Hitachi, Ltd.

Other

Kddi Corporation

Hitachi Communication Technologies, Ltd.

Yuji Ishida

Ken Takei

Kazuyuki Hori

Yoshinori Nagoya

Shouhei Murakami

Nobukazu Doi

Mikio Kuwahara

Takashi Inoue

Toshiro Suzuki

Sumaru Niida

Yoshiaki Hasegawa

Tomoya Uchiike

Toshiaki Kurokawa

Keiichi Hirota

Kenji Yanagi

Takashi Sakai

There is a need for effectively compensating distortion when a predistortion transmitter is subject to not only a memory effect due to nonlinearity of an amplifier, but also a modulator's DC offset, IQ unbalance, or local quadrature error. A predistortor to be used is a polynomial predistortor including a polynomial basis generation portion and an inner product calculation portion. The polynomial basis generation portion delays a real part and an imaginary part of a complex input signal Sx=Ix+jQx for up to M samples to generate 2(M+1) signals, duplicately combines these signals to generate monomials having maximum degree N, and outputs, as a basis vector, all or part of the monomials depending or needs. The inner product calculation portion performs an inner product calculation using a coefficient vector, i.e., a set of complex numbers sized equally to the basis vector to find a polynomial value and outputs the value as a complex signal.

Digital predistortion transmitter

An OFDM modulator having a peak factor reduction function. The OFDM modulator has a peak factor reduction unit between an IFFT unit and a guard interval insertion unit thereof. The peak factor reduction unit converts a complex signal Xoutputted from the IFFT unit into a complex signal Xwith a reduced peak factor based on subcarrier map information. The peak factor reduction unit generates a peak factor reduction signal by a linear combination of complex exponential functions that correspond to subcarrier frequencies to be used for wave transmission, as bases. The peak factor reduction signal is derived by repetition of, for example, a weighted least squares method or convolution processing by a fast Fourier transform.

OFDM modulator

A radio base station apparatus provided with an array antenna having a plurality of antenna elements for calibrating a phase difference among the array antenna elements. The base station has a probe signal adding unit which divides one probe signal and adds the divided probe signals to each receive signals received by the plurality of antenna elements. A probe data extracting unit extracts the probe data from the receive signals added with the probe signal. A phase calibration calculation unit calculates correlating phase calibration values required for calibrating a phase of each receive signal based on the probe data extracted by the probe signal extracting unit. A phase calibration unit calibrates a phase difference among the array antenna elements by calibrating the phase of the each receive signal based on the phase calibration from the phase calibration calculation unit.

Antenna unit and radio base station therewith

In a time-interleaved AD converter which combines together low-speed high-resolution AD converters for effective high speed operation, various deterioration factors possessed by each of the converters, including DC offset, conversion gain error, sampling timing error, and a frequency characteristic, need to be compensated. The compensation is performed through nonlinear filter operation in which a constant term is added to linear filter operation. A high-speed low-resolution AD converter is separately used, and through adaptive signal processing in which an output signal thereof is defined as an instruction signal, a compensation coefficient is calculated. In this condition, the compensation can be performed without the influence of quantization noise attributable to the high-speed low-resolution AD converter.

Time-interleaved AD converter

Phase and amplitude deviations, which are generated, for example, by cables connecting an array antenna of a CDMA base station and the base station, are calibrated in the baseband. The base station comprises: an antenna apparatus; couplers; an RF unitthat converts a receive signal to a baseband signal, converts a transmit signal to a radio frequency, and performs power control; an A/D converterfor converting a receive signal to a digital signal; a receive beam form unitthat multiplies the receive signal by semi-fixed weight; a despreaderfor this signal input; a time-space demodulatorfor demodulating user data; a despreaderfor probe signal; a space modulatorfor user data; a spreaderfor user signal; a channel combiner; a Tx calibraterfor controlling calibration of a signal; a D/A converter; a unitfor calculation of correlation matrix for generating a probe signal used for controlling an Rx calibration system and a TX calibration system; a spreaderfor probe signal; a power control unit; a D/A converter; an RF unitfor probe signal; an A/D converterfor signal from the couplers; and a despreader

It is an object of the present invention to reduce the amount of spurious noise generated by an emission line spectrum of a signal propagating around the PLL of a PLL frequency synthesizer carrying out digital-signal processing. In order to achieve the object described above, the present invention provides a PLL frequency synthesizer with the following configuration. In a PLL frequency synthesizer having a charge-pump circuit, a waveform converter is provided at a stage behind the charge-pump circuit. The waveform converter converts the voltage waveform on a time axis of a rectangular wave output by the charge-pump circuit into a waveform which: is symmetrical with respect to a predetermined point of time; oscillates so as to have no direct-current component; and has a maximum value of the absolute values of maximums of wave heights thereof located at the center wherein the absolute value decreases uniformly as the wave height is separated farther away from the center. As a result, the amplitudes of a limited number of emission line spectra forming a spurious signal superposed on a signal propagating around the PLL can be made uniform and a maximum thereof can be held at a low value, allowing the direct-current component to be eliminated from the signal propagating around the PLL.

PLL frequency synthesizer

The present invention designs and implements a high-speed PLL circuit and a high-speed synthesizer using the high-speed PLL circuit which has an increased switching speed, a reduced number of jitters and a reduced magnitude of spurious response. In order to achieve the above, the present invention provides a PLL circuit forming a closed loop wherein: one of the inputs of a phase comparator 1 serves as the input of the PLL circuit and the output of phase comparator 1 is connected to the input of a loop filter 2; the output of loop filter 2 is connected to the input of a voltage-controlled oscillator (VCO) 3; the output of the VCO 3 serves as the output of the PLL circuit; and the output of the VCO 3 is supplied to the other input of phase comparator 1 through a frequency divider 4. The circuit form and circuit constants of loop filter 2 are determined so that the transfer function of the closed loop becomes a Gaussian function.

High-speed phase-locked loop circuit

In an output-controlled power amplifier of a closed loop type, an input signal is inputted to a main path in which the input signal is power-attenuated by a variable attenuator and power-amplified by a power amplifier. A power divider distributes the amplified input signal between the main path and a feedback path diverging from the main path so that the signal distributed to the main path is outputted from the main path to the exterior while the input signal is controlled on the basis of the signal distributed to the feedback path. The feedback path includes a hold circuit for extracting the signal distributed to the feedback path and holding the value of the power of the extracted signal when the power reaches a predetermined value. A control signal for attenuating the power of the input signal inputted to the main path is generated by the hold circuit and is applied through the feedback path to the variable attenuator on the main path to control the power of the input signal. A transfer function of the closed loop has a Gaussian characteristic.

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Fujisawa, Japan

Yuji Ishida