JP2006157256A - Transmission circuit, wireless communication circuit, wireless base station apparatus, and wireless terminal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a transmission circuit capable of obtaining an output signal with less distortion at a high power efficiency by suppressing increase of a circuit scale. <P>SOLUTION: In the transmission circuit 100a for amplifying an OFDM signal and transmitting the amplified signal, an input signal given to an S/P conversion section 101 is given to an inverse Fourier transform section 103, which applies the inverse Fourier transform to the input signal and an amplifier section 106 amplifies the transformed signal, and thereafter a Fourier transform section 109 applies Fourier transform to the amplified signal to convert it into a subcarrier signal. A comparison arithmetic section 110 applies comparison arithmetic operations to the subcarrier signal subjected to the Fourier transform and a subcarrier signal before receiving modulation processing by a quadrature modulation section 105. A distortion correction arithmetic section 102 detects distortion caused in a step of amplification by the amplifier 106 and uses the subcarrier signal before the amplification to correct the distortion. That is, the distortion correction arithmetic section 102 compares the subcarrier signal components before and after the amplification to correct the distortion component caused by the amplification as its control. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a transmission circuit that amplifies and transmits a radio signal, and in particular, amplifies and outputs a transmission signal in a transmission device used for orthogonal frequency division (OFDM) wireless communication, broadcasting, or the like. The present invention relates to a transmission circuit that performs transmission, a wireless communication circuit including the transmission circuit, a wireless base station device, and a wireless terminal device.

  In recent years, in a transmission apparatus used in the wireless communication field and the broadcast field, a signal having a wide frequency occupation band is used to transmit a large amount of information. In addition, an OFDM modulated signal is often transmitted in order to improve frequency utilization efficiency. OFDM modulation is QPSK (Quadrature Phase Shift Keying), or 16QAM (16 Quadrature), which is a digital modulation method having four types of phases and amplitudes, with a plurality of subcarriers orthogonal to each other on the frequency axis. A transmission signal converted from data on the frequency axis to data on the time axis is obtained by modulating data by a predetermined modulation method such as Amplitude Modulation and performing inverse Fourier transform on the data.

  FIG. 9 is a diagram illustrating an example of a spectrum of a general OFDM modulation signal, where the horizontal axis indicates frequency and the vertical axis indicates signal level. In FIG. 9, a plurality of subcarriers modulated at the symbol rate Rs (s) are multiplexed on the frequency axis at a frequency interval Δfs (Hz). At this time, if fs = 1 / Rs, the subcarriers are orthogonal to each other, so that it is possible to efficiently use the frequency while avoiding mutual interference. For this reason, if the number of subcarriers to be multiplexed is increased, the amount of information that can be transmitted at a time can also be increased. The OFDM modulated wave multiplexed on the frequency axis as described above is subjected to inverse Fourier transform and converted to a signal on the time axis, and then modulated with a carrier wave and transmitted. That is, as shown in FIG. 9, the amplitude (level) of the modulated wave on the time axis (on the frequency axis) fluctuates greatly, resulting in a signal having a maximum amplitude compared to the average amplitude.

  That is, high linearity is required for a transmission circuit that amplifies and transmits such a signal (a signal as shown in FIG. 9). On the other hand, in order to reduce the power consumption of the transmission apparatus, high power efficiency is also required for the amplifier circuit in the transmission apparatus. Therefore, various methods for distortion compensation and efficiency improvement have been proposed in order to achieve both improvement of linearity and power efficiency of the amplifier circuit. For example, as a conventional transmission circuit of this type, in order to compensate for distortion of the signal that amplifies the OFDM signal, a method for estimating the impulse response of the OFDM pilot symbol by feedback control and correcting the signal before amplification is proposed. Has been. According to this method, it is possible to perform efficient amplification processing using not only the linear region but also the nonlinear region in the output amplification unit (see, for example, Patent Document 1).

  One of the conventional transmission circuit systems is called a LINC (Linear Amplification with Nonlinear Components) system. In this method, the transmission signal is branched into two constant envelope signals, and amplified after being amplified by a non-linear amplifier having high power efficiency, and then combined to improve linearity and power efficiency.

  FIG. 10 is a diagram illustrating a general example of the configuration of a conventional transmission circuit. A general example of an amplifier circuit to which the LINC method is applied will be described with reference to FIG. In the transmission circuit 310 shown in FIG. 10, the constant envelope signal generation unit 311 generates two constant envelope signals Sa (t) and Sb (t) from the input signal S (t). For example, when the input signal S (t) is expressed by the following equation (1), the constant envelope signals Sa (t) and Sb (t) are expressed by the following equations (2) and (3). If so, the amplitude directions of the constant envelope signals Sa (t) and Sb (t) are constant.

S (t) = V (t) × cos {ωct + φ (t)} (1)
Sa (t) = Vmax / 2 × cos {ωct + ψ (t)} (2)
Sb (t) = Vmax / 2 × cos {ωct + θ (t)} (3)
However, the maximum value of V (t) is Vmax, the angular frequency of the carrier wave of the input signal is ωc, ψ (t) = φ (t) + α (t), θ (t) = φ (t) −α (t) And

  FIG. 11 is a vector diagram showing the arithmetic operation in the transmission circuit of FIG. 10 on an orthogonal plane. That is, FIG. 11 shows the generation operation of the constant envelope signal using the signal vector on the orthogonal plane coordinates. As shown in this figure, the input signal S (t) is represented by a vector sum of two constant envelope signals Sa (t) and Sb (t) having an amplitude of Vmax / 2.

  Returning to FIG. 10 again, the two amplifiers 312 and 313 amplify the two constant envelope signals Sa (t) and Sb (t), respectively. At this time, assuming that the gains of the amplifiers 312 and 313 are G, the output signals of the amplifiers 312 and 313 are G × Sa (t) and G × Sb (t), respectively. When these output signals G × Sa (t) and G × Sb (t) are combined by the combining circuit 314, an output signal G × S (t) is obtained.

  FIG. 12 is a diagram showing another example of the configuration of a conventional transmission circuit, and a transmission circuit 310a having the same function as in FIG. 10 will be described with reference to FIG. In the constant envelope signal generation unit 311, the constant envelope signal IQ generation unit 315 has baseband signals Sai, Saq, Sbi, which become constant envelope signals Sa, Sb after orthogonal demodulation from baseband input signals Si, Sq. Sbq is generated by digital signal processing, and each baseband signal Sai, Saq, Sbi, Sbq is converted into an analog signal by D / A converters 316a, 316b, 316c, 316d, respectively, and then two orthogonal modulators are used. Two constant envelope signals Sa (t) and Sb (t) are obtained by performing quadrature modulation with the quadrature modulation unit 317. When each signal is amplified by the pre-stage amplifiers (driver amplifiers) 318a and 318b, final amplified by the final stage amplifiers 312 and 313, and further synthesized by the synthesis circuit 314, an output signal G × S (t) is obtained. .

  In the transmission circuit 310a as described above, generation of a constant envelope signal can be realized by digital signal processing by using a baseband signal having a low frequency. However, if an error occurs in the gain or phase of the two amplifiers, the vector of the amplified signal is different from the intended output signal vector. At this time, the error of these vectors becomes a distortion component of the signal. Further, in the transmission circuit 310a, it is difficult not only to predict the cause of these vector errors, but also the characteristics vary depending on the environment such as temperature.

Therefore, as a conventional transmission circuit, in order to compensate for these distortion components and fluctuations in characteristics, for example, an auxiliary wave signal synthesized with an input signal when generating a constant envelope signal is approximately calculated from the input signal. Then, two constant envelope signals are generated by synthesizing the auxiliary wave signal with the input signal, and each constant envelope signal is amplified by two amplifiers, synthesized, and then an output signal or auxiliary wave component is detected. A method for correcting an error in characteristics related to the gain and phase of a system amplifier has been proposed (see, for example, Patent Document 2).
JP 2001-211135 A Japanese Patent No. 2758682

  However, in the above-described conventional transmission circuit, it is necessary to perform arithmetic processing to refer to the signal. At that time, it is necessary to analyze an output signal or auxiliary wave signal having a band component equivalent to the input signal. In particular, the OFDM scheme has a problem in that since the signal band is wide, the necessary calculation speed and amount of calculation processing increase, resulting in an increase in power consumption and circuit scale of the transmission circuit.

  The present invention has been made in view of the above points, and a transmission circuit capable of obtaining an output signal with high power efficiency and less distortion while suppressing an increase in circuit scale, and a radio communication circuit including the transmission circuit An object of the present invention is to provide a radio base station apparatus and a radio terminal apparatus.

  The transmission circuit of the present invention includes an inverse Fourier transform means for performing inverse Fourier transform on a signal on a frequency axis obtained by modulating data with a plurality of subcarriers as an input signal, and converting the signal to a baseband signal on a time axis, and a time axis Modulation means for modulating the upper baseband signal with a carrier wave to generate a transmission signal, amplification means for amplifying the transmission signal, and data on the time axis of the transmission signal amplified by the amplification means to data on the frequency axis Fourier transform means for transforming, one or more subcarriers of the input signal, one or more subcarriers output from the Fourier transform means, a comparison operation means for calculating a difference, and an operation result of the comparison operation means Accordingly, a configuration is provided that includes correction means for calculating and outputting the signal before the input of the amplification means so as to correct the distortion of the output signal of the amplification means.

  Further, the transmission circuit of the present invention includes an inverse Fourier transform unit that performs inverse Fourier transform on a signal on a frequency axis obtained by modulating data with a plurality of subcarriers that are input signals, and converts the signal to a baseband signal on a time axis. A constant envelope signal generating means for generating a plurality of constant envelope signals from a baseband signal on the time axis, an amplifying means for amplifying a plurality of constant envelope signals generated by the constant envelope signal generating means, and an amplifying means Combining means for combining a plurality of amplified constant envelope signals, Fourier transform means for converting data on the time axis of the signal combined by the combining means to data on the frequency axis, and one or more input signals Any of a plurality of constant envelope signals depending on the calculation result of the comparison calculation means, the comparison calculation means for calculating the difference by comparing the subcarrier and one or more subcarriers output from the Fourier transform means A configuration and a correcting means for correcting at least one of gain and phase in.

  In addition to the configuration of the above invention, the transmission circuit of the present invention further includes a plurality of constant envelopes generated by the constant envelope signal generation unit according to a result of the comparison calculation unit comparing and calculating the plurality of subcarriers. A configuration including frequency characteristic correction means for correcting the frequency characteristic of any one of the signals is adopted.

  A TDD (Time Division Duplex) wireless communication circuit of the present invention includes the transmission circuit of the present invention and a received signal Fourier transform means for performing a Fourier transform process on the received signal. A configuration is adopted in which the received signal is Fourier-transformed by switching over time.

  The radio base station apparatus of the present invention employs a configuration including the transmission circuit or the radio communication circuit of the above invention. Furthermore, the wireless terminal device of the present invention employs a configuration including the transmission circuit or wireless communication circuit of the above invention.

  According to the transmission circuit of the present invention, the subcarrier signal before being subjected to inverse Fourier transform and the subcarrier signal after the amplified signal is transformed by the Fourier transform means are compared by the comparison operation means. A comparison operation can be performed on a signal having a wide frequency band after the inverse Fourier transform using a signal having a narrow frequency band. This eliminates the need for a high-speed and large-scale arithmetic circuit, thereby reducing the power consumption and circuit scale of the transmission circuit and obtaining an output signal with high power efficiency and low distortion.

  Further, according to the transmission circuit of the present invention, the subcarrier signal before being subjected to the inverse Fourier transform and the subcarrier signal after being converted by the Fourier transforming means after being converted to a plurality of constant envelope signals and synthesized. The carrier signal is compared with the comparison operation means, and the gain or phase in any of the plurality of constant envelope signals is corrected. As a result, it is possible to calculate and correct the gain error or phase error of a plurality of systems of the amplifier circuit with a signal having a narrow frequency band as compared with a signal having a wide frequency band after inverse Fourier transform. An arithmetic circuit becomes unnecessary. Therefore, the power consumption and circuit scale of the transmission circuit can be reduced, and an output signal with high power efficiency and less distortion can be obtained.

  Further, according to the transmission circuit of the present invention, the frequency characteristic difference between a plurality of systems of the transmission circuit is calculated and corrected by comparing the subcarrier signals, so that an output signal with higher power efficiency and less distortion can be obtained. Can do. Also, according to the wireless communication circuit of the present invention, the subcarrier signals can be easily compared by Fourier transform processing using the Fourier transform means provided in the receiving unit, so that the wireless communication circuit can be configured with a simple circuit configuration. It is possible to correct the phase and amplitude error of a plurality of systems of the transmission circuit. Furthermore, according to the radio base station apparatus of the present invention, since the configuration including the transmission circuit or the radio communication circuit of the present invention is adopted, the same operational effects as those of the transmission circuit or the radio communication circuit can be realized. . Moreover, since the radio | wireless terminal apparatus of this invention has taken the structure provided with the transmission circuit or radio | wireless communication circuit of the said invention, it can implement | achieve the effect similar to said transmission circuit or radio | wireless communication circuit. As described above, according to the present invention, an output signal with high power efficiency and less distortion can be obtained while suppressing an increase in power consumption and circuit scale of the transmission circuit.

<Outline of the invention>
The present invention relates to a transmission circuit that amplifies and transmits an OFDM signal, a subcarrier signal before modulation processing, and a subcarrier signal obtained by Fourier transforming a transmission signal after inverse Fourier transform and amplification. And a distortion generated in the process of amplification by the amplifier is detected, and the distortion is corrected by the subcarrier signal before amplification. As a result, an increase in the circuit scale of the transmission circuit can be suppressed, and an output signal with high power efficiency and less distortion can be obtained.

  Hereinafter, some of the embodiments of the transmission circuit according to the present invention will be described in detail with reference to the drawings. In the drawings used in the embodiments, the same components are denoted by the same reference numerals, and redundant description is omitted as much as possible.

<Embodiment 1>
1 is a block diagram showing a configuration of a transmission circuit according to Embodiment 1 of the present invention. First, the configuration of the transmission circuit 100a shown in FIG. 1 will be described. The transmission circuit 100a includes an S / P conversion unit 101, a distortion correction calculation unit (correction unit) 102, an inverse Fourier transform unit (inverse Fourier transform unit) 103, two D / A converters 104a and 104b, and an orthogonal modulation unit (modulation). Means) 105, amplifier (amplifying means) 106, frequency converter 107, A / D converter 108, Fourier transform section (Fourier transform means) 109, and comparison operation section (comparison operation means) 110. Yes.

  Next, the operation of each component in the transmission circuit 100a will be described. The S / P conversion unit 101 performs serial-parallel conversion on data of a predetermined time unit of the input signal and outputs the data to the distortion correction calculation unit 102. The distortion correction calculation unit 102 performs calculation processing on the amplitude and phase of the signal output from the S / P conversion unit 101 according to the comparison calculation result of the comparison calculation unit 110 and outputs the result. The inverse Fourier transform unit 103 allocates data on the frequency (OFDM subcarrier) orthogonal to the signal output from the distortion correction calculation unit 102, performs inverse Fourier transform, and, when orthogonally modulated, a baseband signal Si that becomes an OFDM signal for transmission, Sq is output.

  The two D / A converters 104a and 104b respectively convert the Si signal and the Sq signal output from the inverse Fourier transform unit 103 from a digital signal to an analog signal. The quadrature modulation unit 105 orthogonally modulates the baseband signals Si and Sq, which are converted into analog signals by the D / A conversion units 104a and 104b and output, and outputs them. The amplifier 106 amplifies the signal output from the quadrature modulation unit 105 and outputs the amplified signal as a transmission OFDM signal output from the transmission circuit 100a.

  The frequency conversion unit 107 converts a part of the OFDM signal obtained from the amplifier 106 into a low frequency band and outputs the converted signal to the A / D converter 108. The A / D converter 108 converts the OFDM signal output from the frequency conversion unit 107 from an analog signal to a digital signal, and outputs the converted signal to the Fourier transform unit 109. The Fourier transform unit 109 Fourier-transforms the analog-digital converted OFDM signal output from the A / D converter 108 and separates it into signals for each OFDM subcarrier, and compares at least one of the subcarrier signals. To 110. The comparison calculation unit 110 compares the subcarrier signal output from the Fourier transform unit 109 with the subcarrier signal output from the S / P conversion unit 101 having the same subcarrier number, and sends the comparison calculation result to the distortion correction calculation unit 102. Output.

  Here, the S / P converter 101, the distortion correction calculator 102, the inverse Fourier transformer 103, the Fourier transformer 109, and the comparison calculator 110 are, for example, a DSP (Digital Signal Processor), a CPU (Central Processing Unit), or It is a digital signal processing circuit composed of an ASIC (Application Specific Integrated Circuit) or the like, and each operation is processed by arithmetic operation of a digital signal. The quadrature modulation unit 105 is, for example, a quadrature modulation circuit that quadrature modulates and outputs baseband signals Si and Sq with a carrier wave signal, and can be easily obtained from a local oscillation unit that outputs a carrier wave, a carrier wave phase circuit, a mixer circuit, or the like. Can be configured.

  Next, the overall operation flow of the transmission circuit 100a configured as shown in FIG. 1 will be described. First, the S / P converter 101 performs serial-parallel conversion on data of one OFDM symbol Ts of the input signal and outputs it to the distortion correction calculator 102. Then, the distortion correction calculation unit 102 performs calculation processing on the amplitude and phase of the signal output from the S / P conversion unit 101 according to the comparison calculation result of the comparison calculation unit 110, and outputs the result to the inverse Fourier transform unit 103. The inverse Fourier transform unit 103 assigns data to orthogonal signals (OFDM subcarriers) having a frequency interval of Δfs (= 1 / Ts) and performs inverse Fourier transform on the signal output from the distortion correction calculation unit 102 to perform orthogonal modulation. Then, baseband signals Si and Sq that are OFDM signals are output. That is, the signals serial-parallel converted by the S / P converter 101 are data per subcarrier of the OFDM signal.

  Next, the D / A converter 104a converts one output signal I of the inverse Fourier transform unit 103 into an analog signal, and the D / A converter 104b converts the other output signal Q of the inverse Fourier transform unit 103 into the analog signal. Convert to analog signal. Then, quadrature modulation section 105 performs quadrature modulation on the analog-converted I and Q signals at the transmission carrier frequency and outputs the transmission OFDM signal component to amplifier 106. Then, the amplifier 106 amplifies and outputs the output signal from the quadrature modulation unit 105 to a predetermined signal level output from the transmission circuit 100a. At this time, if the signal is output at a level having a sufficient margin with respect to the saturation level of the amplifier 106, the transmission signal can be amplified with a small distortion, but the operation efficiency of the amplifier 106 is deteriorated. Conversely, if the output is made at a level close to the saturation level, the efficiency of the amplifier 106 will be improved, but the transmission signal of the amplifier 106 will be distorted.

  The frequency converter 107 converts a part of the output signal into a low frequency band that can be converted from analog to digital by the AD converter 108. Further, the AD converter 108 and the Fourier transform unit 109 perform an operation for performing a general OFDM signal decoding process. That is, the AD converter 108 samples the analog signal of the OFDM signal at a sampling interval of Ts / N (generally N is a power of 2) and converts it into a digital signal, and the Fourier transform unit 109 outputs the output of the AD converter 108. Data of Δfs interval can be obtained by Fourier transforming the digital signal to be performed.

  Further, the comparison operation unit 110 compares the subcarrier signal output from the S / P conversion unit 101 and the subcarrier signal output from the Fourier transform unit 109 including the delay time, and corrects the distortion so that there is no difference. A calculation processing request signal is output to the calculation unit 102.

  The distortion correction calculation unit 102 performs correction calculation of the signal output from the S / P conversion unit 101 in accordance with the request signal from the comparison calculation unit 110. As an adaptation method of the calculation at this time, it is performed with a uniform coefficient for all subcarriers, or the result of comparing a plurality of subcarriers in the comparison calculation unit 110 is that the distortion correction calculation unit 102 applies to each subcarrier. There are methods such as performing a correction operation using different coefficients.

  At this time, for example, when the subcarrier interval Δfs of the OFDM modulation signal is 10 kHz and the number of subcarriers is 1024 (2 to the 10th power), the bandwidth of the transmission signal of the OFDM modulation becomes a wide band of 10 MHz or more. Since the subcarrier signal is in the 10 kHz band, the comparison calculation unit 110 can perform comparison calculation processing for correcting the distortion component generated in the amplifier 106 at a frequency sufficiently lower than the bandwidth of the transmission signal. It becomes possible.

  As described above, according to the first embodiment of the present invention, the distortion of the transmission circuit 100a that amplifies and transmits the OFDM signal is compared between the subcarrier of the OFDM signal before amplification and the subcarrier of the OFDM signal after amplification. Since the correction calculation is performed by the distortion correction calculation unit 102 so as to correct the distortion component by the comparison by the calculation unit 110, a high-speed comparison calculation circuit becomes unnecessary. Therefore, the power consumption of the transmission circuit 100a can be reduced and the circuit scale can be reduced. Furthermore, an OFDM signal with less distortion can be output.

  In the above description, the distortion correction calculation unit 102 has been described as a configuration for correcting the output of the S / P conversion unit 101. However, for example, the amplifier 106 may be configured to correct the output of the inverse Fourier transform unit 103. The same effect can be expected if the signal is the previous stage. In the above description, the distortion component of the amplifier 106 has been corrected. However, it goes without saying that distortion components generated in other circuit components such as the quadrature modulation unit 105 are also corrected. . Furthermore, if a storage unit such as a memory is arranged in the comparison calculation unit 110 and the distortion amount and the correction amount to be adapted are stored in advance, the calculation processing amount can be further reduced, and the power efficiency can be further improved. it can.

<Embodiment 2>
FIG. 2 is a block diagram showing a configuration of a transmission circuit according to Embodiment 2 of the present invention. First, the configuration of the transmission circuit 100b shown in FIG. 2 will be described. The transmission circuit 100b includes an S / P conversion unit 101, an inverse Fourier transform unit (inverse Fourier transform unit) 103, a constant envelope signal generation unit (constant envelope signal generation unit) 111, a vector adjustment unit 112, and two D / A Converters 104a and 104b, two low pass filters (LPF) 115a and 115b, two mixers 116a and 116b, a local oscillator 117, two band pass filters (BPF) 118a and 118b, and a first Amplifier (amplifying means) 119, second amplifier (amplifying means) 120, synthesizer (synthesizing means) 121, frequency converter 107, A / D converter 108, Fourier transform part (Fourier transform means) 109, and comparison operation part (Comparison calculation means) 110 is provided. The vector adjustment unit (correction unit) 112 includes an amplitude adjustment unit 113 and a phase adjustment unit 114.

  Next, the operation of each component in the transmission circuit 100b will be described. The S / P conversion unit 101 performs serial-parallel conversion on the data of a predetermined time unit of the input signal and outputs the result to the inverse Fourier transform unit 103. The inverse Fourier transform unit 103 allocates data on the frequency (OFDM subcarrier) orthogonal to the signal output from the S / P conversion unit 101, performs inverse Fourier transform, and baseband signals Si and Sq that become OFDM signals when orthogonally modulated. Is output.

The constant envelope signal generation unit 111 uses two base envelope signals Si and Sq to generate two constant envelope signals that are equivalent to signals obtained by quadrature modulation of the input signals Si and Sq with the carrier frequency of the frequency ωa. That is, the first constant envelope signal Sωa ₁ and the second constant envelope signal Sωa ₂ are generated and output to the D / A converter 104 a and the vector adjustment unit 112, respectively. The vector adjustment unit 112 is an arithmetic circuit, for example, and changes the gain and phase of the second constant envelope signal Sωa ₂ of the constant envelope signal generation unit 111 based on the control of the comparison calculation unit 110 described later, and the D / A Output to the converter 104b.

More specifically, in the vector adjustment unit 112, the amplitude adjustment unit 113 is based on the calculation result of the comparison calculation unit 110, and the gain of the second constant envelope signal Sωa ₂ output from the constant envelope signal generation unit 111 ( The phase adjustment unit 114 adjusts the phase (phase direction) of the second constant envelope signal Sωa ₂ output from the constant envelope signal generation unit 111 based on the calculation result of the comparison calculation unit 110. Make adjustments.

  Here, the S / P conversion unit 101, the inverse Fourier transform unit 103, the constant envelope signal generation unit 111, the vector adjustment unit 112, the Fourier transform unit 109, and the comparison operation unit 110 are, for example, a DSP, a CPU, an ASIC, or the like. The digital signal processing circuit is configured, and the operation performed in each circuit is processed by the calculation of the digital signal.

The D / A converter 104 a digital-analog converts the first constant envelope signal Sωa ₁ that is an output signal from the constant envelope signal generation unit 111. In addition, the D / A converter 104 b performs digital-analog conversion on the second constant envelope signal Sωa ₂ that is an output signal from the vector adjustment unit 112.

LPF115a, 115b, respectively, D / A converter 104a, to remove the sampling frequency and the aliasing noise component from the output signal from 104b, the first constant envelope signal Esuomegaei ₁ and the second constant envelope signal Esuomegaei after removal ₂ are output to the mixers 116a and 116b, respectively. The mixers 116a and 116b are, for example, mixer circuits that up-convert frequencies, mix the output signals from the LPFs 115a and 115b with the local oscillation signals from the local oscillator 117, and the first constant envelope signal Sωc ₁ after mixing. The second constant envelope signal Sωc ₂ is frequency-converted (up-converted) to a predetermined output signal frequency.

The local oscillator 117 is an oscillation circuit such as a frequency synthesizer using a voltage controlled oscillator (VCO) controlled by a phase negative feedback control system (PLL: Phase Locked Loop), for example. 116a and 116b. The BPFs 118a and 118b are filters that pass signals in a desired frequency band and suppress unnecessary frequency components. The BPFs 118a and 118b convert the first constant envelope signal Sωa ₁ and the second constant envelope signal Sωa ₂ up-converted by the mixers 116a and 116b, respectively. The unnecessary frequency components included, that is, the image components generated in the mixers 116a and 116b and the leakage component of the local oscillation signal are suppressed, and the first constant envelope signal Sωc ₁ and the second constant envelope signal Sωc ₂ after suppression are suppressed. The signals are output to the first amplifier 119 and the second amplifier 120, respectively.

  The first amplifier 119 amplifies the output signal from the BPF 118 a and outputs the amplified signal to the combiner 121. The second amplifier 120 amplifies the output signal from the BPF 118b and outputs the amplified signal to the combiner 121. The synthesizer 121 is a synthesizer that can be realized by, for example, a four-terminal directional coupler using a distributed constant circuit, a Wilkinson synthesizer, or a sylex synthesizer, and includes a first amplifier 119 and a second amplifier 120. The amplified signals are combined to obtain the output signal of the transmission circuit 100b.

  The frequency converter 107 converts the OFDM signal obtained from the synthesizer 121 into a low frequency band and outputs it to the A / D converter 108. The A / D converter 108 converts the OFDM signal output from the frequency conversion unit 107 from an analog signal to a digital signal, and outputs the converted signal to the Fourier transform unit 109. The Fourier transform unit 109 performs Fourier transform on the digitally converted OFDM signal output from the A / D converter 108 and separates it into signals for each OFDM subcarrier, and sends at least one of the subcarrier signals to the comparison operation unit 110. Output. The comparison calculation unit 110 is configured by, for example, a calculation circuit such as a CPU, DSP, or ASIC, a memory, and the like, and is output by the S / P conversion unit 101 having the same subcarrier number as the subcarrier signal output by the Fourier transform unit 109. The subcarrier signal to be compared is compared, and gain and phase adjustment in the vector adjustment unit 112 is controlled according to the comparison calculation result.

  More specifically, assuming that the adjustment amounts in the amplitude direction and the phase direction in the vector adjustment unit 112 are γ and β, respectively, the comparison operation unit 110 outputs the adjustment amount γ in the amplitude direction from the Fourier transform unit 109. The value is set such that the amplitude components of the subcarrier signals output from the S / P converter 101 having the same subcarrier number as the carrier signal are equal to each other. Further, the comparison operation unit 110 sets the phase direction adjustment amount β to each phase component in the subcarrier signal output from the S / P conversion unit 101 having the same subcarrier number as the subcarrier signal output from the Fourier transform unit 109. Are set to be equal to each other.

  Next, the overall operation flow of the transmission circuit 100b configured as shown in FIG. 2 will be described. First, the S / P conversion unit 101 performs serial-parallel conversion on data of a certain time unit of one OFDM symbol Ts in the input signal and outputs the result to the inverse Fourier transform unit 103. The inverse Fourier transform unit 103 assigns data to the orthogonal frequency (OFDM subcarrier) having a frequency interval of Δfs (= 1 / Ts) and performs inverse Fourier transform on the signal output from the S / P conversion unit 101, and performs orthogonal When modulated, baseband signals Si (t) and Sq (t) that are OFDM signals S (t) are output. Here, the relationship among the OFDM signal S (t), the baseband signal Si (t), and the baseband signal Sq (t) can be expressed by the following equation (4).

但し、Ａｋ及びＢｋは送信データ、ｆｋはｋ番目のサブキャリアの周波数でｆｋ＝ｋ／Ｔｓとする。

However, Ak and Bk are transmission data, fk is the frequency of the k-th subcarrier, and fk = k / Ts.

The constant envelope signal generation unit 111 obtains the first constant envelope signal Sωa ₁ (t) and the second constant envelope signal Sωa ₂ (t) from the baseband input signals Si (t) and Sq (t). Generate. When the signal Sωa (t) obtained by orthogonally modulating the input signals Si (t) and Sq (t) with the carrier frequency of the angular frequency ωa is expressed by the following equation (5), the first constant envelope signal Sωa ₁ ( t) and the second constant envelope signal Sωa ₂ (t) are expressed by the equations (6) and (7), the first constant envelope signal Sωa ₁ (t) and the second constant envelope signal Sωa ₂ (t) is a constant envelope signal having a constant amplitude direction.
Sωa (t) = V (t) × cos {ωat + φ (t)} (5)
Sωa ₁ (t) = Vmax / 2 × cos {ωat + ψ (t)} (6)
Sωa ₂ (t) = Vmax / 2 × cos {ωat + θ (t)} (7)
However, the maximum value of V (t) is Vmax,
Let ψ (t) = φ (t) + α (t), θ (t) = φ (t) −α (t).

Then, the vector adjustment unit 112 shifts the output signal Sωa ₂ (t) of the constant envelope signal generation unit 111, for example, by γ times the amplitude in the amplitude direction and phase shifts in the phase direction based on the control of the comparison calculation unit 110. Adjust the amount by β respectively. Thus, the output signal Soutv (t) of the vector adjustment unit 112 can be expressed by the following equation (8).
Soutv (t) = γ × [Vmax / 2 × cos {ωat + θ (t) + β} (8)

The D / A converter 104a converts the output signal Sωa ₁ (t) of the constant envelope signal generation unit 111 into an analog signal, and the D / A converter 104b outputs the output signal Soutv (t) of the vector adjustment unit 112. ) To an analog signal.

Further, the LPFs 115a and 115b respectively suppress aliasing noise components that can be output from the D / A converters 104a and 104b in the digital-analog converted signals. Then, the mixers 116a and 116b frequency-convert the carrier frequencies of the signals after noise component suppression into Sωc ₁ and Sωc ₂ , respectively. Furthermore, the BPFs 118a and 118b suppress unnecessary spurious components such as image components and leakage components of local oscillation signals that may be generated from the mixers 116a and 116b in the frequency-converted signals.

  The first amplifier 119 amplifies the output signal from the BPF 118a, and the second amplifier 120 amplifies the output signal from the BPF 118b. Further, the synthesizer 121 synthesizes output signals from the first amplifier 119 and the second amplifier 120. In this way, an output signal of the transmission circuit 100b is obtained.

Here, the gain and phase shift amount from the D / A converter 104a to the first amplifier 119 are Ga and Ha, respectively, and the gain and phase shift amount from the D / A converter 104b to the second amplifier 120 are Gb, respectively. Assuming Hb, the output signal Souta ₁ from the first amplifier 119 and the output signal Souta ₂ from the second amplifier 120 are expressed by Expression (9) and Expression (10), respectively.
Souta ₁ = Ga × [Vmax / 2 × cos {ωct + ψ (t) + Ha} (9)
Souta ₂ = Gb × γ × [Vmax / 2 × cos {ωct + θ (t) + β + Hb}
(10)

Therefore, the output signal S ′ (t) of the synthesizer 121 is a signal obtained by adding the two signals represented by the above equations (9) and (10) in-phase, and can be represented by the following equation (11). it can.
S ′ (t) = Ga × [Vmax / 2 × cos {ωct + ψ (t) + Ha} + Gb × γ × [Vmax / 2 × cos {ωct + θ (t) + β + Hb} (11)

At this time, if Ga = Gb × γ and Ha = Hb + β, the first term and the second term on the right side of the equation (11) are expressed by the equation (2) representing the constant envelope signal that becomes the equation (1) when combined. And the above equation (11) can be converted into the following equation (12).
S ′ (t) = Ga × V (t) × cos {ωct + φ (t) + Ha} (12)

The first term on the right side of the above equation (12) is a desired wave signal component obtained by orthogonally modulating an input signal with a carrier wave having an angular frequency ωc and gain-Ga multiplied by Ha phase, that is, amplified by gain Ga. When the gain and the amount of phase shift change uniformly within the signal band, the signal for each subcarrier on the right side of the equation (4) also changes uniformly. For example, the signal component Smout (t) of the mth subcarrier can be expressed by the following equation (13).
Smout (t) = Ga × [Am × cos {(ωc + 2πfm) t + Ha} + jBm × sin {(ωc + 2πfm) t + Ha}] (13)

  That is, the term on the right side of the above equation (13) is obtained by shifting the m-th subcarrier signal component of the term on the right side shown in equation (4) by Ga gain and Ha phase and modulating with ωc.

Here, when Ga = Gb × γ and Ha = Hb + β are not established, an error component is generated in the gain and phase. When the above equation (12) is expressed including the error components Gx and Hx, the following equation (14) is obtained.
S ′ (t) = Gx × Ga × V (t) × cos {ωct + φ (t) + Ha + Hx}
(14)

When this error component is uniformly generated in the signal band, the signal component Smout (t) of the mth subcarrier can be expressed by the following equation (15).
Smout (t) = Gx × Ga × [Am × cos {(ωc + 2πfm) t + Ha + Hx} + jBm × sin {(ωc + 2πfm) t + Ha + Hx}] (15)

  That is, the comparison operation unit 110 compares the m-th subcarrier signal component before amplification represented by Equation (4) with the signal component of the m-th subcarrier after amplification, thereby obtaining a desired gain and phase shift amount. Error components Gx and Hx from Ga and Ha can be obtained. At this time, the input signal of the comparison operation unit 110 is distributed from the output signal, and fluctuations in gain and phase due to the frequency conversion unit 107, but can be easily canceled if these differences are measured in advance.

  That is, in the second embodiment of the present invention, a part of the output signal of the transmission circuit 100b is extracted and input to the comparison operation unit 110, and the gain and phase error components Gx and Hx shown on the right side of Expression (15) are obtained. The vector adjustment unit 112 is controlled so that Ga = Gb × γ and Ha = Hb + β are detected.

  Then, the frequency converter 107 converts the output signal into a low frequency band that can be AD converted by the AD converter 108. Further, the AD converter 108 and the Fourier transform unit 109 perform an operation for performing a general OFDM signal decoding process. That is, the AD converter 108 samples the analog signal of the OFDM signal at a sampling interval of Ts / N (generally N is a power of 2) and converts it into a digital signal, and the Fourier transform unit 109 outputs the output from the AD converter 108. The data of Δfs interval can be obtained by Fourier transforming the digital signal to be performed.

  The Fourier transform unit 109 outputs any subcarrier data of the obtained data to the comparison operation unit 110. Then, the comparison calculation unit 110 compares the subcarrier signal output from the S / P conversion unit 101 and the subcarrier signal output from the Fourier transform unit 109 including the delay time, thereby generating error components Gx, Hx. You can know the value of.

  Then, the adjustment of the gain γ and the phase shift amount β by the vector adjustment unit 112 is controlled so that the error components Gx and Hx become small, that is, ideally Gx = 1 and Hx = 0. That is, by this operation, the signal expressed by the above equation (12) can be obtained as the output signal of the amplifier circuit 100b.

  At this time, for example, even if the bandwidth of the OFDM modulation signal is a wide band of several MHz or more, the subcarrier signal component is a signal sampled at Ts = 1 / Δfs, so the comparison operation unit 110 It is possible to perform arithmetic processing for adjusting the amplitude component and the phase component at a frequency that is sufficiently lower than the bandwidth.

  As described above, according to the second embodiment of the present invention, the gain error and the phase error of the two systems in the LINC transmission circuit 100b that amplifies the OFDM signal are divided into the subcarrier of the OFDM signal before amplification and the OFDM after amplification. Since the sub-carrier of the signal is calculated by the comparison operation unit 110 and the vector component 112 adjusts (corrects) the amplitude component and the phase component based on the calculated gain error and phase error, the large-scale operation is performed. A correction arithmetic circuit is unnecessary, and the circuit scale of the transmission circuit 100b can be reduced. As a result, an output OFDM signal with high power efficiency and low distortion can be obtained.

  In the above description, the synthesizer 121 is assumed to be an ideal in-phase synthesizer. However, according to the present embodiment, even when there is a gain difference or phase difference during the synthesis in the synthesizer 121. The difference can be corrected. In the above description, the vector adjustment unit 112 corrects the gain and phase. However, even if a variable gain amplifier using an analog circuit, a variable phase shifter, or the like is used, the same effect as described above can be obtained. Obtainable. For example, if the variable gain means is configured to control the bias of the first amplifier 119 and the second amplifier 120, the power efficiency can be further improved.

  In the above description, the phase adjustment unit 114 is used as the variable phase shift unit. However, if the cause of the phase error is mainly due to the difference in the delay amount, the same as above even if the variable delay unit is used. The effect of this can be obtained. Furthermore, in the above description, the in-phase combiner 121 is used, but the phase characteristics are not limited. For example, instead of the synthesizer 121 described above, even if a directional coupler that synthesizes by shifting the phase by 90 degrees is used, if a constant envelope signal is generated in consideration of the phase shift amount, The same effect as described above can be obtained.

<Embodiment 3>
FIG. 3 is a block diagram showing a configuration of a transmission circuit according to Embodiment 3 of the present invention. The transmission circuit 100c of the third embodiment shown in FIG. 3 has a configuration in which a frequency characteristic correction unit (frequency characteristic correction means) 122 is added to the transmission circuit 100b of the second embodiment shown in FIG. The frequency characteristic correction unit 122 is, for example, an arithmetic circuit, and changes the frequency characteristics of the gain and phase of the output signal of the constant envelope signal generation unit 111 based on the control of the comparison calculation unit 110 and outputs them to the vector adjustment unit 112. To do. The frequency characteristic correction unit 122 is a digital signal processing circuit composed of, for example, a DSP, CPU, ASIC, or the like, and the correction of the frequency characteristic is processed by calculation of a digital signal. Moreover, the frequency characteristic correction | amendment part 122 changes the frequency characteristic of a gain and a phase by changing the coefficient of the digital filter by digital signal processing, for example.

  Based on a plurality of comparison results of the subcarrier signal component output from the Fourier transform unit 109 and the subcarrier signal component output from the S / P conversion unit 101, the comparison operation unit 110 calculates the gain and phase in the vector adjustment unit 112. The adjustment and the correction of the frequency characteristic in the frequency characteristic correction unit 122 are controlled.

  More specifically, when the adjustment amounts in the amplitude direction and the phase direction in the vector adjustment unit 112 are γ and β, respectively, the comparison calculation unit 110 sets the adjustment amount γ in the amplitude direction to the gain of a certain subcarrier signal component. The value is set such that the error component Gx is small, and the adjustment amount β in the phase direction is set so that the phase error component Hx of the subcarrier is small.

  Further, when there is a difference in the frequency characteristics of the two signal paths from the constant envelope signal generation unit 111 to the synthesizer 121, the comparison operation unit 110 outputs the Fourier transform unit 109 and the S / P conversion unit 101 to compare. For example, the coefficient of the digital filter in the frequency characteristic correction unit 122 is determined so that the error component of each of the plurality of subcarrier signal components having different frequencies among the subcarrier signal components to be processed is minimized. Notice.

  Hereinafter, correction of the frequency characteristics of the gain and phase in the third embodiment will be described with reference to FIGS. FIG. 4 is a diagram illustrating an example of gain frequency characteristics of a general high-frequency circuit such as an amplifier or a mixer, where the horizontal axis represents frequency and the vertical axis represents gain. As shown in FIG. 4, the high frequency circuit may have different gains depending on the frequency, and the frequency characteristics also vary. For this reason, for example, even if the gain and phase are corrected using only an arbitrary subcarrier signal component at a low frequency within the band of the transmission signal, those errors increase in the subcarrier signal at a high frequency of the transmission signal. It is conceivable that distortion may occur in the output signal.

  FIG. 5 is a diagram illustrating an example of phase frequency characteristics (represented by a solid line and a broken line) of two paths having different delay amounts, where the horizontal axis represents frequency and the vertical axis represents phase. For example, when an electric circuit is realized on a printed circuit board, a delay amount may be different between a plurality of paths due to an error in the length of the transmission line. In this case, as shown in FIG. 5, the phase difference may differ depending on the frequency. For this reason, for example, even if the phase is corrected by using only an arbitrary subcarrier signal component at a low frequency within the band of the transmission signal, the error is increased in the subcarrier signal at a high frequency of the transmission signal, and the output signal is increased. It is conceivable that distortion may occur. Therefore, in transmission circuit 100c according to Embodiment 3 of the present invention, frequency characteristics are corrected using a plurality of subcarrier signal components.

  FIG. 6 is a diagram showing a spectrum of an OFDM signal that is an output signal of the amplifier circuit according to Embodiment 3 of the present invention, where the horizontal axis represents frequency and the vertical axis represents amplitude. For example, as shown in FIG. 6, the Fourier transform unit 109 in FIG. 3 performs a −m-th subcarrier signal component that is a subcarrier signal component at a low frequency and a + mth subcarrier signal component that is at a high frequency. Are output to the comparison operation unit 110.

  The comparison operation unit 110 compares the −m-th and + m-th subcarrier signal components output from the Fourier transform unit 109 with the unamplified signal output from the S / P conversion unit 101, and obtains each gain and phase. The error component of is calculated. Then, the gain and phase are adjusted by the vector adjusting unit 112 so that the gain and phase error components of the −m-th subcarrier signal component become small. Since this operation is the same as the operation described in the second embodiment, the description thereof is omitted.

  At this time, for example, when the gain has frequency characteristics, the gain error component of the + m-th subcarrier signal component is larger than the gain error component of the -m-th subcarrier signal component. Therefore, the comparison calculation unit 110 controls the frequency characteristic correction unit 122 so that the error component of the gain of the + m-th subcarrier signal component becomes small.

  FIG. 7 is a diagram illustrating an example of gain characteristics of the frequency characteristic correction unit 122 according to Embodiment 3 of the present invention, where the horizontal axis represents frequency and the vertical axis represents gain. As shown in FIG. 7, the frequency characteristic correction unit 122 changes the gain frequency characteristic from gain frequency characteristic No. 1 to gain frequency characteristic No. 2 by changing the coefficient of the digital filter by digital signal processing, for example. It is possible to make it.

  In other words, the gain and phase differences between the two amplification systems are obtained by comparing subcarrier signal components at low frequencies before and after amplification, and the gain and phase adjustment amounts (correction amounts) in the vector adjustment unit 112 are controlled. . Further, a difference in gain frequency characteristics is obtained by comparing subcarrier signal components at high frequencies, and the frequency characteristic correction amount in the frequency characteristic correction unit 122 is controlled.

  In FIG. 7, the correction of the frequency characteristic of the gain has been described. However, the correction of the frequency characteristic of the phase can be performed by the same operation. A variable delay circuit may be used as means for correcting the frequency characteristics of the phase.

  As described above, according to the third embodiment of the present invention, the difference in frequency characteristics between the two systems in the LINC transmission circuit 100c that amplifies the OFDM signal is compared with a plurality of subcarriers in the OFDM signal before amplification, and after amplification. Since the comparison operation unit 110 compares the subcarriers in the OFDM signal with each other and the frequency characteristic is corrected based on the calculated frequency characteristic difference, the frequency characteristic correction unit 122 performs higher power efficiency. An output signal with little distortion can be obtained.

<Embodiment 4>
FIG. 8 is a block diagram showing a configuration of a wireless transmission / reception apparatus according to Embodiment 4 of the present invention. That is, this figure shows a configuration of a wireless transmission / reception apparatus that transmits / receives a TDD OFDM signal. The radio transmission / reception apparatus 200 illustrated in FIG. 8 includes a transmission circuit 100d, an antenna sharing switch 202, an antenna 201, and a radio reception unit 203.

  The transmission circuit 100d includes an S / P conversion unit 101, an inverse Fourier transform unit 103, a constant envelope signal generation unit 111, a vector adjustment unit 112, two D / A converters 104a and 104b, and two low-pass filters (LPF) 115a. 115b, two mixers 116a and 116b, a local oscillator 117, two bandpass filters (BPF) 118a and 118b, a first amplifier 119, a second amplifier 120, a combiner 121, and a comparison operation unit 110 It has become. The wireless reception unit 203 includes a low noise amplifier 204, a reception mixer 205, an A / D converter 206, a Fourier transform unit (reception signal Fourier transform unit) 207, and a P / S conversion unit 208. Yes.

  The transmission circuit 100d performs the same operation as that described in the second embodiment, and the synthesizer 121 outputs an OFDM signal including a pilot signal. The antenna 201 is an antenna that transmits and receives radio signals, and the antenna 201 is shared for transmission and reception. The antenna sharing switch 202 is a switch for using the antenna 201 by switching between transmission and reception according to time.

  The radio reception unit 203 amplifies the received radio signal with the low noise amplifier 204 and performs frequency conversion with the reception mixer 205, and then converts the analog signal into a digital signal with the A / D converter 206 to convert the analog signal into a Fourier transform unit 207. The P / S converter 208 performs parallel-serial conversion to obtain a received signal.

  The wireless transmission / reception device 200 is a TDD wireless transmission / reception device, and does not receive a reception signal by selecting the antenna sharing switch 202 as a transmission side during transmission. However, since the antenna sharing switch 202 is generally configured using a semiconductor, there is signal leakage. That is, an OFDM signal including a pilot signal to be transmitted is leaked and input to the wireless reception unit 203.

  The radio reception unit 203 is a reception circuit that receives an OFDM signal, and the Fourier transform unit 207 is a Fourier transform of the leaked OFDM signal in the same manner as the Fourier transform unit 109 included in the transmission circuit 100b described in the second embodiment of FIG. The subcarrier signal component can be output to the comparison operation unit 110 after conversion.

  As described above, according to the fourth embodiment of the present invention, the radio transmission / reception apparatus 200 that transmits / receives an OFDM signal using the TDD scheme includes two gain errors and phase errors caused by the LINC amplifier that amplifies the transmission OFDM signal. Since the subcarrier signal component for calculation can be separated by Fourier transform processing using the Fourier transform unit 207 provided in the wireless reception unit 203, the apparatus scale can be reduced and included in the transmission signal at a low manufacturing cost. The distortion component that is generated can be reduced. Note that the wireless transmission / reception device 200 described in Embodiment 4 can be applied to a wireless base station device and a communication terminal device used in a wireless communication and broadcasting network.

  Since the transmission circuit of the present invention can obtain an output signal with high power efficiency and low distortion while suppressing an increase in circuit scale of the transmission circuit, the transmission circuit outputs a transmission signal in a transmission device used in the wireless communication field and the broadcast field. It can be effectively used as a circuit.

The block diagram which shows the structure of the transmission circuit which concerns on Embodiment 1 of this invention. The block diagram which shows the structure of the transmission circuit which concerns on Embodiment 2 of this invention. The block diagram which shows the structure of the transmission circuit which concerns on Embodiment 3 of this invention. Diagram showing an example of gain frequency characteristics of a general high-frequency circuit The figure which shows the example of the phase frequency characteristic of two path | routes from which delay amount differs The figure which shows the spectrum of the output signal of the amplifier circuit which concerns on Embodiment 3 of this invention. The figure which shows the example of the gain characteristic of the frequency characteristic correction | amendment part in Embodiment 3 of this invention. The block diagram which shows the structure of the radio | wireless transmitter / receiver which concerns on Embodiment 4 of this invention. Diagram showing the spectrum of a typical OFDM modulated signal The figure which shows the general example of the structure of the conventional transmission circuit The figure which showed the calculation operation in the conventional transmission circuit on the orthogonal plane The figure which shows the general example of the structure of the conventional transmission circuit

Explanation of symbols

100a, 100b, 100c, 100d Transmission circuit 101 S / P conversion unit 102 Distortion correction calculation unit 103 Inverse Fourier transform unit 104a, 104b D / A converter 105 Orthogonal modulation unit 106 Amplifier 107 Frequency conversion unit 108, 206 A / D conversion 109 109 Fourier transform unit 110 Comparison operation unit 111 Constant envelope signal generation unit 112 Vector adjustment unit 113 Amplitude adjustment unit 114 Phase adjustment unit 115a, 115b LPF
116a, 116b Mixer 117 Local oscillator 118a, 118b BPF
119 First amplifier 120 Second amplifier 121 Synthesizer 122 Frequency characteristic correction unit 200 Radio transmission / reception device 201 Antenna 202 Antenna shared switch 203 Wireless reception unit 204 Low noise amplifier 205 Reception mixer 207 Fourier transform unit 208 P / S conversion unit

Claims (6)

Inverse Fourier transform means for performing inverse Fourier transform on a signal on the frequency axis obtained by modulating data with a plurality of subcarriers that are input signals, and converting it to a baseband signal on the time axis;
Modulation means for modulating a baseband signal on the time axis with a carrier wave to generate a transmission signal;
Amplifying means for amplifying the transmission signal;
Fourier transform means for converting data on the time axis of the transmission signal amplified by the amplification means into data on the frequency axis;
Comparison operation means for comparing one or more subcarriers of the input signal and one or more subcarriers output by the Fourier transform means to calculate a difference;
According to the calculation result of the comparison calculation means, a correction means for calculating and outputting the signal before the input of the amplification means so as to correct the distortion of the output signal of the amplification means,
A transmission circuit comprising: Inverse Fourier transform means for performing inverse Fourier transform on a signal on the frequency axis obtained by modulating data with a plurality of subcarriers that are input signals, and converting it to a baseband signal on the time axis;
A constant envelope signal generating means for generating a plurality of constant envelope signals from the baseband signal on the time axis;
Amplifying means for amplifying a plurality of constant envelope signals generated by the constant envelope signal generating means;
Combining means for combining the plurality of constant envelope signals amplified by the amplifying means;
Fourier transform means for converting data on the time axis of the signal synthesized by the synthesis means into data on the frequency axis;
Comparison operation means for comparing one or more subcarriers of the input signal and one or more subcarriers output by the Fourier transform means to calculate a difference;
Correction means for correcting at least one of gain and phase in any of the plurality of constant envelope signals according to the calculation result of the comparison calculation means,
A transmission circuit comprising: Frequency characteristic correcting means for correcting frequency characteristics of any of the plurality of constant envelope signals generated by the constant envelope signal generating means according to a result of the comparison calculating means comparing and calculating a plurality of subcarriers. The transmission circuit according to claim 2. A transmission circuit according to any one of claims 1 to 3,
Receiving signal Fourier transform means for performing Fourier transform processing of the received signal,
A TDD wireless communication circuit characterized in that the received signal Fourier transform means is switched by temporally switching the Fourier transform means of the transmission circuit.   A radio base station apparatus comprising the transmission circuit according to any one of claims 1 to 3 or the radio communication circuit according to claim 4.   A wireless terminal apparatus comprising the transmission circuit according to claim 1 or the wireless communication circuit according to claim 4.

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