Facsimile and static presentation processing – Facsimile – Specific signal processing circuitry
Patent
1989-09-11
1993-04-13
Groody, James J.
Facsimile and static presentation processing
Facsimile
Specific signal processing circuitry
358188, 364731, 375 84, 329306, H04N 560
Patent
active
052027660
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to sound channel circuits for digital television receivers comprising at least one analog-to-digital converter and at least one digital-to-analog converter, as have been commercially available for some time.
2. Description of the Prior Art
In view of the different television sound transmission standards being used throughout the world, it is desirable to have a universally applicable sound channel circuit which makes it possible to demodulate all current and future television sound standards. Among the television sound standards to be expected for the future, a method is of interest in connection with the invention which is presently intended for introduction in Great Britain and Scandinavia and for which the abbreviation "NICAM" appears to be coming into use. It is described in a printed publication issued by the IBA and BBC in September 1986 and entitled "Specification of a Standard for UK Stereo-with-Television Transmissions".
SUMMARY OF THE INVENTION
Accordingly, the object of the invention as claimed is to provide a universally applicable sound channel circuit for digital television receivers. One of the advantages of the invention lies in the fact that a multi-standard television set capable of handling the different sound transmission standards can be built with a single integrated sound channel circuit, with the latter automatically adapting to the different standards during reproduction.
BRIEF DESCRIPTION OF THE DRAWING
The invention will now be explained in more detail with reference to the accompanying drawings, in which:
FIG. 1 is a highly schematic block diagram of a first variant of the solution according to the invention;
FIG. 2 is a highly schematic block diagram of a second variant of the solution according to the invention;
FIG. 3 is a highly schematic block diagram of a third variant of the solution according to the invention, and
FIG. 4 is a highly schematic block diagram of a DQPSK decoder portion of the above-mentioned "NICAM" standard which can be used to advantage in the invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
In the figures of the drawings, the square blocks symbolize the digital subcircuits, which will be defined in more detail below and in which signals are processed in parallel. This parallel signal processing may also be performed by the so-called pipelining technique. The input and output signals are transferred over buses, which are symbolized in the figures of the drawings by the stripelike connecting lines, under control of a clock system. The sound channel circuit according to the invention is especially suitable for implementation with insulated-gate field-effect transistor integrated circuits, i.e., for MOS integration, which is understood to include CMOS integration, i.e., implementation with complementary field-effect transistors.
In the embodiments illustrated in the figures of the drawings it is assumed that, by means of a conventional tuner and a conventional mixer, the desired analog sound and video signal va has already been separated from the signals reaching the television receiver via the antenna and converted to the baseband, as is done in conventional digital television receivers.
In all three variants of the solution according to the invention shown in FIGS. 1 to 3, the analog sound and video signal va is first applied to the analog antialiasing low-pass filter af, and the filtered signal is presented to the input of the single analog-to-digital converter ad. The sampling signal ts of the latter, generated by sampling frequency generator sf, has a frequency of the order of four times the chrominance-subcarrier frequency, i.e., the sampling frequency will generally lie between 15 MHz and 25 MHz. The antialiasing low-pass filter af separates those components from the analog signal which, if present, would result in disturbances after the analog-to-digital conversion.
The output of the analog-to-digital converter ad is connected to the bandpass fil
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Hilpert Thomas
Mehrgardt Sonke
Pfeifer Heinrich
Deutsche ITT Industries GmbH
Groody James J.
Murrell Jeffrey S.
Peterson Thomas L.
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