Touch Sensor Device and Method

A common capacitive touch sensor may have a two dimensional array of transparent conductive strips going from edge to edge on a substrate layer or sheet of a touch sensor. According to some aspects, there is provided a capacitive touch sensor device including a substrate layer and a plurality of resonant circuits. Each resonant circuit includes an electrode, and each resonant circuit has a respective resonance frequency that is unique within the plurality of resonant circuits. The electrodes of the resonant circuits are distributed on the substrate layer. A controller for a touch sensor is also provided that includes a signal generator to drive at least one plurality of resonant circuits, where each resonant circuit has a respective resonance frequency. The signal generator is tunable to generate input signals at each of the resonance frequencies. The controller also includes a detector.

FIELD OF THE DISCLOSURE

The present disclosure relates generally to capacitive touch sensing technology, and more particularly to Radio Frequency (RF) touch sensing devices.

BACKGROUND

Of various interfaces available for interacting with a computer system, one of the easiest to use and understand is the touchscreen. This technology allows a user to simply touch an icon or picture to navigate through the system, display the information the user is seeking, and to enter data. For this reason, this technology is widely used in many applications, including desktop computers, tablet computers, mobile devices, bank machines, information kiosks, restaurants, cars, navigation systems, etc.

A number of different conventional touchscreen technologies exist. These methodologies include resistive, capacitive, surface acoustic wave, infrared, and optical touchscreen technology.

A common capacitive touch sensor (e.g. for a touchscreen) has a two dimensional array (e.g. criss-cross) of transparent conductive strips going from edge to edge on a substrate layer or sheet of a touch sensor. A number of conductor lines connect the strips to the inputs of a microcontroller. The transparent conductive stripes are typically made of indium-tin-oxide (ITO). Alternatively, a thin metal mesh may be deposited on a glass substrate. Each conductive strip may form a capacitor of around 50-200 pF in value, for example. A protective top layer of glass or plastic will typically cover the substrate layer and the conductive strips. When a human finger (or another member with a conductive surface) is applied over one of the conductive strips, the capacitance of this strip with respect to ground changes, and this change in capacitance is detectable. For example, the capacitance for the strip may increase by a value of 10 to 30 pF. Thus, by monitoring each conductive strip, it can be determined where the sensor was touched. For two-dimensional sensing, two overlapping sets of strips in perpendicular directions may be monitored, thereby allowing for determination of the position of the touch in two dimensions.

Conventional capacitive touch sensors may use self-capacitance or mutual capacitance. In self-capacitance touch sensors, the capacitance of each electrode strip is detected separately. In mutual capacitance touch sensors, the mutual capacitance between two electrode strips (e.g. two perpendicular channels) is detected. For example, in a grid of horizontal and vertical electrodes, the mutual capacitance at each intersection of the horizontal and vertical electrodes is monitored.

One method of detecting changes in capacitance is by individually monitoring resonant circuit outputs for changes. A radio frequency (RF) touch sensors may employ a plurality of resonant circuits, each including of inductor and capacitor (LCR circuit). The properties of such LCR resonant circuits, consisting of a series or parallel connection of inductor and capacitor, are well known. If an RF modulated voltage is applied, the impedance of an LCR resonant circuit depends on the frequency of the applied signal. The LCR resonant circuit has a resonance frequency that are a function of the inductance value of the inductor and the capacitance value of the capacitor. When the capacitance of a resonant circuit (or the mutual capacitance of a pair of perpendicular electrodes of two resonant circuits) changes, the resonant frequency for that circuit also changes. Thus, a change in the voltage at a test point on the resonant circuit may be detected due to the impedance change.

A resonant circuit including one or more electrode strips deposited on a substrate may commonly be referred to as a “channel”. A conventional capacitive touch sensor may include multiple channels, each with the same resonant frequency. The multiple channels are typically sequentially scanned. Scanning is typically accomplished by sequentially driving electrodes of the channels with an input signal at the resonant frequency. This scanning method requires an input of each channel to be individually and separately connected to the input signal source so that the channels can be individually and separately driven. The channels must also have outputs individually connected to a detector. A controller including an input signal source and a detector typically controls the scanning process by selectively driving and measuring the output of the channels. As sensor size and/or resolution of the sensor increases, so does the number of electrodes and circuits being scanned. This, in turn, increases the number of connections that must be made between the inputs and outputs of the channels the controller. The high number of connections can take up substantial room on the substrate and also increases the number of wires or other connections between the touch sensor panel itself and the controller.

Another disadvantage of conventional capacitive touch sensors arises from the number of inputs and outputs being dependent on the number of channels included in the sensor. Different controllers and/or controller configurations may be needed to control different sensor devices due to the varying number of inputs and outputs that must be connected and managed. Controller complexity and cost may increase with a higher numbers of channels.

SUMMARY

According to one aspect, there is provided a capacitive touch sensor device comprising: a substrate layer; and a plurality of resonant circuits, each comprising at least one respective electrode, the electrodes of the plurality of resonant circuits being distributed on the substrate layer, and each of the plurality of resonant circuits having a respective resonance frequency that is unique within the plurality of resonant circuits.

In some embodiments, the capacitive touch sensor further comprises, a respective circuit input and a respective circuit output, the plurality of resonant circuits being collectively connected to the respective circuit input and collectively connected to the respective circuit output.

In some embodiments, for each said resonant circuit, the at least one respective electrode comprises at least one electrode strip.

In some embodiments, the at least one electrode strip comprises a first electrode strip and a second electrode strip parallel to and spaced apart from the first electrode strip.

In some embodiments, the capacitive touch sensor further comprises, a signal generator that selectively generates signals at each of the resonance frequencies to drive the plurality of resonant circuits.

In some embodiments, the capacitive touch sensor further comprises, a detector that measures output of the plurality of resonant circuits.

In some embodiments, the capacitive touch sensor further comprises, a processor that controls the tunable signal generator and the detector to scan the plurality of resonant circuits, said scanning comprising sequentially generating the signals at each of the resonant frequencies, and measuring the output of the plurality of resonant circuits.

In some embodiments, the capacitive touch sensor further comprises, a respective circuit input and a respective circuit output, the plurality of resonant circuits being collectively connected to the respective circuit input and collectively connected to the respective circuit output, wherein the touch sensor device comprises a controller that comprises the signal generator, the detector and the processor, the controller being connected to said circuit input to drive the plurality of resonant circuits with the signals, and the controller being connected to said circuit output for the detector to measure the output of the plurality of resonant circuits.

In some embodiments, the capacitive touch sensor further comprises, at least one additional plurality of resonant circuits, each resonant circuit of the at least one additional plurality of resonant circuits comprising at least one respective electrode, the electrodes of the at least one additional plurality of resonant circuits being distributed on the substrate layer, wherein for each said additional plurality of resonant circuits, each said resonant circuit of the additional plurality has a respective resonance frequency that is unique within the additional plurality of resonant circuits.

In some embodiments, the capacitive touch sensor further comprises: a signal generator that selectively generates signals at each of the resonance frequencies of the pluralities of resonant circuits; a detector that measures output of each of the pluralities of resonant circuits; and switching circuitry connected to the signal generator for selectively driving the pluralities of resonant circuits with the signals.

In some embodiments, the capacitive touch sensor further comprises, a processor that controls the signal generator, the detector and the switching circuitry to scan each of the pluralities of resonant circuits, said scanning comprising, for each plurality of resonant circuits, sequentially generating the signals at each of the respective resonant frequencies, and measuring the output of the plurality of resonant circuits.

In some embodiments, at least one of the resonant frequencies for at least two of the pluralities of resonant circuits are substantially similar.

In some embodiments, the detector comprises at least one of: an analog to digital converter (ADC); and a comparator.

In some embodiments, the detector comprises at least one of: an analog to digital converter (ADC); and a comparator.

In some embodiments, each resonant circuit comprises a respective capacitor having a respective capacitance value and a respective inductor having a respective inductance value, a combination of the respective capacitance value and the respective inductance value being unique within the plurality of resonant circuits.

In some embodiments, the inductors of the plurality of resonant circuits are planar inductors, each planar inductor comprising at least one respective conductor layer deposited on the substrate layer.

In some embodiments, for each said planar inductor, the at least one respective conductor layer comprises at least one spiral shaped inductor coil.

In some embodiments, the resonant frequencies of the at least one plurality of resonant circuits are in the Radio Frequency (RF) range, and the signal generator is a tunable RF signal generator.

According to another aspect, there is provided a method for a capacitive touch sensor comprising at least one plurality of resonant circuits, each plurality of resonant circuits having a respective plurality of resonance frequencies, the method comprising: for each said at least one plurality of resonant circuits: sequentially generating signals at each of the respective plurality of resonance frequencies for driving the plurality of resonant circuits; and measuring an output of the plurality of resonant circuits.

In some embodiments, said sequentially generating comprises selectively generating signals at each of the respective plurality of resonance frequencies in a cyclic or random hopping pattern.

According to another aspect, there is provided a controller for a capacitive touch sensor comprising at least one plurality of resonant circuits, each plurality of resonant circuits having a respective plurality of resonance frequencies, the controller comprising: a signal generator to drive the at least one plurality of resonant circuits, the signal generator being tunable to selectively generate signals at each of the resonance frequencies for driving the at least one plurality of resonant circuits; and a detector to measure output the at least one plurality of resonant circuits.

In some embodiments, the controller further comprises a processor that controls the signal generator and the detector to scan the at least one plurality of resonant circuits, said scanning comprising, for each said plurality of resonant circuits, sequentially generating the signals at each of the resonant frequencies, and measuring the output of the plurality of resonant circuits.

In some embodiments, the controller further comprises switching circuitry connected to the signal generator for selectively driving the at least one plurality of resonant circuits with the signals.

In some embodiments, the controller further comprises at least one output, each said at least one output for connecting to a corresponding input of a respective one of the at least one plurality of resonant circuits.

In some embodiments, the detector comprises at least one of: an analog to digital converter (ADC); and a comparator. According to an aspect, the present disclosure provides an apparatus comprising: a radio frequency device; a dielectric substrate layer, such as glass; a first conductive layer such as an ITO layer, a mesh metal layer, or other transparent or translucent conductive material forming strips on the dielectric substrate; another dielectric substrate layer with a second conductive layer forming strips thereon; the strips of the first and second conductive layers forming a criss-cross system; a number of capacitors and inductors connected in pairs around the periphery of the dielectric substrate layers, each pair including one of the conductors and one of the inductors in series or in parallel, and each pair connected to a respective strip to form a respective resonant circuit comprising, the resonant circuits collective connected to an input and an output.

Other aspects and features of the present disclosure will become apparent, to those ordinarily skilled in the art, upon review of the following description of the specific embodiments of the disclosure.

DETAILED DESCRIPTION

The present disclosure provides a capacitive sensing apparatus and method, which may be used for touch sensor panels (e.g. a touchscreen) that may be engaged with a finger or fingers, or any other conductive object such as a stylus. The touch sensor may implement one-dimensional or two-dimensional sensing.

While the embodiments shown in the figures and described below are capacitive touch sensors operating in the RF range, aspects of the disclosure may also be implemented in non-RF touch sensors.

FIG. 1is a schematic diagram of an example serial LCR resonant circuit100. The circuit100consists of a fixed resistor R1, a fixed inductor L, a fixed capacitor C0, a variable capacitance Cf, and an RF signal input102. The fixed resistor R1, the fixed inductor L0and the fixed capacitor C0are connected in series between the RF signal input102and ground103. The fixed capacitor C0is connected to ground108. The variable capacitance Cf is connected in parallel with the fixed capacitor C0and represents additional capacitance induced by an external conductive object like a human finger touching the circuit100. The fixed capacitor C0represents the capacitance of an ITO strip or a mesh metal deposit on a glass substrate and an additional external capacitance. The value of the induced variable capacitance Cf is typically around 10 pF. The variable capacitance Cf will not be present in the absence of touch. The value of the fixed capacitor C0may be set, for example, at a value not more than ten times the variable capacitance Cf. In this example, the fixed capacitor C0is set at 100 pF. The value of the fixed inductance in this example is 10 pH, such that the resonance frequency is in the single digit megahertz range.FIG. 1shows also a series resistor RL, which represents resistance of the inductor and other parasitic resistive losses. The resistance RL in this example is assumed to be 3 ohm in this example. The fixed resistor R1is 100 ohm in this example. Of course, values of the resistors, capacitors, and inductors of LCR resonant circuits used in a touch sensor may vary. The specific values provided above are only by way of example. An output point104of the circuit100is also shown inFIG. 1.

FIG. 2is a graph200of first and second simulated frequency response curves202and204of the circuit100ofFIG. 1taken at the output point104. The first curve202shows the frequency response of the circuit with no touch (i.e. without the variable capacitance Cf). The second curve204shows the frequency response of the circuit including the variable capacitance Cf during a touch event. As shown inFIG. 2, the first curve202is an upside down bell shape curve with the peak resonance frequency of 5.05 MHz. In this example, the resonance frequency goes down to 4.8 MHz when the variable capacitor (from touch) is connected. As shown inFIG. 2, if the frequency of the input signal is continuously 5.05 MHz, and the circuit is touched, the input impedance of the circuit100at that frequency increases (because the resonance frequency has changed) and the voltage amplitude at the output point104(shown inFIG. 1) will rise.FIG. 2shows an approximate rise in voltage of 20 dB at 5.05 MHz. This calculation does not take into account the internal resistance of the voltage source; in real life, the voltage change is typically not so drastic. The width and depth of the first and second curves202and204depend on the specific value of the series resistance R1. Typically, the width of the first and second curves will increase with an increasing resistance for R1, and the depth of the first and second curves will decrease with an increasing resistance for R1.

As discussed above, conventional capacitive touch sensor panels may require a large number of connections between the electrodes in the touch sensor panel and a signal generator (such as an RF signal generator). For example, a touch sensor panel with a 10×10 grid of electrode channels may require 20 separate input connections and 20 separate output connections for a self-capacitance configuration, and 10 inputs and 10 outputs for a mutual capacitance configuration. The inputs and outputs may be an RF signal at a single frequency that is time-multiplexed to all inputs. These connections may require a significant amount of space on the edges of the touch sensor panel and a large bundle of wires to connect the touch sensor panel to the controller. Thus, it may be desirable to reduce the number of connections required, which may free up space near the edges of the touch sensor panel and may simplify controller connection and construction. Some embodiments described herein use what may be considered input signal frequency multiplexing which may reduce the number of inputs and outputs required, as will be described below.

FIG. 3is a schematic diagram of a circuit300design that may be used in a capacitive touch sensor device350according to one embodiment. The circuit300includes a plurality of resonant circuits302a,302b,302c,302d,302e,302f,302g,302h,302iand302jconnected in parallel to a single tunable RF signal generator301. A fixed resistor303is connected in series between the tunable RF signal generator301and the resonant circuits302ato302j. Each resonant circuit302ato302jincludes a respective inductor304ato304jconnected in series to a respective capacitor306ato306jbetween the RF signal generator301(via resistor303) and ground308.FIG. 3also shows an output point310of the circuit300to which all of the resonant circuits302ato302jare connected.

The capacitor306ato306jfor each resonant circuit302ato302jis connected to ground. Each of the resonant circuits302ato302jhas a resonance frequency that is unique within the set of resonant circuits302ato302j. In this example, the inductance value is the same for all inductors304ato304j, but the capacitors306ato306jeach have a different capacitance as follows: first capacitor306ais 220 pF; second capacitor306bis 180 pF; third capacitor306cis 150 pF; fourth capacitor306dis 120 pF; fifth capacitor306eis 100 pF; sixth capacitor82fis 180 pF; seventh capacitor306gis 68 pF; eighth capacitor306his 58 pF; ninth capacitor306iis 47 pF; and tenth capacitor306jis 39 pF. The varying capacitances provide the unique resonance frequencies for the resonant circuit302ato302j. In other embodiments, the inductance of each resonant circuit (in addition to instead of the capacitance) may vary to provide the unique resonance frequencies.

The tunable RF signal generator301is tunable to selectively generate an output at each of the unique resonant frequencies for driving the resonant circuits302ato302j. For an input signal at a given resonant frequency of one of the resonant circuits302ato302j, only the resonant circuit302ato302jhaving that resonant frequency may experience a significant voltage drop, while the remaining resonant circuits302ato302jmay appear to have high input impedance. If the capacitance of one of the resonant circuits302ato302jchanges, due to a touch, then its resonance frequency will also change. Take for example the first resonant circuit302ahaving a first unique resonance frequency. A touch event is represented in by variable capacitance312inFIG. 3. In the event of touch on the first resonant circuit302a, then the actual resonance frequency for the first resonant circuit302achanges due to the combined capacitance312and306a. Thus, when the signal generator V1is tuned to the first unique resonance frequency for the first resonant circuit302a, the measured output will change (a dB increase) in the presence of the touch. By sequentially tuning the tunable RF signal generator301through the unique resonance frequencies for all resonant circuits302ato302j, each of the circuits may be sequentially scanned to detect for a capacitance change due to touch. The tunable RF signal generator301may comprise a single signal generator with one or more tunable elements that alters the frequency of signals generated. In other embodiments, a signal generator may be tunable in that multiple signal generating sources are present for different frequencies, and a switching mechanism may control which signal generating source is actually providing output at a given time.

FIGS. 4 to 6illustrate one example of how the above concepts above may be implemented, including the placement of electrodes.

FIG. 4is a schematic of an example capacitive touch circuit400similar to the circuit300inFIG. 3, according to one embodiment. The capacitive touch circuit400inFIG. 4includes a plurality of resonant circuits402ato402jcollectively connected to a circuit input404, via a resistor R, and to ground406. Ten resonant circuits402ato402jare shown inFIG. 4, but the actual number of resonant circuits will vary in other embodiments. The capacitive touch circuit400also includes a circuit output408connected to each of the resonant circuits402ato402j. The resonant circuits402ato402jare connected in parallel to the input404(via resistor R). The circuit output408and circuit input404are connected to opposite terminals of the resistor R in this embodiment.

The first resonant circuit402aincludes an inductor L1, a capacitor C1, a first ITO strip410aand a second ITO strip412a. The first and second ITO strips410aand412aform a pair and run parallel to each other. The ITO strips are deposited onto a transparent dielectric substrate layer (not shown). The first and second ITO strips effectively form a capacitor. The capacitor C1is connected between the first and second ITO strips410aand412a, thus being connected parallel to the capacitor formed by the first and second parallel and spaced apart ITO strips410aand412a. The capacitance of the pair of ITO strips410aand412ais extremely low, and the capacitor C1and the pair of strips410aand412atogether provide a total capacitance several times higher than the capacitance created by the touching finger.

Embodiments are not limited to ITO for electrodes, and other conductive (possibly transparent or translucent) materials may be used. Electrodes may be deposited or printed using a chemical process, or may also be laser printed onto the substrate layer. Typical ITO strips may have a resistance of approximately 100 ohms/square. A relatively low resistance of the electrode strips may be preferable to reduce diminishment of the RF signals. Electrodes formed by a fine metal mesh may provide a lower resistance than conventional ITO strips, and may, therefore, be more suitable for larger touch panels. Embodiments are not limited to any particular type of electrode. The shape of the electrodes may also vary and electrodes are not necessarily strips. For example, some embodiments may include electrodes in one or more other shapes such as rectangles or circles, rather than strips.

The inductor L1is connected between the RF input (via resistor406) and the first ITO strip410a. The second ITO strip412is connected to ground (as well as the capacitor C1). Thus, as shown inFIG. 4, the inductor L1of the first resonant circuit is in series with the capacitor C1and the effective capacitor formed by the parallel first and second ITO strips410aand410b. The remaining resonant circuits402bto402jare all similarly arranged with respective capacitors (C2, C3, C4, C5, C6, C7, C8, C9, C10), inductors (L2, L3, L4, L5, L6, L7, L8, L9and L10), first ITO strips (410b,410c,410d,410e,410f,410g,410h,410i,410j) and second ITO strips (412b,412c,412d,412e,412f,412g,412h,412i,412j), together forming respective touch sensitive “channels”414bto414j.

The inductors L1to L10and capacitors C1to C10in these resonant circuits402ato402jare chosen to provide a set of unique resonance frequencies, where each resonant circuit resonates at a slightly different frequency. The resonance frequencies are unique within the resonant circuits402ato402j. However, in embodiments including multiple sets of resonant circuits, resonant frequencies in two or more sets may overlap. The set of unique frequencies may be chosen based on a permissible tuning range and bandwidth of the RF input404. For example, in certain environments, the allowable RF frequency operating bandwidth may be limited or dictated by regulations, other equipment, etc. The spread between adjacent resonant frequencies for the channels may be chosen to be sufficiently large to enable clear distinction between channels, though the actual spread may vary in different embodiments.

The capacitors C1to C10may be lumped circuit elements or they may be made as part of multilayer touch panel structure. For example, the capacitors C1to C10may be a chip capacitor or may formed by a deposition of one or more additional layers of conductive material on the substrate layer. A multilayer structure may be preferable since it may typically not be practical to solder surface mount chip capacitors on a glass or any dielectric substrates. The inductors L1to L10may also be lumped circuit elements or they may be made as part of multilayer touch panel structure.

It may be possible to distinguish a touch on any particular channel414ato414j, as will be discussed in more detail below. The touch sensitive channels414ato414jmay be distributed on the substrate layer to form a one-dimensional touch sensor system. For example, the electrodes410ato410jand412ato412jof the channels414ato414jmay extend substantially across the substrate layer to form a touch sensitive panel.

FIG. 5Ashows a graph500of a simulated frequency response of the capacitive touch circuit400shown inFIG. 4when none of the channels414ato414jis touched. The simulation was produced in Spice™. As shown inFIG. 5A, the circuit includes 10 resonant frequencies indicated by the 10 separate valleys or drops in the output decibel level.FIG. 5Bshows a graph550of a simulated frequency response of the capacitive touch circuit400shown inFIG. 4when the sixth channel414f(shown inFIG. 4) is touched. As shown, the sixth resonant frequency552(also shown inFIG. 5A) has shifted from about 8.57 MHz to about 8.11 MHz, due to the capacitance of the channel increasing by 10 pF. If the applied RF input is tuned to 8.57 MHz, then by touching the corresponding pair of ITO strips, the measured output signal amplitude of the capacitive touch circuit400will change the amount ΔdB shown inFIG. 5B(which is approximately 15 dB in this example). The change in output level, when detected, is treated as a touch event for the sixth channel414f.

FIG. 6is a block diagram of a controller600for a capacitive touch sensor according to some embodiments. The controller600may be used to control the capacitive touch sensor circuit400shown inFIG. 4as well as other capacitive touch circuits in various devices. The controller includes a tunable RF signal generator630connected to controller output631, a detector632connected to controller input633, a processor634, and a memory636. The tunable RF signal generator630is output (via wire628) for input to the panel601. The detector632is also connected to the processor634. The tunable RF signal generator630is connected to and controlled by the processor634. The detector632receives and measures output from the panel601via wire629. The memory636is connected to the processor634and stores executable instructions thereon to cause the processor634to control the RF signal generator630and the detector632as described below. In other embodiments, the processor634may be configured without use of external memory to control the RF signal generator630and the detector632.

The controller600shown inFIG. 6may be connected to control the capacitive touch circuit400shown inFIG. 4. Specifically, the controller output631(FIG. 6) may be connected to the circuit input404(FIG. 4) of the touch circuit404, and the controller input633(FIG. 6) may be connected to the circuit output408(FIG. 4) of the touch circuit400. In operation, the RF signal generator630of the controller600may sequentially scan the unique resonant frequencies of all channels414ato414jof the capacitive touch circuit400to detect touch events on the channels414ato414j. The channels414ato414jmay be scanned sequentially or in any random order. If more than one channel414ato414jis out of resonance, a multi-touch event is registered. The scanning sequence may follow a repeating sequence or a random hopping pattern.

To perform the scanning functionality, the processor634of the controller600controls the RF signal generator630to selectively and sequentially generate RF signals at each of the unique resonance frequencies. The detector632measures the output received by the controller (via controller input633) originating from circuit output408inFIG. 4and passes the measurements to the processor. The detector632may include an Analog to Digital Converter (ADC) for converting the RF output to digital signals for transmission to the processor634. The detector632and/or the processor634also include a comparator to compare the measured output levels to the expected non-touch output level. The processor634analyzes the measurements to detect touch events on the channels604and606. For example, if there is a change from the expected amplitude output for a particular resonance frequency, then the processor634determines that the particular channel414ato414jcorresponding to that resonance frequency is touched. The input generated by the RF signal generator may remain at a given selected frequency for period of time. When multiple capacitance changes are detected on multiple channels, the microcontroller may register a multiple touch event.

In other embodiments, some or all of the controller circuitry (including the tunable signal generator and/or the detector) may be integrated directly into a touch sensor panel rather than included in a separate controller.

A person skilled in the art will appreciate that other resonant circuit configurations may also be used where each resonant circuit of a group of resonant circuits has a different resonant frequency. The example circuit configuration shown inFIGS. 2 and 4 to 6are provided by way of example, and embodiments are not limited to this configuration. Any suitable resonant circuits that can be provided with different resonance frequencies may be used, and embodiments are not limited to the LCR type circuits shown in the figures.

In some embodiments, measuring the output (e.g. by the detector632inFIG. 6) is performed by measuring the amplitude of the voltage output from the capacitive touch circuit.

In some embodiments, two perpendicular sets of channels may be used to provide a two-dimensional touch sensor (such as a touchscreen for a mobile device or other electronic display panel). The system may still only require a single RF source may still be used for channel excitation and a single touch registration output. Each of the channels of both perpendicular sets could be connected to the single input and to the single output to enable scanning of both sets of channels.

FIG. 7is a top view of a touch sensor panel700according to another embodiment. The touch sensor panel700includes a substrate layer702. Distributed on the substrate layer702are horizontal channels704and vertical channels706. Each horizontal channel704is a resonant circuit including a respective capacitor710and inductor712connected to a pair of first and second horizontal electrode strips704aand a704bin a manner similar to the channels414ato414jofFIG. 4. Each vertical channel706is a resonant circuit including a respective capacitor710and inductor712connected to a pair of first and second vertical electrode strips706aand a706bin a manner similar to the channels414ato414jofFIG. 4. A resistor713is also shown inFIG. 7and is arranged similarly to the resistor R inFIG. 4.

Each channel704and706inFIG. 7has a unique combination of capacitance and inductance values to provide a unique resonance frequency (similar to the capacitive touch circuit400inFIG. 4). The horizontal channels704and the vertical channels706are distributed on opposite respective faces of the substrate layer702. For example, the vertical channels706may be on a top face705, and the horizontal channels704may be on a bottom face (now shown), or vice versa. Alternatively, the sets of horizontal and vertical channels704and706may be arranged on two different substrate layers (not shown) that are stacked on one another. Any conventional method of arranging a two dimensional array of touch sensitive channels on one or more substrate layers may be used.

As seen in this example, the horizontal channels704extend between opposite side edges714and716of the substrate layer702, while the vertical channels extend substantially from the top718to the bottom720of the substrate layer702. Each channel may include a pair of electrodes, an inductor712and a capacitor710arranged similar to the channels414ato414jof the capacitive touch circuit400shown inFIG. 4. The horizontal and vertical channels704and706are collectively connected to a single circuit input724and also collectively connected to a single circuit output726in this example. A controller (such as the controller600shown inFIG. 6) including a tunable signal generator and/or detector may be connected (e.g. using wires) to the substrate layer702via the circuit input724and the circuit output726to scan the channels704and706. The touch sensor panel700may be integrated together with a controller within a single device housing (not shown). For example, the housing may be in the form of a protective tablet housing complete with gaskets and/or other seals to protect the touch sensor panel700, as well as other parts of a tablet. The touch sensor panel700may typically include a transparent protective layer (not shown) such as glass or plastic covering the substrate layer702and the channels704and706. In other embodiments, some or all of the controller circuitry (including the tunable signal generator and/or the detector) may be integrated in to the touch sensor panel700rather than included in a separate controller.

Each channel the704and706has a unique resonance frequency. Thus, by scanning each of the channels704and706(by cycling through the resonance frequencies and detecting changes in output when tuned to each frequency), touch may be registered in two dimensions. The two dimensional arrangement of the channels704and706will create mutual capacitances between the channels. This may be taken into account when configuring how touch is detected.

A controller, such as the controller600shown inFIG. 6, may selectively drive the channels704and706in the touch sensor panel700and may detect touch events. For the two dimensional sensing, the controller may detect a touch event on at least one horizontal channel704and at least one vertical channel706.

A single touch may affect and be detected for multiple channels to varying degrees. For example, a touch on one channel may affect the adjacent channel(s) to a lesser degree. A touch between two channels may affect those two channels in a similar manner. By measuring the degree of output change for multiple channels, a controller may infer the location of a touch event, even though that touch event is not directly over a given single channel.

As mentioned above, some embodiments may use a multilayer structure to create the capacitors in the resonant circuits (such as capacitors C1to C10inFIG. 4). Examples of calculations of the capacitance that may be achieved using a multilayer structure are provided below. The usual dielectrics used in touch sensor panel manufacturing are the polyethylene terephthalate (PET) and various kinds of adhesives. The dielectric constant of the PET is typically within the range of 3 to 3.5, and most suitable adhesive materials for holding dielectric layers (such as PET) together have dielectric constant around 1.5. The thickness of the PET films varies between 50 um to 250 um, and the thickness of the adhesive layer is usually between 25 and 150 um.

The above results mean that if a mutual capacitive touch sensor panel has ITO strips 1 cm wide each, and they cross each other at the right angle, the capacitance of this two-layer structure at every intersection may be between 8.85 pF to 62 pF depending on the type and thickness of the dielectric substrate. The capacitance may be varied by changing the width of the strip or by adding areas on the periphery of the touch sensor panel. If more than two layers are used this addition may take very little room on the side of the touch sensor panel, since the capacitance doubles, triples, etc. For a self-capacitive touch sensor panel, on the other hand, there may be only a single layer of dielectric substrate. Thus, to increase capacitance may require increasing the capacitive area. Thus, electrodes and/or fixed capacitor elements of resonant circuits with a desired capacitance may be created using planar conductor (e.g. ITO or metal) on a substrate layer.

In some embodiments, inductors (such as the inductors L1to L10inFIG. 4) may be deposited on the dielectric substrate layer, similar to electrode strips. For example, planar spiral inductors may be used in some embodiments. Planar spiral inductors may be less expensive than either chip or coil inductors for surface based designs. Each inductor may include at least one layer of a conductor on a substrate layer. The one or more conductor layers may define one or more spiral-shaped inductor coil.

A multilayer inductor creates mutual inductance, and may be difficult to simulate. The simulation process may take a long time, and the results may be inconsistent. However, for a two layer inductor, the following two equations may be used for the coupling value, KC, to obtain the total inductor value with a mutual inductance:

When both inductor layers have the same pattern, the formula is simplified:

From the experiments the coupling coefficient may be approximately in the range of 0.5-0.7 on a standard Printed Circuit Board (PCB) with 62 mil thickness.

FIGS. 8A to 8Dshow example planar inductor coils, according to some embodiments, that may be deposited or printed onto a substrate, such as a PCB.

FIG. 8Ais a top view of an inductor802with a square spiral shape. The inductor802is created by depositing silver ink or metal mesh on a glass or transparent polyester layer. The inductor802is a single layer inductor with 10 mm outer diameter DOUT1, traces having 125 um width W1that are spaced apart by a 125 um trace spacing S1, and having 15 turns. The inner diameter DIN1shown inFIG. 8Ais 2.75 mm. This inductor may, for example, have approximately to have 1.64 uH inductance, although embodiments are not limited to any particular inductance. The inner diameter DIN provides space for a ferromagnetic core (not shown) to be inserted.

For a two layer structure, with each layer using a layout similar to those shown inFIG. 8A, the coupling coefficient KC has been found to be approximately 0.5 for experiments with 62 mil PCB. However, for a thinner PCB spacer the coupling coefficient KC may be higher. Assuming that KC=0.5, the total inductance of a two layer structure may be approximately 2*1.64 uH*(1+0.5)=4.92 uH. A four-layer inductor may have the value of 14.76 uH, and an eight-layer inductor will have 44.28 uH. A ferromagnetic core in the center of the inductor may increase the inductance value even further.

The total resistance of the coil of an inductor may be very important. The total length of a single layer flat inductor may be estimated as the length of the outer turn multiplied by the number of turns. Using the layout of the inductor802inFIG. 8A, the estimated length would be approximately 60 cm for a single layer inductor. If the inductor802may be printed from silver ink, which has a resistivity approximately twice as high as the resistivity of pure silver and equals to 2*10−6ohm/cm, the total DC resistance of the single layer inductor802may be approximately 3.2 ohm. A two layer or two-sided inductor using the same layout may have a DC resistance of 6.4 ohm. A four layer or four-sided inductor may be approximately 12.8 ohm. An eight layer or eight-sided inductor may be approximately 25.4 ohm.

The series resistance of the coil affects the LCR quality factor Q. The quality factor Q may be calculated by the formula Q=1/R*SQUARE (L/C), where R is the series resistance, L is the inductance and C is the capacitance. The quality factor Q may need to be at least 10 for the circuit to properly resonate. A higher the Q factor may also provide better frequency resolution (channel separation) of the frequency response curve, such that the resonance frequencies of the channels may be placed closer to each other occupying less overall frequency band. To increase the Q factor, it may be necessary to lower the series resistance and/or raise the inductance of the inductor. It may be less practical to alter capacitance to increase the Q factor because the capacitance value may need to stay in the same order of magnitude as the finger touch, which may be around 10 pF.

FIG. 8Bis a top view of an inductor804with a hexagonal spiral shape. The values of DOUT2, DIN2, W2and S2shown inFIG. 8Bmay be the same or different than DOUT1, DIN1, W1and S1shown inFIG. 8Adepending on the desired inductance.

FIG. 8Cis a top view of an inductor806with an octagonal spiral shape. The values of DOUT3, DIN3, W3and S3shown inFIG. 8Bmay be the same or different than DOUT1, DIN1, W1and S1shown inFIG. 8Adepending on the desired inductance.

FIG. 8Dis a top view of an inductor808with a circular spiral shape. The values of DOUT4, DIN4, W4and S4shown inFIG. 8Bmay be the same or different than DOUT1, DIN1, W1and S1shown inFIG. 8Adepending on the desired inductance. The inductance of the example inductors inFIGS. 8A to 8Ddepends on the exact materials (substrate and conductor) used as well as the geometry of the inductor coil. The inductance may range from 1 μH to 100 μH, for example, depending on the specific dimensions and materials.

By varying the dimensions of the inductors802,804,806and808inFIGS. 8A to 8D, including the number of turns, a variety of inductances may be provided as desired. For example, using such designs, variations in the inductances may be provided for achieving multiple unique resonance frequencies in a capacitive touch circuit (such as the circuit400shown inFIG. 4). For example, a plurality of similar inductors could be arranged on a PCB, for either one or two dimensional sensing, with each inductor having a slight variation in one or more dimensions.

The flat inductors made of several layers of silver ink or other conductor printed of a dielectric film have their own capacitance. This capacitance of the inductor may be used as a capacitance part of a resonant circuit, such that an additional external capacitor is not needed. When the number of turns in the inductor coil changes, both the inductance and self-capacitance change, thereby also changing the resonance frequency of the resonant circuit. Thus, by using different numbers of coil turns and/or geometrical variations for inductors in different channels, different resonance frequencies for the channels may achieved.

FIG. 9shows a layout of an example capacitive touch sensor circuit900. The capacitive touch sensor circuit900may be manufactured as a copper-on-PCB circuit. The capacitive touch sensor circuit900includes ten resonant circuits902ato902jforming ten respective channels904ato904jthat are similar to the channels914ato914jinFIG. 4. The number of channels may vary in other embodiments. Each resonant circuit902ato902jand includes a respective includes a respective planar inductor906ato906jdeposited on the PCB and a respective chip capacitor908ato908j. The channels904ato904j, inductors906ato906jand capacitors908ato908jare connected similar to the capacitive touch sensor circuit400shown inFIG. 4.

Each planar inductor906ato906jis a square spiral structure similar to that of the inductor802shown inFIG. 8A, but with several more turns. The planar inductors906ato906jall have the same dimensions and inductance. Unique resonance frequencies in this example are provided by varying the capacitance of varying capacitances of the capacitors908ato908j.

FIG. 10is an enlarged view of the layout of the first single resonant circuit902aof the touch circuit900ofFIG. 9, including the first channel904a, the first inductor906aand the first capacitor908a. Ground connection910aand circuit input connection912aare also visible inFIG. 10. The remaining resonant circuits902bto902j(shown inFIG. 9) are similarly connected.

Turning again toFIG. 9, to obtain an operating frequency range in the single digit megahertz range the value of the inductors906ato906jshould be in the single digit micro Henry range. On the experimental touch panel circuit that was manufactured, the inductors906ato906jwere manufactured as square two-layer inductors. The inductors906ato906jeach have approximate dimensions of 13×13 mm, conductive trace width of 0.2 mm with spacing in between of 0.2 mm, and 14 turns. The measured value of the inductance was approximately 3.9 uH, which was confirmed by the resonant frequency calculation and measurement. The capacitors908ato908jare ceramic capacitors of the0603size, although the particular capacitor used in other embodiments may vary.

The manufactured inductors906ato906jhave shown the following approximate results (per inductor): single side inductance is 1.13 uH; total inductance is 3.90 uH, mutual magnetic coupling is 0.72; inductor series resistance is 2.75 ohms; and parasitic capacitance of capacitor pads is between 7.4 pF and 8.1 pF. To decrease the size of the planar coil inductor a multilayer structure may be used. When the number of layers doubles the inductance may triple because of the mutual inductance between the layers contributes.

The value of inductance may be increased, or the size may be decreased keeping the same value, by inserting a ferrite core inside the coil. Including a ferrite rod may increase the resonance frequency, based on some experimentation.

FIG. 11is a graph1100of a frequency response obtained for the capacitive touch circuit900ofFIG. 9. As seen inFIG. 11, the frequency response shows 10 separate valleys indicating different resonance frequencies for the ten channels.

While the examples described above include two electrode strips per channel, with one electrode strip in each channel connected to ground, other embodiments may not include electrodes connected to ground as part of the channel. Rather, some embodiments may utilize channels that comprise a single electrode and omit the second electrode connected to ground.

Government regulations may limit the total bandwidth available for use in a touchscreen device (e.g. an RF touchscreen), which may limit the number and spread of resonance frequencies that may be used. For this or other reasons it may be desirable to limit the number of resonance frequencies used in a touch sensor device. In some embodiments, a touch sensor device may include two or more sets of resonant circuits (forming two or more sets of channels). Specifically, the touch sensor device may include a first plurality or set of resonant circuits as described above, as well as one or more additional pluralities or sets of resonant circuits. Each of the sets of resonant circuits may include one or more electrodes distributed on the substrate layer. For example, the first set could form horizontal channels, and a second set could form vertical channels. Alternatively, different sets of channels (resonant circuits) could provide coverage for different areas of a panel. Each set of resonant circuits may have a corresponding set of resonance frequencies, each being unique within the respective set.

Each set of resonant circuits may include a separate input connection (e.g. connected to a controller having a signal generator). Output from a single tunable signal generator may be switched between inputs for the sets of resonant circuits to selectively drive sets of resonant circuits. For example, switching circuitry may be connected to the tunable signal generator for selectively driving the sets of resonant circuits. Two or more sets of resonant circuits may include one or more common (i.e. same or substantially similar) resonance frequencies. Thus, the resonance frequencies for two or more sets of resonant circuits may at least partially overlap. Thus, signals from a single tunable signal generator may be used to drive and scan multiple sets of resonant circuits having at least some common resonance frequencies. In this manner, the total number of resonance frequencies used in a touch circuit device may be less than the total number of resonant circuits, but the number of connections (e.g. wires) needed to connect to the resonant circuits (i.e. channels) for scanning may still be reduced in comparison to conventional touch sensor devices. Alternatively, two or more tunable signal generators may be separately connected to drive two or more respective sets of resonant circuits. In still other embodiments, two or more signal generators may be used to drive separate sets of resonant circuits.

FIG. 12is a top view of a layout for a capacitive touch sensor panel1200(in the form of a panel) according to yet another embodiment. The capacitive touch panel includes conductor elements discussed below printed, deposited or etched on a substrate. The substrate in this example is a PCB and including a top PCB layer1202and a bottom PCB layer that underlays the top PCB layer in this example, although another substrate (such as a transparent substrate) may be used as well. The touch sensor panel1200is a single plane pattern.

The capacitive touch sensor panel1200in this embodiment includes horizontal channels1204and vertical channels1206. In this embodiment, each of the vertical and horizontal channels1206arranged as part of resonant circuits similar to the resonant circuits402ato402jinFIG. 4, but with no electrode connected directly to physical ground. Instead, each channel1204and1206includes a single electrode1212or1214, which has a diamond pattern as discussed below. In this capacitive touch sensor panel1200, the human finger acts as a virtual path to ground (via anything touched by the user).

The capacitive touch sensor panel1200may be manufactured using copper (or another conductor) on the top PCB layer1202and the bottom PCB layer. In this embodiment the electrodes1214of the vertical channels1206are formed on a top surface (not visible inFIG. 12) of the bottom PCB layer. The conductor portions of the vertical channels1206including the electrodes1214are shown as solid black inFIG. 12for illustrative purposes, but would normally not be visible through the top PCB layer1202. The electrodes1212of the horizontal channels1204are formed on a bottom surface (not visible inFIG. 12) of the top PCB layer1202, and thus face the electrodes1214of the vertical channels1206. The conductor portions of the horizontal channels1204including the electrodes1212are shown as outlined white inFIG. 12for illustrative purposes, but would not normally be visible through the top PCB layer1202. To prevent contact between the vertical channels1206and the horizontal channels1204, an insulating layer (such as a solder mask) is provided between the horizontal and vertical channels1204and1206. In other embodiments, a single substrate layer (e.g. PCB or a transparent substrate) may be used with horizontal channels on one face of the substrate layer, and horizontal channels on the opposite face. Embodiments are not limited to any particular arrangement of multiple layers of channels and/or substrate layers.

Each horizontal channel1204and each vertical channel1206includes a respective pair of a lump capacitor1208or1218and a lump inductor1209or1219(as opposed to PCB traces for planar inductors and/or capacitor). The lump capacitors1208for the horizontal channels1204are each indicated by the respective vertically arranged capacitor icon1208shown in first legend section1230ofFIG. 10. The lump inductors1209for the horizontal channels1204are each indicated by the respective horizontally arranged inductor icon1209shown in the first legend section1230. The lump capacitors1218for the vertical channels1206are each indicated by the respective horizontally arranged capacitor icon1218shown in second legend section1232ofFIG. 10. The lump inductors1219for the horizontal channels1204are each indicated by the respective vertically arranged inductor icon1219shown in the second legend section1232.

The horizontal channels1204are collectively connected to a first input/output port1240and are collectively connected to ground1242(with each horizontal channel1204having the corresponding capacitor1208and inductor1209connected in series between the first input/output port1240and ground1242). The vertical channels1206are collectively connected to a second input/output port1244and are also collectively connected to ground1242(with each horizontal channel1206having the corresponding capacitor1218and inductor1219connected in series between the second input/output port1244and ground1242).

The horizontal channels1204each have a different respective resonance frequency. The vertical channels1206each have a different respective resonance frequency. The resonance frequencies for the horizontal channels1204and the resonance frequencies for the vertical channels1206partially overlap in this embodiment. In particular, the capacitive touch sensor panel1200includes twelve horizontal channels1204and sixteen vertical channels1206. For each horizontal channel1204, the respective capacitor1208and inductor1209pair are a different combination of capacitance and inductance to provide a resonance frequency for each channel1204and1206that is different than the other horizontal channels. The vertical channels1206similarly each have a respective resonance frequency, provided by the capacitors1218and inductors1219, that is different than the other vertical channels. The twelve resonance frequencies for the horizontal channels1204are repeated for the vertical channels1206, and the vertical channels1206include four additional frequencies (for 16 total). However, it is to be understood that the number of unique frequencies may vary. For example, the number and/or spread of frequencies used may depend on needs of the device and/or government regulations.

The capacitors1208and1218and inductors1209and1219may all located on a top surface1222of the top PCB layer1202and connected through the top PCB layer1202and the bottom PCB layer (not shown) to the electrodes1212and1214, respective first and second input/output ports1240and1244and ground1242as needed. Other arrangements are also possible. Any suitable arrangement connecting circuit elements together into the layout shown inFIG. 12may be used.

A touch event on the capacitive touch sensor panel1200may register a change in capacitance for at least one horizontal channel1204and at least one vertical channel1206, thereby enabling a determination of a position of the touch event in two dimensions.

As shown inFIG. 12, each of the vertical and horizontal channels1204and1206includes the single elongated electrode strip1212or1214that each form several consecutive diamond shapes1215along their length. These diamond shapes1215do not overlap. Rather, horizontal channels1204intersect the vertical channels1206at narrow portions1252of the electrodes1212and1214between adjacent diamond shapes1215.

The electrodes1212and1214are not directly connected to a ground plane, and the capacitors1208and1218and inductors1209and1219do not overlap on the ground plane. Therefore, the electrodes1212and1214will “hover” over the top PCB1202layer and the bottom PCB layer (not shown). The horizontal and vertical channels1204and1206are connected to a physical ground via ground connection1242. The touch of a finger provides a virtual ground through the body. Thus, when a human finger is applied to the touch sensor panel1200, the amplitude read at the outputs will increase due to the change in capacitance, despite the absence the ground plane. In an experimental setting, the layout described above provided an output amplitude change of 5 to 6 percent from a touch event.

FIG. 13is a block diagram of a controller1300that may be connected to control the touch sensor panel1200shown inFIG. 12. The controller1300includes a processor1302, a memory1304, tunable RF signal generator1306, detector1308and switch1310. The memory1304stores computer-executable code thereon for causing the processor1302to perform functions described below. In other embodiments, the memory1304may be incorporated as part of the processor1302, rather than external to the processor1302as shown inFIG. 13. The processor1302is also connected to communicate with the tunable RF signal generator1306, the detector1308, and the switch1310. The communication may include providing control signals to the tunable RF signal generator1306, the detector1308and the switch1310, as well as receiving, as input, data output from the detector1308.

A first output terminal1312of the controller1300may be connected to the first input/output port1240for horizontal channels1204of the touch sensor panel1200ofFIG. 12to drive the horizontal channels1204. A second output terminal1314of the controller1300may be connected to the second input/output port1244for vertical channels1206of the touch sensor panel1200ofFIG. 12to drive the vertical channels1206.

RF signals generated by the tunable RF signal generator1306are selectively output through the switch1310to either a first output terminal1312or a second output terminal1314as directed by the processor1302. The tunable RF signal generator1306in this example is capable of selectively generating signals (for input to the touch sensor panel1200) at each of the resonant frequencies of the horizontal and vertical channels1204and1206(shown inFIG. 12). The processor1302controls the switch1310and the tunable RF signal generator1306to scan each of the horizontal and vertical channels1204and1206. For example, the switch1310may first be set to direct the RF signals to the first output terminal1312while the tunable RF signal generator1306cycles through all of the resonance frequencies for the horizontal channels1204. Then the switch1310may be set to direct the RF signals to the second output1314terminal while the tunable RF signal generator1306cycles through all of the resonance frequencies for the vertical channels1206. Other scanning sequences may also be used (including random sequences).

The detector1308in this example includes an ADC1316and a comparator1318. The detector1308is connected to controller input terminal1320to receive, as input, the output from the touch sensor panel1200(shown inFIG. 12). The controller input terminal1320may also be connected to the first and second output ports1240and1244of the touch sensor panel1200to measure the output for the horizontal and vertical channels1204and1206(shown inFIG. 12). The detector1308receives analog output from the touch sensor panel1200and first converts the analog signal to digital values using the ADC1316. The digital values are compared to expected output levels (e.g. expected output for no touch event) by the comparator1318. The comparison data from the comparator1318is passed to the processor1302. Based on the output from the detector1308, the current state of the switch1310and the current selected resonance frequency, the processor determines which of the horizontal channels1204and which of the vertical channels1206(shown inFIG. 12) is currently touched.

The tunable RF signal generator1306may include a synthesizer chip or circuit. The switch1310of the controller1300may include a PIN diode (not shown) that can divert the RF signal from the tunable RF signal generator1306to the first or second output terminals1312and1314. The processor1302(or possibly the switch1310) may include a switch driver control circuit that controls the PIN diode. The switch driver control circuit may turn the PIN diode on and off, for example, by applying a forward or reverse bias. The switch driver control circuit may use a low-pass filter between the RF signal generator and the switch.FIG. 14is a graph1400of a frequency response obtained for the capacitive touch sensor panel1200ofFIG. 12. A first, solid line1302is shown for the frequency response of the horizontal channels1204and a second, dotted line1304is shown for the frequency response of the vertical channels1206. The first line1302shows 12 valleys or drops for the 12 resonant frequencies of the horizontal channels1204, and the second line1304shows 16 valleys or drops for the resonance frequencies of the vertical channels1206. As shown, the resonant frequencies of the horizontal channels1204(FIG. 12) shown by dips or valleys in line1302are close several of the resonant frequencies of the vertical channels1206(FIG. 12) shown by line1304. In other words, at least some of the resonant frequencies of the horizontal channels1204are the same or similar to at least some of the resonant frequencies of the vertical channels1206. Thus, the total number of resonant frequencies needed to scan all of the channels1204and1206may be less than the total number of channels1204and1206. An exact match of the overlapping resonant frequencies is not necessary to allow a single frequency to be used to scan both a horizontal channel1204and a vertical channel1206.

A controller of the capacitive touch circuits described herein may include functionality for programming or configuring the controller. Such software may provide a graphical interface on a PC. Such software may be created with Borland visual C++ Builder, for example. The software may include various functions and components including, but not limited to: a block of library; the description of variables; the USB block of the Open Communication Port; the ADC block of the Read File; the block of decision of the solution; the visual block that created the graphic interface. The graphic interface may show an image that represents the area covered by channels. The graphic interface may also include controls such as a “start button”, selecting service information, and may display a graphical indicator in the displayed area to represent a detected touch. If multiple touches are detected, two or more graphical indicators to represent the touches may be shown. The touches will be detected at different times due to the sequential scanning. However, the speed of change of the applied RF signal for the scanning is very high, and the touch sensor panel indicators appears as simultaneous multi-touch.

FIG. 15is a flowchart of a method for controlling a touch sensor (such as the touch sensor circuits400and900shown inFIGS. 4 and 9or the touch sensor panels700and1200shown inFIG. 12) according to some embodiments. The touch sensor capacitive touch sensor includes a plurality of resonant circuits, each resonant circuit comprising at least one respective electrode, and each resonant circuit having a respective resonance frequency unique within the plurality of resonant circuits. At block1502, generating input signals at each of the resonance frequencies are sequentially generated for input to the resonant circuits. This generating at block1502may include selectively generating input signals at each of the resonance frequencies in a cyclic or random hopping pattern, as described above. At block1504, the output of the resonant circuits is measured to detect touch. This measurement may include ADC conversion and/or comparison as described above. The method may be adapted for controlling any of the touch sensor panels described above and may include the performing the functions of the controllers (such as controllers600and1300ofFIGS. 6 and 13) described above.

The controller for a touch sensor (such as the controller600or1300shown inFIGS. 6 and 13) may be provided separately from the touch sensor panel. Since only a single input and single output may be required for various sizes, a single controller may be configured to work with touch sensor panels of various sizes and sensor resolutions.

In some embodiments, a single touch panel may include multiple sets channels, where each set of channels is connected to a respective input and output. For example, one set of horizontal channels could have a first input/output, and second set of vertical channels could have a second input/output. Each set of channels may be scanned sedately by a controller. Alternatively, a large panel may have multiple designated areas, where the channels in each area form their own circuit as described above, with their own input and output. A single controller may still control the multiple sets of channels (with resonant circuits), provided the necessary number of inputs and outputs are provided. A first set of resonance frequencies for a first set of channels may be repeated for a second set of channels that are on a different circuit.

The embodiments described herein may reduce the number of input and output connections required for capacitive touch sensor devices. Reducing the number of inputs and outputs required may allow for better use of space around the edges of a substrate layer, reduce controller complexity and increase the adaptability of the controller for use with different sensor devices. Furthermore, a single controller may be programmed to function with multiple differently configured touch sensor devices. The reduction in the amount of wires to be connected to the inputs and outputs may allow a single controller to be configured for both small and large panels by configuring the scanning process (e.g. the frequencies to be scanned).

It is to be understood that a combination of more than one of the approaches described above may be implemented. Embodiments are not limited to any particular one or more of the approaches, methods or apparatuses disclosed herein. One skilled in the art will appreciate that variations, alterations of the embodiments described herein may be made in various implementations without departing from the scope of the claims.