Television receiving section with digital stages

US4901151A · kind A · utility

Assignee

• Deutsche ITT Industries, GmbH · DE

Inventors

• Sonke Mehrgardt · March, DE
• Dietmar Ehrhardt · Glückstadt, DE

Key dates

• Filing date: Dec 22, 1988
• Grant date: Feb 13, 1990
• Expiry date: Dec 22, 2008

Classification

• Technology area (CPC H): Electricity
• CPC primary: H04N5/60
• WIPO field: Audio-visual technology
• WIPO sector: Electrical engineering

Abstract

A television receiving section includes only a single A/D converter, and, thus, only a single interface between the analog portion and the digital portion. Preferably, the A/D converter is positioned after the intermediate-frequency stage of the television receiving section. The A/D converter is clocked at about 20 MHz. The digital portion of the television receiving section includes a video channel and an audio channel. The video channel includes at its input end a band-pass filter whose passband extends from 1 MHz to 6 MHz and whose output signals are fed directly and through a 90.degree. phase shifter to a first absolute-value stage, which delivers the digital composite color signal. The audio channel includes at its input end a quadrature mixer (operating from a locally generated clock having a frequency of 7 MHz to 7.5 MHz) whose two output signals are fed through a first decimator and a second decimator, respectively, to a second absolute-value stage and an angle-computing stage. The output of the angle-computing stage delivers a frequency-demodulated audio signal through a differentiating stage. The output of the second absolute-value stage provides an amplitude-demodulated …