Digital demodulator

• US 6,813,321 B1
• Filed: 07/21/2000
• Issued: 11/02/2004
• Est. Priority Date: 01/30/1998
• Status: Expired due to Term

• Current Assignee: Kabushiki Kaisha Kenwood (JVC Kenwood Corporation), Rakuten, Inc. (Rakuten Group, Inc.)
• Original Assignee: Kabushiki Kaisha Kenwood (JVC Kenwood Corporation)
• Inventors: Itoh, Shigeyuki, Iwadate, Yuichi, Shibuya, Kazuhiko, Saito, Tomohiro, Horii, Akihiro, Hashimoto, Akinori, Shiraishi, Kenichi, Matsuda, Shoji, Katoh, Hisakazu, Shinjo, Soichi, Minematsu, Fumiaki
• Primary Examiner(s): Corrielus, Jean B.
• Application Number:
  US09/582,229
• Time in Patent Office: 1,565 Days
• Field of Search: 375/368, 375/376, 375/326, 375/346, 375/316, 375/324, 375/325, 375/327, 375/331, 375/332, 375/340, 375/371, 375/375, 375/329, 455/3.02
• US Class Current: 375/329
• CPC Class Codes: H04L 2027/0057 quadrature phase
• CPC Class Codes: H04L 2027/0067 Phase error detectors
• CPC Class Codes: H04L 2027/0077 stop and go
• CPC Class Codes: H04L 2027/0095 in a preamble or similar structure
• CPC Class Codes: H04L 27/0014 Carrier regulation of chaotic carriers H04L27/001; for multicarrier receivers H04L27/2657
• CPC Class Codes: H04L 27/2273 associated with quadrature demodulation, e.g. Costas loop
• CPC Class Codes: H04L 7/042 Detectors therefor, e.g. correlators, state machines digital correlators in general G06F17/15

Abstract

A digital demodulator which will need no absolute phasing circuit is provided. A known-pattern BPSK signal generating circuit 6 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 7 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 8 according to the known-pattern BPSK signal outputted from the known-pattern BPSK signal generating circuit 6, 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.

Claims

1. A digital demodulator of a receiver for digital broadcasting which receives and transmits digital modulated waves created by time-base-multiplexing waves modulated by a plurality of modulation systems, comprising:

known-pattern signal generating means for generating in synchronism with known-pattern signals in received digital modulated waves the same known-pattern signal as a known-pattern BPSK signal in the received digital modulated waves;

carrier-reproducing phase error detecting means, which comprises a phase error table having one reference phase as a convergence point between two reference phases of signal point positions of BPSK demodulation baseband signals, for sending out a phase error output based on a phase error between the phase obtained from the signal point position of the demodulation baseband signals and the phase convergence point; and

a carrier-reproducing loop filter which is controlled for enablement based on the known-pattern signals outputted from the known-pattern signal generating means and smoothes the phase error outputs during an enabling period,

wherein carrier reproduction is implemented by controlling the frequency of a reproduced carrier so that, based on the output of the carrier-reproducing loop filter, the phase of said signal point position coincides with the phase convergence point.

2. The digital demodulator according to claim 1, characterized in that the carrier-reproducing loop filter is controlled to enablement for the period of low potential of the known-pattern signals outputted from the known-pattern signal generating means.