PATENT DOCUMENT

Publication Number: US-8810537-B2
Application Number: US-201213397643-A
Country: US
Kind Code: B2

Title: Quadrature demodulation for touch sensitive devices

Abstract:
Demodulation circuits and processes for demodulating touch signals from a touch sensor using the demodulation circuits are provided. The demodulation circuits can include circuitry configured to determine an adjustable phase delay based at least in part on a quadrature component of the touch signal or the phase-adjusted touch signal. The demodulation circuit can further include circuitry for applying the adjustable phase delay to the touch signal to compensate for phase delays in the touch signal caused by the touch sensor and/or other components. The demodulation circuit can dynamically change the adjustable phase delay to compensate for time-varying phase delays caused by the touch sensor and/or other components.

Claims:
What is claimed is: 
     
       1. A demodulation circuit configured to:
 determine an adjustable phase delay to be applied to a touch signal from a touch panel, the adjustable phase delay determined based at least in part on a phase-adjusted quadrature (Q) component of the touch signal; and 
 apply the adjustable phase delay to the touch signal to generate the phase-adjusted Q component of the touch signal. 
 
     
     
       2. The demodulation circuit of  claim 1  further comprising:
 a first integrator configured to output a phase-adjusted in-phase (I-phase) component of the touch signal; and 
 a second integrator configured to output the phase-adjusted Q-component of the touch signal. 
 
     
     
       3. The demodulation circuit of  claim 2  further comprising:
 a matrix circuit configured to multiply the phase-adjusted I-phase component of the touch signal by a matrix to generate a phase-adjusted touch signal representing a touch event on the touch panel. 
 
     
     
       4. The demodulation circuit of  claim 1  further comprising:
 a filter configured to filter the phase-adjusted quadrature (Q) component of the touch signal; and 
 a dither circuit coupled to an output of the filter, wherein the dither circuit is configured to dither the adjustable phase delay to determine a value of the adjustable phase delay corresponding to a minimum value of the phase-adjusted Q-component of the touch signal. 
 
     
     
       5. The demodulation circuit of  claim 1 , wherein the demodulation circuit is located within a touch-sensitive device, and wherein the touch-sensitive device comprises:
 a touch panel comprising:
 a plurality of drive lines, wherein a drive line of the plurality of drive lines is configured to receive a stimulation signal; and 
 a plurality of sense lines, wherein a sense line of the plurality of sense lines is configured to transmit the touch signal in response to the stimulation signal; 
 
 wherein the demodulation circuit is coupled to the sense line. 
 
     
     
       6. The demodulation circuit of  claim 5 , wherein the touch-sensitive device further comprises additional demodulation circuits coupled to each of the plurality of sense lines. 
     
     
       7. A demodulation circuit comprising:
 a phase adjustment circuit configured to generate a first phase adjustment signal and a second phase adjustment signal, the first and second phase adjustment signals generated based at least in part on a quadrature (Q) component of a touch signal and an in-phase (I-phase) component of the touch signal; and 
 a mixing circuit configured to mix the I-phase component of the touch signal with the first phase adjustment signal and the Q-phase component of the touch signal with the second phase adjustment signal. 
 
     
     
       8. The demodulation circuit of  claim 7 , wherein the first phase adjustment signal is 90° out of phase with the second phase adjustment signal. 
     
     
       9. The demodulation circuit of  claim 7 , wherein the mixing circuit comprises:
 a first demodulation mixer configured to mix the I-phase component of the touch signal with the first phase adjustment signal; and 
 a second demodulation mixer configured to mix the Q component of the touch signal with the second phase adjustment signal. 
 
     
     
       10. The demodulation circuit of  claim 7 , wherein the phase adjustment circuit is further configured to determine an adjustable phase delay based at least in part on the Q component of the touch signal and the I-phase component of the touch signal. 
     
     
       11. The demodulation circuit of  claim 7 , wherein the demodulation circuit further comprises a filter configured to filter the first and second phase adjustment signals. 
     
     
       12. A touch-sensitive device comprising:
 a touch panel configured to receive a stimulation signal to drive the touch panel and to transmit a touch signal in response to the stimulation signal; and 
 a demodulation circuit comprising:
 a filter configured to filter a phase-adjusted quadrature (Q) component of a touch signal generated by the touch panel; and 
 a dither circuit coupled to an output of the filter, wherein the dither circuit is configured to dither an adjustable phase delay to determine a value of the adjustable phase delay corresponding to a minimum value of the phase-adjusted Q-component of the touch signal. 
 
 
     
     
       13. The touch-sensitive device of  claim 12 , wherein the filter is a low-pass filter having a bandwidth below 60 Hz. 
     
     
       14. The touch-sensitive device of  claim 12 , wherein the filter and the dither circuit are integrated within a processor. 
     
     
       15. The touch-sensitive device of  claim 12 , wherein the dither circuit is configured to dither the adjustable phase delay during periods of time when no touch events are occurring on the touch panel. 
     
     
       16. The touch-sensitive device of  claim 12 , wherein the dither circuit is configured to maintain the value of the adjustable phase delay during periods of time when touch events are occurring on the touch panel. 
     
     
       17. A method for adjusting a phase delay of a touch signal from a touch panel, the method comprising:
 receiving a touch signal from a touch panel; 
 generating a first phase adjustment signal and a second phase adjustment signal, wherein the first and second phase adjustment signals are generated based at least in part on an in-phase (I-phase) component of the touch signal and a quadrature (Q) component of the touch signal; 
 applying the first phase adjustment signal to the I-phase component of the touch signal to generate a phase-adjusted I-phase component of the touch signal; and 
 applying the second phase adjustment signal to the Q component of the touch signal to generate a phase-adjusted Q component of the touch signal. 
 
     
     
       18. The method of  claim 17 , wherein applying the first phase adjustment signal to the I-phase component of the touch signal comprising mixing the first phase adjustment signal with the I-phase component of the touch signal, and wherein applying the second phase adjustment signal to the Q component of the touch signal comprising mixing the second phase adjustment signal with the Q component of the touch signal. 
     
     
       19. The method of  claim 17  further comprising:
 integrating the phase-adjusted I-phase component of the touch signal with the phase-adjusted Q component of the touch signal to generate an integrated phase-adjusted touch signal; and 
 multiplying the integrated phase-adjusted touch signal with a matrix to generate a phase-adjusted touch signal that is representative of a proximity of an object to the touch panel. 
 
     
     
       20. The method of  claim 17  further comprising:
 prior to applying the first phase adjustment signal to the I-phase component of the touch signal, multiplying the I-phase component of the touch signal by a first matrix; 
 prior to applying the second phase adjustment signal to the Q component of the touch signal, multiplying the Q component of the touch signal by a second matrix; and 
 integrating the phase-adjusted I-phase component of the touch signal with the phase-adjusted Q component of the touch signal to generate a phase-adjusted touch signal that is representative of a proximity of an object to the touch panel. 
 
     
     
       21. A method for adjusting a phase delay of a touch signal from a touch panel, the method comprising:
 receiving a touch signal from a touch panel; 
 determining an adjustable phase delay based at least in part on a phase-adjusted quadrature (Q) component of a touch signal; and 
 applying the adjustable phase delay to the touch signal to generate the phase-adjusted Q component of the touch signal. 
 
     
     
       22. The method of  claim 21 , wherein the applying the adjustable phase delay to the touch signal comprises causing a phase delay in the touch signal equal to the adjustable phase delay. 
     
     
       23. The method of  claim 21 , wherein the touch signal is generated by the touch panel in response to a stimulation signal, and wherein the applying the adjustable phase delay to the touch signal comprises:
 causing a phase delay in the stimulation signal equal to the adjustable phase delay; and 
 mixing the phase-delayed stimulation signal with the touch signal. 
 
     
     
       24. The method of  claim 21  further comprising multiplying a phase-adjusted in-phase (I-phase) component of the touch signal by a matrix to generate a phase-adjusted touch signal that is representative of a proximity of an object to the touch panel. 
     
     
       25. The method of  claim 21  further comprising applying a constant phase delay to the touch signal, wherein the constant phase delay represents a phase difference between a desired component of the touch signal and an undesired component of the touch signal.

Description:
FIELD 
     This relates generally to touch sensitive devices and, more specifically, to demodulation circuits for touch sensitive devices. 
     BACKGROUND 
     Touch sensitive devices have become popular as input devices to computing systems due to their ease and versatility of operation as well as their declining price. A touch sensitive device can include a touch sensor panel, which can be a clear panel with a touch sensitive surface, and a display device such as a liquid crystal display (LCD) that can be positioned partially or fully behind the panel or integrated with the panel so that the touch sensitive surface can cover at least a portion of the viewable area of the display device. The touch sensitive device can allow a user to perform various functions by touching the touch sensor panel using a finger, stylus or other object at a location often dictated by a user interface (UI) being displayed by the display device. In general, the touch sensitive device can recognize a touch event and the position of the touch event on the touch sensor panel, and the computing system can then interpret the touch event in accordance with the display appearing at the time of the touch event, and thereafter can perform one or more actions based on the touch event. 
     One type of touch sensor panel that can be used is a capacitive touch sensor panel. Capacitive touch sensor panels can by driven by stimulation signals and can output touch signals representative of touch events detected on the surface of the panel. In order to obtain accurate touch detection, it is important that the touch sensor panel output strong touch signals. However, the touch sensor panel and other components within a touch sensitive device can cause phase delays in the touch signals, resulting in weaker outputs. These phase delays can be due at least in part to signal transmission and/or processing delays in the panel and other components. Conventional touch sensors account for these phase delays by hardwiring a phase adjustment, with the adjustment amount being based on an average expected phase delay. While this may reduce the effects of the phase delays caused by the touch sensor panel and other components, it does not account for the variation in phase delays that can be present in different touch sensor panels (e.g., due to manufacturing tolerances) and changes in phase delay over time (e.g., due to environmental factors 
     SUMMARY 
     Demodulation circuits for demodulating touch signals from a touch sensor are disclosed. The demodulation circuits can include circuitry configured to determine an adjustable phase delay for a touch signal based at least in part on a quadrature component of the touch signal or the phase-adjusted touch signal. The demodulation circuit can further include circuitry for applying the adjustable phase delay to the touch signal to compensate for phase delays in the touch signal caused by the touch sensor and/or other components. The demodulation circuit can dynamically change the adjustable phase delay to compensate for time-varying phase delays caused by the touch sensor and/or other components. 
     Processes for demodulating touch signals from a touch sensor are also disclosed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates an exemplary touch sensor panel that can be used with a demodulation circuit according to various embodiments. 
         FIG. 2  illustrates a functional diagram of an exemplary demodulation circuit according to various embodiments. 
         FIG. 3  illustrates a functional diagram of another exemplary demodulation circuit according to various embodiments. 
         FIG. 4  illustrates a functional diagram of another exemplary demodulation circuit according to various embodiments. 
         FIG. 5  illustrates a functional diagram of another exemplary demodulation circuit according to various embodiments. 
         FIG. 6  illustrates a functional diagram of another exemplary demodulation circuit according to various embodiments. 
         FIG. 7  illustrates a functional diagram of another exemplary demodulation circuit according to various embodiments. 
         FIG. 8  illustrates a functional diagram of another exemplary demodulation circuit according to various embodiments. 
         FIG. 9  illustrates a functional diagram of another exemplary demodulation circuit according to various embodiments. 
         FIG. 10  illustrates a functional diagram of another exemplary demodulation circuit according to various embodiments. 
         FIG. 11  illustrates an exemplary process for demodulating a signal according to various embodiments. 
         FIG. 12  illustrates an exemplary computing system for demodulating a signal according to various embodiments. 
         FIG. 13  illustrates an exemplary personal device having a demodulation circuit according to various embodiments. 
         FIG. 14  illustrates an exemplary personal device having a demodulation circuit according to various embodiments. 
         FIG. 15  illustrates an exemplary personal device having a demodulation circuit according to various embodiments. 
     
    
    
     DETAILED DESCRIPTION 
     In the following description of example embodiments, reference is made to the accompanying drawings in which it is shown by way of illustration specific embodiments that can be practiced. It is to be understood that other embodiments can be used and structural changes can be made without departing from the scope of the various embodiments. 
     This relates to demodulation circuits and processes for demodulating touch signals from a touch sensor using the demodulation circuits. The demodulation circuits can include circuitry configured to determine an adjustable phase delay in a touch signal based at least in part on a quadrature component of the touch signal or the phase-adjusted touch signal. The demodulation circuit can further include circuitry for applying the adjustable phase delay to the touch signal to compensate for phase delays in the touch signal caused by the touch sensor and/or other components. The demodulation circuit can dynamically change the adjustable phase delay to compensate for time-varying phase delays caused by the touch sensor and/or other components. These will be described in more detail below. 
       FIG. 1  illustrates touch sensor panel  100  that can be used to detect touch events on a touch sensitive device, such as a mobile phone, tablet, touchpad, portable computer, portable media player, or the like. Touch sensor panel  100  can include an array of pixels  105  that can be formed at the crossing points between rows of drive lines  101  (D 0 -D 3 ) and columns of sense lines  103  (S 0 -S 4 ). Each pixel  105  can have an associated mutual capacitance Csig  111  formed between the crossing drive lines  101  and sense lines  103  when the drive lines are stimulated. The drive lines  101  can be stimulated by stimulation signals  107  provided by drive circuitry (not shown) and can include an alternating current (AC) waveform. The sense lines  103  can transmit touch signals  109  indicative of a touch at the panel  100  to sense circuitry (not shown), which can include a sense amplifier for each sense line. 
     To sense a touch at the touch sensor panel  100 , drive lines  101  can be stimulated by the stimulation signals  107  to capacitively couple with the crossing sense lines  103 , thereby forming a capacitive path for coupling charge from the drive lines  101  to the sense lines  103 . The crossing sense lines  103  can output touch signals  109 , representing the coupled charge or current. When a user&#39;s finger (or other object) touches the panel  100 , the finger can cause the capacitance Csig  111  to reduce by an amount ΔCsig at the touch location. This capacitance change ΔCsig can be caused by charge or current from the stimulated drive line  101  being shunted through the touching finger to ground rather than being coupled to the crossing sense line  103  at the touch location. The touch signals  109  representative of the capacitance change ΔCsig can be transmitted by the sense lines  103  to the sense circuitry for processing. The touch signals  109  can indicate the pixel where the touch occurred and the amount of touch that occurred at that pixel location. 
     While the embodiment shown in  FIG. 1  includes four drive lines  101  and five sense lines  103 , it should be appreciated that touch sensor panel  100  can include any number of drive lines  101  and any number of sense lines  103  to form the desired number and pattern of pixels  105 . Additionally, while the drive lines  101  and sense lines  103  are shown in  FIG. 1  in a crossing configuration, it should be appreciated that other configurations are also possible to form the desired pixel pattern. While  FIG. 1  illustrates mutual capacitance touch sensing, other touch sensing technologies may also be used in conjunction with embodiments of the disclosure, such as self-capacitance touch sensing, resistive touch sensing, projection scan touch sensing, and the like. Furthermore, while various embodiments describe a sensed touch, it should be appreciated that the touch sensor panel  100  can also sense a hovering object and generate hover signals therefrom. 
     As mentioned above, touch sensor panel  100 , along with other components within a device, can cause phase delays in touch signals  109 . Thus, demodulation circuits, such as those described below with respect to  FIGS. 2-11 , can be coupled to each sense line  103  (S 0 -S 4 ) to compensate for these phase delays. 
       FIG. 2  illustrates a functional diagram of an exemplary touch sensitive device having a demodulation circuit to compensate for phase delays in touch signals. Device  200  can include drive circuitry  201  for generating a stimulation signal, such as stimulation signal  107 . The output of drive circuitry  201  can be transmitted to an input buffer, such as transmitter  203 , before being sent to panel  205 . Device  200  can also include panel  205 , which can be a touch sensitive panel similar or identical to touch sensor panel  100 . Touch panel  205  can output touch signals similar or identical to touch signals  109  in response to the stimulation signal. The touch signals output by panel  205  can be transmitted to an amplifier, such as pre-amp  207 . The output of pre-amp  207  can be transmitted to demodulation mixers  209  and  211 . 
     Device  200  can further include a demodulation circuit to determine an adjustable phase delay and to apply the adjustable phase delay to the touch signals. The demodulation circuit can include delay circuitry  213  configured to receive the stimulation signal from drive circuitry  201  and cause a phase delay of φ in the stimulation signal. The output of delay circuitry  213  can be transmitted to demodulation mixer  215 , where it can be combined with demodulation envelope window  220 . Demodulation envelope window  220  can be a low or band-pass filter, such as a Chebyschev filter. The output of demodulation mixer  215  can be transmitted to demodulation mixer  209 , where it can be combined with the touch signal output by pre-amp  207  to compensate for the phase delay in the touch signal. 
     The demodulation circuit can further include delay circuitry  217  configured to receive the stimulation signal from drive circuitry  201  and cause a phase delay of (φ+90°) in the stimulation signal. The output of delay circuitry  217  can be transmitted to demodulation mixer  219 , where it can be combined with demodulation envelope window  220 . The output of demodulation mixer  219  can be transmitted to demodulation mixer  211 , where it can be combined with the touch signal output of pre-amp  207  to determine the adjustable phase delay to be applied by delay circuitry  213  and  217 . 
     The demodulation circuit can further include integrators  225  and  227  coupled to the outputs of demodulation mixers  209  and  211 , respectively. Integrators  225  and  227  can integrate the output of demodulation mixers  209  and  211  over time. The output of integrator  225  can be the phase-adjusted in-phase (I-phase) component of the touch signal output by panel  205  and the output of integrator  227  can be the quadrature (Q) component of the phase-adjusted touch signal output by panel  205 . The I-phase component can be transmitted to matrix  229  where the signal can be multiplied by a matrix to generate a phase-adjusted touch signal representing a touch event detected by the sense line of panel  205  that is coupled to the demodulation circuit. In some embodiments, matrix  229  can be an inverse of a matrix having a gain greater than one that is similar or identical to that described in U.S. patent Ser. No. 12/208,329, entitled “Multiple Stimulation Phase Determination.” Specifically, each row of the matrix can represent a single step among multiple steps needed to compute values for generating an image of touch. Each column of the matrix can represent a drive line of touch sensor panel  205  to be stimulated. Each element of the matrix can represent the phase of stimulation signal  107  to be applied to a particular drive line in a particular step. 
     To determine the phase delay φ that is to be applied by delay circuitry  213  and  217  to the stimulation signal from drive circuitry  201 , the demodulation circuit can further include filter  221  and dither circuitry  223 . Filter  221  can be configured to receive the Q-component of the phase-adjusted touch signal that is output by integrator  227 . In some embodiments, filter  221  can be a low pass filter with a bandwidth below 60 Hz. In other embodiments, other bandwidths can be used. The output of filter  221  can be transmitted to dither circuitry  223 . Dither circuitry  223  can be configured to dither the value of φ to produce a reduced or minimum value of the Q-component of the signal. For example, in one embodiment, a digital implementation in which delays are generated by shifting a digital representation of the reference stimulation signal  107  using a parallel bit shift register can be used. The dither in φ can be a shift in time (degree phase shift/stimulation frequency) that is introduced to perturb the filtered Q (output by filter  221 ) to determine whether or not Q is at its minimum value. The output of dither circuitry  223  can be transmitted to delay circuitry  213  and  217 . Since the phase delay φ that causes the Q-component to be at its minimum value corresponds to the phase delay φ that causes the I-phase component to be at its maximum value, dither circuitry  223  can be used to improve the signal strength of the touch signal output by matrix  229 . In this way, dither circuitry  223  can dynamically adjust the phase delay applied to the Q and I-phase components of the touch signal to compensate for non-constant phase delays caused by circuitry located between drive circuitry  201  and the outputs of integrators  225  and  227 , thereby improving the signal strength of the touch signal output by matrix  229 . 
     In some embodiments, filter  221  and dither circuitry  223  can be used to adjust the value of φ only when no touch events are occurring at panel  205 . In these embodiments, when touch events are occurring at panel  205 , φ can be held constant at the most recently determined value of φ. 
     In some embodiments, filter  221  and dither circuitry  223  can be implemented in an ARM processor or other processor since the functions performed by these elements do not need to be performed with a high frequency. The remaining components (excluding panel  205 ), can be implemented in an application specific integrated circuit (ASIC) since the functions performed by these elements relate to the sensing of touch events on panel  205  and can be performed at a higher frequency. In other embodiments, all components of device  200  (excluding panel  205 ) can be implemented in an ASIC. 
     It should be appreciated that  FIG. 2  (and  FIGS. 3-10 ) is a functional diagram of the demodulation circuit of touch sensitive device  200 . The actual components used to implement the demodulation circuit can vary and one of ordinary skill, given the functional diagram, can select known circuit elements to implement the demodulation circuit. 
       FIG. 3  illustrates a functional diagram of an exemplary touch sensitive device  300  having a demodulation circuit. The demodulation circuit of device  300  is similar to that of device  200 , except that the phase delay φ can be introduced into the touch signal at the output of pre-amp  207  by delay circuitry  301  rather than into the stimulation signal by delay circuitry  213  and  217 . Delay circuitry  301  can be similar or identical to delay circuitry  213 . Since phase delay φ can be introduced into the output of pre-amp  207  rather than into the stimulation signal output by drive circuitry  201 , delay circuitry  213  can be removed and delay circuitry  317 , which can be configured to cause a phase delay of 90°, can be used in place of delay circuitry  217 . 
       FIG. 4  illustrates a functional diagram of an exemplary touch sensitive device  400  having a demodulation circuit. The demodulation circuit of device  400  is similar to that of device  200 , except that delay circuitry  213  and  217  can be used to apply the phase delay φ and (φ+π 90 °) to the touch signal inputs of demodulation mixers  209  and  211 , respectively. As a result, the demodulation circuit of device  400  may exclude demodulation mixer  215  and the output of demodulation mixer  219  can be applied to the inputs of both demodulation mixers  209  and  211 . 
       FIG. 5  illustrates a functional diagram of an exemplary touch sensitive device  500  having a demodulation circuit. The demodulation circuit of device  500  is similar to that of device  400 , except that delay circuitry  213  can be used to apply the phase delay φ to the stimulation signal output by drive circuitry  201 . The phase delayed stimulation signal output by delay circuitry  213  can then be transmitted to demodulation mixer  219 , where it can be combined with demodulation envelope window  220  and transmitted to both demodulation mixers  209  and  211 . As a result, the demodulation circuit of device  500  can include delay circuitry  517  in place of delay circuitry  217  to introduce a 90° phase delay into the input of demodulation mixer  211 . 
       FIG. 6  illustrates a functional diagram of an exemplary touch sensitive device  600  having a demodulation circuit. The similarly named components of device  600  can be similar or identical to those of device  200 . Device  600  can include drive circuitry  601  for generating a stimulation signal, such as stimulation signal  107 . The output of drive circuitry  601  can be transmitted to an input buffer, such as transmitter  603 , before being sent to panel  605 . Device  600  can also include panel  605 , which can be a touch sensitive panel similar or identical to touch sensor panel  100 . The touch signals output by panel  605  can represent touch events detected on panel  605 . Touch panel  605  can output touch signals similar or identical to touch signals  109  in response to the stimulation signal. The output of panel  605  can be transmitted to an amplifier, such as pre-amp  607 . The output of pre-amp  607  can be transmitted to demodulation mixers  609  and  611 . 
     Device  600  can further include a demodulation circuit to determine an adjustable phase delay and to apply the adjustable phase delay to touch signals of the panel  605 . The demodulation circuit can include demodulation mixer  613  configured to combine the stimulation signal from drive circuitry  601  and demodulation envelope window  620 . Demodulation envelope window  620  can be a low or band-pass filter, such as a Chebyschev filter. The output of demodulation mixer  613  can be transmitted to demodulation mixer  609 , where it can be combined with the touch signal output by pre-amp  607 . 
     The demodulation circuit can further include delay circuitry  615  configured to receive the stimulation signal from drive circuitry  601  and cause a phase delay of 90° in the stimulation signal. The output of delay circuitry  615  can be transmitted to demodulation mixer  617  where it can be combined with demodulation envelope window  620 . The output of demodulation mixer  617  can be transmitted to demodulation mixer  611 , where it can be combined with the touch signal output by pre-amp  607 . 
     The demodulation circuit can further include integrators  619  and  621  coupled to the outputs of demodulation mixers  609  and  611 , respectively. Integrators  619  and  621  can integrate the output of demodulation mixers  609  and  611  over time. The output of integrator  619  can be the I-phase component of the touch signal output by pre-amp  607  and the output of integrator  621  can be the Q-component of the touch signal output by pre-amp  607 . 
     The I-phase and Q-components output by integrators  619  and  621  can be transmitted to demodulation mixers  623  and  625 , respectively. Demodulation mixers  623  and  625  can be configured to mix the I-phase and Q-components with cosine (C) and sine (S) phase adjustment signals generated by phase adjustment circuitry  627  and filtered by filter  629  (described in greater detail below). The phase-adjusted I-phase and Q-components of the touch signal output by demodulation mixers  623  and  625  can be transmitted to integrator  631 , where the outputs can be combined. The output of integrator  631  can be transmitted to matrix  633  where the signal can be multiplied by a matrix to generate a phase-adjusted touch signal representing touch events detected by the sense line of panel  605  that is coupled to the demodulation circuit. 
     As mentioned above, the demodulation circuit can further include phase adjustment circuitry  627  for generating sine and cosine phase adjustment signals that can be modulated with the I-phase and Q-components of the touch signal output by integrators  619  and  621 , respectively. Phase adjustment circuitry  627  can be configured to receive I-phase and Q-components output by integrators  619  and  621  and output a sine phase adjustment signal, where sin(φ)=Q/(Q 2 +I 2 ) −1/2 , and a cosine phase adjustment signal, where cos(φ)=I/(Q 2 +I 2 ) −1/2 . The sine and cosine phase adjustment signals can be transmitted to filter  629 . In some embodiments, filter  629  can be a low pass filter with a bandwidth below 60 Hz. In other embodiments, other bandwidths can be used. The filtered sine (S) and cosine (C) phase adjustment signals can be transmitted to demodulation mixers  625  and  623 , respectively. In this way, phase adjustment circuitry  627  can dynamically adjust the phase offset applied to the I-phase and Q-components of the touch signal output by panel  605  to compensate for phase delays caused by circuitry located between drive circuitry  601  and the outputs of integrators  619  and  621 , thereby improving the signal strength of the touch signal output by matrix  633 . 
     In some embodiments, phase adjustment circuitry  627  and filter  629  can be used to adjust the sine and cosine phase adjustment signals transmitted to demodulation mixers  623  and  625  only when no touch events are occurring at panel  605 . In these embodiments, when touch events are occurring at panel  605 , φ can be held constant at the most recently determined value of φ. 
     In some embodiments, phase adjustment circuitry  627 , filter  629 , demodulation mixer  623 , demodulation mixer  625 , integrator  631 , and matrix  633  can be implemented in an ARM processor or other processor since the functions performed by these elements do not need to be performed with a high frequency. The remaining components (excluding panel  605 ), can be implemented in an ASIC since the functions performed by these elements relate to the sensing of touch events on panel  605  and can be performed at a higher frequency. In some embodiments, the components located in the ASIC can be configured to scan the output of panel  605  and store the I-phase and Q-components. The components in the ARM processor can then perform decoding on the saved I-phase and Q-components after the ASIC performs the scanning. In other embodiments, phase adjustment circuitry  627  and filter  629  can be located in an ARM processor and the remaining components (excluding panel  605 ) can be located in an ASIC. In some embodiments, since demodulation mixers  623  and  625  can be used infrequently, demodulation mixers  623  and  625  can be shared with demodulation circuits for other sense lines (not shown) of panel  605 . In still other embodiments, all components of device  600  (excluding panel  605 ) can be implemented in an ASIC. 
       FIG. 7  illustrates a functional diagram of an exemplary touch sensitive device  700  having a demodulation circuit. The demodulation circuit of device  700  is similar to that of device  600 , except that the I-phase and Q-components of the touch signal can be multiplied with a matrix using matrices  733  and  735  before being transmitted to demodulation mixers  623  and  625 , respectively. Matrices  733  and  735  can be similar or identical to matrix  633  of device  600 . Since the I-phase and Q-components can be multiplied with a matrix using matrices  733  and  735  before being transmitted to demodulation mixers  623  and  625 , device  700  may exclude matrix  633 . As a result, the output of integrator  631  can be the phase-adjusted touch signal representative of touch events detected at panel  605 . Additionally, similar to the demodulation circuit of device  600 , phase adjustment circuitry  627  and filter  629  can be located in an ARM processor or other processor while the remaining components (excluding panel  605 ) can be located in an ASIC. Alternatively, all of the components (excluding panel  605 ) can be implemented on an ASIC. 
       FIG. 8  illustrates a functional diagram of an exemplary touch sensitive device  800  having a demodulation circuit. The demodulation circuit of device  800  is similar to that of device  200 , except that an additional phase delay of β can be applied to the stimulation signal output by drive circuitry  201  and transmitted to demodulation mixer  209 . Thus, delay circuitry  813 , which can be configured to introduce a phase delay of (φ+β), can be used in place of delay circuitry  213  of the demodulation circuit of device  200 . The phase delay β can represent a phase difference between a large, undesired signal in the touch signal output by panel  205  and a smaller, desired signal in the touch signal. The large, undesired signal can be generated by portions of the stimulation signal input of panel  205  traveling around the panel to the output. This can be a result of the manufacturing design of the panel. Thus, as long as remains relatively constant, the demodulation circuit of device  800  can be used to extract the smaller, desired signal from the output of the panel. In some embodiments, can be calculated or determined experimentally. 
       FIG. 9  illustrates a functional diagram of an exemplary touch sensitive device  900  having a demodulation circuit. The demodulation circuit of device  900  is similar to that of device  400 , except that an additional phase delay of β can be applied to the input of demodulation mixer  209 . Thus, delay circuitry  913 , which can be configured to introduce a phase delay of (φ+β), can be used in place of delay circuitry  213  of the demodulation circuit of device  400 . Similar to the demodulation circuit of device  800 , the phase delay β can represent a phase difference between a large, undesired signal in the output of panel  205  and a smaller, desired signal in the touch signal. The large, undesired signal can be generated by portions of the stimulation signal input of panel  205  traveling around the panel to the output. This can be a result of the manufacturing design of the panel. Thus, as long as remains relatively constant, demodulation circuit of device  900  can be used to extract the smaller, desired signal from the output of the panel. In some embodiments, can be calculated or determined experimentally. 
       FIG. 10  illustrates a functional diagram of an exemplary touch sensitive device  1000  having a demodulation circuit. The demodulation circuit of device  1000  is similar to that of device  600 , except that an additional phase delay of β can be used when generating the sine and cosine phase adjustment signals that can be applied to demodulation mixers  623  and  625 . Specifically, the filtered sine phase adjustment signal (S) can include signal sin (φ+β), where sin(φ)=Q/(Q 2 +I 2 ) −1/2 , and the filtered cosine phase adjustment signal can include signal cos(φ+β), where cos(φ)=I/(Q 2 +I 2 ) −1/2 . Thus, phase adjustment circuitry  1027  can be used in place of phase adjustment circuitry  627  of the demodulation circuit of device  600 . Similar to the demodulation circuit of device  800 , the phase delay β can represent a phase difference between a large, undesired signal in the output of panel  605  and a smaller, desired signal in the touch signal. The large, undesired signal can be generated by portions of the stimulation signal input of panel  605  traveling around the panel to the output. This can be a result of the manufacturing design of the panel. Thus, as long as β remains relatively constant, demodulation circuit of device  1000  can be used to extract the smaller, desired signal from the output of the panel. In some embodiments, β can be calculated or determined experimentally. 
     It should be appreciated that any of the demodulation circuits for devices  200 ,  300 ,  400 ,  500 ,  600 , and  700  can be modified in a similar manner as the demodulation circuits of devices  800 ,  900 , and  1000  to include the compensation for undesired signals. 
     In some embodiments, each sense line column (e.g., sense lines  103  of touch sensor panel  100 ) can be coupled to a demodulation circuit, such as any of the demodulation circuits shown in  FIGS. 2-10 . Additionally, for each sense line column, the coupled demodulation circuit can be configured to apply a different phase delay φ for each row (e.g., drive lines  101  of touch sensor panel  100 ). This can be done because the phase delay between each drive line row and sense line column can be different. For instance, the phase delay that results from a capacitive coupling between drive line D 0  and sense line S 0  can be different than a phase delay resulting from a capacitive coupling between drive line D 2  and sense line S 0 . Thus, separate phase delays φ can be applied to each column-row pairing. In some embodiments, this can be accomplished by replicating some or all of the components in each demodulation circuit for each column. In this way, separate phase delays φ can be determined for each column-row pairing. For example, demodulation mixers  209  and  211 ,  215  and  219 ,  609  and  611 , or  613  and  617  can be replicated for each row-channel pairing. In other embodiments, the same physical or logical components can be used for each row-channel pairing. In these embodiments, time-division multiplexing can be used to assign time slots for each row within the channel. 
       FIG. 11  shows an exemplary process  1100  for demodulating a touch signal. In some embodiments, process  1100  can be used to compensate for variable phase delays in a touch sensitive panel using a demodulation circuit that is similar or identical to demodulation circuits of devices  200 ,  300 ,  400 ,  500 ,  600 ,  700 ,  800 ,  900 , or  1000 . 
     At block  1101  of process  1100 , at least a portion of a touch signal can be received. In some embodiments, a filter (e.g., filter  221 ) can receive the quadrature component of a phase-adjusted touch signal from an integrator (e.g., integrator  227 ). In other embodiments, phase adjustment circuitry (e.g., circuitry  627  or  1027 ) can receive the quadrature component of a non-phase-adjusted touch signal from an integrator (e.g., integrator  621 ). In these embodiments, the phase adjustment circuitry (e.g., circuitry  627  or  1027 ) can also receive the in-phase component of the non-phase-adjusted touch signal from an integrator (e.g., integrator  619 ). 
     At block  1103 , an adjustable phase delay may be determined based at least in part on the quadrature component of the phase-adjusted or non-phase-adjusted touch signal. In some embodiments, as described above with respect to  FIGS. 2-5  and  8 - 9 , the adjustable phase delay φ can be determined by dithering the adjustable phase delay φ around an expected value (e.g., as determined through calculations or experimentation) until a reduced or minimum value of the quadrature component of the phase-adjusted touch signal is obtained. This determined adjustable phase delay φ can also correspond to the phase delay that causes the in-phase component of the phase-adjusted touch signal to be at its maximum value. One of ordinary skill in the art will be capable of implementing known techniques for dithering a phase delay φ until reaching a reduced or minimum value of the quadrature component of the phase-adjusted touch signal. 
     In other embodiments, as described above with respect to  FIGS. 6-7  and  10 , the adjustable phase delay φ can be determined using both the quadrature and in-phase components of the non-phase-adjusted touch signal and the following equations: sin(φ)=Q/(Q 2 +I 2 ) −1/2  and cos(φ)=I/(Q 2 +I 2 ) −1/2 . The functions performed at block  1103  can be performed using an ASIC processor, ARM processor, other electrical components, or combinations thereof. 
     At block  1105 , the adjustable phase delay φ determined at block  1103  can be applied to the touch signal. In some embodiments, as described above with respect to  FIGS. 3 and 4 , the phase delay φ can be applied to the touch signal by causing a phase delay of φ in the non-phase-adjusted touch signal. This can be done, for example, using delay circuitry, such as delay circuitry  213 ,  217 , or  301 . 
     In other embodiments, as described above with respect to  FIGS. 2 and 5 , the phase delay φ can be applied to the touch signal by causing a phase delay of φ in the stimulation signal, and mixing the phase-delayed stimulation signal with the non-phase adjusted touch signal. This can be done, for example, using delay circuitry, such as delay circuitry  213  and  217 , and a mixer, such as demodulation mixer  209  and  211 . 
     In yet other embodiments, as described above with respect to  FIGS. 6-7 , the phase delay φ can be applied to the touch signal by mixing the non-phase-adjusted touch signal with sine and cosine phase adjustment signals having phase delays of cp. This can be done, for example, using phase adjustment circuitry, such as phase adjustment circuitry  627 , and mixers, such as demodulation mixers  623  and  625 . 
     In yet other embodiments, as described above with respect to  FIGS. 8-10 , a phase delay of β can be applied to the touch signal in addition to the phase delay of φ. The phase delay β can represent a phase difference between a large, undesired signal in the touch signal and a smaller, desired signal in the touch signal. The phase delay β can be determined experimentally and configured into the demodulation circuit. In some embodiments, as described above with respect to  FIG. 8 , a phase delay of (φ+β) can be applied to the touch signal by causing a phase delay of (φ+β) in the stimulation signal, and mixing the phase-delayed stimulation signal with the non-phase-adjusted touch signal using delay circuitry, such as delay circuitry  813 , and a mixer, such as demodulation mixer  209 . In other embodiments, as described above with respect to  FIG. 9 , a phase delay of (φ+β) can be applied to the touch signal by causing a phase delay of (φ+β) in the non-phase-adjusted touch signal using delay circuitry, such as delay circuitry  913  of circuit  900 . In yet other embodiments, as described above with respect to  FIG. 10 , a phase delay of (φ+β) can be applied to the touch signal by mixing the non-phase-adjusted touch signal with sine and cosine phase adjustment signals having phase delays of (φ+β). This can be done, for example, using phase adjustment circuitry, such as phase adjustment circuitry  1027 , and mixers, such as demodulation mixers  623  and  625 . 
     One or more of the functions relating to the demodulation of a touch signal can be performed by a computing system similar or identical to computing system  1200  shown in  FIG. 12 . Computing system  1200  can include instructions stored in a non-transitory computer readable storage medium, such as memory  1203  or storage device  1201 , and executed by processor  1205 . The instructions can also be stored and/or transported within any non-transitory computer readable storage medium for use by or in connection with an instruction execution system, apparatus, or device, such as a computer-based system, processor-containing system, or other system that can fetch the instructions from the instruction execution system, apparatus, or device and execute the instructions. In the context of this document, a “non-transitory computer readable storage medium” can be any medium that can contain or store the program for use by or in connection with the instruction execution system, apparatus, or device. The non-transitory computer readable storage medium can include, but is not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus or device, a portable computer diskette (magnetic), a random access memory (RAM) (magnetic), a read-only memory (ROM) (magnetic), an erasable programmable read-only memory (EPROM) (magnetic), a portable optical disc such a CD, CD-R, CD-RW, DVD, DVD-R, or DVD-RW, or flash memory such as compact flash cards, secured digital cards, USB memory devices, memory sticks, and the like. 
     The instructions can also be propagated within any transport medium for use by or in connection with an instruction execution system, apparatus, or device, such as a computer-based system, processor-containing system, or other system that can fetch the instructions from the instruction execution system, apparatus, or device and execute the instructions. In the context of this document, a “transport medium” can be any medium that can communicate, propagate or transport the program for use by or in connection with the instruction execution system, apparatus, or device. The transport medium can include, but is not limited to, an electronic, magnetic, optical, electromagnetic or infrared wired or wireless propagation medium. 
     Computing system  1200  can further include touch sensor  1207  coupled to processor  1205 . Touch sensor  1207  can be included within a touch panel and can be similar or identical to touch sensor panel  100 , described above. In some embodiments, additional circuitry (not shown), such as the components of the demodulation circuits of devices  200 ,  300 ,  400 ,  500 ,  600 ,  700 ,  800 ,  900 , or  1000  can also be included within computing system  1200 . These components can be coupled to processor  1205  and/or touch sensor  1207 , or can be integrated with either or both of processor  1205  and touch sensor  1207 . In some embodiments, processor  1205  can receive the touch signals from touch sensor  1207  and can demodulate them in a manner similar or identical to that described above with respect to process  1100 . 
     It is to be understood that the computing system is not limited to the components and configuration of  FIG. 12 , but can include other or additional components in multiple configurations according to various embodiments. Additionally, the components of computing system  1200  can be included within a single device, or can be distributed between two or more devices. 
       FIG. 13  illustrates an exemplary personal device  1300 , such as a tablet, that can include a demodulation circuit according to various embodiments. 
       FIG. 14  illustrates another exemplary personal device  1400 , such as a mobile phone, that can include a demodulation circuit according to various embodiments. 
       FIG. 15  illustrates another exemplary personal device  1500 , such as a laptop computer, that can include a demodulation circuit according to various embodiments. 
     Although embodiments have been fully described with reference to the accompanying drawings, it is to be noted that various changes and modifications will become apparent to those skilled in the art. Such changes and modifications are to be understood as being included within the scope of the various embodiments as defined by the appended claims.

Metadata:
Filing Date: 20120215
Publication Date: 20140819
Grant Date: 20140819
Priority Date: 20120215
Inventors: YOUSEFPOR MARDUKE
WHITE KEVIN J.
KRAH CHRISTOPH HORST
Assignee: APPLE INC
CPC Classifications: [{"code": "G06F3/044", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/0446", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/04166", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/04182", "inventive": true, "first": true, "tree": "[]"}, {"code": "H03D2200/0029", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F3/0418", "inventive": true, "first": true, "tree": "[]"}, {"code": "G06F3/0418", "inventive": true, "first": true, "tree": "[]"}, {"code": "H03D2200/0029", "inventive": false, "first": false, "tree": "[]"}]
Family ID: 48945179