Nippon Hoso' Kyokai

Other

Kabushikikaisha Kenwood

Yuichi Iwadate

Kazuhiko Shibuya

Shigeyuki Itoh

Tomohiro Saito

Akinori Hashimoto

Hisakazu Katoh

Junji Kumada

Fumiaki Minematsu

Yutaka Tanaka

Kenichi Shiraishi

Yuichi Ninomiya

Shoji Tanaka

Akihiro Horii

Yoshinori Izumi

Seiichi Gohshi

Shoji Matsuda

Soichi Shinjo

Toshihiro Nomoto

Taiji Nishizawa

Taiichiro Kurita

Hajime Matsumura

Yukihiro Nishida

Isao Kondo

Makoto Okui

Minoru Honda

Ryoichi Yajima

Kouichi Takano

Jun'ichi Ishida

Hiroyuki Hamazumi

Masaru Takechi

Toshihiko Susaki

A digital demodulator which will need no absolute phasing circuit is provided. A known-pattern BPSK signal generating circuit generates the same known-pattern BPSK signal as a known-pattern BPSK signal in a received digital modulated wave in synchronism with the known-pattern BPSK signal in the received digital modulated wave, a carrier-reproducing phase error detecting circuit has a phase error table where one of reference phases in a signal point position of a demodulation baseband signal is made a convergence point, a phase error voltage corresponding to a phase error between a phase determined from the signal point position of the demodulation baseband signals and a phase convergence point is sent out, by enable-controlling a carrier-reproducing loop filter according to the known-pattern BPSK signal outputted from the known-pattern BPSK signal generating circuit , the phase error voltage is smoothed, and carrier reproduction is performed while controlling the frequency of a reproduced carrier according to the smoothed output so that the phase in the signal point position coincides with the phase convergence point.

Digital demodulator

Stabilized carrier recovery is achieved even at the time of a low C/N ratio by measuring the phase of a signal and controlling VCO or NCO (Numerical Controlled Oscillator) using only a period having few constellation points. At this time, false lock phenomenon is avoided as follows. That is, relatively short SYNC modulated by an already-known pattern is entered into a modulation wave, VCO or NCO oscillation frequency is swept in a wide range and sweep is stopped at a frequency in which the SYNC can be received, thereby carrying out coarse control AFC. Further, a period having long to some extent, having few constellation points is provided in the modulation wave and then, a difference between the frequency of a received modulated signal and a local oscillation signal of VCO or NCO is obtained in this period. This frequency difference is analyzed according to the phase differential function method, self-correlation function method or count method, and the VCO or NCO is controlled based on this result of analysis.

AFC circuit, carrier recovery circuit and receiver device capable of regenerating a carrier reliably even at the time of low C/N ratio

A multiple sub-sampling encoding/decoding system performing interfield and interframe offset sub-sampling of a broad bandwidth television signal. The system compresses the television signal to fit, for example, to the transmission bandwidth of the standard television systems, compensates the transmission characteristics, and achieves the optimal frequency allocation of the modulated transmission signal.

Multiple sub-sampling transmitting/receiving system performing

A decoding equalizer of high definition television signal transmission mode, such as MUSE, and a subrange-type A/D converter suitable for the equalizer. The decoding equalizer samples input data in equalization at a frequency twice the sampling frequency of the trunk system, with the equalizing A/D converter operating at a lower resolution and higher speed than the A/D converter for the trunk system. The subrange-type A/D converter includes A/D converters in multiple stages, with their driving clock frequencies having a specified relationship so that they are used commonly for the A/D conversdion of the high definition television signal and the A/D conversion of a test signal for detecting the transmission characteristics.

Decoding equalizer

Growing community of inventors

Tokyo, Japan

Yuichi Iwadate