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Method and apparatus for digital multi-standard colour signal demodulation

A technology of color signal and digital demodulation, applied to color signal processing circuits, TV transmission systems characterized by the combination of various color image signal components, color TV, etc., can solve problems such as inconvenient combination

Inactive Publication Date: 2006-01-11
DEUTSCHE THOMSON-BRANDT GMBH
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Problems solved by technology

[0005] However, since PAL and NTSC use AM modulation for color information in composite video signals, SECAM uses FM modulation with two different carriers, as shown in EP-A-0 597 160 Digital SECAM color with Hilbert filter Conventional solutions for demodulators have little in common with digital PAL and / or NTSC color demodulators using quadrature mixers
Therefore, it seems inconvenient to combine the two schemes on one multi-standard color demodulator chip for all three formats

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[0018] The digital input signal to the multi-standard color demodulator is the modulated color component signal c(t) separated from the composite video signal (CVBS). The signal c(t) is fed to two parallel paths in the quadrature mixer QUMX. In the first path, c(t) is multiplied by the first digital multiplier signal C1 in the first digital multiplier M1, and the output of M1 is digitally low-pass filtered by the first filter LP1 to generate the first output signal x (t). In the second path, c(t) is multiplied by the second digital multiplier signal C2 in the second digital multiplier M2. The output of M2 is digitally low-pass filtered by the second filter LP2 to generate the second output signal y(t). C1 can be used for example cos(2πf m t) to express, C2 is expressed by ±sin(2πf m t) to express, where f m is the mixing frequency. If c(t) is a PAL or NTSC color component signal, x(t) represents the U or I component, and y(t) represents the V or Q component, respectively...

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Abstract

The key component of a digital PAL or NTSC color decoder is a quadrature demodulator for these AM modulated signals. For a SECAM color decoder, however, an FM demodulation is required which is conventionally implemented using a Hilbert filter which is followed by a CORDIC processor and a differentiation stage. It would be advantageous if for multi-standard applications a general-purpose color demodulator for PAL, NTSC and SECAM systems could be implemented on one chip having as much as possible common demodulation processing stages. According to the invention a single common quadrature mixer is used for all three color systems. A resulting bias effect caused by the use of a single mixing frequency is corrected in a clamping stage. The bias effect can also be used for line identification.

Description

technical field [0001] The invention relates to a digital multi-standard PAL / NTSC / SECAM color signal demodulation method and device. Background technique [0002] A key component of a digital PAL or NTSC color decoder is the quadrature demodulator for these AM modulated signals. However, for a SECAM color decoder, an FM demodulator is required, which is usually implemented using a CORDIC processor (Coordinated Rotary Digital Computer) followed by a micro-graded Hilbert filter. EP-A-0 597 160 discloses a corresponding digital stand-alone SECAM decoder. [0003] CORDIC processors are described in more detail in EP-A-0 329 812 and EP-A-0 597 160 and the articles cited therein. [0004] For multi-standard TV or VCR applications, it would be beneficial to be able to implement a multi-standard digital color demodulator for PAL, NTSC and SECAM television formats on one chip with as many demodulation processing stages in common. [0005] However, since PAL and NTSC use AM modulat...

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): H04N9/64H04N11/18H04N9/66
CPCH04N11/186H04N9/642
Inventor 林纪南马克西米利安·厄尔巴
Owner DEUTSCHE THOMSON-BRANDT GMBH
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