Hitachi-kokusai Electric Inc.

Naoki Hongo

Yoichi Okubo

Masaki Suto

Toshio Takada

Tetsuhiko Miyatani

Masato Horaguchi

Manabu Nakamura

Yasuhiro Takeda

Kiyoshi Funada

Takashi Okazaki

Yoshihiko Akaiwa

Taizo Ito

Masaru Adachi

Taizo Yamawaki

Masashi Naito

Kenzo Urabe

Takashi Kawamoto

Takashi Uchida

Takehiko Kobayashi

Satoshi Furuta

Akira Maeki

Junya Dosaka

Kazuyoshi Sato

Shuhei Miura

Yasuo Sera

Hidefumi Ito

Zhou Changming

A wireless apparatus is configured such that: a correlation calculation unit calculates a correlation coefficient for signals received from respective antennas; and a cyclic shift control unit compares the correlation coefficient with a threshold value. If the correlation coefficient is equal to or higher than the threshold value, the cyclic shift control unit determines that there is a direct wave, allocates a common shift amount to a cyclic shift unit, and causes a beam forming unit to form and transmit a narrow beam. Meanwhile, if the correlation coefficient is lower than the threshold value, the cyclic shift control unit determines that there is no direct wave, allocates different shift amounts to the cyclic shift unit, and causes the cyclic shift unit to diversify the cyclic shift.

Wireless apparatus, communication system, and communication method

A wireless communication system includes a transmitter that discretely inserts null subcarriers into an OFDM-demodulated signal in time and frequency domains, and a receiver that receive signals by a first and second antennas. The receiver calculates a complex coefficient wherein a result of multiplying a first reception vector for each of the null subcarriers received by the first antenna by the complex coefficient is equal to an amplitude of a second reception vector of the corresponding null subcarrier received by the second antenna and is opposite in phase thereto, calculates a fourth reception vector by multiplying a third reception vector of any data subcarrier received by the first antenna by a coefficient that is obtained by interpolating the complex coefficient, and adds the fourth reception vector to a fifth reception vector of the any data subcarrier received by the second antenna.

Wireless communication system

A wireless communication system having a plurality of antennas is disclosed. A combination of transmission antennas and reception antennas is selected, the combination allowing &#x3a6; to be the closest to &#x3c0; radians, where &#x3a6; represents an absolute value of an angle obtained by subtracting &#x3c6;from &#x3c6;, where &#x3c6;represents an angle formed by signal vectors transmitted from an i-th and a j-th transmission antennas of the first wireless device on an orthogonal plane on which a reception signal of a k-th reception antenna of the second wireless device is quadrature-detected or demodulated, and &#x3c6;represents an angle formed by the signal vectors transmitted from the i-th and the j-th transmission antennas of the first wireless device on an orthogonal plane on which a reception signal of an l-th reception antenna of the second wireless device is quadrature-detected or demodulated.

To effectively control the amplitude vs. power supply voltage characteristics, for example, in an ET amplifier. An amplifying device for amplifying an input signal wherein: amplifier means () amplifies the input signal; amplification control means () control the power supply voltage to the amplification means on the basis of the input signal; first detection means () detects the amplification factor between the input signal and a feedback signal obtained by means of a feedback of the signal that has been amplified by the amplification means; second detection means () detects the variance of the amplification factors for each value or range of the amplitude of the input signal; and amplification control update means () performs an update so as to increase the power supply voltage with respect to a value or range of amplitude that exhibits a variance in excess of a predetermined threshold value, or to reduce the power supply voltage with respect to a value or range of amplitude that exhibits a variance lower than the predetermined threshold value.

Amplifying device

An efficient amplifying device is achieved. An amplifying device that amplifies a signal subject to amplification is configured as follows. That is, an amplifier (PA) that amplifies a signal is provided. Level control meansconverts a level of the signal subject to amplification according to the level of this signal. Power supply control meansandsupply the amplifier (PA) with a power supply voltage determined according to the level of the signal subject to amplification. The amplifier (PA) amplifies a signal at the level converted by the level control meanswith the power supply voltage supplied from the power supply control meansand

A distortion compensation amplification device includes a level detecting means that detects a signal level, a correspondence storage means that outputs a distortion compensation coefficient depending on the signal level, a pre-distortion executing means that gives distortion with an inverse characteristic to the signal, a filtering means that outputs a distortion component from a feedback signal output from an amplifier, and a correspondence acquiring means that updates a learning coefficient constituting a function that gives the inverse characteristic so as to reduce the distortion component. Each orthogonal function is the total sum of products of functions of the input signal and parameters. The parameter values are set to cause the orthogonal functions to be orthogonal to each other when functions are replaced for the functions of the input signal constituting the orthogonal functions.

Distortion compensation amplification device

A power circuit used for an amplifier, which includes an amplifier provided with a linear amplifier serving as a voltage source, a DC/DC converter serving as a current source, a hysteresis comparator controlling the DC/DC converter, and a current detector detecting output current from the linear amplifier to output the detected output current to the hysteresis comparator; and a switching restricting device for restricting a switching interval in the DC/DC converter such that the switching interval is not equal to or less than a constant time or is not shorter than the constant time.

Power circuit used for an amplifier

The present invention provides a non-linear distortion detection method and a distortion compensation amplifying device capable of suppressing increase of the circuit size and the power consumption even if the signal band is widened. A signal obtained by feeding back an output of a power amplifier is sampled by an A/D converter. An equalizer of a distortion detection unit uses an input signal d(n) of a predistorter as a reference symbol to detect an equalization error e(n) of the orthogonal demodulation signal u(n). An absolute value averaging unit outputs an absolute value of the equalization error e(n) which has been temporally averaged to E(n) as a distortion value to a control unit. According to the distortion value, the control unit adaptively controls the predistorter to perform distortion compensation.

Non-linear distortion detection method and distortion compensation amplifying device

The invention aims to converge predistortion coefficients efficiently in a predistorter adapted to compensate for distortion generated in an amplifier. Level detection means detects the level of a signal input to an amplifier. Signal acquisition means acquire a signal output from the amplifier as a feedback signal. Correspondence acquisition means updates a predistortion coefficient expressed using a set of orthogonal polynomials so that a distortion component contained in the acquired feedback signal is reduced and acquires a correspondence between the level of the signal input to the amplifier and a control coefficient for predistortion (contents of a distortion compensation table). Predistortion executing means applies distortion for predistortion with respect to the signal input to the amplifier in accordance with the control coefficient for predistortion that corresponds to the detected level based on the acquired correspondence.

Predistorter

An amplifying apparatus includes a splitting unit for splitting an input signal into a first split signal and a second split signal; phase-shifting unit for phase-shifting the first split signal and the second split signal, respectively; a first amplifying unit for amplifying a first phase-shifted signal and outputting the signal as a first output signal; a second amplifying unit for amplifying, in a substantially identical manner to the first amplifying unit, a second phase-shifted signal and outputting the signal as a second output signal; and a matching unit for matching the first output signal and the second output signal to a first transmission unit and a second transmission unit, respectively. The first transmission unit is for transmitting the first output signal from the matching unit to a load resistor, and the second transmission unit is for transmitting the second output signal from the matching unit to the load resistor.

LINC amplifying device

The invention provides a spectrum analyzing method, a distortion detector and a distortion compensation amplifying device for performing time/frequency conversion processing at high speed, and reducing a convergent time of a compensation coefficient. The distortion detector for detecting distortion in a frequency area with respect to an input signal includes a time window processing section for multiplying the input signal by a time window; an averaging processing section for averaging an output of the time window processing section; an FFT processing section for converting an output of the averaging processing section from a time area to a frequency area; and a distortion extracting section for extracting a distortion component from an output of the FFT processing section.

Spectrum analyzing method, distortion detector and distortion compensation amplifying device

A predistorter for correcting distortion caused by a memory effect in amplifying a signal by an amplifier is provided. In the memory PDprovided to the predistorter, the level detection meansdetects the level of the signal, the coefficient output meansoutputs the coefficient corresponding to the detected level, the delay meansdelays the output coefficient, the difference detection meansdetects the difference between the output coefficient and the delayed coefficient, the multiplication meansmultiplies the detected difference with the signal, and the combination meanscombines the result of the multiplication and the signal. Thus, the result of the combination is output to the amplifier.

An amplifier apparatus for providing a pre-distortion to perform a distortion compensation, wherein even if the frequency of occurrence of levels around the input signal peak is small, a distortion compensation table is efficiently updated so as to improve the performance of the distortion compensation. The compensation values of a distortion compensation table () are divided into a first group of compensation values corresponding to large input levels that lead to large output distortions and a second group of compensation values corresponding to the other small input levels. If a level detected by a level detecting part () exceeds a threshold value, a control part () updates the first group of compensation values. Otherwise, the control part () updates the second group of compensation values. In this way, the updating process can be effectively performed even for signals having small frequencies of occurrence of the peak values of the signal levels as in the CDMA or OFDM system, thereby improving the performance of the distortion compensation.

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Tokyo, Japan

Naoki Hongo