Hitachi-kokusai Electric Inc.

Hitachi Denshi Kabushiki Kaisha

Hitachi, Ltd.

Masaru Adachi

Yoichi Okubo

Yasuhiro Takeda

Manabu Nakamura

Naoki Hongo

Toshio Nojima

Masaki Suto

Makoto Ohnishi

Yukinari Fujiwara

Sumie Nakabayashi

Masayuki Kanazawa

Masaaki Ohta

Atsushi Sassa

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

There is provided an amplifier for combining outputs of a plurality of amplifying circuits to generate an amplifier output. The amplifier includes a first amplifying circuit for operating a first amplifying device in class-AB, wherein the first amplifying circuit is one among the plurality of the amplifying circuits; a second amplifying circuit for operating a second amplifying device in class-B or class-C, wherein the second amplifying circuit is one among the plurality of the amplifying circuits; and a summing node at which an output of the first amplifying circuit is combined with an output of the second amplifying circuit via a first impedance transformer containing a transmission line of an electrical length other than &#x3bb;/4. The second amplifying device is connected to the summing node via an output matching circuit and a second impedance transformer containing a transmission line.

Amplifier

The performance of an amplifying system is improved by achieving adequate matching. The amplifying system for amplifying signals includes distributing meansthat distribute a signal, a carrier amplifierthat amplifies the distributed first signal in Class AB, a peak amplifierthat amplifies the distributed second signal in Class B or Class C, a first transmission line having a given electric length and being connected to an output of the carrier amplifier, a second transmission line having a given electric length and being connected to an output of the peak amplifier, and a combining endfor combining an output of the first transmission line and an output of the second transmission line. An impedance of the combining end is differentiated from a parallel impedance of load impedances of the carrier amplifier and the peak amplifier at the maximum power converted respectively by the first transmission line and the second transmission line, or is set as a parallel impedance in which the load impedances of the carrier amplifier and the peak amplifier at the maximum power are changed.

Amplifying system

A first control unit controls a bias applied to the peak amplifier to (a) make a peak amplifier operate as class C when the level of the input signal is lower than a first threshold value, to (b) make the peak amplifier operate as class AB with a second conduction angle substantially equal to a first conduction angle, when the level of the input signal is higher than a second threshold value higher than the first threshold value, and to (c) make the peak amplifier operate as class AB with a third conduction angle smaller than the first conduction angle, when the level of the input signal is not less than the first threshold value and not more than the second threshold value.

Doherty amplifier with improved linearity

An error correction encoding rate selection table is provided in an error correction processing unit of a packet transfer apparatus, and the table stores an error correction encoding rate preset to maintain a desired QoS in correspondence with a protocol type and an application type. When a transmission packet is transferred to a wireless transmission path, an encoding control unit judges the protocol type and application type of a transmission packet from a header of the transmission packet, in accordance with a judgment result and the error correction encoding rate selection table, an error correction encoding rate is selected, and the transmission packet is subjected to error correction encoding and transferred.

Wireless packet transfer apparatus and method

A mobile communication system, and method, having, in an operational area of the base station, a plurality of mobile stations each capable of operating in an arbitrary one of two kinds of communication mode, i.e., a base station dependent mode for conducting communication via a base station and a direct communication mode for conducting direct communication between mobile stations. Information containing an important message to be received by all mobile stations is transmitted from the base station in the base station dependent mode. Upon receiving the information containing the important message, a mobile station placed in the base station dependent mode transmits the information containing the important message in the direct communication mode. As a result, all mobile stations placed in the direct communication mode receive the important message.

Mobile communication system and method having base station dependent mode and a direct mode

A multi-carrier modulation apparatus to which transmultiplexers are applied. A multiplexing signal is treated as a synthesis of a plurality of multiplexed signals which are separated by a wider interval than the multiplexing frequency interval. Signals of channels to M continuously frequency-multiplexed at a channel interval f are treated as a synthetic signal of signals of channel to channel N&minus;1 and signals of channel to channel N which are frequency-multiplexed at a channel interval f . Individual multiplexed signals are synthesized by a plurality of transmultiplexers of less multiplexing number to make characteristics of polyphase filters required for the transmultiplexers less sharp.

Multi-carrier modulation apparatus and transmitter using the same

In a radio communication device which includes at least a modulator, a power amplifier, a demodulator, and a carrier oscillator wherein an input signal to the radio communication device is corrected with a feedback demodulated signal to compensate for possible non-linear distortions in the power amplifier, a phase shift quantity for correction of the phase of the carrier which demodulates the feedback modulated signal in the demodulator is separated into a fixed phase quantity and a variable phase quantity smaller than the fixed phase quantity. The carrier is phase-corrected such that a phase shifter shifts the phase of the carrier by the fixed phase quantity and a second phase shifter shifts the phase of the carrier by the variable phase quantity smaller than the fixed phase quantity.

Non-linear compensation circuit for a power amplifier

A communication system of a time division multiple access method in which transmission data are transmitted in a unit of a frame having a predetermined number of symbols in which a pilot symbol is periodically inserted in a series of data symbols for compensation of fading distortion and a carrier is reset at each frame. A phase correction circuit for correcting phase variation due to the reset of carrier phase at each frame is provided. When pilot symbols except a frame in which fading distortion is to be compensated are used in a receiving side, the pilot symbols corrected by the phase correction circuit can be selected to thereby compensate fading distortion exactly regardless of an insertion position of pilot symbols in the frame even by using the interpolation method.

Fading distortion compensation method and circuit

In a complex modulation/demodulation method and system, the data frequency f.sub.C1 of data signals I and Q inputted to a constellation mapping circuit is converted by a digital interpolation circuit into a sampling frequency f.sub.C2 equal to f.sub.S /N, where f.sub.S is an operation sampling frequency and N is selected such that the signal maximum frequency of the data signals I and Q becomes lower than f.sub.C2 /2. The interpolated data signals I and Q are respectively inputted to real and imaginary input terminals of a complex coefficient band pass filter to extract a real signal output. An output signal of the complex coefficient band pass filter is converted by a DA converter into an analog signal from which desired frequency components are extracted by an analog band pass filter, thereby performing a quadrature modulation.

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Kodaira, Japan

Masaru Adachi