Inter-symbol interfence reduction for touch panel systems

Abstract

A touch panel system is described that is configured to reduce inter-symbol interference (ISI). In an implementation, the touch panel system includes a touch panel assembly that includes a plurality of drive electrodes arranged one next to another and a plurality of sensor electrodes arranged one next to another across the drive electrodes to form a plurality of pixels having a mutual capacitance. The touch panel system also includes a transmitter configured to drive the drive electrodes with drive signals derived at least partially from excitation values. The transmitter is configured to apply a window function to the drive signals. The system also includes a receiver configured to sense signals furnished from the sensor electrodes and to determine the mutual capacitance of the pixels.

1 . A controller for a touch panel assembly comprising a plurality of drive electrodes arranged one next to another and a plurality of sensor electrodes arranged one next to another across the drive electrodes to form a plurality of pixels having a mutual capacitance, the controller comprising:
 a transmitter configured to drive the drive electrodes with drive signals derived at least partially from one or more excitation values, the drive signals having periodic waveform characteristics, the transmitter configured to apply a window function to the drive signals; and   a receiver configured to sense signals furnished from the sensor electrodes and to determine the mutual capacitance of the pixels.   
     
     
         2 . The controller as recited in  claim 1 , wherein the receiver comprises an operational amplifier having a capacitive feedback, the operational amplifier configured to furnish an output signal, the output signal comprising an amplified signal furnished from the sensor electrodes. 
     
     
         3 . The controller as recited in  claim 2 , the receiver further comprising an integrate-and-dump module that is coupled to the output of the operational amplifier, the integrate-and-dump module configured to generate a signal comprising the cumulative sum of the output signal furnished from the operational amplifier over a predefined time interval. 
     
     
         4 . The controller as recited in  claim 2 , wherein the receiver includes a channel pass filter coupled to the operational amplifier. 
     
     
         5 . The controller as recited in  claim 4 , wherein the channel pass filter comprises at least one of a Bessel filter, Nyquist filter, a raised cosine filter, or the like. 
     
     
         6 . The controller as recited in  claim 1 , the transmitter further comprising an excitation matrix module configured to furnish the one or more excitation values. 
     
     
         7 . The controller as recited in  claim 6 , the transmitter further comprising a signal generator coupled to the excitation matrix, the signal generator configured to generate the drive signal at least partially based upon the one or more excitation values. 
     
     
         8 . The controller as recited in  claim 7 , the transmitter further comprising a pulse shaping module coupled to the signal generator, the pulse shaping module configured to modulate the drive signal. 
     
     
         9 . The controller as recited in  claim 1 , wherein the drive signal comprises a signal having sine wave form characteristics. 
     
     
         10 . A touch panel system comprising:
 a touch panel assembly comprising a plurality of drive electrodes arranged one next to another and a plurality of sensor electrodes arranged one next to another across the drive electrodes to form a plurality of pixels having a mutual capacitance;   a transmitter configured to drive the drive electrodes with drive signals derived at least partially from one or more excitation values, the drive signals having periodic waveform characteristics, the transmitter configured to apply a window function to the drive signals; and   a receiver configured to sense signals furnished from the sensor electrodes and to determine the mutual capacitance of the pixels, the receiver comprising an offset signal generator configured to generate an offset signal to at least substantially cancel the drive signal.   
     
     
         11 . The touch panel system as recited in  claim 10 , wherein the receiver comprises an operational amplifier having a capacitive feedback, the operational amplifier configured to furnish an output signal, the output signal comprising an amplified signal furnished from the sensor electrodes. 
     
     
         12 . The touch panel system as recited in  claim 11 , the receiver further comprising an integrate-and-dump module that is coupled to the output of the operational amplifier, the integrate-and-dump module configured to generate a signal comprising the cumulative sum of the output signal furnished from the operational amplifier over a predefined time interval. 
     
     
         13 . The touch panel system as recited in  claim 11 , wherein the receiver includes a channel pass filter coupled to the operational amplifier. 
     
     
         14 . The touch panel system as recited in  claim 13 , wherein the channel pass filter comprises at least one of a Bessel filter, Nyquist filter, a raised cosine filter, or the like. 
     
     
         15 . The touch panel system as recited in  claim 10 , the transmitter further comprising an excitation matrix module configured to furnish the one or more excitation values. 
     
     
         16 . The touch panel system as recited in  claim 15 , the transmitter further comprising a signal generator coupled to the excitation matrix, the signal generator configured to generate the drive signal at least partially based upon the one or more excitation values. 
     
     
         17 . The touch panel system as recited in  claim 16 , the transmitter further comprising a pulse shaping module coupled to the signal generator, the pulse shaping module configured to modulate the drive signal. 
     
     
         18 . A touch panel system comprising:
 a touch panel assembly comprising a plurality of drive electrodes arranged one next to another and a plurality of sensor electrodes arranged one next to another across the drive electrodes to form a plurality of pixels having a mutual capacitance;   a transmitter configured to drive the drive electrodes with drive signals derived at least partially from one or more excitation values, the drive signals having periodic waveform characteristics, the transmitter configured to apply a window function to the drive signals; and   a receiver configured to sense signals furnished from the sensor electrodes and to determine the mutual capacitance of the pixels, the receiver comprising an offset signal generator configured to generate an offset signal to at least substantially cancel the drive signal, the receiver configured to apply the window function to the offset signal.   
     
     
         19 . The touch panel system as recited in  claim 18 , wherein the receiver comprises an operational amplifier having a capacitive feedback, the operational amplifier configured to furnish an output signal, the output signal comprising an amplified signal furnished from the sensor electrodes. 
     
     
         20 . The touch panel system as recited in  claim 18 , the transmitter further comprising an excitation matrix module configured to furnish the one or more excitation values.