WO2012035713A1 - Class d amplifier and wireless communication device - Google Patents

Class d amplifier and wireless communication device Download PDF

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Publication number
WO2012035713A1
WO2012035713A1 PCT/JP2011/004944 JP2011004944W WO2012035713A1 WO 2012035713 A1 WO2012035713 A1 WO 2012035713A1 JP 2011004944 W JP2011004944 W JP 2011004944W WO 2012035713 A1 WO2012035713 A1 WO 2012035713A1
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signal
class
switching voltage
amplifier
output
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PCT/JP2011/004944
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French (fr)
Japanese (ja)
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和司 高梨
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パナソニック株式会社
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    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03F—AMPLIFIERS
    • H03F3/00—Amplifiers with only discharge tubes or only semiconductor devices as amplifying elements
    • H03F3/20—Power amplifiers, e.g. Class B amplifiers, Class C amplifiers
    • H03F3/24—Power amplifiers, e.g. Class B amplifiers, Class C amplifiers of transmitter output stages
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03F—AMPLIFIERS
    • H03F1/00—Details of amplifiers with only discharge tubes, only semiconductor devices or only unspecified devices as amplifying elements
    • H03F1/02—Modifications of amplifiers to raise the efficiency, e.g. gliding Class A stages, use of an auxiliary oscillation
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03F—AMPLIFIERS
    • H03F3/00—Amplifiers with only discharge tubes or only semiconductor devices as amplifying elements
    • H03F3/20—Power amplifiers, e.g. Class B amplifiers, Class C amplifiers
    • H03F3/21—Power amplifiers, e.g. Class B amplifiers, Class C amplifiers with semiconductor devices only
    • H03F3/217—Class D power amplifiers; Switching amplifiers
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
    • H04B1/02—Transmitters
    • H04B1/04—Circuits
    • H04B2001/0408—Circuits with power amplifiers
    • H04B2001/045—Circuits with power amplifiers with means for improving efficiency

Definitions

  • the present invention relates to a class D amplifier for amplifying a transmission signal level in a digital wireless communication system such as a digital cellular phone and a wireless communication apparatus using the same.
  • a base station of a digital wireless communication system it is necessary to amplify a transmission signal to a large power of several tens of watts to several hundreds of watts. Greatly contributes to power generation. Also in the mobile station, it is important to reduce the power consumption of the device including the amplifier.
  • a class D amplifier is well known as one of the amplifier configurations with high power utilization efficiency.
  • the class D amplifier realizes power amplification by switching a signal ON / OFF using a saturation region of an amplifying element such as a transistor.
  • a class D amplifier is used to amplify a signal in an audible low frequency band up to about 20 kHz.
  • an amplified signal for example, a 1 bit ⁇ modulated high SNR (Signal to Noise ⁇ ⁇ Ratio) These signals are used.
  • the sampling frequency of this signal is about 128 times or 256 times the signal frequency band (the higher the sampling frequency, the higher the SNR).
  • Such a bandpass ⁇ modulator is actively used in an RF signal receiving circuit. This is because, in reception, after the received signal is applied to the band-pass ⁇ modulator, only a narrow-band signal having a good SNR around the carrier frequency fc is extracted by the band-pass filter, so that good demodulation is possible.
  • the analog circuit of the RF signal is a distributed multiplier circuit, it is necessary to achieve frequency matching of the circuit in a necessary frequency band, and it is difficult to flatten the band characteristics in a wide frequency range. Further, it is necessary to cut off the DC signal in order to prevent destruction of the amplifier, and the analog circuit of the RF signal always has band characteristics. For this reason, it is technically difficult to amplify the RF signal with a class D amplifier.
  • FIG. 1 shows a wireless communication apparatus including a class D amplification unit disclosed in Patent Document 1.
  • a baseband signal generation unit 11 generates a narrowband ( ⁇ several tens of MHz) baseband modulation signal, and the baseband signal output from the baseband signal generation unit 11 is transferred to a carrier in the upconversion unit 12. Up-converted to frequency fc.
  • the class D amplification unit 14 performs class D amplification.
  • the signal output from the class D amplification unit 14 is transmitted as a radio signal from the antenna unit 16 via the bandpass filter unit 15 centered on the carrier frequency fc.
  • FIGS. 2 shows a constellation of a QPSK quadrature modulated wave that is an output of the baseband signal generator 11
  • FIG. 3 shows a frequency characteristic of an output signal of the baseband signal generator 11
  • FIG. 4 shows an upconverter.
  • 12 shows frequency characteristics of 12 output signals.
  • 5 shows the frequency characteristics of the output signal of the bandpass ⁇ modulator 13 in a wide band
  • FIG. 6 shows the frequency characteristics of the output signal of the bandpass ⁇ modulator 13 in a narrow band near the carrier frequency fc. Show.
  • FIG. 5 shows that the output signal of the bandpass ⁇ modulator 13 is a pulse signal, and thus has a wide frequency component of 0 Hz to ⁇ Hz. Further, it can be seen from FIG. 6 that the output signal of the bandpass ⁇ modulator 13 has a good SNR in the vicinity of the carrier frequency fc. This is a characteristic shape of the frequency characteristic of ⁇ modulation.
  • a baseband signal generation unit 11, an up-conversion unit 12, and a bandpass ⁇ modulation unit 13 can be realized by digital signal processing using a DSP (Digital Signal Processor) or an FPGA (Field Programmable Gate Array). Is possible. In this case, since the signal level of the high-speed sampling signal that is the output of the bandpass ⁇ modulation unit 13 is inevitably small, a drive amplification unit is required.
  • DSP Digital Signal Processor
  • FPGA Field Programmable Gate Array
  • FIG. 7 is a diagram showing a configuration in which a drive amplification unit 21 is provided in front of the class D amplification unit 14 in FIG.
  • the same reference numerals as those in FIG. 7 are identical reference numerals as those in FIG.
  • FIG. 8 shows the frequency characteristics of the drive amplifier 21
  • FIG. 9 shows the frequency characteristics of the output signal of the drive amplifier 21.
  • the frequency characteristic of the input signal to the drive amplifier 21 is as shown in FIG.
  • FIG. 8 shows an example of the frequency characteristics of the drive amplifier 21 when frequency matching is performed in the vicinity of the carrier frequency fc for the drive amplifier 21, and a band-pass filter-like filter that passes only frequency components in the vicinity of the carrier frequency fc. It can be seen that it has frequency characteristics and has band characteristics.
  • FIG. 9 shows the frequency characteristic of the output signal when the signal having the frequency characteristic of FIG.
  • the time axis waveform of the signal is a beautiful pulse waveform.
  • the frequency characteristic of the output signal of the drive amplifier 21 is that the signal is band-limited as shown in FIG.
  • the time axis waveform of the input / output signal of the drive amplifier 21 is as shown in FIG. In FIG. 10, the thin line shows the time axis waveform of the input pulse signal, and the thick line shows the time axis waveform of the output signal. From FIG. 10, it can be seen that the time-axis waveform has greatly deteriorated due to the band characteristics of the drive amplifier 21.
  • the output signal of the drive amplifier 21 is input to the class D amplifier 14 and amplified.
  • the time axis waveform of the input / output signal of the class D amplifier 14 is as shown in FIG. In FIG. 11, the thin line shows the time axis waveform of the input signal, and the thick line shows the time axis waveform of the output signal.
  • the class D amplification unit 14 needs to linearly amplify the output pulse signal of the bandpass ⁇ modulation unit 13, and the drive amplification unit having frequency characteristics between the bandpass ⁇ modulation unit 13 and the class D amplification unit 14. 21 is arranged, the amplified output pulse (bold line in FIG. 11) that is the output of the class D amplifier 14 is the output pulse of the bandpass ⁇ modulator 13 (the thin line in FIG. 10) that is the amplified signal. ) Is completely different. For this reason, the EVM of the transmission signal amplified by the class D amplification unit 14 is deteriorated, and the transmission constellation is as shown in FIG. 12, for example, and the EVM is about 10.2%.
  • An object of the present invention is to provide a class D amplifier and a wireless communication apparatus that suppress the degradation of EVM of a class D amplified radio signal.
  • a class D amplifier includes a bandpass ⁇ modulation unit that performs ⁇ modulation on a carrier frequency signal at a predetermined frequency, a first amplification unit that amplifies the signal subjected to ⁇ modulation to a certain signal level, A second amplifying means for switching and amplifying the signal amplified by one amplifying means based on a switching voltage threshold; and a switching voltage for determining and controlling the switching voltage threshold based on the signal amplified by the first amplifying means. And a control means.
  • wireless communication apparatus containing the class D amplification part disclosed by patent document 1 The figure which shows the constellation of the QPSK quadrature modulation wave which is an output of a baseband signal generation part The figure which shows the frequency characteristic of the output signal of the baseband signal generation part The figure which shows the frequency characteristic of the output signal of the up-conversion part The figure which shows the frequency characteristic in the wide band of the output signal of the band pass ⁇ modulator The figure which shows the frequency characteristic in the narrow band in the carrier frequency fc vicinity of the output signal of a band pass delta-sigma modulation part. The figure which shows the structure by which the drive amplification part was provided in the front stage of the class D amplification part of FIG.
  • FIG. 13 is a diagram showing a configuration of a wireless communication apparatus according to an embodiment of the present invention. Hereinafter, the configuration of the wireless communication apparatus will be described with reference to FIG.
  • the baseband signal generation unit 101 generates a narrowband (up to several tens of MHz) baseband signal and outputs it to the up-conversion unit 102.
  • the up-conversion unit 102 up-converts the baseband signal output from the baseband signal generation unit 101 to the carrier frequency fc, and outputs the carrier frequency signal to the bandpass ⁇ modulation unit 104 of the class D amplifier 103.
  • the class D amplifier 103 includes a bandpass ⁇ modulator 104, a drive amplifier 105, a switching voltage controller 106, and a class D amplifier 107.
  • the drive amplifier 105 amplifies the signal output from the bandpass ⁇ modulator 104 to a signal level at which the subsequent class D amplifier 107 can operate, and outputs the amplified signal to the switching voltage controller 106 and the class D amplifier 107. .
  • Switching voltage control unit 106 determines switching voltage threshold value SWVth of class D amplification unit 107 based on the signal output from drive amplification unit 105, and outputs the determined switching voltage threshold value SWVth to class D amplification unit 107. A method for determining the switching voltage threshold SWVth will be described later.
  • the class D amplifier 107 performs switching amplification of the signal output from the drive amplifier 105 based on the switching voltage threshold SWVth output from the switching voltage controller 106, and outputs the amplified signal to the bandpass filter 108.
  • the band-pass filter unit 108 passes the band centered on the carrier frequency fc in the signal output from the class D amplification unit 107 and transmits it as a radio signal from the antenna unit 109.
  • the signal before the class D amplification unit 107 is the same as that described in the background art.
  • 2 shows the constellation of the QPSK quadrature modulated wave that is the output of the baseband signal generation unit 101
  • FIG. 3 shows the frequency characteristics of the output signal of the baseband signal generation unit 101
  • FIG. The frequency characteristic of the output signal of the conversion part 102 is shown.
  • 5 shows the frequency characteristics of the output signal of the bandpass ⁇ modulator 104 in a wide band
  • FIG. 6 shows the frequency characteristics of the output signal of the bandpass ⁇ modulator 104 in the narrow band near the carrier frequency fc. Show.
  • FIG. 8 shows the frequency characteristics of the drive amplifier 105 when frequency matching is performed in the vicinity of the carrier frequency fc for the drive amplifier 105
  • FIG. 9 shows the frequency characteristics of the output signal of the drive amplifier 105.
  • the time axis waveform of the input signal of the drive amplifier 105 is indicated by a thin line in FIG. 10
  • the time axis waveform of the output signal is indicated by a thick line in FIG.
  • the EVM of the signal of FIG. 15 is about 7.4%, which is an improvement of 2.8% compared to FIG. 12, and it can be seen that the class D amplifier of the present invention contributes to the EVM improvement.
  • the time response of the rise and fall of the signal is delayed, and the signal waveform is the original switching of the class D amplification unit 107.
  • the time to reach 0 which is the voltage threshold becomes longer. This delay in arrival time can be offset by switching the class D amplifier 107 at the voltage level before the signal waveform reaches the voltage level 0, so that the EVM improvement effect as described above can be obtained.
  • FIG. 16 shows an example of the EVM when the switching voltage threshold value of the switching voltage control unit 106 is changed.
  • the vertical axis represents the EVM
  • the horizontal axis represents the switching voltage threshold.
  • FIG. 17 shows RMS (Root Mean Square) which is an effective power value of the output signal of the drive amplifier 105 and switching voltage control in various cases where the frequency characteristic of the drive amplifier 105 is line symmetric with respect to the carrier frequency fc.
  • FIG. 10 is a diagram plotting an optimum value (voltage level when EVM is the best) SWVth_opt of a switching voltage threshold output by a unit 106.
  • the vertical axis represents SWVth_opt and the horizontal axis represents RMS.
  • the optimum value of the switching voltage threshold output by the switching voltage control unit 106 increases as the RMS of the output signal of the drive amplification unit 105 increases. From this, the switching voltage control unit 106 calculates the RMS value from the output signal of the drive amplification unit 105 using the relationship shown in FIG. 17, and the switching voltage threshold value of the class D amplification unit 107 based on the calculated RMS value. Can be improved to determine the transmission EVM. In addition, when the modulation type and modulation band applied to the transmission signal are different on the time axis, or when the band characteristics of the drive amplifier 105 and other analog circuits are different from one object to another, signal degradation caused by these is reduced. can do.
  • the switching voltage threshold value of the class D amplification unit is determined to an optimum level based on the RMS power value RMS of the input signal to the class D amplification unit, and the determined switching voltage threshold value is determined. Since the class D amplification unit performs switching amplification using the, the degradation of the EVM of the radio signal amplified by the class D amplification unit can be suppressed even when the drive amplification unit is arranged in the previous stage of the class D amplification unit. Therefore, the wireless communication apparatus including the class D amplifier can transmit a wireless signal with good EVM.
  • a single wireless communication device has been described.
  • a wireless communication system including the wireless communication device of the present invention may be configured.
  • at least one of radio communication apparatuses RS1, RS2,..., RSm of a mobile station or a fixed station includes the class D amplifier shown in FIG.
  • the base station may also include the class D amplifier shown in FIG.
  • the switching voltage threshold SWVth has been described as being determined based on the RMS of the output signal of the drive amplifier, but the value at this time may be fixed or variable. Further, as the switching voltage threshold SWVth, a fixed value that does not depend on the RMS of the output signal of the drive amplifier may be set.
  • the class D amplifier and the wireless communication apparatus according to the present invention can be applied to a wireless communication system or the like.

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  • Power Engineering (AREA)
  • Amplifiers (AREA)
  • Transmitters (AREA)

Abstract

A class D amplifier, for limiting the degradation of the EVM of a wireless signal subjected to class D amplification, and a wireless communication device are provided. A bandpass ΔΣ modulator (104) applies bandpass ΔΣ modulation to a signal output from an up-converter (102). A drive amplifier (105) amplifies a signal output from the bandpass ΔΣ modulator (104) up to a signal level operable for a class D amplification unit (107). A switching voltage controller (106) sets the switching voltage threshold of the class D amplification unit (107) to the optimum level on the basis of the effective power value (RMS) of the output signal of the drive amplifier (105). The class D amplification unit (107) uses the switching voltage threshold set by the switching voltage controller (106) to switch and amplify the output signal of the drive amplifier (105).

Description

Ｄ級増幅器及び無線通信装置Class D amplifier and wireless communication device
　本発明は、デジタル携帯電話等のデジタル無線通信システムにおいて送信信号レベルを増幅するＤ級増幅器及びこれを用いた無線通信装置に関する。 The present invention relates to a class D amplifier for amplifying a transmission signal level in a digital wireless communication system such as a digital cellular phone and a wireless communication apparatus using the same.
　デジタル無線通信システムの基地局では、送信信号を数十Ｗ～数百Ｗの大電力に増幅する必要があるが、大電力を扱うゆえに、増幅器の電力効率を高めることは、基地局の低消費電力化に大きく寄与する。また、移動局においても増幅器を含めた装置の低消費電力化は重要である。 In a base station of a digital wireless communication system, it is necessary to amplify a transmission signal to a large power of several tens of watts to several hundreds of watts. Greatly contributes to power generation. Also in the mobile station, it is important to reduce the power consumption of the device including the amplifier.
　電力利用効率が高い増幅器の構成の一つとして、Ｄ級増幅器がよく知られている。Ｄ級増幅器は、トランジスタなどの増幅素子の飽和領域を用いて、信号をＯＮ／ＯＦＦスイッチングすることによって、電力増幅を実現するものである。 A class D amplifier is well known as one of the amplifier configurations with high power utilization efficiency. The class D amplifier realizes power amplification by switching a signal ON / OFF using a saturation region of an amplifying element such as a transistor.
　一般に、Ｄ級増幅器は、およそ２０ｋＨｚ程度までの可聴域の低周波数帯域の信号の増幅に用いられており、被増幅信号としては、例えば、１ビットΔΣ変調された高ＳＮＲ（Signal to Noise Ratio）の信号が用いられる。この信号のサンプリング周波数は、信号周波数帯域の１２８倍又は２５６倍程度のものが用いられている（なお、サンプリング周波数が高いほど高ＳＮＲとなる）。 In general, a class D amplifier is used to amplify a signal in an audible low frequency band up to about 20 kHz. As an amplified signal, for example, a 1 bit ΔΣ modulated high SNR (Signal to Noise さ れ Ratio) These signals are used. The sampling frequency of this signal is about 128 times or 256 times the signal frequency band (the higher the sampling frequency, the higher the SNR).
　また、無線で用いられる高周波数帯域の信号（ＲＦ信号）の増幅器としては、近年、ドハティー増幅器やＥＴ（Envelope Tracking）増幅器の検討が盛んに行われているが、電力効率の観点から、Ｄ級増幅器の採用も模索され始めている。 In recent years, Doherty amplifiers and ET (Envelope Tracking) amplifiers have been actively studied as amplifiers for high frequency band signals (RF signals) used wirelessly. From the viewpoint of power efficiency, class D The use of amplifiers is beginning to be explored.
　Ｄ級増幅器でＲＦ信号を増幅するためには、ＲＦ信号を１ビットのパルス信号に変換する必要がある。このパルス信号を生成する際に、普通にΔΣ変調（以後、「ローパスΔΣ変調」と呼ぶ）をかけてしまうと、高ＳＮＲの送信信号を得るためには、高速なサンプリング信号が必要となる。例えば、ＲＦ信号のキャリア周波数がｆｃ＝２ＧＨｚである場合、サンプリング周波数ｆｓ＝２ＧＨｚ×１２８＝２５６ＧＳａ（Samples）／ｓといった非常に高速なサンプリング信号が必要となり、現実的ではない。 In order to amplify an RF signal with a class D amplifier, it is necessary to convert the RF signal into a 1-bit pulse signal. When this pulse signal is generated, if ΔΣ modulation (hereinafter referred to as “low-pass ΔΣ modulation”) is normally applied, a high-speed sampling signal is required to obtain a high SNR transmission signal. For example, when the carrier frequency of the RF signal is fc = 2 GHz, a very high-speed sampling signal of sampling frequency fs = 2 GHz × 128 = 256 GSa (Samples) / s is required, which is not realistic.
　そこで考え出されたのが、バンドパスΔΣ変調器である。例えば、キャリア周波数ｆｃ＝２ＧＨｚであれば、２ＧＨｚの４倍である８ＧＳａ／ｓのサンプリング周波数ｆｓで、（変調信号の帯域が数十ＭＨｚ程度であれば）ローパスΔΣ変調器と遜色のないＳＮＲの信号が得られる。 Therefore, the band-pass ΔΣ modulator was conceived. For example, if the carrier frequency fc = 2 GHz, the sampling frequency fs is 8 GSa / s, which is 4 times 2 GHz, and the SNR is comparable to the low-pass ΔΣ modulator (if the modulation signal band is about several tens of MHz). A signal is obtained.
　このようなバンドパスΔΣ変調器は、ＲＦ信号の受信回路に積極的に用いられている。受信においては、受信信号をバンドパスΔΣ変調器にかけた後に、キャリア周波数ｆｃ周辺のＳＮＲの良い狭帯域の信号のみをバンドパスフィルタで取り出せば、良好な復調が可能となるからである。 Such a bandpass ΔΣ modulator is actively used in an RF signal receiving circuit. This is because, in reception, after the received signal is applied to the band-pass ΔΣ modulator, only a narrow-band signal having a good SNR around the carrier frequency fc is extracted by the band-pass filter, so that good demodulation is possible.
　一方、バンドパスΔΣ変調器をＲＦ信号の送信回路（増幅回路）で用いる場合には、理論上、アナログ回路が０Ｈｚ～∞Ｈｚの周波数領域においてフラットな帯域特性を持たなければならない。そうでなければ、送信信号は歪んでしまい、例えば、送信信号の品質指標であるＥＶＭ（Error Vector Magnitude）が劣化してしまう。 On the other hand, when a bandpass ΔΣ modulator is used in an RF signal transmission circuit (amplification circuit), theoretically, an analog circuit must have a flat band characteristic in a frequency range of 0 Hz to ∞ Hz. Otherwise, the transmission signal is distorted and, for example, EVM (Error Vector Magnitude) which is a quality indicator of the transmission signal is deteriorated.
　ここで、ＲＦ信号のアナログ回路は分布乗数回路になることから、必要な周波数帯域において回路の周波数整合を取る必要があり、広い周波数範囲において帯域特性をフラットにすることは困難である。また、増幅器の破壊を防止するためにＤＣ信号を遮断する必要もあり、ＲＦ信号のアナログ回路は必ず帯域特性を有することになる。このため、ＲＦ信号をＤ級増幅器で増幅することは技術的に困難である。 Here, since the analog circuit of the RF signal is a distributed multiplier circuit, it is necessary to achieve frequency matching of the circuit in a necessary frequency band, and it is difficult to flatten the band characteristics in a wide frequency range. Further, it is necessary to cut off the DC signal in order to prevent destruction of the amplifier, and the analog circuit of the RF signal always has band characteristics. For this reason, it is technically difficult to amplify the RF signal with a class D amplifier.
　バンドパスΔΣ変調器を用いたＤ級増幅部として、例えば、特許文献１に開示の技術が知られている。特許文献１に開示のＤ級増幅部を含む無線通信装置を図１に示す。 As a class D amplifier using a bandpass ΔΣ modulator, for example, a technique disclosed in Patent Document 1 is known. FIG. 1 shows a wireless communication apparatus including a class D amplification unit disclosed in Patent Document 1.
　図１において、ベースバンド信号発生部１１では、狭帯域（～数十ＭＨｚ）のベースバンド変調信号が生成され、ベースバンド信号発生部１１から出力されたベースバンド信号は、アップコンバート部１２においてキャリア周波数ｆｃにアップコンバートされる。アップコンバート部１２から出力された信号は、バンドパスΔΣ変調部１３において、例えば、サンプリング周波数ｆｓ＝４×ｆｃにてバンドパスΔΣ変調が施され、バンドパスΔΣ変調部１３から出力された信号は、Ｄ級増幅部１４においてＤ級増幅される。Ｄ級増幅部１４から出力された信号は、キャリア周波数ｆｃを中心としたバンドパスフィルタ部１５を介して、アンテナ部１６から無線信号として送信される。 In FIG. 1, a baseband signal generation unit 11 generates a narrowband (˜several tens of MHz) baseband modulation signal, and the baseband signal output from the baseband signal generation unit 11 is transferred to a carrier in the upconversion unit 12. Up-converted to frequency fc. The signal output from the up-conversion unit 12 is subjected to, for example, bandpass ΔΣ modulation at the sampling frequency fs = 4 × fc in the bandpass ΔΣ modulation unit 13, and the signal output from the bandpass ΔΣ modulation unit 13 is The class D amplification unit 14 performs class D amplification. The signal output from the class D amplification unit 14 is transmitted as a radio signal from the antenna unit 16 via the bandpass filter unit 15 centered on the carrier frequency fc.
　図１の各ブロックの出力信号の時間軸波形及び周波数特性等について図２～図６に例示する。図２は、ベースバンド信号発生部１１の出力であるＱＰＳＫ直交変調波のコンスタレーションを示し、図３は、ベースバンド信号発生部１１の出力信号の周波数特性を示し、図４は、アップコンバート部１２の出力信号の周波数特性を示す。また、図５は、バンドパスΔΣ変調部１３の出力信号の広帯域での周波数特性を示し、図６は、バンドパスΔΣ変調部１３の出力信号のキャリア周波数ｆｃ近傍における狭帯域での周波数特性を示している。 The time axis waveform and frequency characteristics of the output signal of each block in FIG. 1 are illustrated in FIGS. 2 shows a constellation of a QPSK quadrature modulated wave that is an output of the baseband signal generator 11, FIG. 3 shows a frequency characteristic of an output signal of the baseband signal generator 11, and FIG. 4 shows an upconverter. 12 shows frequency characteristics of 12 output signals. 5 shows the frequency characteristics of the output signal of the bandpass ΔΣ modulator 13 in a wide band, and FIG. 6 shows the frequency characteristics of the output signal of the bandpass ΔΣ modulator 13 in a narrow band near the carrier frequency fc. Show.
　図５より、バンドパスΔΣ変調部１３の出力信号は、パルス信号であることから、０Ｈｚ～∞Ｈｚの広い周波数成分を有することが分かる。また、図６より、バンドパスΔΣ変調部１３の出力信号は、キャリア周波数ｆｃ近傍でのＳＮＲが良好となっていることが分かる。これは、ΔΣ変調の周波数特性の特徴的な形状である。 FIG. 5 shows that the output signal of the bandpass ΔΣ modulator 13 is a pulse signal, and thus has a wide frequency component of 0 Hz to ∞ Hz. Further, it can be seen from FIG. 6 that the output signal of the bandpass ΔΣ modulator 13 has a good SNR in the vicinity of the carrier frequency fc. This is a characteristic shape of the frequency characteristic of ΔΣ modulation.
　ところで、主増幅部であるＤ級増幅部１４に入力される信号は、Ｄ級増幅部１４が動作可能な信号レベルに増幅されている必要がある。図１において、ベースバンド信号発生部１１、アップコンバート部１２、バンドパスΔΣ変調部１３は、ＤＳＰ（Digital Signal Processor）やＦＰＧＡ（Field Programmable Gate Array）を用いてデジタル信号処理にて実現することが可能である。この場合、バンドパスΔΣ変調部１３の出力となる高速サンプリング信号の信号レベルは必然的に小さくなるため、駆動増幅部が必要となる。 By the way, the signal input to the class D amplification unit 14 which is the main amplification unit needs to be amplified to a signal level at which the class D amplification unit 14 can operate. In FIG. 1, a baseband signal generation unit 11, an up-conversion unit 12, and a bandpass ΔΣ modulation unit 13 can be realized by digital signal processing using a DSP (Digital Signal Processor) or an FPGA (Field Programmable Gate Array). Is possible. In this case, since the signal level of the high-speed sampling signal that is the output of the bandpass ΔΣ modulation unit 13 is inevitably small, a drive amplification unit is required.
　図７は、図１のＤ級増幅部１４前段に駆動増幅部２１が設けられた構成を示す図である。図７において、図１と共通する構成には図１と同一の符号を付す。 FIG. 7 is a diagram showing a configuration in which a drive amplification unit 21 is provided in front of the class D amplification unit 14 in FIG. In FIG. 7, the same reference numerals as those in FIG.
　図８に駆動増幅部２１の周波数特性を示し、図９に駆動増幅部２１の出力信号の周波数特性を示す。ここで、駆動増幅部２１への入力信号の周波数特性は図５に示すものである。 8 shows the frequency characteristics of the drive amplifier 21, and FIG. 9 shows the frequency characteristics of the output signal of the drive amplifier 21. As shown in FIG. Here, the frequency characteristic of the input signal to the drive amplifier 21 is as shown in FIG.
　一般にアナログ高周波回路では、取り扱う信号の周波数において回路整合を取る。図８は、駆動増幅部２１について、キャリア周波数ｆｃ近傍における周波数整合を取ったときの駆動増幅部２１の周波数特性の例であり、キャリア周波数ｆｃ近傍の周波数成分のみを通過させるバンドパスフィルタ様の周波数特性となっており、帯域特性を有していることが分かる。図９は、駆動増幅部２１に、図５の周波数特性を有する信号を入力したときの、出力信号の周波数特性を示す。 Generally, analog high-frequency circuits take circuit matching at the frequency of signals handled. FIG. 8 shows an example of the frequency characteristics of the drive amplifier 21 when frequency matching is performed in the vicinity of the carrier frequency fc for the drive amplifier 21, and a band-pass filter-like filter that passes only frequency components in the vicinity of the carrier frequency fc. It can be seen that it has frequency characteristics and has band characteristics. FIG. 9 shows the frequency characteristic of the output signal when the signal having the frequency characteristic of FIG.
　駆動増幅部２１の入力信号の周波数特性は、図５に示すように０Ｈｚ～∞Ｈｚの広い周波数成分を有しているため、信号の時間軸波形は綺麗なパルス波形である。一方、駆動増幅部２１の出力信号の周波数特性は、図９に示すように信号が帯域制限されてしまっているため、信号の時間軸波形はなまってしまう。この駆動増幅部２１の入出力信号の時間軸波形は図１０に示すようになる。図１０において、細線が入力パルス信号の時間軸波形を示し、太線が出力信号の時間軸波形を示す。図１０より、駆動増幅部２１の帯域特性によって、時間軸波形が大きく劣化してしまっている様子が分かる。 Since the frequency characteristic of the input signal of the drive amplifier 21 has a wide frequency component of 0 Hz to ∞ Hz as shown in FIG. 5, the time axis waveform of the signal is a beautiful pulse waveform. On the other hand, the frequency characteristic of the output signal of the drive amplifier 21 is that the signal is band-limited as shown in FIG. The time axis waveform of the input / output signal of the drive amplifier 21 is as shown in FIG. In FIG. 10, the thin line shows the time axis waveform of the input pulse signal, and the thick line shows the time axis waveform of the output signal. From FIG. 10, it can be seen that the time-axis waveform has greatly deteriorated due to the band characteristics of the drive amplifier 21.
　駆動増幅部２１の出力信号は、Ｄ級増幅部１４に入力され、増幅される。このＤ級増幅部１４の入出力信号の時間軸波形は図１１に示すようになる。図１１において、細線が入力信号の時間軸波形を示し、太線が出力信号の時間軸波形を示す。Ｄ級増幅部１４ではスイッチング動作が行われ、信号レベルが０以上のときには１、信号レベルが０未満のときには－１が出力される。このとき、スイッチング電圧閾値ＳＷＶｔｈ＝０であるから、Ｄ級増幅部１４からの出力信号の時間軸波形は、図１１の太線のようになる（ただし、増幅率は無視している）。 The output signal of the drive amplifier 21 is input to the class D amplifier 14 and amplified. The time axis waveform of the input / output signal of the class D amplifier 14 is as shown in FIG. In FIG. 11, the thin line shows the time axis waveform of the input signal, and the thick line shows the time axis waveform of the output signal. The class D amplifier 14 performs a switching operation, and outputs 1 when the signal level is 0 or more, and -1 when the signal level is less than 0. At this time, since the switching voltage threshold value SWVth = 0, the time axis waveform of the output signal from the class D amplifier 14 is as shown by the thick line in FIG. 11 (however, the amplification factor is ignored).
　しかしながら、Ｄ級増幅部１４は、バンドパスΔΣ変調部１３の出力パルス信号を線形増幅する必要があり、バンドパスΔΣ変調部１３とＤ級増幅部１４との間に周波数特性を有する駆動増幅部２１が配置されていることから、Ｄ級増幅部１４の出力である増幅された出力パルス（図１１の太線）は、被増幅信号であるバンドパスΔΣ変調部１３の出力パルス（図１０の細線）とは全く異なるものになってしまっている。このため、Ｄ級増幅部１４で増幅された送信信号のＥＶＭは劣化しており、送信コンスタレーションは、例えば、図１２のようになり、ＥＶＭは約１０．２％である。 However, the class D amplification unit 14 needs to linearly amplify the output pulse signal of the bandpass ΔΣ modulation unit 13, and the drive amplification unit having frequency characteristics between the bandpass ΔΣ modulation unit 13 and the class D amplification unit 14. 21 is arranged, the amplified output pulse (bold line in FIG. 11) that is the output of the class D amplifier 14 is the output pulse of the bandpass ΔΣ modulator 13 (the thin line in FIG. 10) that is the amplified signal. ) Is completely different. For this reason, the EVM of the transmission signal amplified by the class D amplification unit 14 is deteriorated, and the transmission constellation is as shown in FIG. 12, for example, and the EVM is about 10.2%.
　本発明の目的は、Ｄ級増幅された無線信号のＥＶＭの劣化を抑制するＤ級増幅器及び無線通信装置を提供することである。 An object of the present invention is to provide a class D amplifier and a wireless communication apparatus that suppress the degradation of EVM of a class D amplified radio signal.
　本発明のＤ級増幅器は、キャリア周波数信号に所定の周波数でΔΣ変調を施すバンドパスΔΣ変調手段と、ΔΣ変調が施された信号を一定の信号レベルまで増幅する第１増幅手段と、前記第１増幅手段によって増幅された信号を、スイッチング電圧閾値に基づいて、スイッチング増幅する第２増幅手段と、前記第１増幅手段によって増幅された信号に基づいて、前記スイッチング電圧閾値を決定制御するスイッチング電圧制御手段と、を具備する構成を採る。 A class D amplifier according to the present invention includes a bandpass ΔΣ modulation unit that performs ΔΣ modulation on a carrier frequency signal at a predetermined frequency, a first amplification unit that amplifies the signal subjected to ΔΣ modulation to a certain signal level, A second amplifying means for switching and amplifying the signal amplified by one amplifying means based on a switching voltage threshold; and a switching voltage for determining and controlling the switching voltage threshold based on the signal amplified by the first amplifying means. And a control means.
　本発明によれば、Ｄ級増幅された無線信号のＥＶＭの劣化を抑制することができる。 According to the present invention, it is possible to suppress degradation of EVM of a D-class amplified radio signal.
特許文献１に開示のＤ級増幅部を含む無線通信装置の構成を示す図The figure which shows the structure of the radio | wireless communication apparatus containing the class D amplification part disclosed by patent document 1 ベースバンド信号発生部の出力であるＱＰＳＫ直交変調波のコンスタレーションを示す図The figure which shows the constellation of the QPSK quadrature modulation wave which is an output of a baseband signal generation part ベースバンド信号発生部の出力信号の周波数特性を示す図The figure which shows the frequency characteristic of the output signal of the baseband signal generation part アップコンバート部の出力信号の周波数特性を示す図The figure which shows the frequency characteristic of the output signal of the up-conversion part バンドパスΔΣ変調部の出力信号の広帯域での周波数特性を示す図The figure which shows the frequency characteristic in the wide band of the output signal of the band pass ΔΣ modulator バンドパスΔΣ変調部の出力信号のキャリア周波数ｆｃ近傍における狭帯域での周波数特性を示す図The figure which shows the frequency characteristic in the narrow band in the carrier frequency fc vicinity of the output signal of a band pass delta-sigma modulation part. 図１のＤ級増幅部前段に駆動増幅部が設けられた構成を示す図The figure which shows the structure by which the drive amplification part was provided in the front stage of the class D amplification part of FIG. 駆動増幅部の周波数特性を示す図Diagram showing frequency characteristics of drive amplifier 駆動増幅部の出力信号の周波数特性を示す図The figure which shows the frequency characteristic of the output signal of the drive amplification part 駆動増幅部の入出力信号の時間軸波形を示す図The figure which shows the time-axis waveform of the input / output signal of the drive amplifier Ｄ級増幅部の入出力信号の時間軸波形を示す図The figure which shows the time-axis waveform of the input-output signal of a class D amplification part Ｄ級増幅部で増幅された送信信号の送信コンスタレーションを示す図The figure which shows the transmission constellation of the transmission signal amplified by the class D amplifier 本発明の一実施の形態に係る無線通信装置の構成を示す図The figure which shows the structure of the radio | wireless communication apparatus which concerns on one embodiment of this invention スイッチング電圧閾値がＳＷＶｔｈ＝＋０．２のときのＤ級増幅部の入力信号と出力信号の時間軸波形を示す図The figure which shows the time-axis waveform of the input signal and output signal of a class D amplification part when switching voltage threshold value is SWVth = + 0.2 スイッチング電圧閾値ＳＷＶｔｈ＝＋０．２のときの送信コンスタレーションを示す図The figure which shows the transmission constellation when switching voltage threshold value SWVth = + 0.2 スイッチング電圧閾値を変化させた場合のＥＶＭの例を示す図The figure which shows the example of EVM at the time of changing a switching voltage threshold value ＲＭＳ（Root Mean Square）とスイッチング電圧制御部が出力するスイッチング電圧閾値の最適値ＳＷＶｔｈ＿ｏｐｔをプロットした図The figure which plotted RMS (Root | Mean | Square) and the optimal value SWVth_opt of the switching voltage threshold value which a switching voltage control part outputs 本発明の一実施の形態に係る無線通信システムの構成を示す図The figure which shows the structure of the radio | wireless communications system which concerns on one embodiment of this invention
　以下、本発明の実施の形態について、図面を参照して詳細に説明する。 Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
　（一実施の形態）
　図１３は、本発明の一実施の形態に係る無線通信装置の構成を示す図である。以下、図１３を用いて無線通信装置の構成について説明する。 (One embodiment)
FIG. 13 is a diagram showing a configuration of a wireless communication apparatus according to an embodiment of the present invention. Hereinafter, the configuration of the wireless communication apparatus will be described with reference to FIG.
　ベースバンド信号発生部１０１は、狭帯域（～数十ＭＨｚ）のベースバンド信号を生成し、アップコンバート部１０２に出力する。 The baseband signal generation unit 101 generates a narrowband (up to several tens of MHz) baseband signal and outputs it to the up-conversion unit 102.
　アップコンバート部１０２は、ベースバンド信号発生部１０１から出力されたベースバンド信号をキャリア周波数ｆｃにアップコンバートし、キャリア周波数信号をＤ級増幅器１０３のバンドパスΔΣ変調部１０４に出力する。 The up-conversion unit 102 up-converts the baseband signal output from the baseband signal generation unit 101 to the carrier frequency fc, and outputs the carrier frequency signal to the bandpass ΔΣ modulation unit 104 of the class D amplifier 103.
　Ｄ級増幅器１０３は、バンドパスΔΣ変調部１０４、駆動増幅部１０５、スイッチング電圧制御部１０６及びＤ級増幅部１０７を備えている。 The class D amplifier 103 includes a bandpass ΔΣ modulator 104, a drive amplifier 105, a switching voltage controller 106, and a class D amplifier 107.
　バンドパスΔΣ変調部１０４は、アップコンバート部１０２から出力されたキャリア周波数信号に、例えば、サンプリング周波数ｆｓ＝４×ｆｃにてバンドパスΔΣ変調を施し、バンドパスΔΣ変調を施した信号を駆動増幅部１０５に出力する。 The bandpass ΔΣ modulation unit 104 performs bandpass ΔΣ modulation on the carrier frequency signal output from the up-conversion unit 102 at, for example, a sampling frequency fs = 4 × fc, and drives and amplifies the signal subjected to the bandpass ΔΣ modulation. Output to the unit 105.
　駆動増幅部１０５は、バンドパスΔΣ変調部１０４から出力された信号を後段のＤ級増幅部１０７が動作可能な信号レベルにまで増幅し、スイッチング電圧制御部１０６及びＤ級増幅部１０７に出力する。 The drive amplifier 105 amplifies the signal output from the bandpass ΔΣ modulator 104 to a signal level at which the subsequent class D amplifier 107 can operate, and outputs the amplified signal to the switching voltage controller 106 and the class D amplifier 107. .
　スイッチング電圧制御部１０６は、駆動増幅部１０５から出力された信号に基づいて、Ｄ級増幅部１０７のスイッチング電圧閾値ＳＷＶｔｈを決定し、決定したスイッチング電圧閾値ＳＷＶｔｈをＤ級増幅部１０７に出力する。なお、スイッチング電圧閾値ＳＷＶｔｈの決定方法については後述する。 Switching voltage control unit 106 determines switching voltage threshold value SWVth of class D amplification unit 107 based on the signal output from drive amplification unit 105, and outputs the determined switching voltage threshold value SWVth to class D amplification unit 107. A method for determining the switching voltage threshold SWVth will be described later.
　Ｄ級増幅部１０７は、スイッチング電圧制御部１０６から出力されたスイッチング電圧閾値ＳＷＶｔｈに基づいて、駆動増幅部１０５から出力された信号をスイッチング増幅し、バンドパスフィルタ部１０８に出力する。 The class D amplifier 107 performs switching amplification of the signal output from the drive amplifier 105 based on the switching voltage threshold SWVth output from the switching voltage controller 106, and outputs the amplified signal to the bandpass filter 108.
　バンドパスフィルタ部１０８は、Ｄ級増幅部１０７から出力された信号のうち、キャリア周波数ｆｃを中心とした帯域を通過させ、アンテナ部１０９から無線信号として送信する。 The band-pass filter unit 108 passes the band centered on the carrier frequency fc in the signal output from the class D amplification unit 107 and transmits it as a radio signal from the antenna unit 109.
　ここで、図１３の各ブロックの出力信号の時間軸波形及び周波数特性等について説明する。Ｄ級増幅部１０７よりも前段の信号については、背景技術で説明した図と同一である。すなわち、図２は、ベースバンド信号発生部１０１の出力であるＱＰＳＫ直交変調波のコンスタレーションを示し、図３は、ベースバンド信号発生部１０１の出力信号の周波数特性を示し、図４は、アップコンバート部１０２の出力信号の周波数特性を示す。また、図５は、バンドパスΔΣ変調部１０４の出力信号の広帯域での周波数特性を示し、図６は、バンドパスΔΣ変調部１０４の出力信号のキャリア周波数ｆｃ近傍における狭帯域での周波数特性を示している。 Here, the time axis waveform and frequency characteristic of the output signal of each block in FIG. 13 will be described. The signal before the class D amplification unit 107 is the same as that described in the background art. 2 shows the constellation of the QPSK quadrature modulated wave that is the output of the baseband signal generation unit 101, FIG. 3 shows the frequency characteristics of the output signal of the baseband signal generation unit 101, and FIG. The frequency characteristic of the output signal of the conversion part 102 is shown. 5 shows the frequency characteristics of the output signal of the bandpass ΔΣ modulator 104 in a wide band, and FIG. 6 shows the frequency characteristics of the output signal of the bandpass ΔΣ modulator 104 in the narrow band near the carrier frequency fc. Show.
　また、駆動増幅部１０５について、キャリア周波数ｆｃ近傍における周波数整合を取ったときの駆動増幅部１０５の周波数特性を図８に示し、駆動増幅部１０５の出力信号の周波数特性を図９に示す。さらに、駆動増幅部１０５の入力信号の時間軸波形は図１０の細線で示し、出力信号の時間軸波形は図１０の太線で示す。 FIG. 8 shows the frequency characteristics of the drive amplifier 105 when frequency matching is performed in the vicinity of the carrier frequency fc for the drive amplifier 105, and FIG. 9 shows the frequency characteristics of the output signal of the drive amplifier 105. Further, the time axis waveform of the input signal of the drive amplifier 105 is indicated by a thin line in FIG. 10, and the time axis waveform of the output signal is indicated by a thick line in FIG.
　いま、Ｄ級増幅部１０７でのスイッチング増幅において、スイッチング電圧制御部１０６からのスイッチング電圧閾値がＳＷＶｔｈ＝＋０．２のときのＤ級増幅部１０７の入力信号と出力信号の時間軸波形を図１４に示す。図１４において、細線が駆動増幅部１０５の帯域特性に起因して劣化したパルス入力信号を示し、太線がＤ級増幅部１０７の出力信号を示す。 Now, in the switching amplification in the class D amplification unit 107, the time axis waveforms of the input signal and the output signal of the class D amplification unit 107 when the switching voltage threshold value from the switching voltage control unit 106 is SWVth = + 0.2 are shown in FIG. Shown in In FIG. 14, the thin line indicates a pulse input signal that has deteriorated due to the band characteristics of the drive amplifier 105, and the thick line indicates the output signal of the class D amplifier 107.
　図１１の太線で示した、スイッチング電圧制御部がないときのＤ級増幅部１４の出力と、図１４の太線で示した、スイッチング電圧制御部１０６があるときのＤ級増幅部１０７の出力とを比較すると、後者の方が被増幅信号であるバンドパスΔΣ変調部の出力波形（図１０の細線）に近いことが分かる。 The output of the class D amplifying unit 14 when there is no switching voltage control unit shown by the thick line in FIG. 11 and the output of the class D amplification unit 107 when there is the switching voltage control unit 106 shown by the thick line in FIG. Is compared, the latter is closer to the output waveform (thin line in FIG. 10) of the bandpass ΔΣ modulation unit that is the amplified signal.
　スイッチング電圧制御部１０６で決定したスイッチング電圧閾値がＳＷＶｔｈ＝＋０．２のときの送信コンスタレーションは、例えば、図１５に示すようになり、図１２に示した場合よりも改善していることが分かる。なお、図１５の信号のＥＶＭは約７．４％であり、図１２と比べると２．８％改善しており、本発明のＤ級増幅器がＥＶＭ改善に寄与することが分かる。 The transmission constellation when the switching voltage threshold determined by the switching voltage control unit 106 is SWVth = + 0.2 is, for example, as shown in FIG. 15, and it is understood that the transmission constellation is improved from the case shown in FIG. . The EVM of the signal of FIG. 15 is about 7.4%, which is an improvement of 2.8% compared to FIG. 12, and it can be seen that the class D amplifier of the present invention contributes to the EVM improvement.
　図９の信号の周波数特性に見られるように、パルス信号の高周波成分が通過しない場合には、信号の立ち上がりや立ち下がりの時間応答が遅くなり、信号波形がＤ級増幅部１０７の本来のスイッチング電圧閾値である０に到達する時間が長くなる。この到達時間の遅延は、信号波形が電圧レベル０に達する前の電圧レベルでＤ級増幅部１０７をスイッチング動作させることで相殺できるため、上述のようなＥＶＭ改善効果が得られる。 As can be seen from the frequency characteristics of the signal in FIG. 9, when the high-frequency component of the pulse signal does not pass, the time response of the rise and fall of the signal is delayed, and the signal waveform is the original switching of the class D amplification unit 107. The time to reach 0 which is the voltage threshold becomes longer. This delay in arrival time can be offset by switching the class D amplifier 107 at the voltage level before the signal waveform reaches the voltage level 0, so that the EVM improvement effect as described above can be obtained.
　ここで、スイッチング電圧制御部１０６のスイッチング電圧閾値を変化させた場合のＥＶＭの例を図１６に示す。図１６では、縦軸をＥＶＭ、横軸をスイッチング電圧閾値としている。従来、スイッチング電圧閾値はＳＷＶｔｈ＝０に固定であることから、ＥＶＭは約１０．２％にとどまる。これに対し、本発明では、スイッチング電圧制御部１０６によってＤ級増幅部１０７のスイッチング電圧閾値を最適値（ここではＳＷＶｔｈ＝－０．１７）に設定することにより、ＥＶＭが６．７％まで改善できることが図１６から読み取れる。したがって、駆動増幅部１０５の周波数特性が図８に示されるような場合には、スイッチング電圧制御部１０６が出力するスイッチング電圧閾値をＳＷＶｔｈ＝－０．１７の固定値とすればよい。 Here, FIG. 16 shows an example of the EVM when the switching voltage threshold value of the switching voltage control unit 106 is changed. In FIG. 16, the vertical axis represents the EVM, and the horizontal axis represents the switching voltage threshold. Conventionally, since the switching voltage threshold is fixed to SWVth = 0, the EVM is only about 10.2%. In contrast, in the present invention, the switching voltage control unit 106 sets the switching voltage threshold value of the class D amplification unit 107 to an optimum value (here, SWVth = −0.17), thereby improving the EVM to 6.7%. It can be read from FIG. Therefore, when the frequency characteristics of the drive amplifier 105 are as shown in FIG. 8, the switching voltage threshold output from the switching voltage controller 106 may be set to a fixed value of SWVth = −0.17.
　なお、ＥＶＭの値はＳＷＶｔｈ＝０の軸に関してほぼ線対称であることが図１６から読み取れるように、ＳＷＶｔｈ＝＋０．１７を固定値として用いてもよい。 It should be noted that SWVth = + 0.17 may be used as a fixed value so that it can be read from FIG. 16 that the value of EVM is substantially line symmetric with respect to the axis of SWVth = 0.
　以上の説明では、駆動増幅部１０５の周波数特性が図８に示されるような場合の信号の時間軸波形や周波数特性について見てきた。しかしながら、実際には、駆動増幅部１０５の周波数特性は、回路の実現方法や整合の取り方によって様々な形状を取りうる。図１７は、駆動増幅部１０５の周波数特性がキャリア周波数ｆｃに対して線対称となる種々のケースにおいて、駆動増幅部１０５の出力信号の電力実効値であるＲＭＳ（Root Mean Square）とスイッチング電圧制御部１０６が出力するスイッチング電圧閾値の最適値（ＥＶＭが最良となるときの電圧レベル）ＳＷＶｔｈ＿ｏｐｔをプロットした図である。図１７では、縦軸をＳＷＶｔｈ＿ｏｐｔ、横軸をＲＭＳとしている。 In the above description, the time axis waveform and frequency characteristic of the signal when the frequency characteristic of the drive amplifier 105 is as shown in FIG. 8 have been seen. However, in practice, the frequency characteristics of the drive amplification unit 105 can take various shapes depending on the circuit implementation method and the matching method. FIG. 17 shows RMS (Root Mean Square) which is an effective power value of the output signal of the drive amplifier 105 and switching voltage control in various cases where the frequency characteristic of the drive amplifier 105 is line symmetric with respect to the carrier frequency fc. FIG. 10 is a diagram plotting an optimum value (voltage level when EVM is the best) SWVth_opt of a switching voltage threshold output by a unit 106. In FIG. 17, the vertical axis represents SWVth_opt and the horizontal axis represents RMS.
　図１７を参照すると、駆動増幅部１０５の出力信号のＲＭＳが大きくなるに従って、スイッチング電圧制御部１０６が出力するスイッチング電圧閾値の最適値が大きくなっている。このことから、スイッチング電圧制御部１０６が、図１７に示す関係を利用し、駆動増幅部１０５の出力信号からＲＭＳ値を算出し、算出したＲＭＳ値に基づいてＤ級増幅部１０７のスイッチング電圧閾値を最適なレベルに決定することにより、送信ＥＶＭを改善することができる。また、送信信号に適用する変調種別や変調帯域が時間軸上で異なったり、駆動増幅部１０５やその他アナログ回路の帯域特性が固体間で異なったりするときにも、これらに起因する信号劣化を低減することができる。 Referring to FIG. 17, the optimum value of the switching voltage threshold output by the switching voltage control unit 106 increases as the RMS of the output signal of the drive amplification unit 105 increases. From this, the switching voltage control unit 106 calculates the RMS value from the output signal of the drive amplification unit 105 using the relationship shown in FIG. 17, and the switching voltage threshold value of the class D amplification unit 107 based on the calculated RMS value. Can be improved to determine the transmission EVM. In addition, when the modulation type and modulation band applied to the transmission signal are different on the time axis, or when the band characteristics of the drive amplifier 105 and other analog circuits are different from one object to another, signal degradation caused by these is reduced. can do.
　このように、本実施の形態によれば、Ｄ級増幅部への入力信号の電力実効値ＲＭＳに基づいて、Ｄ級増幅部のスイッチング電圧閾値を最適なレベルに決定し、決定したスイッチング電圧閾値を用いてＤ級増幅部がスイッチング増幅することにより、Ｄ級増幅部前段に駆動増幅部を配置した場合でも、Ｄ級増幅部で増幅された無線信号のＥＶＭの劣化を抑制することができる。よって、Ｄ級増幅器を含む無線通信装置は、ＥＶＭが良好な無線信号を送信することができる。 Thus, according to the present embodiment, the switching voltage threshold value of the class D amplification unit is determined to an optimum level based on the RMS power value RMS of the input signal to the class D amplification unit, and the determined switching voltage threshold value is determined. Since the class D amplification unit performs switching amplification using the, the degradation of the EVM of the radio signal amplified by the class D amplification unit can be suppressed even when the drive amplification unit is arranged in the previous stage of the class D amplification unit. Therefore, the wireless communication apparatus including the class D amplifier can transmit a wireless signal with good EVM.
　なお、本実施の形態では、無線通信装置単体について説明したが、本発明の無線通信装置を含む無線通信システムを構成してもよい。例えば、図１８に示すように、移動局又は固定局の無線通信装置ＲＳ１、ＲＳ２、…、ＲＳｍのうち少なくとも一つは図１３に示したＤ級増幅器を含むものとする。また、基地局にも図１３に示したＤ級増幅器が含まれてもよい。 In this embodiment, a single wireless communication device has been described. However, a wireless communication system including the wireless communication device of the present invention may be configured. For example, as shown in FIG. 18, it is assumed that at least one of radio communication apparatuses RS1, RS2,..., RSm of a mobile station or a fixed station includes the class D amplifier shown in FIG. The base station may also include the class D amplifier shown in FIG.
　図１８に示す無線通信システムは、図１３に示すＤ級増幅器を備える無線通信装置が多いほど、システム全体としてＥＶＭが良好な無線信号が使用される頻度が増える。また、各無線通信装置の受信においては、送信信号の品質が良好であることから、その受信性能も良好となり、結果として通信品質のよい無線通信システムを構築することができる。また、電力利用効率が高いＤ級増幅器を備える無線通信装置を使用していることから、全体として電力利用効率が高いシステムを構築することができる。 In the radio communication system shown in FIG. 18, the more radio communication apparatuses including the class D amplifier shown in FIG. 13, the more frequently a radio signal having a good EVM is used as the entire system. Moreover, since the quality of the transmission signal is good at the reception of each wireless communication device, the reception performance is also good, and as a result, a wireless communication system with good communication quality can be constructed. In addition, since a wireless communication apparatus including a class D amplifier with high power utilization efficiency is used, a system with high power utilization efficiency as a whole can be constructed.
　なお、本実施の形態では、スイッチング電圧閾値ＳＷＶｔｈを駆動増幅部の出力信号のＲＭＳに基づいて決定するものとして説明したが、このときの値は固定としてもよいし、可変としてもよい。また、スイッチング電圧閾値ＳＷＶｔｈとして、駆動増幅部の出力信号のＲＭＳに依存しない固定値を設定してもよい。 In the present embodiment, the switching voltage threshold SWVth has been described as being determined based on the RMS of the output signal of the drive amplifier, but the value at this time may be fixed or variable. Further, as the switching voltage threshold SWVth, a fixed value that does not depend on the RMS of the output signal of the drive amplifier may be set.
　２０１０年９月１３日出願の特願２０１０－２０４２８１の日本出願に含まれる明細書、図面及び要約書の開示内容は、すべて本願に援用される。 The disclosure of the specification, drawings and abstract contained in the Japanese application of Japanese Patent Application No. 2010-204281 filed on September 13, 2010 is incorporated herein by reference.
　本発明にかかるＤ級増幅器及び無線通信装置は、無線通信システム等に適用できる。 The class D amplifier and the wireless communication apparatus according to the present invention can be applied to a wireless communication system or the like.
　１０１　ベースバンド信号発生部
　１０２　アップコンバート部
　１０３　Ｄ級増幅器
　１０４　バンドパスΔΣ変調部
　１０５　駆動増幅部
　１０６　スイッチング電圧制御部
　１０７　Ｄ級増幅部
　１０８　バンドパスフィルタ部
　１０９　アンテナ部 DESCRIPTION OF SYMBOLS 101 Baseband signal generation part 102 Up-conversion part 103 Class D amplifier 104 Band pass delta-sigma modulation part 105 Drive amplification part 106 Switching voltage control part 107 Class D amplification part 108 Band pass filter part 109 Antenna part

Claims (4)

  1. 　キャリア周波数信号に所定の周波数でΔΣ変調を施すバンドパスΔΣ変調手段と、
    　ΔΣ変調が施された信号を一定の信号レベルまで増幅する第１増幅手段と、
    　前記第１増幅手段によって増幅された信号を、スイッチング電圧閾値に基づいて、スイッチング増幅する第２増幅手段と、
    　前記第１増幅手段によって増幅された信号に基づいて、前記スイッチング電圧閾値を決定制御するスイッチング電圧制御手段と、
    　を具備するＤ級増幅器。     Bandpass ΔΣ modulation means for performing ΔΣ modulation on the carrier frequency signal at a predetermined frequency;
    First amplifying means for amplifying the signal subjected to ΔΣ modulation to a certain signal level;
    Second amplification means for switching and amplifying the signal amplified by the first amplification means based on a switching voltage threshold;
    Switching voltage control means for determining and controlling the switching voltage threshold based on the signal amplified by the first amplification means;
    A class D amplifier comprising:
  2. 　前記スイッチング電圧閾値を固定値とする請求項１に記載のＤ級増幅器。 The class D amplifier according to claim 1, wherein the switching voltage threshold value is a fixed value.
  3. 　前記スイッチング電圧制御手段は、前記第１増幅手段によって増幅された信号のレベルに応じて可変制御する請求項１に記載のＤ級増幅器。 The class D amplifier according to claim 1, wherein the switching voltage control means variably controls the switching voltage control means according to the level of the signal amplified by the first amplifying means.
  4. 　請求項１に記載のＤ級増幅器を備える無線通信装置。 A wireless communication apparatus comprising the class D amplifier according to claim 1.
PCT/JP2011/004944 2010-09-13 2011-09-02 Class d amplifier and wireless communication device WO2012035713A1 (en)

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