Hitachi-kokusai Electric Inc.

Nobuo Hirose

Nobuo Tsukamoto

Satoshi Sakata

Kazuhiko Nakamura

Jun Abe

Seiichi Sano

Nobuo Murata

Yoshiro Kokuryo

Kunihiko Kondo

Fumihito Tomaru

Hiroyuki Ando

Yasutoshi Tada

A rebroadcasting system for retransmitting a television broadcast, which was received from a satellite, in a segment broadcasting, such as one-segment broadcasting and three-segment broadcasting, comprises: charging a solar battery during the daytime; recording broadcasts during the retransmission halt time; retransmitting television broadcasts, which are received from the satellite, in real time by use of central (one or three) segments and the charged power during any time when the output of the solar battery is low, for example, during the night, before sunset, after sunrise, or a rainy day; reproducing the recorded broadcasts; and retransmitting the reproduced recorded programs by use of any remaining segments, for example, segments adjacent to the central segments.

Rebroadcasting system

The purpose of the invention is to reduce Cartesian loop transmission delay for compensating the distortion occurring in a high-frequency power amplifier and make the distortion compensation converge quickly, thereby increasing the efficiency. A transmission device has: a high-frequency power amplifier; a pre-distortion compensation circuit for independently generating the coefficients of the distortion compensation signal for each order of the odd and even symmetric distortions of the high-frequency power amplifier; a means for varying the power supply voltage of the high-frequency power amplifier with an orthogonal modulation OFDM input signal; a digital frequency converter; a high-frequency band ADC; and a high-frequency band DAC. In the transmission device, an error distortion compensation signal is created from the output of the high-frequency power amplifier and the orthogonal modulation OFDM input signal, and a delay device is inserted at the previous stage of a distortion compensation circuit, said delay device having a delay equivalent to a time constant for varying the power supply voltage of the high-frequency power amplifier with the orthogonal modulation OFDM input signal.

Distortion compensation circuit and transmission device using distortion compensation circuit and high-frequency power amplifier

In order to shorten the convergence time for compensating distortion generated by a high-frequency power amplifier, a distortion compensation circuit which independently generates coefficients of odd-symmetrical amplitude distortion compensation signals and coefficients of odd-symmetrical phase distortion compensation signals of respective orders of a high-frequency power amplifier includes an even-symmetrical distortion compensation signal generation circuit for generating an even-symmetrical amplitude distortion compensation signal and an even-symmetrical phase distortion compensation signal from a difference between the input signal amplitude and a signal obtained by delaying the input signal amplitude and a difference between the input signal and a signal obtained by delaying the input signal, respectively independently and independently of the odd-symmetrical distortion compensation signals, and an even-symmetrical distortion compensation signal superposition circuit for superposing the even-symmetrical distortion compensation signals on the input signal, and conducts pre-compensation on odd-symmetrical distortion and even-symmetrical distortion independently.

Distortion compensation circuit, and transmission device using distortion compensation circuit and high-frequency power amplifier

A distortion compensating circuit for a power amplifier attains raised compensating accuracy with shorter convergence time by accurately and quickly generating a distortion compensation signal for pre-distortion. An error signal representing the difference between the input and output signals of the power amplifier is generated. From the error signal and the input signal, the coefficients of the third-order intermodulation distortion, fifth-order intermodulation distortion and seventh-order intermodulation distortion are calculated. According to these coefficients, a distortion compensating signal which is characteristically opposite in phase and gain to the intermodulation distortions is generated.

Distortion compensation circuit, power amplifier using distortion compensation circuit, and distortion compensation signal generating method

Distortion compensation circuit, distortion compensation signal generating method, and power amplifier

A demodulation method, and apparatus, for reproducing data from a received signal. The demodulation method includes the steps of: receiving a signal including a series of frames each containing a training signal for automatic equalization processing and a data signal; controlling an amplitude of the received signal by AGC processing so as to make the amplitude a predetermined level; conducting demodulation processing on the signal subjected to the AGC processing; periodically conducting automatic equalization processing so as to adapt the modulated signal to characteristics of the signal transmission path based on each training signal of the frame; and setting values of a time constant of the AGC processing and an update repetition period of the automatic equalization processing so as to satisfy a predetermined relation.

Growing community of inventors

Hino, Japan

Nobuo Hirose