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. 01, 2000
Filed:
Jan. 19, 1996
Abraham E Rindal, Fremont, CA (US);
Ronald H Ih, San Francisco, CA (US);
Michele K Law, Mountain View, CA (US);
Sun Microsystems, Inc., Palo Alto, CA (US);
Abstract
Electromagnetic interference ('EMI') is reduced in a CRT video display system by spreading-out the EMI-producing spectra present in the video pixel data and/or clock signals. A clock dropping circuit coupled between the display generator main oscillator and the timing generator periodically phase-modulates the timing generator clock signal such that it comprises N phases, where N.gtoreq.2. As a result, each horizontal line of video data and the horizontal synchronization signals is phase shifted. This dual-shifting effect eliminates display image distortion that would result if only the video signal were shifted. Video distortion is further minimized by deriving the horizontal and vertical synchronizing signals from a common constant clock. EMI energy associated with each clock harmonic is spread by a frequency amount .DELTA.f proportional to the rate of phase change in the clock signal, the rate of phase change exceeding half the bandwidth f.sub.m of a standard EMI measurement reference window. This disperses adjacent spectral energy sufficiently so the reference window measures but one, decreased, amplitude at a time.