High noise immunity sensing methods and apparatus for a capacitive touch device

Abstract

High noise immunity sensing methods and apparatus are provided for a capacitive touch device, which sense the capacitive touch device for self capacitance or mutual capacitance or both with different scan frequencies in a frame, to thereby suppress certain frequency noise interference. By combining time domain and space domain noise-eliminating approaches, probabilities of noise interference are reduced, without compromising other parameters.

What is claimed is: 
     
         1 . A high noise immunity sensing method for a capacitive touch device, the improvement comprising sensing a self capacitance of a selected trace in the capacitive touch device with different scan frequencies in a single frame. 
     
     
         2 . The sensing method of  claim 1 , wherein the step of sensing a self capacitance of a selected trace in the capacitive touch device with different scan frequencies in a single frame comprises:
 repeatedly sensing the self capacitance of the selected trace with at least two different scan frequencies; and   averaging sensed values of the self capacitance of the selected trace obtained by the previous step to produce an average regarded as the self capacitance of the selected trace.   
     
     
         3 . A high noise immunity sensing apparatus for a capacitive touch device, comprising:
 an excitation unit;   a sampling unit; and   a control unit connected to the excitation unit and the sampling unit, controlling the excitation unit and the sampling unit to sense a self capacitance of a selected trace in the capacitive touch device with different scan frequencies in a single frame.   
     
     
         4 . The sensing apparatus of  claim 3 , wherein the excitation unit and the sampling unit are connected to a plurality of traces in the capacitive touch device, and the control unit repeatedly senses the self capacitance of the selected trace of the plurality of traces with at least two different scan frequencies in the single frame. 
     
     
         5 . The sensing apparatus of  claim 4 , further comprising an averaging unit connected to the sampling unit, averaging sensed values of the self capacitance of the selected trace to produce an average regarded as the self capacitance of the selected trace. 
     
     
         6 . A high noise immunity sensing method for a capacitive touch device, the improvement comprising sensing a mutual capacitance between two traces in the capacitive touch device with different scan frequencies in a single frame. 
     
     
         7 . The sensing method of  claim 6 , wherein the step of sensing a mutual capacitance between two traces in the capacitive touch device with different scan frequencies in a single frame comprises:
 repeatedly sensing the mutual capacitance between the two traces with at least two different scan frequencies; and   averaging sensed values of the mutual capacitance obtained by the previous step to produce an average regarded as the mutual capacitance between the two traces.   
     
     
         8 . The sensing method of  claim 6 , wherein the step of sensing a mutual capacitance between two traces in the capacitive touch device with different scan frequencies in a single frame comprises:
 sensing mutual capacitances between a plurality of first traces and a first part of a plurality of second traces in the capacitive touch device with at least one first scan frequency in the single frame; and   sensing mutual capacitances between the plurality of first traces and a second part of the plurality of second traces with at least one second scan frequency which is different from the at least one first scan frequency.   
     
     
         9 . A high noise immunity sensing apparatus for a capacitive touch device, comprising:
 an excitation unit;   a sampling unit; and   a control unit connected to the excitation unit and the sampling unit, controlling the excitation unit and the sampling unit to sense a mutual capacitance between two traces in the capacitive touch device with different scan frequencies in a single frame.   
     
     
         10 . The sensing apparatus of  claim 9 , wherein the excitation unit is connected to a first trace of the two traces, the sampling unit is connected to a second trace of the two traces, and the control unit controls the excitation unit and the sampling unit to repeatedly sense the mutual capacitance between the first trace and the second trace with at least two different scan frequencies in the single frame. 
     
     
         11 . The sensing apparatus of  claim 10 , further comprising an averaging unit connected to the sampling unit, averaging sensed values of the mutual capacitance to produce an average regarded as the mutual capacitance between the first trace and the second trace. 
     
     
         12 . The sensing apparatus of  claim 9 , wherein the excitation unit and the sampling unit are connected to a plurality of first traces and a plurality of second traces in the capacitive touch device, and in the single frame the control unit controls the excitation unit and the sampling unit to sense mutual capacitances between a plurality of first traces and a first part of a plurality of second traces in the capacitive touch device with at least one first scan frequency, and mutual capacitances between the plurality of first traces and a second part of the plurality of second traces with at least one second scan frequency which is different from the at least one first scan frequency.