Fujitsu Corporation

Yoshimasa Daido

Hiroshi Kurihara

Naofumi Okubo

Kazuhiko Kobayashi

Toru Maniwa

Shuji Kobayakawa

Yoshihiko Asano

Hiroshi Nakamura

Eisuke Fukuda

Sadao Takenaka

Yasuyuki Oishi

Takanori Iwamatsu

Morihiko Minowa

Susumu Sasaki

Toshiyuki Saito

Yoshihito Aono

Yukio Takeda

Yasuyuki Tokumitsu

An amplifier module is expressed by a model having a first filter that is a linear time-invariant filter for limiting the bandwidth of an input signal, an amplifier unit that amplifies a signal output from the first filter, and a second filter that is a linear time-invariant filter for limiting the bandwidth of a signal output from the amplifier unit. A memoryless amplifier unit calculates an output from the amplifier module when being memoryless, using AM-to-AM distortion and AM-to-PM distortion of the amplifier unit. A cross-correlation calculating unit calculates a correlation between the signal output from the amplifier module and the output calculated by the memoryless amplifier unit and calculates an estimate of a transfer function of the first filter and the second filter. A distortion compensating unit compensates the input signal based on the estimate of the transfer function and outputs the signal to the amplifier module.

Distortion compensating apparatus, transmitter, distortion compensating method, and transfer function calculating method

A constant-amplitude wave combination type amplifier includes a first amplifier outputting a first amplified output, and a second amplifier outputting a second amplified output. The constant-amplitude wave combination type amplifier also includes a first constant-amplitude wave generating circuit for combining an input wave and the second amplified output from the second amplifier and for generating a first constant-amplitude wave which is input to the first amplifier, and a second constant-amplitude wave generating circuit for combining the input wave and the first amplified output from the first amplifier and for generating a second constant-amplitude wave. Further, the constant-amplitude wave combination type amplifier includes a wave combining circuit for combining the first and second constant-amplitude waves and for generating an output wave.

Constant-amplitude wave combination type amplifier

A high frequency amplifier containing: a constant envelope signal generation circuit for transforming an input signal to form two constant envelope signals where phases of the constant envelope signals correspond to an amplitude of an envelope of the input signal; two amplifying circuits for separately amplifying two constant envelope signals; and a power synthesizing circuit for synthesizing the first and second amplified signals to generate an amplified signal of the input electric signal, and reflecting remaining components of the first and second amplified signals which remaining components remain in the above synthesizing operation, toward the first and second amplifying circuits. Further, an input impedance of the power synthesizing circuit may be controlled by shifting phases of the above reflected components by respectively predetermined amounts, or by adaptively shifting phases of the above reflected components responding to an input level, so that a total efficiency of the high frequency amplifier is maximized. The high frequency amplifier may contain, instead of the above two amplifying circuits and the power synthesizing circuit, a circuit for inverting a phase of one of the two constant envelope signals; and a single-ended push-pull amplifier circuit for receiving the other of the two constant envelope signals, and an output of the phase inversion circuit, and synthesizing the received signals to generate an amplified signal of the input electric signal.

High frequency power amplifier with high efficiency and low distortion

An amplifier circuit includes a high-gain amplifier, and a feedback circuit for extracting an unstable output having a level equal to or less than a threshold level from an amplified signal from the amplifier and for feeding back the unstable signal to the amplifier, so that the amplifier oscillates at a predetermined oscillation frequency. The amplifier circuit also includes a band rejection filter for passing signal components of the amplified signal other than an oscillation output which is obtained at the output terminal of the amplifier when the amplifier oscillates at the predetermined oscillation frequency. The signal components obtained from the band rejection filter are an output signal of the amplifier circuit.

Amplifier circuit having feedback circuit

A digital communication system using a QAM signal and a honeycomb constellation multilevel signal. The digital communication system includes a modulator having a unit for transforming in-phase and quadrature-phase data arranged in a quadrature lattice constellation into two data arranged in a honeycomb constellation, and a unit for amplitude-modulating the transformed data. A demodulator demodulates a transmitted signal output from the modulator.

Multilevel amplitude modulation and demodulation communication system

A radio communication system using a QAM system. In the transmission system, the data of each channel to be transmitted is divided into data groups having frame slots. When the polarity of the mean value of a data summed in a present data group is the same as the polarity of the mean value of the deviation of all data group coming before, all data in the present data group is inverted, a direct current component and a lower frequency component near the direct current component are suppressed, and carrier waves are injected after encoding. In the receiving system, a decoder decodes a received signal to obtain the original data before the encoding by the transmission system.

Radio communication system

A device for distributing and combining microwave electric power which is used, for example, in a high power microwave amplifier and combines or distributes microwave electric power between a first microwave path such as a standard waveguide and a plurality of second microwave paths such as a plurality of waveguides or MIC transmission lines. The device comprises a horn whose throat portion is coupled to the first microwave path, a oversized waveguide coupled to the opening portion of the horn at one end and coupled to the plurality of the second microwave paths, and, for example, a dielectric lens, or one or more reflectors, for uniformalizing the phases of the microwave signals distributed by the horn or for adjusting the phases of the microwave signals output from the second microwave paths.

Growing community of inventors

Yokohama, Japan

Yoshimasa Daido