Sun Microsystems, Inc.

Michele K Law

Abraham E Rindal

Joseph V Miseli

Ronald H Ih

A method and apparatus for driving a plurality of addressable elements consist of driving and selectively enabling one or more addressable elements arranged as an M&times;N array using two drivers. A first and a second driver are used to drive first and second signals at slightly different frequencies on a first and a second display conductor. A plurality of pixels, coupled between the first and second display conductors, is addressed according to a pixel location in which the first signal is approximately in phase with the second signal. The pixel scan rate is proportional to the difference between the first and second signal frequencies. The first and second conductors may contain a plurality of delay elements and tap-off points. Conducting lines may be terminated by their characteristic impedance to prevent any reflection of the traveling signals. The periods of the first and second signals may be greater than or approximately equal to a propagation delay of between first and last tap-off points on the first and second conductors, respectively. The pulse width of the first and second signals may be less than or approximately equal to a propagation time of the first and second signal between adjacent tap-off points on the first and second display conductors, respectively. The matrix display pixels are selectively enabled by modulating an amplitude of the first signal and/or an amplitude of the second signal when the selected pixel location(s) is addressed so that the voltage differential between the first and second signals is sufficient to enable the addressed pixel.

Method and apparatus for selective enabling of addressable display elements

A method and apparatus for driving a plurality of addressable elements consist of driving and selectively enabling one or more addressable elements arranged as an M.times.N array using two drivers. A first and a second driver are used to drive first and second signals at slightly different frequencies on a first and a second display conductor. A plurality of pixels, coupled between the first and second display conductors, is addressed according to a pixel location in which the first signal is approximately in phase with the second signal. The pixel scan rate is proportional to the difference between the first and second signal frequencies. The first and second conductors may contain a plurality of delay elements and tap-off points. Conducting lines may be terminated by their characteristic impedance to prevent any reflection of the traveling signals. The periods of the first and second signals may be greater than or approximately equal to a propagation delay of between first and last tap-off points on the first and second conductors, respectively. The pulse width of the first and second signals may be less than or approximately equal to a propagation time of the first and second signal between adjacent tap-off points on the first and second display conductors, respectively. The matrix display pixels are selectively enabled by modulating an amplitude of the first signal and/or an amplitude of the second signal when the selected pixel location(s) is addressed so that the voltage differential between the first and second signals is sufficient to enable the addressed pixel.

Method and apparatus for selective enabling of addressable display

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.

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Mountain View, CA, United States of America

Michele K Law