USOO9024790B2
`
`(12) United States Patent
`Philipp
`
`(10) Patent No.:
`(45) Date of Patent:
`
`US 9,024,790 B2
`*May 5, 2015
`
`(54)
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`(75)
`(73)
`(*)
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`(21)
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`(63)
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`CAPACTIVE KEYBOARD WITH
`NON-LOCKING REDUCED KEYING
`AMBIGUITY
`
`Inventor: Harald Philipp, Zug (CH)
`Assignee: Atmel Corporation, San Jose, CA (US)
`Notice:
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`U.S.C. 154(b) by 444 days.
`This patent is Subject to a terminal dis
`claimer.
`
`Appl. No.: 13/347,312
`
`Filed:
`
`Jan. 10, 2012
`
`Prior Publication Data
`US 2012/O 105260 A1
`May 3, 2012
`
`Related U.S. Application Data
`Continuation of application No. 12/899.229, filed on
`Oct. 6, 2010, now Pat. No. 8,102,286, which is a
`continuation of application No. 1 1/279.402, filed on
`Apr. 12, 2006, now Pat. No. 7,821,425, which is a
`(Continued)
`
`(51)
`
`Int. C.
`H03M II/00
`G06F 3/023
`G06F 3/04
`
`(2006.01)
`(2006.01)
`(2006.01)
`(Continued)
`
`(52)
`
`(58)
`
`U.S. C.
`CPC ............ G06F 3/0237 (2013.01); G06F 3/04 16
`(2013.01); G06F 3/044 (2013.01); H03K
`17/9622 (2013.01); H03K 17/9643 (2013.01);
`H03K 2217/960705 (2013.01)
`Field of Classification Search
`CPC. H03M 11/20: G06F 3/0237; G06F 3/0416;
`G06F 3/044
`
`USPC ............ 341/20, 22, 26, 33: 345/173; 715/773
`See application file for complete search history.
`
`(56)
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`4,616,213 A 10, 1986 Danish
`4,651,133 A
`3/1987 Ganesan et al.
`(Continued)
`
`FOREIGN PATENT DOCUMENTS
`
`1381 160 A1
`EP
`WO WO 2012/129247 A2
`
`1/2004 ............ HO3M 11/20
`9, 2012
`
`OTHER PUBLICATIONS
`
`Intellectual Property Office (IPO), Taiwan Office Action and English
`Translation of Text and Search Report, ROC (Taiwan) Patent Appl.
`No. 095123644, file 080900.0489 (14pgs), Jan. 23, 2013.
`(Continued)
`
`Primary Examiner — Albert Wong
`(74) Attorney, Agent, or Firm — Baker Botts LLP
`
`ABSTRACT
`(57)
`Keyboards, keypads and other data entry devices can Suffer
`from a keying ambiguity problem. In a small keyboard, for
`example, a user's finger is likely to overlap from a desired key
`to onto adjacent ones. An iterative method of removing key
`ing ambiguity from a keyboard comprising an array of capaci
`tive keys involves measuring a signal strength associated with
`each key in the array, comparing the measured signal
`strengths to find a maximum, determining that the key having
`the maximum signal strength is the unique user-selected key,
`and maintaining that selection until either the initially
`selected key’s signal strength drops below some threshold
`level or a second key’s signal strength exceeds the first key’s
`signal strength.
`
`24 Claims, 7 Drawing Sheets
`
`
`
`Signal
`Strength
`
`Threshold
`
`Key #
`
`1
`
`Petitioner STMICROELECTRONICS, INC.,
`Ex. 1011, IPR2021-01161 Page 1 of 14
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`

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`US 9,024,790 B2
`Page 2
`
`Related U.S. Application Data
`continuation-in-part of application No. 1 1/160,885,
`filed on Jul. 14, 2005, now Pat. No. 7,256,714, which is
`a continuation of application No. 10/617,602, filed on
`Jul. 11, 2003, now Pat. No. 6,993,607.
`(60) Provisional application No. 60/597.851, filed on Dec.
`21, 2005, provisional application No. 60/395,368,
`filed on Jul. 12, 2002.
`(51) Int. Cl
`we
`G06F 3/044
`HO3K 17/96
`
`(2006.01)
`(2006.01)
`
`(56)
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`4,920,343 A
`4, 1990 Schwartz
`5,508,700 A
`4/1996 Taylor et al.
`5,933,102 A
`8, 1999 Miller et al.
`6,657,616 B2 12/2003 Sims
`7.487,461 B2
`2/2009 Zhai et al.
`7,663,607 B2
`2/2010 Hotelling
`7,864,503 B2
`1/2011 Chang
`
`w w
`
`Otelling
`
`1/2011 Chen
`7,875,814 B2
`4/2011 Hotelling
`7920,129 B2
`8,031,094 B2 10/2011 Hotelling
`E. E: 1939. Hathis
`8,049,732 B2 11/2011 Hotelling
`8,179,381 B2
`5/2012 Frey
`8,217,902 B2
`T/2012 Ch
`8,723,824 B2
`5/2014 R
`2004,0008129 A1
`1/2004 Philipp
`2004/0104826 A1
`6/2004 Philipp
`2008/0309635 A1 12/2008 Matsuo
`20090315854 A1 12/2009 Matsuo
`2012fO242588 A1
`9/2012 Myers
`2012/0242592 A1
`9/2012 Rothkopf
`2012fO243151 A1
`9/2012 Lynch
`2012fO243719 A1
`9/2012 Franklin
`2013/0076612 A1
`3/2013 Myers
`OTHER PUBLICATIONS
`
`The Electroquasistatics of the Capacitive Touch Panel, May/Jun.
`1990 IEEE, vol. 26, No. 3, P.T. Krein and R.D. Meadows.
`Office Action (and English translation) for CN 200600528529, dated
`Jan. 19, 2011.
`U.S. Appl. No. 61/454,936, filed Mar. 21, 2011, Myers.
`U.S. Appl. No. 61/454,950, filed Mar. 21, 2011, Lynch.
`U.S. Appl. No. 61/454,894, filed Mar. 21, 2011, Rothkopf.
`
`Petitioner STMICROELECTRONICS, INC.,
`Ex. 1011, IPR2021-01161 Page 2 of 14
`
`

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`U.S. Patent
`US. Patent
`
`May 5, 2015
`May 5, 2015
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`Sheet 1 of 7
`Sheet 1 of7
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`US 9,024,790 B2
`US 9,024,790 B2
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`Petitioner STMICROELECTRONICS, INC.,
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`EX. 1011,1PR2021-01161 Page 3 of 14
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`Petitioner STMICROELECTRONICS, INC.,
`Ex. 1011, IPR2021-01161 Page 3 of 14
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`

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`U.S. Patent
`US. Patent
`
`May 5, 2015
`May 5, 2015
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`Petitioner STMICROELECTRONICS, INC.,
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`EX. 1011,1PR2021-01161 Page 4 of 14
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`Petitioner STMICROELECTRONICS, INC.,
`Ex. 1011, IPR2021-01161 Page 4 of 14
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`

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`May 5, 2015
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`Petitioner STMICROELECTRONICS, INC.,
`
`EX. 1011,1PR2021-01161 Page 5 of 14
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`Petitioner STMICROELECTRONICS, INC.,
`Ex. 1011, IPR2021-01161 Page 5 of 14
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`

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`U.S. Patent
`US. Patent
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`May 5, 2015
`May 5, 2015
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`Sheet 4 of 7
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`etitioner STMICROELECTRONICS, INC.,
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`EX. 1011,1PR2021-01161 Page 6 of 14
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`Petitioner STMICROELECTRONICS, INC.,
`Ex. 1011, IPR2021-01161 Page 6 of 14
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`

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`EX. 1011,1PR2021-01161 Page 7 of 14
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`Petitioner STMICROELECTRONICS, INC.,
`Ex. 1011, IPR2021-01161 Page 7 of 14
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`U.S. Patent
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`May 5, 2015
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`Sheet 6 of 7
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`US 9,024,790 B2
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`24
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`
`Petitioner STMICROELECTRONICS, INC.,
`Ex. 1011, IPR2021-01161 Page 8 of 14
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`U.S. Patent
`
`May 5, 2015
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`Sheet 7 Of 7
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`US 9,024,790 B2
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`
`FIG. 5B
`
`Petitioner STMICROELECTRONICS, INC.,
`Ex. 1011, IPR2021-01161 Page 9 of 14
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`

`

`US 9,024,790 B2
`
`1.
`CAPACTIVE KEYBOARD WITH
`NON-LOCKING REDUCED KEYING
`AMBIGUITY
`
`RELATED APPLICATIONS
`
`This application is a continuation of U.S. application Ser.
`No. 12/899,229 filed Oct. 6, 2010, which is a continuation of
`U.S. application Ser. No. 1 1/279,402 filed Apr. 12, 2006, now
`U.S. Pat. No. 7,821,425, which claims priority from U.S.
`Provisional Application No. 60/597,851 filed Dec. 21, 2005,
`and is a continuation-in-part of U.S. application Ser. No.
`1 1/160,885 filed Jul 14, 2005, now U.S. Pat. No. 7,256,714,
`which is a continuation of U.S. application Ser. No. 10/617,
`602 filed Jul. 11, 2003, now U.S. Pat. No. 6,993,607, which
`claims priority from U.S. Provisional Application No.
`60/395,368, filed Jul. 12, 2002.
`
`10
`
`15
`
`BACKGROUND INFORMATION
`
`The invention relates to method and apparatus for control
`ling an array of non-bistable keys, such as capacitive position
`sensors, and, more specifically for preventing accidental false
`inputs from keys adjacent to a selected key in a capacitive
`keyboard.
`Arrays of capacitive proximity sensors are often used in
`keyboards, keypads and other touch-input apparatus. Two
`characteristics of capacitive sensors that lead to their use
`instead of conventional metallic Switches are: 1) Capacitive
`sensors can be made in Small sizes, which is desirable if a
`Small, tightly packed keyboard is required; and 2) Capacitive
`sensors are particularly easy to environmentally seal, which is
`desirable if the keyboard is to be used in a wet environment or
`where there is a concern that contaminants may be spilled on
`the keyboard.
`Conventional capacitive sensors, when tightly packed, or
`when used in the presence of conductive liquid films, suffer a
`keying ambiguity problem. In a small keyboard, for example,
`a user's finger is likely to overlap from a desired key to onto
`adjacent ones. This is especially problematic if the user has
`large fingers or if he or she presses on the keyboard Surface
`hard enough to deform his or her finger. The same sort of
`effect is found when a conducting film is spilled on a key
`board, in which case the user's finger is sensed as though it
`were the size of the puddle. Problems of this sort are particu
`larly acute in cash register keyboards used in food service
`establishments where beverage and food sauce spills are a
`frequent occurrence.
`In his U.S. Pat. No. 5,730,165, the inventor teaches a
`capacitive field sensor employing a single coupling plate and
`a method of detecting a change in capacitance of the coupling
`plate, CX, to ground. The apparatus taught in U.S. Pat. No.
`5,730,165 comprises pulse circuitry for charging the coupling
`plate and for Subsequently transferring the charge from the
`plate into a charge detector, which may be a sampling capaci
`tor, Cs. The transferring operation is carried out by means of
`a transfer Switch electrically connected between the coupling
`plate and the charge detector. The disclosure of U.S. Pat. No.
`5,730,165 is herein incorporated by reference.
`In his U.S. Pat. No. 6,466,036 the inventor teaches pulse
`circuitry for measuring capacitance to ground, the circuitry
`comprising a plurality of electrical Switching elements, each
`of which has one side electrically connected to either a power
`Supply Voltage or to a circuit ground point. This circuit
`arrangement, which may be used with a keyboard as well as
`for many other applications, is more compatible with avail
`able integrated circuit design and manufacturing practices
`
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`than is prior art pulse circuitry, which commonly had one side
`of at least one Switching element floating. These improved
`arrangements thereby provide Superior performance at a
`lower manufacturing cost. The disclosure of U.S. Pat. No.
`6,466,036 is herein incorporated by reference.
`
`SUMMARY OF THE INVENTION
`
`One aspect of the invention is that it may provide an itera
`tive method of removing keying ambiguity by measuring a
`detected signal strength associated with each key in an array,
`comparing the measured signal strengths to find a maximum,
`determining that the key having the maximum signal strength
`is the unique user-selected first key, and maintaining that
`selection until either the first key’s signal strength drops
`below some threshold level or a second key’s signal strength
`exceeds the first key’s signal strength. When any key is
`selected its signal strength value may enhanced relative to all
`the other keys So as to deselect all other keys. In this aspect,
`the array under consideration may be a keyboard, or any
`convenient subset thereof.
`A particular preferred embodiment of the invention is an
`array of capacitive keys in which each key has a respective
`detection integrator counter (DI) associated with it. Each DI
`is a clocked counter that counts up by one incremental value
`on each capacitive acquisition cycle during which a signal
`strength from the associated key is above some nominal
`threshold value, and that counts down toward Zero if the
`signal strength is less than the nominal value. A controller
`receives a respective input from each DI and determines that
`one of the keys is selected, e.g., wins, when the detection
`integration (DI) count associated with that key meets a
`respectively selected terminal count value, TC. The incre
`mental magnitude used for counting down can be the same as
`that for counting up, e.g., 1, or it can be different, e.g., 2, to
`preferentially accelerate the count-down losing process
`over the winning process, in order to facilitate better Suppres
`sion of noise. The rate of counting down any of the DI
`counters can also be the complete value, i.e., the DI can be
`cleared in one cycle. In this embodiment, when two or more
`keys have signal strengths above their nominal thresholds, the
`key with the lesser signal strength will have its associated DI
`decremented or cleared each cycle while this condition exists.
`If any two or more keys have equal and maximal signal
`strengths, such keys' DI’s will continue to increment until the
`first to reach its TC wins and is set as the unique user
`selected key.
`In another aspect of the invention, the DI of a key selected
`at a first instant may be decremented or cleared and that key
`deselected even if the signal strength of that key is above the
`threshold value and its DI equals its associated TC value, if
`second key becomes selected at a later instant by virtue of its
`signal strength being greater than the signal strength of the
`first key while also being above its own threshold value and
`having its associated DI equal its associated TC. If there are
`multiple keys with signal strengths above their associated
`threshold values, their associated DIs will count up and down
`in competition, until one key’s DI finally equals its TC and
`wins over all others including over the previously selected
`key.
`In the above discussions, it should be understood that the
`principle of having one signal greater than another has been
`Somewhat simplified for explanatory purposes. In order to
`avoid indecisiveness and eliminate oscillation between two or
`more keys having more or less the same signal strengths, the
`winning key may preferably be given a slight advantage in
`Subsequent repetitions of the decision process. This may be
`
`Petitioner STMICROELECTRONICS, INC.,
`Ex. 1011, IPR2021-01161 Page 10 of 14
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`3
`done, for example, by requiring a non-selected key’s signal to
`exceed the currently selected key’s signal by a small amount.
`This can be done by Subtracting a small amount off the signals
`of non-selected keys, or by adding a small amount onto the
`selected key’s signal.
`An advantage of this method over those disclosed in my
`U.S. Pat. No. 6,993,607 is that the method disclosed herein
`permits the Smooth rollover of key selection as a finger slides
`from one key to the next, while still reducing key ambiguity.
`In the aforementioned patent, the first key to win remains
`selected even if the maximal signal strength has shifted to a
`new key, provided that the first key has enough signal strength
`left to retain its state, i.e., by having its signal strength in
`excess of its associated threshold value. Therefore the instant
`invention may be referred to as non-locking key ambiguity
`reduction.
`In yet another aspect of the invention, if the signal strengths
`of two keys that are approaching a detection threshold value
`and that are both in a defined keyboard neighborhood both
`exceed the threshold value and their signal strengths are equal
`to each other (or are within a selected tolerance value) at the
`same time, an algorithm executed by a controller may be used
`to declare one of the two keys to be active and the other to be
`inactive. It will be recognized that a wide variety of algo
`rithms are possible and include, but are not limited to, a
`random, or pseudo-random selection of the active key, or a
`declaration of activity based on which key was scanned first.
`The principle also applies in the minimal case where the
`DI’s terminal count (TC) is chosen to be equal to one. This is
`functionally the same as though there were no DI, but rather
`just a simple signal comparison function with an inhibiting
`logic gate following it. Here, the inputs to the inhibiting gate
`also includes the logical comparisons of the signal strengths
`among the keys in a neighborhood in order to skew Subse
`quent comparisons to favor the already selected key over
`competing keys having respective output signals above
`respective threshold values.
`Those skilled in the keyboard arts will understand that the
`above-mentioned neighborhoods can be defined in a wide
`variety of ways. In some cases, a neighborhood of a given key
`may consist of all the keys immediately adjacent the given
`key, or may comprise all the keys having no more than one key
`between them and the given key. In other cases, the neighbor
`hood may comprise all the keys in a matrix array—e.g., in a
`keyboard for use in a numerical data entry application in
`which only one key is to be active at a time so that the
`sequence of input digits is uniquely determined. In other
`cases, such as in a typing or computer-input keyboard, the
`neighborhood of a key may comprise all other keys in the
`keyboard except for special purpose keys, such as a capitali
`zation shift key, a control key, and the like. Moreover, some
`embodiments of the invention provide a keyboard that is
`configurable by a user who programs a controller to selec
`tively consider or ignore various keys in an array. In some
`cases there might be two neighborhoods, each acting inde
`pendently of the other for key ambiguity resolution purposes.
`Although it is believed that the foregoing rather broad
`Summary description may be of use to one who is skilled in
`the art and who wishes to learn how to practice the invention,
`it will be recognized that the foregoing recital is not intended
`to list all of the features and advantages. Those skilled in the
`art will appreciate that they may readily use both the under
`lying ideas and the specific embodiments disclosed in the
`following Detailed Description as a basis for designing other
`arrangements for carrying out the same purposes of the
`present invention and that such equivalent constructions are
`within the spirit and scope of the invention in its broadest
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`form. Moreover, it may be noted that different embodiments
`of the invention may provide various combinations of the
`recited features and advantages of the invention, and that less
`than all of the recited features and advantages may be pro
`vided by some embodiments.
`
`DESCRIPTION OF THE DRAWING
`
`FIGS. 1a to 1c show an array of tightly spaced capacitive
`buttons.
`FIG. 2 shows a 2-D touch surface such as a capacitive
`mouse Surface or a capacitive touch screen, with buttons
`around it.
`FIG. 3 shows a 2-D touch surface such as a capacitive
`mouse Surface or a capacitive touch screen, with a guard ring
`disposed around it to Suppress activation of the touch screen
`area when a finger strays just outside the 2-D mouse or screen
`aca.
`FIG. 4 is a schematic block diagram of a preferred appa
`ratus of the invention.
`FIG. 5a is a flow chart showing logical operations carried
`out in a preferred method of the invention when Key 1 is
`initially active.
`FIG. 5b is a flow chart showing logical operations carried
`out in a preferred method of the invention when Key 1 is
`initially inactive.
`
`DETAILED DESCRIPTION
`
`In studying this Detailed Description, the reader may be
`aided by noting definitions of certain words and phrases used
`throughout this patent document. Wherever those definitions
`are provided, those of ordinary skill in the art should under
`stand that in many, if not most instances, such definitions
`apply to both preceding and following uses of Such defined
`words and phrases. At the outset of this Description, one may
`note that the terms “include and “comprise.” as well as
`derivatives thereof, mean inclusion without limitation; the
`term “or” is inclusive, meaning and/or. The word key as
`generally used in this Disclosure and as specifically used in
`the Claims attached hereto refers to a touchable portion of a
`mechanical to electrical transducing device that is non
`bistable in nature. This term specifically excludes conven
`tional mechanical switches in which two or more electrical
`conductors are moved into or away from contact with each
`other to make or break an electrical connection. The terms
`keyboard, keypad and the like all refer to arrays of keys for
`data input without limitation as to the size or configuration of
`the array. A key can also be a dimensional sensing Surface
`Such as an XY touch screen or a trackpad, or a sensing Zone
`not intended for normal human data entry Such as an object or
`body part sensor. Touch can mean either human or mechani
`cal contact or proximity to a key. User can mean either a
`human or a mechanical object. A finger can be, interalia, a
`human finger, a mechanical finger or a stylus.
`Capacitive sensors, unlike bistable electromechanical
`Switches which are either open or closed, provide a signal that
`varies with the degree of touch or extent or coupling between
`a user's finger and a sensing element of a keyboard. Other
`non-bistable touch sensors, such as an array of piezoelectric
`sensors in which the output from a given sensor increases
`with increasing activation force, share many of the properties
`of capacitive keys. Thus, much of the Subsequent disclosure
`should be understood as being relevant to non-capacitive keys
`that also provide an output signal responsive to a degree of
`
`Petitioner STMICROELECTRONICS, INC.,
`Ex. 1011, IPR2021-01161 Page 11 of 14
`
`

`

`US 9,024,790 B2
`
`5
`coupling between the key and a user's finger, stylus, or other
`key-activating or pointing implement that is proximate the
`key.
`Turning now to FIG. 1A, one finds an array of N tightly
`spaced capacitive keys in a key panel 11 which would benefit
`from the invention. When using such small key panels it is
`inevitable that a finger will encompass much more than the
`intended key. A finger touching a principle desired key elec
`trode 1 could easily create a fingerprint outline 3, as shown
`in dashed lines, where the fingerprint has a centroid location
`A. This fingerprint also encompasses keys other than the
`intended key. The amount of intersecting Surface area
`between the dashed line and each key area is a reasonable
`representation of the amount of signal level change each
`intersected key will receive due to the touch, although even
`non-touched keys will also see an increase in signal due to
`mere finger proximity and to fringe-field effects within the
`touch panel.
`In this case, the desire is to select the one and only one key
`which is intended by the user while Suppressing outputs from
`adjacent keys intersected by the fingerprint. In this non
`locking key Suppression invention, if the finger slides to a
`new key location 4, shown dotted with its centroid at location
`B, where the movement is shown by the arrow from A to B.
`this movement will not cause the first key 1 to remain solely
`active even though it has sufficient signal to still retain its
`state, i.e., its signal still lies above its threshold level despite
`being reduced by the movement to a new key. Instead, the
`invention provides that the newly intended key 2, having a
`larger signal level due to a higher degree offingerprint inter
`section than key 1, becomes the solely active key by Switching
`off the active state of key 1.
`FIGS. 1b and 1c further detail the change in signals on the
`keys of FIG. 1a by virtue of the relative electrode surface
`intersections with the fingerprint first at location A (FIG.1b)
`and then at location B (FIG. 1c). The signal strengths are
`shown in the bar plots in the lower portions of the respective
`figures. It is desired that in order for a key to win the status
`of user-selected key, its signal change must exceed a thresh
`old value, and its signal has to be the largest. In FIG. 1b, key
`1 wins. In FIG. 1c, key 2 wins.
`If the key selection method operates solely by picking a
`maximum signal strength, the keyboard may be subject to an
`undesirable rapid switching back and forth between two keys
`having nearly-identical signal strengths (e.g., fingerprint
`areas). This sort of chatter is preferably prevented by biasing
`or skewing the key selection method to favor an already
`selected key. That is, the Switchover process is made slightly
`more difficult than would occur with Straight equivalence.
`This bias may be provided in many ways in Subsequent key
`selection decisions. These ways may be equivalent to adding
`an incremental value to the signal associated with the selected
`key; multiplying the signal strength of the selected key by a
`value greater than one in Subsequent selections; Subtracting a
`respective incremental value from the signal strengths asso
`ciated with each of the non-selected keys; or multiplying the
`signal strength of each of the non-selected keys by a respec
`tive value less than one.
`FIG. 2 shows a configuration of a capacitive mouse or
`capacitive touch screen area 6 with Surrounding buttons 7.
`The principles of operation described in conjunction with
`FIG. 1a-capply similarly to FIG. 2, in that the area 6 can be
`treated as a single key with a single signal strength for pur
`poses of key suppression. FIG. 2 applies when the keys 7 are
`very close to pointing Surface 6 and fingerprints 3 and 4 can
`overlap both the capacitive screen and one or more capacitive
`buttons. Moreover, it should be recognized that although the
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`45
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`6
`drawing depicts a two-dimensional touch Surface, the same
`considerations apply to a one-dimensional touch Surface of
`the sort commonly referred to as a slider, scroll-wheel, or the
`like.
`FIG. 3. shows a configuration of a capacitive touch input
`area 6 with a surrounding key 8. The principles of operation
`described in conjunction with FIG. 1 apply similarly to FIG.
`3, in that the area 6 can be treated as a single key with a single
`signal strength for purposes of key suppression, while the
`outer key 8 acts to detect errant touch which falls partially on
`both 6 and 8. The area 6 can comprise any suitable input
`arrangement Such as a capacitive mouse Surface, a capacitive
`touch screen or a keypad comprising discrete keys.
`In this example, the guard electrode 8 is not necessarily
`intended as an actual control key. A finger sliding from 3 to 4
`would still potentially leave the active screen 6, but in fact the
`touch would not be legal since its areal centroid at B lies
`principally outside the input area. Key 8 detects this out-of
`position fingerprint and appropriate logic causes the screen 6
`to fall out of detection or to be ignored by further processing.
`It may be noted that some uses of the guard ring structure do
`not involve having a finger touching the keypad. For example,
`one could arrange a guard ring around a capacitive cellphone
`keypad and use the guard ring output to Suppress readings
`from all the keys in the keypad while the user was talking on
`the cellphone and holding the keypad of the phone against his
`or her head.
`The guard electrode key 8 in the latter case can also be a
`discrete solid electrode shape, for example a rectangle, disk,
`arc, or stripe or other shape, placed in some other location
`reasonably proximate input area 6. This guard electrode
`would be activated by placing the product against the user's
`head or other body part (for example placing the product in a
`clothing pocket with the keypadside towards the user's body)
`in order to Suppress further output from the keypad under
`Such adverse conditions. A Suitable position for Such a key
`might be near the earpiece of a cell phone, Some distance
`away from the keypad or touchscreen.
`The guard electrode key 8 can also be either a ring as
`shown in FIG.3, or a discrete solid electrode shape, such as a
`rectangle, disk, arc, or stripe or other shape, placed in some
`other location reasonably proximate the input area 6 so as to
`be activated by a mechanical closure. This could provide a
`cover which, when closed, would cause the guard key 8 to
`induce the Suppression of input area 6.
`In order to make the determination of an out-of-position
`fingerprint for use with the apparatus shown in FIG. 3, the
`same sorts of biasing arrangements can be used to prevent
`chatter as discussed Supra. However, relationships described
`above with respect to FIG. 2 presume the gain of the sensing
`channels with respect to finger Surface area to be comparable,
`so that equivalent fingerprint Surface areas on different keys
`produce comparable signal changes. This is not always the
`case in any of the instances described with respect to FIGS.
`1a-c, 2 or 3. The electrode sizes of different keys may not be
`equal, and for various reasons (such as Stray loading capaci
`tance variations, etc.) the electrical gains among the various
`keys can differ. In these instances the incremental values
`added might be negative. Alternatively, signals from compet
`ing keys could be scaled into a state of equivalence by using
`Scaling constants that are experimentally determined to
`accord with a particular configuration. In any event, one can
`scale and/or offset the signals into equivalence for compari
`son purposes and thereby create the desired suppression
`effect without chatter.
`Turning now to FIG. 4, one finds a schematic representa
`tion of apparatus of the invention 10, comprising an array of
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`Petitioner STMICROELECTRONICS, INC.,
`Ex. 1011, IPR2021-01161 Page 12 of 14
`
`

`

`US 9,024,790 B2
`
`10
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`N capacitive proximity sensors 12 labeled “Key 1, ..., “Key
`N. Each of the sensors 12 has an output to a respective
`counter logic 14 that Supplies data to and is controlled by
`suitable control logic 16. Those skilled in the electronic arts
`will appreciate that although the counters 14 and control logic
`16 are depicted with discrete blocks in the schematic diagram,
`these features could be provided either by separate physical
`circuit elements, or could all be provided by a single micro
`controller, as depicted by the dashed phantom line 18 in FIG.
`4. Moreover, although the array of keys 12 is depicted as
`being a simple linear array, it will be appreciated by one who
`reads the complete disclosure contained herein that many
`other sorts of arrays can be used and will encompass, without
`being limited to, arrays used as computer keyboards, keypads
`of the sort commonly used in telephony and automated bank
`ing, cash register data input keyboards, etc., as well as various
`other configurations discussed in conjunction with FIG. 3.
`The addition of counters 14, or of the logical function
`equivalent thereof, when used in the accordance with the
`teachings of this disclosure, can remove or resolve ambigu
`ities by methods involving comparison of signal strengths
`from various keys 12. This process involves examining the
`differences over one or more sequential signal samples.
`Turning now to FIGS. 5a and 5b, one finds flow charts
`depicting a preferred method of the invention for operating
`the apparatus 10 So as to Suppress extraneous key signals or to
`otherwise resolve keying ambiguities. This method may be
`carried out by a microprocessor 18 operating under control of
`a program Stored in a, preferably, non-volatile memory, or
`may