DIRECT-CONVERSION TUNER INTEGRATED CIRCUIT FOR DIRECT BROADCAST SATELLITE TELEVISION

摘要

A converter for the direct down-conversion of direct broadcast satellite signals such as those used for digital television. The direct broadcast satellite signal received from the satellite dish is amplified and then downshifted within the Low Noise Block (LNB), a subsystem contained with the satellite dish assembly, to a predetermined frequency band, typically in the L-band in the range 950 MHz to 2150 MHz. The signal is then sent via a coaxial cable to the set-top box unit located indoors, and there directly converted from the received frequency to baseband, in the preferred embodiment by a single integrated circuit, which may include on chip active filters for further integration and for rejection of adjacent channels and anti-aliasing of analog to digital converters. Use of a wide range variable gain amplifier, generation of closely controlled inphase and quadrature components of the down-converting mixers and offset compensation provides baseband inphase and quadrature components of sufficient quality for data recovery using conventional techniques.