Title:
DIGITAL CABLE SERVICE RECEIVER
Document Type and Number:
Japanese Patent JP3804093
Kind Code:
B2
Abstract:
PURPOSE: To stably receive a digital modulated signal such as a multi-level QAM by removing interference from an analog modulated signal by providing a low-pass filter means for attenuating signals of a differential frequency from the respective carrier frequencies of analog modulated signals adjacent to the synchronizing detected digital modulated signal.
CONSTITUTION: At a carrier wave reproducing circuit 110, the orthogonal carrier waves of sine and cosine matching phases with the carrier wave of the digital modulated signal are reproduced. Two signals of I and Q obtained detecting synchronizing corresponding to those carrier waves are respectively impressed to a digital signal processing circuit 113 after their high frequency components are removed through low-pass filters 113 and 112. In this case, signal components near the respective carrier frequencies such as the video carrier frequency of analog modulated signal adjacent to the upside frequency of digital modulated signal and the chrominance sub-carrier frequency and voice carrier frequency of analog modulated signal adjacent to the downside frequency of digital modulated signal can be attenuated by the low-pass filters 113 and 112.
Inventors:
Hiroyuki Mizukami
Tsutomu Noda
Takatoshi Josugi
Tsutomu Noda
Takatoshi Josugi
Application Number:
JP2092196A
Publication Date:
August 02, 2006
Filing Date:
February 07, 1996
Export Citation:
Assignee:
株式会社日立製作所
International Classes:
H04N5/46; H04N7/08; H04B1/10; H04N5/44; H04N7/081; H04N7/16; H04N7/167; H04N7/171; H04N9/66; H04N21/426; (IPC1-7): H04N9/66; H04N7/08; H04N7/081; H04N7/16; H04N7/171; H04N7/167
Domestic Patent References:
| JP7030824A | ||||
| JP6177921A | ||||
| JP6205325A | ||||
| JP6509691A |
Attorney, Agent or Firm:
Manabu Inoue