modulation unit 13 and outputs a high frequency wireless signal. This high-frequency radio signal is wirelessly transmitted to the outside via an antenna (not shown). The high-power amplifier 14 is composed of a transistor device such as a bipolar transistor or a field effect transistor.

  Here, the high-power amplifier 14 actually includes not only a signal (desired wave) obtained by amplifying a high-frequency signal but also distortion (interference wave; hereinafter referred to as output distortion) generated in the high-power amplifier 14. Output as a high-frequency radio signal. Hereinafter, a specific description will be given with reference to FIG.

  FIG. 2 is a diagram schematically showing the relationship between the input signal and output signal of the high-power amplifier 14 alone. The vertical axis represents the spectrum, and the horizontal axis represents the frequency. In the example of FIG. 2, the high-power amplifier 14 amplifies a high-frequency signal (broken arrow) including two frequency components having a difference of Δf, and outputs a high-frequency radio signal (solid arrow).

  As shown in FIG. 2, when a high frequency signal is input to the high output amplifier 14, not only a signal (desired wave) obtained by amplifying the high frequency signal but also output distortion (interference wave) is output as a high frequency radio signal. The Note that FIG. 2 shows only third-order distortion (IM3) and fifth-order distortion (IM5) as output distortion.

  Returning to FIG. 1, the distortion compensation unit 11 performs distortion compensation processing on the baseband signals I and Q using a distortion compensation coefficient for compensating for output distortion included in the output signal of the high-power amplifier 14. Output as baseband signals Ia and Qa. The distortion compensation unit 11 performs so-called digital predistortion distortion compensation. Hereinafter, a specific description will be given with reference to FIG.

  FIG. 3 is a diagram for explaining a distortion compensation method by the distortion compensator 11. As shown in FIG. 3, the output signal of the high-power amplifier 14 before distortion compensation includes output distortion (dotted arrow). Therefore, the distortion compensator 11 generates a distortion compensation component such that the input distortion (dotted arrow) opposite to the output distortion (dotted arrow) is input to the high-power amplifier 14 as baseband signals I and Q. And output as baseband signals Ia and Qa. As a result, the output distortion included in the output signal of the high-power amplifier 14 before distortion compensation is canceled by the input distortion. Therefore, the high-power amplifier 14 can output a high-frequency radio signal (solid arrow) with high accuracy in which output distortion is suppressed. Note that since the frequency of the baseband signal is about half that of the band frequency of the modulated high-frequency signal, distortion compensation or the like needs to be performed in consideration of this point. In the example of FIG. 3, assuming that the modulated wave (carrier wave) is in the center of the high-frequency radio signal (solid arrow), the IM3 component represented by the detuning frequency of Δf in the case of the high-frequency signal is the baseband signal. Then, the frequency becomes Δf / 2.

  Returning to FIG. 1, the filter 12 includes a frequency component whose amplitude becomes equal to or higher than a predetermined value due to resonance generated in the high-power amplifier 14 and its peripheral frequency component (of the frequency components included in the baseband signals Ia and Qa). That is, the resonance frequency component) is attenuated until the amplitude becomes less than a predetermined value. As described above, since the frequency of the baseband signal is about half as small as the band frequency of the modulated high frequency signal, it is necessary to perform filtering in consideration of this point.

  As described above, a high-frequency signal having a resonance frequency component (for example, a video band frequency component around 100 MHz) directly or a high-frequency signal mainly including a resonance frequency component in an envelope component such as a high-frequency signal or intermodulation distortion is high output. When the signal is input to the amplifier 14 or output from the high-power amplifier 14, the reliability of the high-power amplifier may be lowered due to the influence of resonance generated at the resonance frequency. Here, the high-power amplifier 14 is generally driven so as to output electric power in the vicinity of saturation power in order to realize high-efficiency operation. Therefore, when the amplitude of the frequency component generated by the resonance generated in the high-power amplifier 14 is larger than a predetermined value, the voltage applied to the transistor is the signal amplitude that is the desired wave, the power supply voltage, and the amplitude of the resonance frequency component As a result, the margin with respect to the withstand voltage of the transistor decreases or exceeds the withstand voltage. As a result, the characteristics of the transistor may be deteriorated or the transistor may be destroyed. Therefore, the transmission apparatus 1 suppresses a frequency component (that is, a resonance frequency component) at which resonance occurs in the high-power amplifier 14 by performing the filtering using the filter 12. As a result, the margin for the operation of the transistor becomes higher and the characteristic deterioration and destruction are suppressed, so that the reliability of the transmission device 1 is improved. Further, not only in a steady state but also in a transient state such as during a distortion pull-in operation or a sudden change in traffic, a further margin can be ensured, which contributes to an improvement in the reliability of the transmission apparatus 1.

  FIG. 4 is a diagram showing the relationship between the difference frequency Δf of the high-frequency signal input to the high-power amplifier 14 and the output distortion (third-order distortion) included in the high-frequency radio signal output from the high-power amplifier 14. The vertical axis represents the D / U ratio (ratio of the intensity of the desired wave and the interference wave), and the horizontal axis represents the difference frequency Δf.

  As shown in FIG. 4, when the difference frequency Δf is a resonance frequency (for example, a video band frequency around 100 MHz), it can be seen that the D / U ratio is deteriorated (third-order distortion is increased). As described above, this is because a high-frequency signal including a resonance frequency component (in this example, two frequency components whose difference frequency Δf is the resonance frequency) is input to the high-power amplifier 14 having nonlinearity. This is because the transistor provided in the high-power amplifier 14 is excited at the resonance frequency.

  The same applies to the case where the difference frequency Δf of the input distortion for compensating the third-order distortion is the resonance frequency. Therefore, in the transmission apparatus 1 according to the present embodiment, the input distortion for third-order distortion compensation whose difference frequency Δf is the resonance frequency is attenuated by the filter 12. As a result, the frequency component that causes resonance in the high-power amplifier 14 is suppressed, and deterioration and destruction of the characteristics of the transistor are suppressed, so that the reliability of the transmission device 1 is improved. At this time, the third-order distortion component output from the high-power amplifier 14 is not compensated by the distortion compensator 11 as compared with the case where the filter 12 is not provided. It can be suppressed by means.

  Note that filtering by the filter 12 is basically performed for input distortion that compensates for third-order distortion. Of course, for other input distortion that compensates for higher-order distortion, for example, For example, a plurality of notch zones may be provided.

  As described above, the transmission apparatus 1 according to the present embodiment has a frequency whose amplitude becomes equal to or higher than a predetermined value due to resonance generated in the high-power amplifier 14 among the frequency components included in the input signal of the high-power amplifier 14. A filter 12 for attenuating the component (that is, the resonance frequency component) is provided. As a result, the transmission apparatus 1 according to the present embodiment can suppress the frequency component that causes resonance in the high-power amplifier 14 to further increase the margin for the operation of the transistor, or suppress the deterioration and destruction of characteristics. Therefore, reliability can be improved. In a market situation where the frequency band used for wireless communication in the future increases as a countermeasure against traffic increase, the frequency components that cause resonance in the high-power amplifier 14 within the distortion compensation band. Since there is a high possibility that (that is, a resonance frequency component) will enter, the transmission device 1 according to the present embodiment is particularly effective.

(Specific configuration example of the transmission device 1)
FIG. 5 is a block diagram illustrating a specific configuration example of the transmission device 1 according to the present embodiment as the transmission device 1a. 5 includes a distortion compensation unit 11, a filter 12, a modulation unit 13, and a high-power amplifier 14, a low-pass filter (LPF) 15, a DA converter (DAC) 16, a frequency converter 17, and a band-pass filter. 18, an antenna 19 and a local oscillator 20 are further provided. The distortion compensation unit 11 includes a frequency converter 111, an AD converter 112, a demodulation unit 113, a low-pass filter 115, a distortion calculation unit 116, a power calculation unit 117, a memory 118, and a signal processing unit 119.

  The low-pass filter 15 removes unnecessary high-frequency components contained in the baseband signals Ia and Qa and outputs them to the filter 12. Note that the low-pass filter 15 may be provided after the filter 12. Alternatively, one filter may be configured by the filter 12 and the low-pass filter 15. Alternatively, the filter 12 and the low-pass filter 15 may be incorporated in a part of the distortion compensation unit 11.

  The DA converter 16 DA-converts the output signal (here, an intermediate signal) from the modulation unit 13 and outputs the result. The frequency converter 17 mixes the output signal (intermediate signal) of the DA converter 16 and the local signal LO from the local oscillator 20 and outputs a high-frequency signal.

  The bandpass filter 18 removes unnecessary components contained in the high-frequency radio signal output from the high-power amplifier 14 and outputs the result. The high-frequency radio signal that has passed through the band-pass filter 18 is wirelessly transmitted to the outside via the antenna 19.

  In the distortion compensator 11, the frequency converter 111 mixes the high-frequency radio signal output from the high-power amplifier 14 with the local signal LO from the local oscillator 20 and outputs an intermediate signal. The AD converter 112 AD-converts and outputs the output signal (intermediate signal) of the frequency converter 111. The demodulator 113 demodulates the output signal (intermediate signal) of the AD converter 112 and outputs baseband signals (feedback signals) Ib and Qb. The low-pass filter 115 removes unnecessary high-frequency components contained in the baseband signals Ib and Qb and outputs them.

  The distortion calculation unit 116 calculates the output distortion included in the output signal of the high-power amplifier 14 from the baseband signals Ib and Qb. For example, the distortion calculation unit 116 compares the baseband signals Ia and Qa with the baseband signals Ib and Qb and calculates the difference as output distortion. The power calculation unit 117 calculates the power of the baseband signals I and Q. The memory 118 stores a plurality of distortion compensation coefficients, and outputs one of the distortion compensation coefficients selected based on the calculation results of the distortion calculation unit 116 and the power calculation unit 117 to the signal processing unit 119. The signal processing unit 119 performs distortion compensation processing on the baseband signals I and Q using the distortion compensation coefficient read from the memory 118, and outputs the baseband signals Ia and Qa. In other words, the signal processing unit 119 adds distortion compensation components for compensating output distortion to the baseband signals I and Q, and outputs them as baseband signals Ia and Qa.

  FIG. 6 is a diagram for explaining the characteristics of the filters 12 and 15. The vertical axis represents the attenuation amount of each of the filters 12 and 15, and the horizontal axis represents the frequency (Δf / 2) of the baseband signals Ia and Qa. FIG. 6 further shows a diagram illustrating the relationship between the difference frequency Δf of the high-frequency signal described in FIG. 4 and the IM3 component.

  As shown in FIG. 6, the low-pass filter 15 removes unnecessary high frequency components of 200 MHz or more from the frequency components included in the baseband signals Ia and Qa. This is equivalent to removing the difference frequency Δf of about 400 MHz or more in terms of the difference frequency Δf of the high-frequency signal input to the high-power amplifier 14. Therefore, the low-pass filter 15 passes not only the signal band but also a distortion compensation band of about 5 to 7 times the signal band, for example.

  Further, the filter 12 includes a frequency component whose amplitude is equal to or greater than a predetermined value due to resonance generated in the high-power amplifier 14 among frequency components included in the baseband signals Ia and Qa and its peripheral frequency components (that is, resonance). Frequency component) is attenuated until its amplitude is less than a predetermined value. Specifically, the filter 12 attenuates a frequency component around 50 MHz at which resonance occurs in the high-power amplifier 14. In terms of the difference frequency Δf of the high-frequency signal input to the high-power amplifier 14, this is equivalent to attenuating the difference frequency Δf around 100 MHz. Therefore, a frequency component (that is, a resonance frequency component) at which resonance occurs in the high output amplifier 14 is suppressed. As a result, the margin for the operation of the transistor becomes higher and the characteristic deterioration and destruction are suppressed, so that the reliability of the transmission device 1 is improved.

The filter 12 preferably does not completely remove the resonance frequency component.
Hereinafter, with reference to FIG. 7, a problem when the resonance frequency component is completely removed by the filter 12 will be described. FIG. 7 is a diagram showing the relationship between the frequency of the input / output signal of the high-power amplifier 14 and the power spectrum.

  In the example of FIG. 7, the signal component obtained by completely removing the resonance frequency component using the filter 12 is input to the high-power amplifier 14. In this case, the resonant frequency component is certainly not input to the high output amplifier 14, but as a result, the output distortion near the resonant frequency among the distortions generated in the high output amplifier 14 is not performed. For this reason, there is a possibility that the operation margin with respect to the breakdown voltage of the transistor may be reduced, or the characteristics may be deteriorated or broken due to the influence of the output distortion in the vicinity of the resonance frequency which is not compensated.

  In short, when a signal component from which the resonance frequency component has been completely removed using the filter 12 is input to the high output amplifier 14, the operation margin with respect to the breakdown voltage of the transistor is reduced due to the influence of the output distortion in the vicinity of the remaining resonance frequency. Or deterioration of characteristics or destruction may occur. On the other hand, when an input distortion that can substantially compensate for the output distortion is directly input to the high-output amplifier 14 without using the filter 12, the input distortion near the resonance frequency excites the resonance, and the influence causes the transistor. There is a possibility that the operating margin with respect to the withstand voltage will be reduced, and that characteristic deterioration and destruction may occur. That is, the video band resonance frequency component of the transistor may be excited by output distortion remaining without compensation, excitation by input distortion, or both. Therefore, it is desirable that the attenuation amount of the resonance frequency by the filter 12 is determined in consideration of this point.

  FIG. 8 is a diagram for explaining a method of determining the attenuation amount of the resonance frequency by the filter 12. In FIG. 8, a vector IMo represents a vector of output distortion before distortion compensation of the high-power amplifier 14, and a vector IMin represents a vector obtained by converting input distortion for compensating output distortion near the resonance frequency to the output side. , Vector IMout represents a vector of output distortion after distortion compensation of the high-power amplifier 14.

  As shown in FIG. 8, when the vector IMo is canceled by the vector IMin, the cancellation amount C [dB] is expressed as follows when α = | IMin | / | IMo |.

C = 10 × log (1 + α ² −2 · α · cos (Δθ))

In the true value, C = (1 + α ² −2 · α · cos (Δθ))

  In order to simplify the explanation, θ = 0 deg and the absolute value of the vector IMin is normalized with the absolute value of the vector IMout when distortion compensation is not performed, as shown in FIG. As shown in FIG. 9, when the absolute value of the vector IMin is not equal to the vector IMo, which is a value to be compensated for, but is half of that (ie, α = 0.5), the input distortion And the magnitude of output distortion becomes equal. Specifically, -6 dB compensation is obtained for output distortion, and -6 dB reduction in excitation component is obtained for input distortion. This is an example for compensating the output distortion while lowering the distortion excitation level on the input side, and it is possible to compensate for the input distortion and the distortion according to the characteristics of the transistor used, the distortion compensation method, the distortion compensation operation speed, etc. It is preferable to determine the attenuation amount of the resonance frequency by the filter 12 so that the output distortion is comprehensively suppressed and the operation margin with respect to the breakdown voltage of the transistor is further increased. The determination of the attenuation amount of the filter 12 is not limited to a static one but may be a dynamic one.

<Embodiment 2>
FIG. 10 is a block diagram of a specific configuration example of the transmission device 1b according to the second embodiment. A transmission device 1b illustrated in FIG. 10 includes a distortion compensation unit 11b instead of the distortion compensation unit 11 as compared with the transmission device 1a illustrated in FIG. The distortion compensation unit 11b further includes a filter (second filter) 114. Since the other configuration and operation of the transmission device 1b are the same as those of the transmission device 1a, description thereof is omitted.

  The filter 114 attenuates frequency components in the same frequency band as the frequency component attenuated by the filter 12 among the frequency components included in the baseband signals Ib and Qb demodulated by the demodulation unit 113. Thereby, it is possible to cause the distortion compensator 11b to determine that the output distortion of the frequency band is suppressed. As a result, the subsequent processing load on the distortion compensator 11b is reduced.

  Thus, the transmission device 1b according to the present embodiment can achieve the same effects as the transmission device 1a according to the first embodiment. Furthermore, the transmission apparatus 1b according to the present embodiment includes a filter 114 that attenuates a frequency component in the same frequency band as the frequency component attenuated by the filter 12 on the feedback path. Thereby, the transmission apparatus 1b according to the present embodiment can cause the distortion compensation unit 11b to determine that the output distortion of the frequency band has been suppressed, and can reduce the processing load on the subsequent distortion compensation unit 11b.

  FIG. 11 is a diagram for explaining the characteristics of the filters 114 and 115 provided on the feedback path. The vertical axis represents the attenuation amount of each of the filters 114 and 115, and the horizontal axis represents the frequency (Δf / 2) of the baseband signals Ib and Qb.

  As shown in FIG. 11, the low-pass filter 115 removes unnecessary high-frequency components of 200 MHz or more from the frequency components included in the baseband signals Ib and Qb demodulated by the demodulator 113. This is equivalent to removing the difference frequency Δf of about 400 MHz or higher in terms of the difference frequency Δf of the high-frequency signal output from the high-power amplifier 14. Therefore, the low-pass filter 115 passes not only the signal band but also a distortion compensation band of about 5 to 7 times the signal band, for example.

  Further, the filter 114 is a frequency component in the same frequency band (around 50 MHz in this example) as the frequency component attenuated by the filter 12 among the frequency components included in the baseband signals Ib and Qb demodulated by the demodulation unit 113. Is attenuated. This is equivalent to removing the difference frequency Δf of around 100 MHz in terms of the difference frequency Δf of the high-frequency signal output from the high-power amplifier 14. As a result, it is possible to cause the distortion compensator 11b to determine that the output distortion of the frequency band has been suppressed, and to reduce the subsequent processing burden on the distortion compensator 11b.

  The configuration of the filter 114 is not limited to the above. For example, the filter 114 may be configured to remove a frequency component in the same frequency band as the frequency component attenuated by the filter 12 from the frequency components included in the baseband signals Ib and Qb. Hereinafter, the filter 114 having such a configuration is referred to as a filter 114a.

  FIG. 12 is a diagram for explaining the characteristics of the filters 114a and 115. FIG. The vertical axis represents the attenuation amount of each of the filters 114a and 115, and the horizontal axis represents the frequency (Δf / 2) of the baseband signals Ib and Qb.

  As shown in FIG. 12, the filter 114a has the same frequency band as the frequency component attenuated by the filter 12 among the frequency components included in the baseband signals Ib and Qb demodulated by the demodulation unit 113 (in this example, 50 MHz). The frequency component before and after) is removed. Accordingly, the filter 114a can cause the distortion compensator 11b to determine that the output distortion of the frequency band is suppressed, similarly to the case of the filter 114, and can reduce the processing load on the subsequent distortion compensator 11b.

  In addition, the filter 114 is a filter of the frequency components included in the baseband signals Ib and Qb in accordance with the processing content of the subsequent distortion compensation unit 11b and the circuit configuration of the transistor used for amplification, particularly the circuit related to video band resonance. 12 may be configured to amplify the same frequency component as that attenuated by 12. Hereinafter, the filter 114 having such a configuration is referred to as a filter 114b.

  FIG. 13 is a diagram for explaining the characteristics of the filters 114b and 115. FIG. The vertical axis represents the attenuation amount of each of the filters 114b and 115, and the horizontal axis represents the frequency (Δf / 2) of the baseband signals Ib and Qb.

  As illustrated in FIG. 13, the filter 114 b has the same frequency band as the frequency component attenuated by the filter 12 among the frequency components included in the baseband signals Ib and Qb demodulated by the demodulation unit 113 (in this example, 50 MHz). The frequency component of the front and rear is amplified. Even in such a configuration, the distortion compensator 11b may determine that output distortion in the frequency band has been suppressed, and the subsequent processing burden on the distortion compensator 11b may be reduced.

  Further, instead of including the filter 114, the distortion compensator 11b excludes output distortion in the frequency band of the frequency component attenuated by the filter 12 from the components to be compensated among the frequency components included in the baseband signals Ib and Qb. May be configured to perform processing.

<Embodiment 3>
FIG. 14 is a block diagram of an outline of the transmission device 2 according to the third embodiment. The transmission apparatus 2 illustrated in FIG. 14 does not include the distortion compensation unit 11 as compared with the transmission apparatus 1 illustrated in FIG. Other configurations and operations of the transmission apparatus 2 illustrated in FIG. 14 are the same as those of the transmission apparatus 1 illustrated in FIG.

  For example, the transmitter 2 shown in FIG. 14 uses the filter 12 to resonate the high-frequency signal including a resonance frequency component (for example, a component of a video band frequency around 100 MHz) so that the high-power amplifier 14 does not intentionally input the resonance signal. The frequency component is attenuated.

  Thereby, the transmission apparatus 2 concerning this Embodiment can have an effect equivalent to the case of Embodiment 1. FIG.

(Specific configuration example of the transmission device 2)
FIG. 15 is a block diagram of a specific configuration example of the transmission device 2 according to the third embodiment as the transmission device 2a. The transmission apparatus 2a illustrated in FIG. 15 does not include the distortion compensation unit 11 as compared with the transmission apparatus 1a illustrated in FIG. Other configurations and operations of the transmission apparatus 2a illustrated in FIG. 15 are the same as those of the transmission apparatus 1a illustrated in FIG.

  As described above, the transmission apparatus according to the first to third embodiments has a frequency at which the amplitude becomes a predetermined value or more due to resonance generated in the high-power amplifier 14 among the frequency components input to the high-power amplifier 14. A filter 12 for attenuating the component is provided. Thereby, the transmitter according to the first to third embodiments suppresses frequency components that cause resonance in the high-power amplifier 14 to further increase the margin for the operation of the transistor, and suppress deterioration and destruction of characteristics. Therefore, reliability can be improved.

  In the first to third embodiments, the case where the filter 12 is provided in front of the modulation unit 13 has been described as an example. However, the present invention is not limited to this. The filter 12 may be provided at a stage subsequent to the modulation unit 13.

  Note that the filter inserted in the IQ baseband band of a transmission apparatus that normally employs the DPD method is a low-pass filter having a signal band and a distortion compensation band as a pass band, and exhibits distortion compensation capability. In general, the frequency characteristics in the passband are generally flattened. On the other hand, the transmitting apparatus according to the above embodiment intentionally attenuates or amplifies the frequency characteristic in the vicinity of the video band frequency of the amplifying element in the pass band, while the other band in the pass band generally By maintaining the distortion compensation capability, the reliability of the transmission apparatus is further improved.

  Although the present invention has been described with reference to the exemplary embodiments, the present invention is not limited to the above. Various changes that can be understood by those skilled in the art can be made to the configuration and details of the present invention within the scope of the invention.

  This application claims the priority on the basis of Japanese application Japanese Patent Application No. 2014-019503 for which it applied on February 4, 2014, and takes in those the indications of all here.

1, 1a, 1b Transmitting device 2, 2a Transmitting device 11 Distortion compensation unit 11b Distortion compensation unit 12 Filter (first filter)
DESCRIPTION OF SYMBOLS 13 Modulation part 14 High output amplifier 15 Low pass filter 16 DA converter 17 Frequency converter 18 Filter 19 Antenna 20 Local oscillator 111 Frequency converter 112 AD converter 113 Demodulation part 114 Filter (2nd filter)
114a filter 114b filter 115 low-pass filter 116 distortion calculation unit 117 power calculation unit 118 memory 119 signal processing unit

Claims (9)

Modulation means for modulating a baseband signal and outputting a high-frequency signal;
An amplifier for amplifying the high-frequency signal;
Distortion compensation means for performing distortion compensation processing on the baseband signal using a distortion compensation coefficient for compensating output distortion included in the output signal of the amplifier;
A first filter for attenuating frequency components included in the baseband signal that has undergone distortion compensation processing such that the amplitude is equal to or greater than a predetermined value due to resonance generated by the amplifier; Transmitter device.   The first filter includes, among the frequency components included in the baseband signal subjected to distortion compensation processing, a frequency component whose amplitude is equal to or greater than the predetermined value due to resonance generated in the amplifier, The transmission device according to claim 1, wherein the transmission device attenuates until the predetermined value is reached. The distortion compensation means includes
Demodulation means for demodulating the output signal of the amplifier and outputting a feedback signal;
A second filter that gives a predetermined gain to a frequency component in the same frequency band as the frequency component attenuated by the first filter among the frequency components included in the feedback signal;
3. The transmission device according to claim 1, wherein the distortion compensation unit obtains the output distortion included in an output signal of the amplifier from the feedback signal that has passed through the second filter.   The transmission device according to claim 3, wherein the second filter attenuates a frequency component in the same frequency band as the frequency component attenuated by the first filter among frequency components included in the feedback signal.   The transmission apparatus according to claim 1, wherein the distortion compensation unit excludes the output distortion in a frequency band of a frequency component attenuated by the first filter from a compensation target. The distortion compensation means adds an input distortion for compensating the output distortion to the baseband signal,
The amount of attenuation of the frequency component attenuated by the first filter is determined based on the magnitudes of the input distortion in the frequency component and the output distortion after being compensated by the input distortion. The transmission apparatus as described in any one of Claims 1-4. Modulation means for modulating a baseband signal and outputting a high-frequency signal;
An amplifier for amplifying the high-frequency signal;
A transmission apparatus comprising: a filter that attenuates a frequency component having an amplitude that is greater than or equal to a predetermined value due to resonance generated in the amplifier among frequency components included in the baseband signal. Modulation means for modulating a baseband signal and outputting a high-frequency signal;
An amplifier for amplifying the high-frequency signal;
Distortion compensation means for performing distortion compensation processing on the baseband signal using a distortion compensation coefficient for compensating output distortion included in the output signal of the amplifier;
A transmission apparatus comprising: a band rejection filter that attenuates a predetermined frequency component among frequency components included in the baseband signal subjected to distortion compensation processing. Modulate baseband signal and output high frequency signal,
Amplifying the high frequency signal by an amplifier;
Using a distortion compensation coefficient for compensating for output distortion included in the output signal of the amplifier, performing distortion compensation processing on the baseband signal,
A transmission method for attenuating a frequency component having an amplitude equal to or greater than a predetermined value due to resonance generated by the amplifier, among frequency components included in the baseband signal subjected to distortion compensation processing.

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