Patent Publication Number: US-10310667-B2

Title: Multi-bar capacitive sense electrode

Description:
FIELD OF DISCLOSURE 
     This relates generally to touch sensing, and more particularly, to improving position calculation for objects touching a touch sensor panel. 
     BACKGROUND OF THE DISCLOSURE 
     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. 
     As touch sensing technology continues to improve, touch sensitive devices are increasingly being used to compose and mark-up electronic documents. In particular, styli have become popular input devices as they emulate the feel of traditional writing instruments. The effectiveness of a stylus, however, can depend on the ability to accurately calculate the position of the stylus on a touch sensor panel. 
     SUMMARY OF THE DISCLOSURE 
     Touch screens can allow a user to perform various functions by touching the touch sensor panel using a finger, stylus or other object. In some examples, the touch sensor panel can have errors in position detection, referred to herein as wobble error, when the touch object (e.g., a finger or stylus) is positioned between two of a plurality of sense electrodes. In some cases, wobble error can correlate to the signal profile between the touch object and electrodes within the touch sensor panel. Specifically, signal profiles which are narrower (i.e., less linear) can correlate to higher wobble error, while signal profiles which are widened within a range (i.e., to be more linear) can correlate to lower wobble error. This can be particularly evident in configurations in which the touch object is a stylus. Accordingly, in some examples, sense electrodes can be configured such that the signal profile associated with each sense electrode is spread to be wider, and thus, more linear. In some configurations, sense electrodes can include two or more bars extending along the length of the electrode with each bar connected to one another at one or both ends. In some examples, bars within a sensor can be non-uniformly spaced. Some bars (i.e., “split bars”) can be positioned in groups of two or more, with the distance between bars within a group being relatively small (e.g., smaller than the individual width of a bar). Some adjacent bars within the sensor (e.g., two adjacent bars from two separate but adjacent groups) can be positioned at a greater distance than those bars within the group. Additionally, in some cases, adjacent electrodes can be positioned such that the distance between two electrodes is relatively small (e.g., as small as the distance between split-bars in a group). In some examples, sense electrodes can be configured to interleave with one another, including examples where interleaving electrodes also include split bars. It should be understood that although examples of the disclosure are discussed herein primarily in terms of a stylus, the examples of the disclosure are not so limited, but include other small objects, including small fingers, that can cause wobble error similar to a stylus. Similarly, although the examples of the disclosure are focused on the configuration of sense electrodes, other examples are contemplated within the scope of this disclosure including, but not limited to, configurations in which the configurations discussed herein are applied to drive electrodes or self-capacitance electrodes. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates an exemplary computing system capable of reducing stylus tip wobble according to examples of the disclosure. 
         FIGS. 2A and 2B  illustrate an exemplary mutual capacitance touch sensor panel that can be used to detect touch or hover (proximity) events according to examples of the disclosure. 
         FIGS. 3A and 3B  illustrate examples of the disparity between actual position and calculated position as a stylus moves along one axis of a touch sensor panel according to examples of the disclosure. 
         FIGS. 4A and 4B  illustrate example signal profiles as a stylus moves along an axis of a touch sensor panel according to examples of the disclosure. 
         FIGS. 5A and 5B  illustrate various signal profiles corresponding to various electrode configurations and levels of wobble error correlating with the signal profiles according to examples of the disclosure. 
         FIG. 6  illustrates an exemplary touch sensor panel system in which sense electrodes are in a multiple-bar configuration according to examples of this disclosure. 
         FIGS. 7A-7B  illustrate a customary sense electrode configuration and corresponding signal profile according to examples of this disclosure. 
         FIGS. 8A-8B  illustrate an exemplary 3-bar sense electrode configuration and corresponding signal profile according to examples of this disclosure. 
         FIGS. 9A-9B  illustrate an exemplary 4-bar sense electrode configuration and corresponding signal profile according to examples of this disclosure. 
         FIGS. 10A-10B  illustrate an exemplary multiple-bar sense electrode in a split-bar configuration and corresponding signal profile according to examples of this disclosure. 
         FIG. 11  illustrates an exemplary multiple-bar sense electrode in a split-bar configuration in a touch sensor panel layout which includes dummy elements. 
         FIGS. 12A-12B  illustrate exemplary multiple-bar sense electrodes in a touch sensor panel layout which includes overlapping electrodes according to examples of this disclosure. 
         FIGS. 13A-13B  illustrate exemplary sense electrodes in an interleaving configuration according to examples of this disclosure. 
         FIGS. 14A-14C  illustrate exemplary sense electrodes in interleaving split-bar configurations according to examples of this disclosure. 
         FIGS. 15A-15B  illustrate other exemplary sense electrodes in an interleaving configuration in which each sense electrodes can have four sets of projections according to examples of this disclosure. 
         FIGS. 16A-16D  illustrate example systems in which the multiple-bar sense electrode configurations for reducing stylus tip wobble according to examples of the disclosure can be implemented. 
     
    
    
     DETAILED DESCRIPTION 
     In the following description of examples, reference is made to the accompanying drawings which form a part hereof, and in which it is shown by way of illustration specific examples that can be practiced. It is to be understood that other examples can be used and structural changes can be made without departing from the scope of the disclosed examples. 
     Touch screens can allow a user to perform various functions by touching the touch sensor panel using a finger, stylus or other object. In some examples, the touch sensor panel can have errors in position detection, referred to herein as wobble error, when the touch object (e.g., a finger or stylus) is positioned between two of a plurality of sense electrodes. In some cases, wobble error can correlate to the signal profile between the touch object and electrodes within the touch sensor panel. Specifically, signal profiles which are narrower (i.e., less linear) can correlate to higher wobble error, while signal profiles which are widened within a range (i.e., to be more linear) can correlate to lower wobble error. This can be particularly evident in configurations in which the touch object is a stylus. Accordingly, in some examples, sense electrodes can be configured such that the signal profile associated with each sense electrode is spread to be wider, and thus, more linear. In some configurations, sense electrodes can include two or more bars extending along the length of the electrode with each bar connected to one another at one or both ends. In some examples, bars within a sensor can be non-uniformly spaced. Some bars (i.e., “split bars”) can be positioned in groups of two or more, with the distance between bars within a group being relatively small (e.g., smaller than the individual width of a bar). Some adjacent bars within the sensor (e.g., two adjacent bars from two separate but adjacent groups) can be positioned at a greater distance than those bars within the group. Additionally, in some cases, adjacent electrodes can be positioned such that the distance between two electrodes is relatively small (e.g., as small as the distance between split-bars in a group). In some examples, sense electrodes can be configured to interleave with one another, including examples where interleaving electrodes also include split bars. It should be understood that although examples of the disclosure are discussed herein primarily in terms of a stylus, the examples of the disclosure are not so limited, but include other small objects, including small fingers, that can cause wobble error similar to a stylus. Similarly, although the examples of the disclosure are focused on the configuration of sense electrodes, other examples are contemplated within the scope of this disclosure including, but not limited to, configurations in which the configurations discussed herein are applied to drive electrodes or self-capacitance electrodes. 
       FIG. 1  illustrates an exemplary computing system capable of reducing wobble according to examples of the disclosure. Computing system  100  can include one or more panel processors  102 , peripherals  104 , and panel subsystem  106 . Peripherals  104  can include, but are not limited to, random access memory (RAM) or other types of memory or storage, watchdog timers and the like. Panel subsystem  106  can include, but is not limited to, one or more sense channels  108 , channel scan logic (analog or digital)  110  and driver logic (analog or digital)  114 . In mutual capacitance touch sensor panel examples, the panel can be driven and sensed using separate drive and sense lines, as shown in  FIG. 1 . However, in self-capacitance touch sensor panel examples, the sense electrodes can be driven and sensed using the lines. Channel scan logic  110  can access RAM  112 , autonomously read data from sense channels  108  and provide control for the sense channels. In addition, channel scan logic  110  can control driver logic  114  to generate stimulation signals  116  at various phases that can be simultaneously applied to touch sensor panel  124 . In some examples, panel subsystem  106 , panel processor  102  and peripherals  104  can be integrated into a single application specific integrated circuit (ASIC). 
     In mutual capacitance sensing examples, touch sensor panel  124  can include a capacitive sensing medium having a plurality of drive lines and a plurality of sense lines, although other sensing media can also be used. The drive and sense lines can be formed from a transparent conductive medium such as Indium Tin Oxide (ITO) or Antimony Tin Oxide (ATO), although other transparent and non-transparent materials such as copper can also be used. The drive and sense lines can be formed on a single side of a transparent substrate, on opposite sides of the substrate, or on two separate substrates separated by dielectric material. Each intersection of drive and sense lines can represent a capacitive sensing node and can be viewed as picture element (pixel)  126 , which can be particularly useful when touch sensor panel  124  is viewed as capturing an “image” of touch. (In other words, after panel subsystem  106  has determined whether a touch event has been detected at each sense electrode in the touch sensor panel, the pattern of sense electrodes in the multi-touch panel at which a touch event occurred can be viewed as an “image” of touch (e.g., a pattern of fingers touching the panel).) The capacitance between the drive and sense lines and local system ground can appear as a stray capacitance Cstray, and the capacitance at the intersections of the drive and sense lines, i.e., the touch nodes, can appear as a mutual signal capacitance Csig between the drive and sense lines when the given drive line is stimulated with an alternating current (AC) signal. The presence of a finger or other object (such as a stylus) near or on the touch sensor panel can be detected by measuring changes to a signal charge present at the nodes being touched, which can be a function of Csig. Each sense line of touch sensor panel  124  can be coupled to a sense channel  108  in panel subsystem  106 . Touch sensor panel  124  can cover a portion or all of a surface of a device. 
     In self-capacitance sensing examples, touch sensor panel  124  can include a capacitive sensing medium having a plurality of sense electrodes. The sense electrodes can be formed from a transparent conductive medium such as ITO or ATO, although other transparent and non-transparent materials such as copper can also be used. The sense electrodes can be formed on a single side of a transparent or semi-transparent substrate, on opposite sides of the substrate, or on two separate substrates separated by dielectric material. In some examples, the sense electrodes can be viewed as picture element (pixel)  126 , which can be particularly useful when touch sensor panel  124  is viewed as capturing an “image” of touch. In other examples, the sense electrodes can be configured as elongated sense rows and/or sense columns. The capacitance between the sense electrodes and system ground can represent the self-capacitance of those electrodes. The presence of a finger or other object (such as a stylus) near or on the touch sensor panel can be detected by measuring changes to the self-capacitance of nearby sense electrodes. Each sense electrode of touch sensor panel  124  can be coupled to a sense channel  108  in panel subsystem  106 . Touch sensor panel  124  can cover a portion or all of a surface of a device 
     In some examples, computing system  100  can also include a stylus as an input device. In some examples, the stylus can actively capacitively couple with the drive and/or sense lines of touch sensor panel  124  by, for example, transducing a signal from the stylus to the drive and/or sense lines. In some examples, the stylus can act as a passive input device in a mutual capacitance system, as described above. In some examples, the touch sensor panel  124  includes a conductive sensing media having a plurality of sense rows and a plurality of sense columns, or a plurality of sense electrodes. In these examples, a stylus can capacitively couple with the sense rows, sense columns, or sense electrodes. 
     Computing system  100  can also include host processor  128  for receiving outputs from panel processor  102  and performing actions based on the outputs that can include, but are not limited to, moving one or more objects such as a cursor or pointer, scrolling or panning, adjusting control settings, opening a file or document, viewing a menu, making a selection, executing instructions, operating a peripheral device coupled to the host device, answering a telephone call, placing a telephone call, terminating a telephone call, changing the volume or audio settings, storing information related to telephone communications such as addresses, frequently dialed numbers, received calls, missed calls, logging onto a computer or a computer network, permitting authorized individuals access to restricted areas of the computer or computer network, loading a user profile associated with a user&#39;s preferred arrangement of the computer desktop, permitting access to web content, launching a particular program, encrypting or decoding a message, and/or the like. Host processor  128  can also perform additional functions that may not be related to panel processing, and can be coupled to program storage  132  and display device  130  such as an LCD display for providing a UI to a user of the device. Display device  130  together with touch sensor panel  124 , when located partially or entirely under the touch sensor panel, can form a touch screen. 
     In some examples, touch sensor panel  124  and display device  130  together can form an integrated touch screen in which touch sensing circuit elements of the touch sensing system (e.g., sense electrodes) can be integrated into the display pixel stackups of display device  130 . The circuit elements in an integrated touch screen can include, for example, elements that can exist in LCD or other displays, such as one or more pixel transistors (e.g., thin film transistors (TFTs)), gate lines, data lines, pixel electrodes and common electrodes. It is noted that circuit elements are not limited to whole circuit components, such as a whole capacitor, a whole transistor, etc., but can include portions of circuitry, such as only one of the two plates of a parallel plate capacitor. In some configurations, each common electrode in an integrated touch screen can serve as a multi-function circuit element that can operate as display circuitry of the display system of the touch screen and can also operate as elements of the touch circuitry of the touch sensing system. Specifically, each common electrode can operate as a common electrode of the display circuitry of the touch screen (e.g., during a display phase), and can also operate as a common electrode (i.e., a sense electrode) of the touch circuitry of the touch screen (e.g., during a touch sensing phase). It should be understood that a display phase and a touch sensing phase of an integrated touch screen may be operated at the same time, e.g., partially or completely overlapping, or the display phase and touch sensing phase may operate at different times. 
     In general, each of the touch sensing circuit elements may be either a multi-function circuit element that can form part of the touch circuitry and can perform one or more other functions, such as forming part of the display circuitry, or may be a single-function circuit element that can operate as touch circuitry only. Similarly, each of the display circuit elements may be either a multi-function circuit element that can operate as display circuitry and perform one or more other functions, such as operating as touch circuitry, or may be a single-function circuit element that can operate as display circuitry only. Therefore, in some examples, some of the circuit elements in the display pixel stackups can be multi-function circuit elements and other circuit elements may be single-function circuit elements. In other examples, all of the circuit elements of the display pixel stackups may be single-function circuit elements. 
     Note that one or more of the functions described above can be performed by firmware stored in memory (e.g., one of the peripherals  104  in  FIG. 1 ) and executed by panel processor  102 , or stored in program storage  132  and executed by host processor  128 . The firmware 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 (excluding a signal) 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 medium storage 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 firmware 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 readable medium can include, but is not limited to, an electronic, magnetic, optical, electromagnetic or infrared wired or wireless propagation medium. 
       FIG. 2A  symbolically illustrates an exemplary mutual capacitance touch sensor panel that can be used to detect touch or hover (proximity) events according to examples of the disclosure. In some mutual capacitance examples, touch sensor panel  200  can include an array of touch nodes  206  formed at the crossing points of row electrodes (e.g., drive lines)  201   a  and column electrodes (e.g., sense lines)  202   a , although as discussed above, it should be understood that other drive and sense configurations can be used. A stylus can include an electrode configured to alter the capacitive coupling between a crossing row electrode and column electrode. Each of the column electrodes  202  can output its capacitance readings to one or more touch sensing circuits, which can be used to detect a touch or hover event. 
     The distance between each adjacent touch node in the same row can be a fixed distance, which can be referred to as the pitch P 1  for column electrodes. The distance between each adjacent touch node in the same column can be a fixed distance, which can be referred to as the pitch P 2  for row electrodes. In some examples, the pitch for row electrodes and column electrodes can be the same, but in other examples, P 1  and P 2  can be different. 
     During a mutual capacitance scan, one or more drive rows  201   a  can be stimulated to drive the touch sensor panel  200 . Touch nodes  206  can have a mutual capacitance Cm at the touch nodes  206  when there is no object touching or hovering over touch nodes  206 . When an object touches or hovers over the touch node  206  (e.g. a stylus), the mutual capacitance Cm can be reduced by ΔCm, i.e., (Cm−ΔCm), corresponding to the amount of charge shunted through the object to ground. This mutual capacitance change can used to detect a touch or hover event and its location. 
       FIG. 2B  symbolically illustrates an exemplary mutual capacitance touch sensor panel operable with an active stylus according to examples of the disclosure. In some mutual capacitance examples, an active stylus can generate stimulation signals (effectively operating as a drive electrode), and column electrodes  202   b  and row electrodes  201   b  can effectively operate as sense electrodes. During a stylus scan, one or more stimulation signals can be injected by stylus  208  into the touch sensor panel and can cause mutual capacitive coupling Cmr between the stylus  208  and the row traces  201   b  and capacitive coupling Cmc between the stylus  208  and the column traces  202   b . The capacitance Cmr and Cmc can be transmitted to one or more touch sensing circuits for processing. In some examples, row traces  201   b  and column traces  202   b  can correspond to row electrodes  201   a  and sense columns  202   a , however, during the stylus scan, stimulation signals are not applied to row electrodes  201  apart from signals generated by the active stylus. Additionally, in some examples, the touch sensor panel can include a stylus scan, a row scan, and a column scan, which can each operate as set forth above. 
     In some self-capacitance examples, touch sensor panel  200  can include a plurality of sense electrodes (touch nodes). In some examples, the sense electrodes can be configured as elongated sense rows  201  and/or sense columns  202 . In other examples each sense electrode can be electrically isolated from the other sense electrodes and configured to represent a particular x-y location (e.g. touch node  206 ) on the panel. Such a touch screen can be referred to as a pixelated self-capacitance touch screen. A stylus can include an electrode configured to capacitively couple to a sense electrode. Each of the sense electrodes can output its capacitance readings to one or more touch sensing circuits, which can be used to detect a touch or hover event. 
     In some cases, an object, such as a stylus, may touch or hover at a position not directly over a touch node  206 , but in between two touch nodes  206 . For example, a stylus may touch or hover at a position between two row electrodes  201 , between two column electrodes  202 , or both. In these examples, the signal sensed at a plurality of touch nodes  206  may be used to estimate the location of the touch or hover event. In some examples, a centroid estimation algorithm can calculate the location of the touch or hover event using the signal sensed at the plurality of touch nodes  206 . For example, the position of a stylus on a touch sensor panel along an x-axis can be calculated by computing a weighted centroid defined in Equation (1): 
     
       
         
           
             
               
                 
                   
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     where x calc  can be the calculated position along the x-axis, S i  can be the signal measured at the i th  electrode, such as a sense electrode, along the x-axis, and x i  can be the position of the i th  electrode along the x-axis. It is to be understood that the centroid estimation algorithm defined in equation (1) is given only as an example, and the configurations described herein need not be limited to such examples. Instead, the calculation of a touch or hover location of an object can be accomplished using any appropriate method. 
     Ideally, as an object such as a stylus traverses between two touch nodes, the calculated position of the stylus on the touch screen and the actual position of the stylus should be the same. In reality, the calculated position may be different from the actual position due to limitations in the circuit configuration and the position estimation algorithms used. Errors resulting from the disparity between calculated position and actual position as an object moves along a touch sensor panel can be referred to as wobble error. 
     It can be useful to consider wobble error in the context of a stylus moving along a single axis of a touch sensor panel having conventional sense electrodes (i.e., single-bar electrodes). This concept is illustrated by example in  FIGS. 3A and 3B .  FIGS. 3A and 3B  illustrate examples of the disparity between actual position and calculated position as an object, such as a stylus, moves along an x-axis of a customary touch sensor panel (e.g., a touch panel without multiple-bar electrodes) according to examples of the disclosure.  FIG. 3A  illustrates a plot of the calculated position of the stylus versus the actual position of the stylus when calculating position by using a weighted centroid algorithm including a subset of the electrodes (e.g., five electrodes) along an x-axis. In an ideal case, where calculated position and actual position are the same, the plot can be a straight line at a 45 degree angle. However, because of non-idealities in the coupling between the stylus and the touch sensor panel and the algorithm used to calculate stylus position, there can be non-ideal results that can appear as a wobble in the plot of  FIG. 3A  as the stylus moves between electrodes along the x-axis. In other words, the signal coupling between the stylus and touch sensor panel and the calculated position metric can introduce an error in calculated position (discrepancy with actual position) that can cause a wobble to be displayed when plotting the actual versus calculated position. 
       FIG. 3B  illustrates a plot of the error in position calculation versus the actual position when calculating position by taking a weighted centroid including a subset of the electrodes (e.g., five electrodes) along an x-axis. The oscillation of the error plot can be representative of the wobble due to remaining error in the position calculation in a customary touch panel (e.g., a touch panel without multiple-bar sense electrodes). 
     It should be noted that the scope of this disclosure can extend beyond the context of an active stylus coupling to sense electrodes, however, the examples of this disclosure focus on a stylus-sense electrode configuration for ease of description.  FIGS. 3A and 3B  relate to calculating position using a subset of the electrodes, however, it should be understood that the position could be calculated using any number of electrodes, including all of the electrodes in a touch sensor panel. Moreover, although  FIGS. 3A and 3B  are described with reference to the x-axis, in some examples, similar effects can be observed when moving the stylus across the touch sensor panel along the y-axis. 
     It can be useful to discuss the characteristics of the electrode configuration of a touch sensor panel in terms of the signal profile between a stylus and an electrode. This concept is explained by example with reference to  FIGS. 4A and 4B .  FIGS. 4A and 4B  relate to an example signal profile in an x-axis of an example electrode  411  having a pitch with a distance D 1  as shown. As shown in  FIG. 4A , an object, such as a stylus  421 , can be at a distance above an electrode  411  and moved in an x-direction across electrode  411 . At each point along the x-axis, a signal coupling Csig exists between the stylus and the electrode, which varies as the stylus moves from the midpoint M of electrode  411 .  FIG. 4B  illustrates a plot of an example signal profile, which can correlate to the signal Csig sensed on electrode  411  from stylus  421  as the stylus is moved in the x-direction. In some examples, such as when the stylus  421  is an active stylus, the signal Csig may represent a signal transduced by the stylus on the electrode. In some examples, the signal Csig may correspond to a self-capacitance of an object detected by the electrode or a change in mutual capacitance between a drive electrode and sense electrode. The x-axis of the plot in  FIG. 4B  can correlate to the position of the stylus in the x-axis relative to a midpoint M of an electrode  411 , and the y-axis of the plot in  FIG. 4B  can correlate to a normalized signal measurement at each x-position along the x-axis. The midpoint M of the x-axis of the plot in  FIG. 4B  can correspond to the midpoint M of electrode  411  shown in  FIG. 4A . As shown in  FIGS. 4A and 4B , the signal level can have a maximum value  423  when the stylus is at the midpoint of electrode  411 , and the signal level can decrease as the stylus traverses the x-axis away from the midpoint. In some examples, the signal profile can be non-linear. As discussed in more detail below, the signal profile between a stylus and an electrode can vary greatly based on a variety of factors including, for example, the circuit configuration of the electrodes. 
     In some examples, the wobble error of a touch sensor panel can correlate with the signal profile between a stylus and electrodes formed on the touch sensor panel.  FIGS. 5A and 5B  illustrate the correlation between three different example signal profiles  531 - 533  and the wobble error  541 - 543  associated with each of the example signal profiles.  FIG. 5A  illustrates plots of three example signal profiles  531 ,  532  and  533 . As described above with reference to  FIG. 4A and 4B , each signal profile can represent a signal Csig sensed on an electrode  411  from a stylus  421  as the stylus is moved in an x-direction. Each of the signal profiles  531 ,  532  and  533  in  FIG. 5A  can correspond to three hypothetical electrode configurations (not shown) A, B and C, each indicated by a different line pattern. Electrode configurations A-C can differ, for example, in electrode shape or circuit configuration. 
       FIG. 5B  illustrates three example plots of the error in position calculation versus the actual position (i.e., wobble error) when calculating position of a stylus by taking a weighted centroid including a set of electrodes along an x-axis, with each error plot  541 ,  542  and  543  corresponding to a set of electrodes with electrode configurations A, B, and C, respectively.  FIG. 5B  is similar to the plot of  FIG. 3B , however, unlike the plot in  FIG. 3B , which has an x-axis spanning the length of the touch sensor panel, the x-axis of  FIG. 5B  spans only the distance D 1  (e.g., the distance of the pitch) immediately surrounding a single electrode as shown. In some examples, the single oscillation in the error plots  541 ,  542  and  543  shown in  FIG. 5B  can be similar to one of the many oscillations shown in  FIG. 3B . For clarity, each of the example electrode configurations A-C in  FIGS. 5A and 5B  are assumed to have an equal pitch and midpoint. 
     In some examples, if a signal profile is very non-linear, position estimation algorithms, such as that listed in equation (1), can produce higher wobble error when a stylus is positioned between touch nodes. In the example of  FIGS. 5A and 5B , an electrode configuration A can correspond to signal profile  531  and wobble error plot  541 . As shown in  FIG. 5A , the shape of signal profile  531  corresponding to electrode configuration A is the least “spread” of signal profiles  531 - 533 . In other words, signal profile  531  is the least linear signal profile as a stylus is moved away from the peak. As shown in  FIG. 5B , error plot  541  corresponding to electrode configuration A has the most wobble error of the error plots  541 - 543 .  FIG. 5A  also illustrates that the shape of signal profile  532  corresponding to electrode configuration B is more linear than signal profile  531 . As shown in  FIG. 5B , error plot  542  corresponding to electrode configuration B has less wobble error than error plot  541  corresponding to electrode configuration A.  FIG. 5A  further illustrates that the shape of signal profile  533  corresponding to electrode configuration C is the most linear of signal profiles  531 - 533 , and its corresponding error plot  543  in  FIG. 5B  has the least wobble error of error plots  544 - 543 . Thus, as illustrated in these examples, electrode configurations with more linear signal profiles are correlated with lower wobble error. 
     The configurations and plots represented in  FIGS. 5A and 5B  are presented only as examples of how a more linear signal profile can be correlated with lower wobble error, and should not be understood to represent specific values or scale. It should be understood that wobble error of a touch sensor panel can be determined by other factors in addition to configuration of the electrodes in the touch sensor panel, such as, for example, position calculation algorithms used, stylus shape, and electrode pitch. Moreover, the solutions discussed in this disclosure can apply to configurations different from those discussed with respect to  FIGS. 5A and 5B , including configurations of mutual capacitance, self-capacitance, and configurations wherein the touch object is not a stylus. 
     As discussed above, electrodes having a more linear signal profile can correlate to a lower wobble error. Therefore, it can be beneficial to configure each electrode in a touch sensor panel to have a more linear signal profile by, for example, spreading the signal profile associated with each electrode outwardly toward adjacent electrodes. Thus, in some examples, it can be beneficial to form sense electrodes to include multiple bars extending along the length of the sense electrode and connected at one or both ends. Some examples of these multiple-bar sense electrode configurations will now be discussed below with reference to  FIGS. 6-18 . 
       FIG. 6  illustrates a simplified diagram of an exemplary touch sensor panel system  600  including a plurality of sense electrodes  611 - 613 , drive electrodes  641 - 643 , touch sensing circuitry  621 , and a plurality of conductive traces  630  coupling electrodes to the touch sensing circuitry  621 . Electrodes can correspond, for example, to electrodes in a row electrode  201  or column electrode  202  as shown in  FIG. 2A . Touch sensing circuitry  621  can perform touch position estimation based on the signals detected by one or more of the plurality of sense electrodes, as discussed above with reference to  FIG. 2A . For ease of description, only three sense electrodes and three drive electrodes are shown, however, it is understood that the scope of this disclosure includes touch sensor panels with more sense electrodes as well as other supporting circuitry (e.g., drive circuitry) not shown in  FIG. 6 . 
     In some examples, each sense electrode (e.g., sense electrode  611 ) can include two or more bars (e.g., bars  650 ) extending along the sensor with each bar electrically connected to one another at one or both ends, although it should be understood that in other examples, not all bars may be connected at both ends, and in still other examples, all bars are disconnected at the end away from the touch sensing circuitry. As shown in  FIG. 6 , some bars can extend along the length of the sense electrode, while other bars (not shown) may only extend partially along the length of the sense electrode, or may have one or more conductive breaks along the bar. In some examples, the bars of sense electrodes may be connected to one another in the bezel areas of the touch sensor panel. The examples disclosed herein may include bars that are uniformly or non-uniformly spaced. Additionally, the examples disclosed herein may include sense electrodes having bars that are of uniform or non-uniform width. The dimensions and layout of the sense electrodes will be discussed in more detail below, but it should be noted here that sense electrodes can be configured to have any number of bars and any combination of widths and spacing which produce a more desirable (e.g., more linear) signal profile. 
     An exemplary mathematical procedure for engineering output signal profiles for the sense electrodes disclosed herein will now be described.  FIGS. 7A-7B and 8A-8B  compare a customary sense electrode configuration with an exemplary multiple-bar configuration according to examples of this disclosure. 
       FIG. 7A  illustrates a customary sense electrode configuration  700  according to examples of this disclosure wherein sense electrodes having a pitch P 1  equal to a distance D PITCH , where each sense electrode includes a single bar  751 .  FIG. 7B  illustrates a corresponding example signal profile  760  for a sense electrode in the configuration shown in  FIG. 7A . The x-axis of the graph in  FIG. 7B  represents the position of an object (e.g., a stylus) along an x-direction of a touch sensor panel, and the y-axis represents the signal amplitude (e.g., the coupling capacitance) detected at the sense electrode at each point along the x-axis, as similarly described above with reference to  FIGS. 4A and 4B . The midpoint M marked on the graph can represent the midpoint of the sense electrode, and the distance D PITCH  indicated on the graph can correspond to the distance of the pitch P 1 . 
       FIG. 8A  illustrates an exemplary 3-bar sense electrode configuration  800  according to examples of this disclosure. As shown, each of sense electrodes  811 - 814  can be separated into three bars  851 ,  852 , and  853 , which can be electrically connected to one another at both ends. For ease of explanation, bars  851 - 853  shown in  FIG. 8A  are assumed to be of uniform weight and spacing. Moreover, for ease of comparison, pitch P 1  shown in the configuration of  FIG. 8A  is assumed to be equal to pitch P 1  shown in the configuration of  FIG. 7A . As shown, the additional bars extend the sense electrodes closer to adjacent cells. 
       FIG. 8B  illustrates an example signal profile  860  for a 3-bar sense electrode in the configuration shown in  FIG. 8A . As in  FIG. 7B , the x-axis of the graph in  FIG. 8B  represents the position of an object (e.g., a stylus) along an x-direction of a touch sensor panel, and the y-axis represents the signal amplitude (e.g., the coupling capacitance) detected at the sense electrode at each point along the x-axis, as similarly described above with reference to  FIGS. 4A and 4B . The midpoint M marked on the graph can represent the midpoint of the sense electrode, and the distance D 1  indicated on the graph can correspond to the distance of the pitch P 1 . As illustrated in  FIG. 8B , the signal profile  860  of sense electrode  811  can be constructed as a superposition of weighted adjacent coupling capacitance profiles  861 ,  862 , and  863  corresponding to bars  851 ,  852 , and  853 , respectively. That is, the capacitance profile of sensor  811  can be modeled as three separate capacitance profiles representing bars  851 - 853 , even though the actual signal amplitude detected at sense electrode  811  does not distinguish between the coupling capacitance at the bars. In some examples, the superposition of the bars within a sensor to construct the signal profile of the sensor can be a linear or polynomial superposition. 
     As illustrated by comparing the signal profile  760  of the single bar sense electrode  711  (i.e., a customary sense electrode) shown in  FIG. 7A  with the signal profile  860  of the multiple-bar sense electrode  811  shown in  FIG. 8A , the signal profile of a multiple-bar sense electrode can be more linear than the signal profile of a customary sense electrode. As discussed above with reference to  FIGS. 4A-4B , a more linear signal profile can correlate to less wobble error in a touch sensor panel. 
     In general, the signal profile of a sense electrode having multiple bars can be represented by Equation (2) below:
 
 S   i   =W   1   ×P   1   +W   2   ×P   2   +W   3   ×P   3   +W   4   ×P   4   +W   5   ×P   5 + . . .   (2)
 
     Where S i  represents the output signal of the multiple-bar sense electrode, P N  represents the capacitance coupling profile of an n th  bar, and W N  represents the weight applied to the n th  bar. For example, applying Equation (2) to the 3-bar sense electrode discussed with reference to  FIG. 8A , the output signal S i  can be represented as shown below in Equation (3):
 
 S   i   =W   1   ×P   1   +W   2   ×P   2   +W   3   ×P   3    (3)
 
Assuming bars 1-3 have equal weight (e.g., W 1 =W 2 =W 3 =1) and are equally spaced, the output signal S i  can be further simplified as a linear superposition of three adjacent signals, as shown in the graph of  FIG. 8B , and represented as in Equation (4) below:
 
 S   i   =P   1   +P   2   +P   3    (4)
 
     In some examples, the weight attached to a sense electrode bar can correspond to one or more of the dimensions (e.g., width and thickness) of the bar, the material the bar is composed of, the spacing of the bar in relation to the rest of the sense electrode, and additional circuitry (e.g., resistors) coupled to the bar, though the scope of this disclosure is not limited to these specific examples. By mixing adjacent signals with certain weights, output signal S i  can be engineered to achieve a desired peak signal amplitude, profile width, and shape. 
     It should be understood that the number of bars implemented in a multiple-bar sense electrode can vary depending on the configuration of the touch panel (e.g., the stackup of the touch sensor panel), as well as design goals and constraints (e.g., layout, pitch size, and routing concerns). Moreover, as discussed in more detail below, the width and/or spacing of bars in a multiple-bar sensor may be non-uniform. 
       FIG. 9A  illustrates an exemplary 4-bar sense electrode configuration  900  according to examples of this disclosure. As shown, sense electrodes  911 - 913  are in a 4-bar configuration having bars  951 - 954 . As shown, the width of bars  951 - 954  can be non-uniform. In this example, bars  951  and  954  having a width W 1  can be positioned on or near the outside of the sense electrode, while bars  952  and  953  having a greater width W 2  can be positioned toward the center of the sense electrode. As will be explained, this configuration can also correspond to a more linear signal profile than a customary (i.e., single-bar) sense electrode, which can correlate to lower wobble error in the touch sensor panel. 
       FIG. 9B  illustrates an example signal profile of the sense electrode in a 4-bar configuration illustrated in  FIG. 9A , wherein the bars  951 - 954  are of non-uniform width. As illustrated in  FIG. 9B , the signal profile  960  can be constructed as a superposition of weighted adjacent coupling capacitance profiles of the bars in the sense electrode. Referring back to  FIG. 9A , because bars  952  and  953  are of a greater width W 2  than the width W 1  of bars  951  and  954 , the corresponding capacitance profiles shown in  FIG. 9B  are higher, resulting in an overall signal profile  960  which is more linear than the signal profile  760  of the single-bar sensor as shown in  FIG. 7B  or the signal profile  860  of the three-bar sensor as shown in  FIG. 8B . The output signal of the 4-bar sense electrode can be expressed mathematically as Equation (5) below:
 
 Si=W   1   ×P   1   +W   2   ×P   2   +W   3   ×P   3   +W   4   ×P   4    (5)
 
Where W 1 -W 4  can represent the respective weight assigned to bars 1-4. If bars 1 and 4 are of equal weight (e.g., of equal width), and bars 2 and 3 are of equal weight, the mathematical representation of the output signal simplifies to Equation (6) below:
 
 Si=W   1 ( P   1   +P   4 )+ W   2 ( P   2   +P   3 )   (6)
 
Where W 2  is greater than W 1 .
 
     As discussed with reference to  FIGS. 9A-9B  above, it can be beneficial to configure sense electrodes to have multiple bars of non-uniform width. However, in some examples, sense electrodes having non-uniform width can also cause optical non-uniformities in the touch sensor panel. Specifically, when multiple-bar sense electrodes such as  951 - 954  in  FIG. 9A  are formed in a repeated pattern across a touch screen, the distinction between bars  951 ,  954  and bars  952 ,  953  can be visually perceived by a touch screen user. Accordingly, in some examples, it can be beneficial to form multiple-bar sense electrodes which have a desired (e.g., more linear) signal profile, but which are also more optically uniform. 
       FIG. 10A  illustrates exemplary multiple-bar sense electrodes  1011 - 1013  in a split-bar configuration  1000  according to examples of this disclosure. As will be discussed, this configuration can correspond to a more linear signal profile, while overcoming the visual non-uniformities of multiple-bar sense electrodes having bars of non-uniform width. Conceptually, in this configuration, bars of a greater width in a non-split-bar configuration (e.g., bars  952  and  953  shown in the configuration of  FIG. 9A ) can essentially be divided in half lengthwise to form “split bars.” In the example configuration shown in  FIG. 10A , sense electrode  1011  has 6 bars  1051 - 1056 , including 4 split bars  1052 ,  1053 ,  1054 , and  1055  (i.e., a “6 bar 4 split sense electrode”). Split bars can be spaced closely together in groups of two or more, with the distance D 1  between adjacent split bars in a group being relatively small, while other adjacent bars within the sensor (e.g., two adjacent bars belonging to two separate groups) can be spaced at a greater distance D 2 . For example, the distance D 1  between adjacent split bars can be small enough that the signal profile of the split-bar sense electrode resembles the signal profile of a multiple-bar sense electrode having bars of non-uniform width, as will be explained in more detail below. In some examples, the distance D 1  between split bars can be smaller than the width W 1  of the split bars. Moreover, in some examples, the width of the split bars can be the same as the width of the non-split bars, that is, all bars are of uniform width. One of skill in the art would appreciate that the same widths includes tolerances that result in a 20% deviation. 
     Similar to the configuration described with reference to  FIG. 9A , split bars  1052 - 1055  can be positioned toward the inside of sense electrode  1011 , while non-split bars  1051  and  1056  can be positioned at the outside edges of the sense electrode. In some examples, the distance D 3  between two adjacent sense electrodes can be the same as the distance D 1  between adjacent split bars, which can improve optical uniformity by making the separation between split bars  1052 - 1053  and  1054 - 1055  resemble the separation between non-split bars at the edges of two adjacent sense electrodes (e.g.,  1056  and  1057 ). As shown in the example configuration of  FIG. 10A , the width W 1  of split bars can be the same as the width of non-split bars, which can further improve optical uniformity, although in other examples, the width of split bars may be different from the width of non-split bars. One of skill in the art would appreciate that the same widths and same distances mentioned here can include tolerances that result in a 20% deviation. 
       FIG. 10B  illustrates an example signal profile  1060  of the 6-bar, 4-split touch electrode configuration shown in  FIG. 10A . As indicated in the graph shown in  FIG. 10B , signal profile  1060  can be constructed as a superposition of weighted adjacent coupling capacitance profiles  1061 - 1066 , respectively corresponding to bars  1051 - 1056  in electrode sensor  1011 . As indicated in  FIG. 10B , the signal profile  1060  of an electrode sensor in a split-bar configuration can effectively match a signal profile of a sense electrode in a multiple-bar configuration where the split bars are combined (e.g., the signal profile  960  shown in  FIG. 9B ). The output signal of a 6-bar 4-split sensor electrode (e.g., the sense electrode in the configuration shown in  FIG. 10A ) can be expressed mathematically as Equation (7) below:
 
 S   i   =W   1   ×P   1   +W   2   ×P   2   +W   3   ×P   3   +W   4   ×P   4   +W   5   ×P   5   +W   6   ×P   6    (7)
 
When split bars 2, 3, 4, and 5 have equal weight (e.g., equal width) such that W 2  =W 3 =W 4 =W 5 , and non-split bars 1 and 6 also have equal weight such that W 1 =W 6 , Equation (7) simplifies as shown in Equation (8) below:
 
 S   i   =W   1 ( P   1   +P   6 )+ W   2 ( P   2   +P   3   +P   4   +P   5   ) (8)
 
     It should be noted that sense electrodes in a split-bar configuration are not limited to the examples shown here, but can include configurations which have more than two sets of split bars. Moreover, sense electrode configurations in which split bars and non-split bars of a non-uniform width and spacing are also contemplated within the scope of this disclosure. In addition, although the weight assigned to each bar has been primarily discussed herein with reference to the width of bars, the weight assigned to a bar can be affected by a multitude of factors including, but not limited to, one or more of the material of the bar, cross sectional dimensions of the bar, and any additional circuitry (e.g., resistors) coupled to the bar. 
     In some examples, the optical uniformity of sense electrodes in a split-bar configuration can be further improved by adding dummy (e.g., floating) features in the space between bars.  FIG. 11  illustrates a magnified view of an exemplary split-bar sense electrode layout which includes dummy elements  1170 . The sense electrode  1111  shown in  FIG. 11  can correspond, for example, to sense electrode  1011  shown in  FIG. 10A , and includes 6 bars  1151 - 1156 , 4 of which ( 1152 - 1155 ) are split bars. Dummy elements  1170  may be rectangular, square, or some other shape. By including dummy elements in the space between bars, optical transparency and reflection can appear more visually uniform throughout the touch sensor panel. 
     In some examples, dummy elements  1170  can be of the same width of one or more of the bars in the sense electrode. Though the example illustrated in  FIG. 11  includes dummy elements only between adjacent bars that are not in a split bar group, other configurations not shown may include dummy elements between split bars within a group. In this example, all bars and dummy elements have the same width W and separation distance D, which is less than W, though one skilled in the art would appreciate that the same width and distance can include tolerances that result in a 20% deviation. 
     In general, the width of dummy elements and bars can be calculated mathematically as in Equation (9) below:
 
Width=Pitch/( N   BARS   +N   DUMMY ×( N   BARs /2))− D    (9)
 
where “Width” is the width of bars and dummy elements, N BARS  represents the total number of bars in each sense electrode, N DUMMY  represents the number of dummy elements between each bar, D is the separation distance between each bar or dummy element, and “Pitch” is the pitch of the sense electrodes.
 
     It should be noted that dummy elements can be of any shape (e.g., a squiggle shape) and need not be rectangular. In some examples, the material forming dummy elements  1170  can be a transparent conductive material such as ITO. In some examples, the dummy elements can be formed of the same material as the ITO that forms sense electrodes  1110  in order to provide the best optical index matching to the ITO. In other examples, index matching materials may be applied to the ITO layer forming floating conductive segments to better match the optical index of the ITO layer forming electrodes. Moreover, dummy elements  1170  can be formed on either the same layer or a different layer from the layer forming sense electrodes  1110 . 
     As discussed with reference to  FIGS. 4A-4B  above, it can be beneficial to configure sense electrodes such that the sensor profile of the sense electrode is widened in order to reduce wobble error in the touch sensor panel. Accordingly, in some examples, the sensor profile of a sense electrode can be widened by spreading sense electrodes across adjacent electrodes. In other words, the width of the sense electrode can be configured as to exceed the pitch. 
       FIGS. 12A-12B  illustrate exemplary multiple-bar sense electrodes in a touch sensor panel layout which includes overlapping electrodes according to examples of this disclosure. In such examples, sense electrodes can be implemented in a dual-sided touch arrangement on a dual-sided substrate (e.g., a dual-sided Indium Tin Oxide (DITO) substrate)  1280  with a first set of sense electrodes (e.g., sense electrode  1211  and  1213 ) formed on a first side of the substrate, and a second set of sense electrodes (e.g., sense electrode  1212 ) formed on a second side of the substrate as to overlap with the first set of sense electrodes. In other configurations, the first and second set of electrodes can be formed on different layers (e.g., on different substrates). Each sense electrode can include three bars  1251 - 1253  (although the third bars in sense electrodes  1211  and  1213  are not shown in  FIG. 12A  for purposes of simplifying the figure). In these configurations, sense electrodes can be positioned such that the spacing is collectively uniform between all of the bars of the first and second sets of sense electrodes. In other examples not shown, sense electrodes in an overlapping configuration can also utilize split bars as similarly discussed with reference to  FIGS. 10A-10B  above. 
     Although the overlapping configuration shown in  FIGS. 12A-12B  can produce a desirable signal profile, the use of dual-sided substrate for sense electrodes can increase manufacturing complexities and costs. Therefore, it can be beneficial to maintain the desirable signal profile of an overlapping configuration, but without requiring a DITO substrate. 
       FIGS. 13A-13B  illustrates exemplary sense electrodes in an interleaving configuration formed on a single-sided Indium Tin Oxide (SITO) substrate according to examples of this disclosure. In some examples, a first set of sense electrodes are formed on the SITO substrate, and a second set of sense electrodes are also formed on the same side of the SITO substrate as the first set of sense electrodes such that the first set of sense electrodes and the second set of sense electrodes are interleaved. In the example shown in  FIG. 13A , sense electrode  1311  can have a center bar  1352 , and can include two sets of projections  1391 - 1392 , which are positioned at opposite sides of the center bar. Projections in one electrode (e.g., projections  1392  in electrode  1311 ) can interleave with projections in an adjacent electrode (e.g., projections  1393  in electrode  1312 ). Projections can be L-shaped and can include a vertical portion (that is, a portion in the direction parallel to the length of the sense electrode) and a horizontal portion (that is, a portion in the direction perpendicular to the length of the sense electrode). The vertical portion of the projections can be conceptually compared to the bars of the overlapping configuration discussed with reference to  FIG. 12A . For example, projections  1391  in  FIG. 13A  can be conceptually compared to bar  1251  in  FIG. 12A . 
       FIG. 13B  illustrates a magnified view of a portion of sense electrode  1311 . As shown, adjacent bars can be separated by a distance D BAR , the vertical portions of projections  1391  can have a width W P , and center bar  1351  can have a width W C  which is greater than width W C . In some examples, the distance D TOTAL  between the outermost points of the sense electrode in a direction perpendicular to the length of the sense electrode can be greater than the pitch. 
       FIGS. 14A-14C  illustrate exemplary sense electrodes in an interleaving split-bar configuration according to examples of this disclosure. As shown, sense electrode  1411  can include two split-bars  1451  and  1452  toward the center of the sense electrode, and two sets of projections  1491 - 1492  positioned toward the edges at opposite sides of the split-bars. The projections can be L-shaped and can each include a horizontal portion and a vertical portion. As with the examples discussed with reference to  FIG. 12A-12B , the projections of sensor electrodes in these configurations can interleave with projections in adjacent sense electrodes. 
       FIG. 14B  illustrates an exemplary sense electrode in another interleaving split-bar configuration according to examples of this disclosure. As shown, sense electrode  1414  can include 4 bars, including two bars ( 1453 ,  1454 ) in a split-bar configuration. As similarly discussed with reference to  FIG. 10A  above, the distance between split bars  1453  and  1454  can match the distance between sense electrodes  1414  and  1415 . In some examples, adjacent bars that are not in a split bar group (e.g.,  1454  and  1455 ) can be interleaved as similarly described with reference to  FIG. 14A  above. Moreover, in some examples, the configurations of  FIGS. 14A and 14B  can be combined, for example, such that a sense electrode interleaves with an adjacent sense electrode on a first side (as in  FIG. 14A ) and is separated by a small distance from an another adjacent sense electrode on a second side (as in  FIG. 14B ). 
       FIG. 14C  illustrates a magnified view of a portion of sense electrode  1411  shown in  FIG. 14A . As shown, center bars  1451  and  1452  can be separated by a distance D CENTER , while vertical portions of projections  1491  can be horizontally separated from the nearest center bar by a distance D PROJ , which can be greater than D CENTER . Additionally, the vertical portions of projections  1491  can have a width W P , and center bars  1451  and  1452  can both have a width W C  which can be greater than width W P . As in the example discussed with reference to  FIGS. 13A-13B , the distance D TOTAL  between the outermost points of the sense electrode in a direction perpendicular to the length of the sense electrode can be greater than the pitch. 
       FIGS. 15A-15B  illustrate other exemplary sense electrodes in an interleaving configuration in which each sense electrode can have four sets of projections according to examples of this disclosure. As shown in  FIG. 15A , each sense electrode  1511  can have a center bar  1551  and four sets of projections  1591 - 1594 , with two sets of projections each positioned on opposite sides of the center bar. As with the examples discussed with reference to  FIGS. 13A-13B , the projections in these configurations can interleave with projections in adjacent sense electrodes. 
       FIG. 15B  illustrates a magnified view of a portion of sense electrode  1511 . As shown, center bar  1551  can be separated from the nearest projection by a distance D P1 , and vertical projection  1591  can also be separated horizontally from the nearest adjacent vertical projection by distance D P1 . Additionally, the vertical portions of innermost projections  1592  can have a width W P1 , while the vertical portion of outermost projections  1591  can have a width W P2  which is greater than width W P1 . As in the examples discussed with reference to  FIGS. 13A-13B , the distance D TOTAL  between the outermost points of the sense electrode in a direction perpendicular to the length of the sense electrode can be greater than the pitch. 
       FIGS. 16A-16D  illustrate example systems in which the multiple-bar sense electrode configurations for reducing wobble error (e.g., stylus tip wobble) according to examples of the disclosure can be implemented.  FIG. 16A  illustrates an example mobile telephone  1636  that includes a touch screen  1624  and other computing system blocks that can implement the multiple-bar sense electrode configurations for reducing wobble error according to various examples.  FIG. 16B  illustrates an example digital media player  1640  that includes a touch screen  1626  and other computing system blocks that can implement the multiple-bar sense electrode configurations for reducing wobble error according to various examples.  FIG. 16C  illustrates an example personal computer  1644  that includes a touch screen  1628  and other computing system blocks that can implement the multiple-bar sense electrode configurations for reducing wobble error according to various examples.  FIG. 16D  illustrates an example tablet computing device  1648  that includes a touch screen  1630  and other computing system blocks that can implement the multiple-bar sense electrode configurations for reducing wobble error according to various examples. The touch screen and computing system blocks that can implement the multiple-bar sense electrode configurations for reducing wobble error can be implemented in other devices including in wearable devices. 
     Thus, the examples of the disclosure provide various multiple-bar sense electrode configurations which make the signal profile associated with the sense electrode more linear, thus reducing stylus tip wobble and increasing touch sensor panel performance. 
     Some examples of the disclosure are related to touch sensor panel comprising: a first electrode including a first plurality of electrically connected bars extending in a first direction parallel to a length of the first electrode, wherein a first set of bars of the first plurality of bars are immediately adjacent to one another and are each separated from one another by a first distance, and a second set of bars of the first plurality of bars are immediately adjacent to one another and are each separated from one another by a second distance, greater than the first; and a second electrode, wherein the second electrode is separated from the first electrode by the first distance. Additionally or alternatively to one or more of the examples disclosed above, in some examples the second electrode has a second plurality of electrically connected bars, and a first edge bar in the first plurality of electrical connected bars in the first electrode is separated from a second edge bar in the second plurality of electrically connected bars by the first distance. Additionally or alternatively to one or more of the examples disclosed above, in some examples the first edge bar has a first width greater than the first distance. Additionally or alternatively to one or more of the examples disclosed above, in some examples the second electrode is the same shape as the first electrode. Additionally or alternatively to one or more of the examples disclosed above, in some examples the first plurality of electrically connected bars are connected at a first and second end of the electrode and separated along the length of the electrode between the first and second end of the touch sensor. Additionally or alternatively to one or more of the examples disclosed above, in some examples at least one of the first and second ends of the electrode are located in a bezel area of the touch sensor panel. Additionally or alternatively to one or more of the examples disclosed above, in some examples the first electrode is symmetric about a separation line between two of the first set of bars. Additionally or alternatively to one or more of the examples disclosed above, in some examples the first electrode and second electrode are symmetric to one another about a separation line between the first and second electrode. Additionally or alternatively to one or more of the examples disclosed above, in some examples a first bar is in both the first set of bars and the second set of bars. Additionally or alternatively to one or more of the examples disclosed above, in some examples the number of bars in the first set is two and the number of bars in the second set is two. Additionally or alternatively to one or more of the examples disclosed above, in some examples the first set of bars is positioned further from the second electrode than the second set of bars. Additionally or alternatively to one or more of the examples disclosed above, in some examples each of the bars in the first plurality of bars have a same width. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the touch sensor panel further comprises: a plurality of dummy elements between two or more bars in the second set of bars in the first plurality of bars. Additionally or alternatively to one or more of the examples disclosed above, in some examples no dummy elements are positioned between any two of the first set of bars in the first plurality of bars. Additionally or alternatively to one or more of the examples disclosed above, in some examples the dummy elements each have a width equal to a width of each of the second set of bars in the first plurality of bars. Additionally or alternatively to one or more of the examples disclosed above, in some examples the dummy elements are separated from each other by the first distance. Additionally or alternatively to one or more of the examples disclosed above, in some examples: the first plurality of bars comprises a number of bars; the plurality of dummy elements comprises a number of dummy elements; a distance between any adjacent dummy element or bar is the same as the first distance; the first and second electrodes each have a same pitch; and the dummy elements and the first plurality of bars all have a same width; and the width is governed by the pitch, number of bars, number of dummy elements, and first distance. 
     Some examples of the disclosure are related to touch sensor panel comprising: a first electrode including: a first bar extending in a first direction parallel to a length of the first electrode and having a first width; a second bar electrically connected to the first bar, parallel to the first bar, and having the first width; a first set of projections, each having an L shape and extending from the first bar; a second electrode including a second set of projections, each having an L shape and; wherein the first set of projections and the second set of projections interleave. Additionally or alternatively to one or more of the examples disclosed above, in some examples each of the first set of projections has a horizontal portion and a vertical portion, and wherein the vertical portion of each of the first set of projections has a second width different from the first width. Additionally or alternatively to one or more of the examples disclosed above, in some examples, the touch sensor panel further comprises:: a third set of projections, each having an L shape in a same orientation as each of the first set of projections, wherein each of the third set of projections is connected to a corresponding projection of the first set of projections and is located further from the first bar than each of the first set of projections; each of the third set of projections has an L shape in a same orientation as each of the first set of projections. Additionally or alternatively to one or more of the examples disclosed above, in some examples: a distance across the first electrode in a second direction perpendicular to the first direction is greater than a pitch of the touch sensor panel. 
     Although the disclosure and examples 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 disclosure and examples as defined by the appended claims.