The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Feb. 03, 2004
Filed:
Feb. 15, 2000
Qin Zhang, Bensalem, PA (US);
General Instrument Corporation, Horsham, PA (US);
Abstract
A direct quadrature amplitude modulation (QAM) modulator provides amplitude and phase pre-equalization to reduce complexity and cost. In-phase (I) and quadrature-phase (Q) QAM signal components are provided from an analog modulator. A radio-frequency (RF) driver provides a RF signal with the QAM components. A monitoring device monitors phase and amplitude errors in the RF signal, and provides a feedback signal to a digital complex phase and amplitude equalizer embedded in a digital Nyquist filter. The equalizer uses the feedback signal to provide a pre-equalizing signal to a digital-to-analog converter, which provides a corresponding analog equalizing signal. This signal is, in turn, low-pass filtered and fed back to the analog I/Q modulator to equalize the phase and amplitude of the I and Q components there. The invention is particularly suitable for generating 64/256-QAM signals in the 50 MHz-880 MHz range without an Intermediate Frequency (IF) stage and double-conversion, and may be used, e.g., for communicating digital television data via a cable network.