Filter configuration and slope detector for quadrature amplitude modulated signals

US6353639B1 · kind B1 · utility

Assignee

• Infineon Technologies AG · DE

Inventors

• Stefan Prange · Munich, DE
• Heribert Geib · Grafing, DE
• Erik De Man · Hersbruck, DE

Key dates

• Filing date: Mar 20, 2000
• Grant date: Mar 5, 2002
• Expiry date: Mar 20, 2020

Classification

• Technology area (CPC H): Electricity
• CPC primary: H04N5/455
• WIPO field: Audio-visual technology
• WIPO sector: Electrical engineering

Abstract

A filter configuration for a demodulated QAM signal has a first channel for a cosine demodulated component of the QAM signal, a second channel for a sine demodulated component of the QAM signal, a filter circuit, which receives the two signal components and for each signal component has one transfer function that is composed of terms in phase with this signal component and terms phase-shifted from it by &pgr;/2 and/or −&pgr;/2. The circuit configuration also includes a cross branch for picking up signal portions from the respectively other channel that correspond to the phase-shifted terms of the transfer function. In a first state, the circuit configuration connects the input of the cross branch to the first channel and the output of the cross branch to the second channel, and in a second state connects the input of the cross branch to the second channel and the output of the cross branch to the first channel. A slope detector especially suitable for use with this filter configuration is also provided. The circuit configuration requires a reduced amount of circuitry and can be integrated on a small surface area of a semiconductor substrate.