TOUCH SENSE DETERMINED BY CHARACTERIZING IMPEDANCE CHANGES IN A TRANSMISSIOM LINE

摘要

The touch panel or screen has a spiral transmission line made of a substrate, for example a printed circuit board, LCD, plasma or LED screen, etc., and has a constant impedance. Touches to the touch panel will cause impedance changes in the transmission line at the location of the touches. The time domain reflectometry (TDR) determines the positions for the impedance changes of the transmission line by accurately measuring the return pulse times at the source of the plurality of pulses and then converting the return pulse times to the XY coordinates of the touch panel or screen .