`(12)United States Patent
`Philipp
`
`I 1111111111111111 11111 111111111111111 IIIII IIIII lllll 111111111111111 11111111
`(10)Patent No.:US 6,452,514 Bl
`
`(45)Date of Patent:
`Sep.17,2002
`
`US006452514Bl
`
`(54) CAPACITIVE
`SENSOR AND ARRAY
`
`(76) Inventor: Harald Philipp, 7 Cirrus Gardens,
`
`
`
`
`Ramble Hampshire SD31 4RH (GB)
`
`5,973,623 A * 10/1999 Gupta et al. .................. 341/33
`
`
`
`
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`
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`6,256,022 Bl * 7/2001 Manaresi et al. ........ 178/18.06
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`
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`6,288,707 Bl * 9/2001 Philipp ........................ 341/22
`
`*cited by examiner
`( *) Notice: Subject
`to any disclaimer, the term of this
`
`
`Primary Examiner-Timothy Edwards, Jr.
`
`
`
`
`
`patent is extended or adjusted under 35
`
`
`(74)Attorney, Agent, or Firm-David Kiewit
`
`U.S.C. 154(b) by O days.
`
`(21) Appl. No.: 09/491,129
`
`(22)
`Filed: Jan. 26, 2000
`
`(57)
`
`ABSTRACT
`
`Proximity of a body, which may be a user's finger, to an
`
`
`
`
`
`
`electrode pair is sensed by a charge transfer capacitive
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`
`
`measurement approach. The electrode pair thus acts as a key
`Related U.S. Application Data
`
`
`
`that can be arrayed with other electrode pairs to form a
`(60)
`
`
`Provisional application No. 60/117,326, filed on Jan. 26,
`
`
`
`
`
`
`keypad, keyboard, linear slider control, or liquid level sen­
`1999.
`
`
`sor. In one embodiment of the invention each key is asso­
`(51)
`
`
`Int. Cl.7 ................................................ H03K 17/94
`
`
`
`ciated with an alternating voltage source and a pair of
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`
`
`
`
`(52) U.S. Cl. ......................... 341/33; 341/22; 178/18.06
`
`
`
`
`
`electrodes mounted on or within a solid dielectric substrate
`(58)
`
`or panel so as to be separated from each other by a gap. The
`
`
`Field of Search .................. 341/33, 22; 178/18.06,
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`
`
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`voltage source is connected to a driven electrode, a sampling
`
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`178/18.07; 200/343; 345/168
`
`
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`charge detector is connected to a second, receiving,
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`
`
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`electrode, and the output of the charge detector is, in turn,
`
`
`fed into a signal processor. Disturbances in coupling
`
`
`
`
`between the two electrodes are detected through the solid
`
`
`
`substrate or panel material when a substance or object
`
`
`
`
`approaches or contacts the panel. The receiving electrode is
`
`
`a low-impedance node during the sampling phase of the
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`
`
`process, which aids in keeping the sensor from being
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`
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`affected by wiring length or by extraneous objects near an
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`output lead ..
`
`(56)
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`
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`
`
`
`4,550,221 A 10/1985 Mabusth
`
`
`
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`4,651,133 A 3/1987 Ganesan et al.
`
`
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`4,879,461 A 11/1989 Philipp
`
`
`
`5,543,591 A 8/1996 Gillespie et al.
`
`
`
`
`5,572,205 A 11/1996 Caldwell et al.
`
`
`
`5,730,165 A 3/1998 Philipp
`
`
`
`
`5,841,078 A 11/1998 Miller et al.
`
`
`
`
`5,861,583 A 1/1999 Schediwy et al.
`
`
`
`
`
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`5,914,465 A * 6/1999 Allen et al. ................... 341/33
`
`
`
`10 Claims, 7 Drawing Sheets
`
`100
`
`401
`
`405
`
`y
`
`101
`
`I
`I C
`I ;!
`
`I
`I
`
`I
`
`I
`I
`I
`I
`402404 L _______
`
`I
`I
`I
`I
`_J
`
`A�T){ : �I:
`r----' 4 0 3 407 \400
`)
`
`408
`
`._______,
`
`10
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`U.S. Patent Sep.17,2002
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`Sheet 1 of 7 US 6,452,514 Bl
`
`FIG. ta
`
`102 100 1 OS
`
`104
`
`112
`
`\_'.
`110
`
`10
`
`206 106
`
`�
`
`X
`101
`
`206
`
`FIG. 1b
`
`---
`
`--..._
`
`-------
`
`101
`
`X
`
`-- 10
`Y 103
`112
`104
`100
`�113
`109
`
`111 108
`
`output
`of 101
`
`- - _.....___.....- _____._ ---.- - - -
`I v
`
`FIG. 1c
`
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`U.S. Patent Sep. 17, 2002
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`
`Sheet 2 of 7 US 6,452,514 Bl
`
`109 111 FIG. 1d
`
`108
`OUTPUT OF 101
`
`401
`
`C SAMPLE GATE
`
`114
`Iv
`
`FIG. 2a 201
`
`110
`
`103
`
`100 104
`
`y
`
`112
`
`-=-z_113
`
`201
`
`x---�
`
`FIG. 2b
`
`100
`
`X- ---1
`
`y _ _______..
`
`104
`
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`U.S. Patent Sep.17,2002
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`Sheet 3 of 7 US 6,452,514 Bl
`
`FIG. 3a
`
`303
`
`��-----------"--------
`
`304
`
`206
`
`I I I I I I I
`\ \ I I / / / _______ _
`\ \ I I / / / .,,.- ----- '-.
`\ \ \ I / / ,
`.,,. .,,.,., -
`'-...._ ',
`
`,,
`
`X--�
`
`110
`100 104
`
`.___ __ y
`
`FIG. 3b 100
`
`303
`
`x-------,
`
`Y--____,
`
`104
`
`' 10 206
`
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`U.S. Patent Sep.17,2002
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`Sheet 4 of 7 US 6,452,514 Bl
`
`FIG. 4a
`
`100
`
`401
`104
`
`405
`
`101
`
`I
`I C
`i!
`I
`
`I
`I
`I
`I
`
`I
`I
`I
`
`I
`I
`I
`I
`
`'----
`
`-
`
`-----I
`
`L _______
`
`_J
`
`: �I:
`A�T)[
`402404
`407
`4 0 8
`\400
`� ,---------, 4 0 3
`10
`109
`100
`404
`401
`402J--� �' -,,,_i_ ___ ;_
`
`100 104
`
`I
`
`I
`I
`
`FIG. 4b
`
`FIG. 5a
`
`'---- - - - - -----, 4 0 8
`
`402
`
`y
`
`+_y 5 05 �
`)
`
`1 0 1
`
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`U.S. Patent Sep.17,2002
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`Sheet 5 of 7 US 6,452,514 Bl
`
`100 f-------'--�---�- -�---�----6
`
`I="-,- -------,-- - - - - -
`
`��
`
`- - - - - 1
`
`501
`510 ------��-----�� .. --6
`� - - - - - ��
`402 � -----
`V
`t v-0
`402
`
`1
`
`0
`
`FIG. 5b
`
`705
`
`N
`
`� Y1 SEL
`M � 2-=S_EL_ -_ -_ -_ -_ -_
`-_ -_ -_ -_-_-----I
`y3_SEL --------
`4_SEL -------
`
`------r'------'-t"-----r----t-t------'+------r--
`
`206
`
`10
`
`0 1
`
`FIG. 6
`
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`U.S. Patent Sep.17,2002
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`Sheet 6 of 7 US 6,452,514 Bl
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`FIG. 7
`101 X1
`70
`
`402a 402b 402c 402d
`
`�
`
`�
`
`�
`702 703 704
`701
`measurement measurement
`measurement
`circuit #1 circuit #1 circuit #1
`
`circuit #1
`
`�
`
`measurement
`
`FIG. Ba 706 7os
`101 x1
`
`41
`
`105
`(1 of 16)
`
`N
`
`�
`702
`
`M
`
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`U.S. Patent Sep.17,2002
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`Sheet 7 of 7 US 6,452,514 Bl
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`--- - - ----L---
`
`__
`
`_
`
`706 ___._ _ __,_ - - - ----L-------'
`ao2 ______ _,__ _ ___._ ____ ----L---_ ___J
`
`501 b --=::;:-i
`1 ____ -L-1 __ ______,__I ____ --'-1 __
`51 0 b ______ _____.____ __ _,_ .____
`
`_.,__ - - -
`
`_
`
`100
`
`105
`
`FIG. Bb
`104
`/ (1 of 9)
`n=
`Y1
`-1
`X1 -----+-----< I 1---1 ---Y2
`
`X2 -----
`
`X 1 ---+--------<
`
`1---------
`
`Y3
`
`FIG. 9
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`US 6,452,514 Bl
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`1
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`
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`CAPACITIVE SENSOR AND ARRAY
`
`CROSS REFERENCE TO RELATED
`APPLICATIONS
`
`2
`is connected to a voltage drive source and the second of each
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`
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`pair is connected to a charge detector. In the general case for
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`a matrix there are X drive lines and Y charge detectors.
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`Although a minimal matrix could comprise two drive lines
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`5 and a single charge detector, or vice versa, an N by M matrix
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`This application claims the priority date of a U.S. Provi­
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`
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`is expected to usually involve at least four keys; e.g., an
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`
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`sional Application for Patent having Ser. No. 60/117,326,
`
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`X=2, Y =2 arrangement. It may be noted that arrangements
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`which was filed on Jan. 26, 1999
`
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`having the same number of drive lines as they do charge
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`
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`detectors (hereinafter referred to as "square matrices") are
`BACKGROUND OF THE INVENTION
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`greatest number these yield the 10 generally preferred because
`1.Field of the Invention
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`of keys for a given amount of circuitry and wiring. It may
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`The invention pertains to the sensing of matter in contact
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`be noted that the terms 'matrix' and 'square' have nothing to
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`or in close proximity to a surface. One specific area of
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`do with the physical form of the key matrix. The keys can
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`interest is in human interfaces, such as switches, keys, and
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`be arrayed linearly, circularly, or randomly on a single
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`keyboards, used for entry of data or for control of an
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`of surfaces. desired on a plurality 15 surface, or in any fashion
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`apparatus or process. Another specific area of interest is the
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`Moreover, the keys do not have to be the same physical size
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`sensing of inanimate matter such as powders and fluids, as
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`or shape; some can be large and circular, other small and
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`is done in the sensing of the level or volume of a fluent
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`triangu lar, others medium and rectangu lar.
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`material in a container.
`
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`In one embodiment of the invention, each key is associ-
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`20 ated with an alternating voltage source and a pair of elec­
`
`2. Background Information
`
`
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`
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`trodes mounted on or within a solid dielectric substrate or
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`
`
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`The invention employs capacitance sensing, and in par­
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`panel so as to be separated from each other by a gap. The
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`ticular a form of sensing known as 'charge-transfer' (or
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`voltage source is connected to a first electrode, a sampling
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`'QT') sensing which has been taught by the inventor in his
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`charge detector is connected to the second electrode, and the
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`U.S. Pat. No. 5,730,165, the disclosure of which is herein
`
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`25 output of the charge detector is, in turn, fed into a signal
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`incorporated by reference. Charge transfer sensing uses
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`processing means. Disturbances in coupling between the
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`electronic switch closures to induce a charge onto an elec­
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`two electrodes are detected through the solid substrate or
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`trode. A disturbance in the resulting electric field is sensed
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`panel material when a substance or object approaches or
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`by measuring the amount of charge on the electrode and to
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`contacts the panel.
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`thereby determine the change in capacitance at the electrode.
`
`
`Caldwell et al., in U.S. Pat. No. 5,572,205, teach a 30
`In another embodiment of the invention, each key is
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`associated with an alternating voltage source and a pair of
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`capacitive touch control system that is responsive to a user
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`electrodes so as to be separated from each other by a gap.
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`input selection and that can be pad configu red as a touch
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`The voltage source is connected to a first electrode, a
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`disposed on an electrically non-conducting substrate, such
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`sampling charge detector is connected to the second
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`as glass ceramic electrical cook-top. A source signal having
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`35 electrode, and the output of the charge detector is, in turn,
`a primary frequency that is greater than 150 kHz, and
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`fed into a signal processing means. Disturbances in coupling
`preferably in the range of between 150 kHz and 500 kHz, is
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`between the two electrodes are detected when a substance or
`applied to one portion of their touch pad. The touch pad
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`object approaches or contacts the electrode set directly,
`couples the electrical signal to another portion of the touch
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`without an intervening solid dielectric layer.
`pad in order to develop a detection signal, which is decoded
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`in order to determine the presence of the capacitance of a 40
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`In operation of a preferred embodiment of the invention
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`an alternating voltage source is connected to a first (X)
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`user. The decoder preferably includes a peak detector com­
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`electrode that projects a time-varying e-field across a gap.
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`posed of a low gain circuit in order to avoid distortion of the
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`This field is, at least in part, received by a second, receiving
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`detection signal.
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`(Y), electrode. The receiving electrode is connected to a
`BRIEF SUMMARY OF THE INVENTION
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`45 sampling charge detector which acts to sample the change in
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`the charge coupled across the gap caused by the dV/dt of the
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`In the present invention two or more electrodes are
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`pulsed voltage. It is a feature of the invention that the
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`arranged to create an electric field transmitted through an
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`receiving electrode is a low-impedance node during the
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`adjacent dielectric which can be disturbed by the proximity
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`sampling phase of the process. This ensures that the charge
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`circuit is con­measurement of an object A charge transfer
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`50 coupled to the second electrode does not cause an appre­
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`nected to one of the electrodes.
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`ciable voltage rise on the second electrode.
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`Because one of the major anticipated applications of the
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`Although it is believed that the foregoing recital of
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`invention is in keyboards used in data entry, the sensing
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`features and advantages may be of use to one who is skilled
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`elements are sometimes hereinafter referred to as 'keys'. It
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`in the art and who wishes to learn how to practice the
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`will be understood that this is done to simplify the presen­
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`55 invention, it will be recognized that the foregoing recital is
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`tation and to avoid reciting lists of known sensing or
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`not intended to list all of the features and advantages.
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`switching products that could employ the invention, and that
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`Moreover, it may be noted that various embodiments of the
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`'key', when so used, represents a proximity detection zone
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`invention may provide various combinations of the herein­
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`for any possible application.
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`before recited features and advantages of the invention, and
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`Thus, one aspect of the invention is the provision of
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`60 that less than all of the recited features and advantages may
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`apparatus and method for detecting proximity to an elec­
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`be provided by some embodiments.
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`trode pair to form a key. Another aspect of the invention is
`
`BRIEF DESCRIPTION OF THE SEVERAL
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`the provision of apparatus and method for detecting prox­
`VIEWS OF THE DRAWING
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`
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`imity to one or more of a matrix of electrodes so as to form
`FIG. la is
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`
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`a keypad, keyboard, slider switch analog, or level sensor.
`an electrical schematic of one embodiment of
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`65
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`the invention having an alternating signal source and an
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`The creation of a key matrix follows from the arrange­
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`electrode pair.
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`ment of a plurality of electrode pairs, where one of each pair
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`US 6,452,514 Bl
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`
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`4
`3
`FIG. lb is a partial schematic depiction showing a section
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`pulses, etc. can be used instead, for example, to suppress
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`of a solid, fixed dielectric substrate having two electrodes
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`radiated RFI. The nature of the waveform used is not crucial
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`disposed thereon, or alternatively, two fixed electrodes adja­
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`to the discussion of the operation of the invention. Through­
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`cent to a moving dielectric material, solid or fluid, which is
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`out the remainder of the discussion pulses are depicted for
`to be sensed.
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`5 convenience, but these may just as easily be other wave­
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`forms for the above and other reasons, and thus the use of
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`FIG. le is a schematic depiction of the waveform output
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`pulses or square waves should not be construed as a limi­
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`by the alternating signal generator of FIGS. la and lb,
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`tation with regard to any X-drive voltage source depicted in
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`wherein the signal generator is a pulse source.
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`any figure or discussed in conjunction therewith.
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`FIG. ld is a schematic depiction of the waveform output
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`by the alternating signal generator of FIGS. la and lb, 10
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`The receiving electrode 104 receives or sinks the e-field
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`110 via a coupling capacitance 105 that is generally indi­
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`wherein the signal generator is a sinusoidal source.
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`in cated in the drawing with the symbol CD which results
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`FIG. 2a is a partly schematic depiction similar to that of
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`current signal 114 due to the capacitive differentiation of 108
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`FIB. lb, wherein a thin conductive film, such as water, is
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`by means of capacitance 105. An output lead 112 from the
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`shown on the dielectric substrate.
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`15 receiving electrode 104 conducts this current signal to a
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`to FIG. FIG. 2b is an electrical schematic corresponding
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`charge measurement circuit described in conjunction with
`2a.
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`further figures. This differentiation occurs because of the
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`FIG. 3a is a partial schematic depiction, similar to those
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`equation governing current flow through a capacitor:
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`of FIGS. lb and 2a, wherein a massive conducting body,
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`such as a container of water, is shown adjacent the elec-20
`trodes.
`where CE is the inter-electrode capacitance and V is the
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`FIG. 3b is an electrical schematic corresponding to FIG.
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`drive voltage. The amount of charge coupled across each key
`3a
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`during an edge transition is defined as the integral of the
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`FIG. 4a is an electrical schematic of one embodiment of
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`above equation over time, or:
`
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`a charge transfer measurement circuit.
`
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`FIG. 4b is a schematic depiction of timing relationships
`
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`used in the operation of the circuit of FIG. 4a.
`The charge coupled on these transitions, QE is independent
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`FIG. Sa is an electrical schematic of a second embodiment
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`
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`of the rise time of V, which is an important r�sult. Moreover,
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`of a charge transfer measurement circuit.
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`drive elec­30 QE is proportional to the voltage swing on the
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`105coupling capacitance of the trode 100 and the magnitude FIG. Sb is an electrical timing diagram for the circuit of
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`between the driven 100 and receiving 104 electrodes. As is
`FIG. Sa.
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`known in the art, the degree of coupling is dependent on the
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`FIG. 6 is an electrical schematic of an X -Y multiplexed
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`proximity, size, geometry, and relative attitude of the two
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`array of charge measurement circuits of the type depicted in
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`35 electrodes, the material composition of the substrate
`FIG. 4a.
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`dielectric, and the proximity of the composite sense element
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`FIG. 7 is an electrical schematic of an X -Y multiplexed
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`to other objects, such as fluids and human fingers. Inasmuch
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`array of charge measurement circuits of the type depicted in
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`as solid dielectrics, such as plastic and glass, have a much
`FIG. Sa.
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`higher dielectric constant than air, if the substrate is thick
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`FIG. Sa is an electrical schematic of circuitry adapted to 40
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`enough the coupling between the two electrodes 100 and
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`use both the leading and falling edges of the drive signal.
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`104 will principally be through the substrate.
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`FIG. Sb is a schematic depiction of timing relationships in
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`If an external contact is made with the composite sense
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`the operation of the circuit of
`FIG. Sa.
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`element by a conductive film 201, such as by a metal, or by
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`FIG. 9 is a schematic depiction of a slider control or fluid
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`an ionic aqueous fluid as shown in FIG. 2a, the coupling
`level sensing probe made according to the invention.
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`45 between the two electrodes will increase because the exter­
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`nal film will have coupled to it the signal from the emitting
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`electrode 100. The film will then act as a secondary radiator
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`of the same signal, and in turn will strongly couple the same
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`A schematic view of the simplest form of the invention is signal into the receiving electrode 104. FIG. 2b shows
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`shown in FIGS. la, lb, le and ld. A key, or composite
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`50 schematically what occurs when such a film is present. Two
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`sensing element 10 comprises a first, drive, electrode 100
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`additional capacitors 202 and 203 are formed. One of these
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`driven by a signal generator 101, which in one embodiment
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`202 is from the drive electrode to the film, the other 203 is
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`can be a simple CMOS logic gate powered from a conven­
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`from the film to the receive electrode. These act in unison to
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`tionally regulated supply 102 to provide a periodic plurality
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`increase the amount of capacitive signal coupling from the
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`of voltage pulses having some selected duration.
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`driven to the receiving electrode. These effects are prevalent
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`Alternatively, the voltage source 101 can be a sinusoidal
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`in many situations where keypads or contact sensors are to
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`generator or generator of a cyclical voltage having another
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`be used. For example, both outdoor controls exposed to
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`suitable waveform. In one embodiment, a dielectric material
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`condensing humidity and rain, and appliance keypads in
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`or substrate 103 supports the drive electrode 100 as well as
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`kitchens must commonly contend with extraneous films. In
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`a second, receiving, electrode 104 connected to a receiving 60
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`such instances the film should be ignored if at all possible in
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`circuit having a low impedance or 'virtual ground' charac­
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`order to prevent false detection.
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`teristic as depicted in cursory, not literal, fashion by 113. A
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`In practice, electrodes 100 and 104 are typically
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`changing electric field 110 is generated in the dielectric 103
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`interdigitated, which is known in the art to facilitate a higher
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`on the rising 109 and failing 111 edges of the train of voltage
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`amount of coupling of e-field from and to the respective
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`cycles 108 applied to the driven electrode 100 FIG. le shows 65
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`electrodes via the dielectric layer. Interdigitation increases
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`these as pulses, while ld depicts sinusoidal waveforms;
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`the effective 'gain' of the key and reduces the need for higher
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`other waveforms such as triangle waves, slew-rate-limited
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`gain amplification or higher levels of drive signal. Interdigi-
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`25
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`55
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`
`DETAILED DESCRIPTION OF IBE
`
`INVENTION
`
`IPR2020-00778
`Apple EX1014 Page 10
`
`

`

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`US 6,452,514 Bl
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`6
`5
`tation also tends to localize the fields in a more defined area
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`synchronizing means, which may be a microprocessor or
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`and permits the key shape to cover a larger surface than
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`other digital controller 408. In the implementation shown,
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`otherwise possible with simple neighboring electrodes as
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`the reset switch 404 is initially closed in order to reset the
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`FIG. 2b. depicted in FIG. la through
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`charge integrator 402 to a known initial state ( e.g., zero
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`If, on the other hand, external contact is made with the
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`5 volts). The reset switch 404 is then opened, and at some time
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`composite sense element 10 by a large body, such as a
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`thereafter the sampling switch 401 is connected to charge
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`human, or perhaps by a large volume of fluid as shown in
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`integrator 402 via terminal 1 for an interval during which the
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`FIG. 3a, the coupling of charge between 100 and 104 will be
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`voltage source 101 emits a positive transition, and thereafter
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`reconnects to terminal 0, which is an electrical ground or
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`reduced because the large object has a substantial capaci­
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`tance to earth 206 ( or to other nearby structures whose path
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`10 other suitable reference potential. The voltage source 101
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`will complete to the ground reference potential of the
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`then returns to ground, and the process repeats again. At the
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`circuitry controlling the sense elements). This reduced cou­
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`end of a repetition of 'n' of these cycles, (where n is a finite
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`pling occurs because the coupled e-field between the driven
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`non-zero integer) the sampling switch 401 is held at position
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`100 and receiving 104 electrodes is in part diverted away
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`0 while the voltage on the charge integrator 402 is measured
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`from the receiving plate 104 to earth. This is shown sche­
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`15 by a measurement means 407, which may comprise an
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`matically in FIG. 3b. Capacitances 301 and 302 are set up,
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`amplifier, ADC or other circuitry as may be appropriate to
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`which in conjunction with capacitance 304 from the third
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`the application at hand. After the measurement is taken, the
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`object to free space or a local ground, and which act to shunt
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`reset switch 404 is closed again, and the cycle is restarted
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`the e-field away from the direct coupling 105 present
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`when next desired. The process is referred to herein as being
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`between 100 and 104. The coupling capacitance 105 in FIG.
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`20 a measurement 'burst' of length 'n'. where 'n' can range
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`3b is significantly less than is the corresponding coupling
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`from 1 to any finite number. The circuit's sensitivity is
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`capacitance 105 of FIG la as a result of the diversion of field
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`directly related to 'n' and inversely to the value of the charge
`
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`lines to the object 303. If the receive electrode 104 is
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`integrator 402.
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`connected to a 'virtual ground', then the effect of the added
`It should be understood that the circuit element designated
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`capacitance 302 will not be significant. If the receiving
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`25 as 402 provides a charge integration function that may also
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`electrode 104 is connected to a high impedance amplifier,
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`be accomplished by other means, and that the invention is
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`then the effect of 302 can be significant, because it will act
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`not limited to the use of a ground-referenced capacitor as
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`to reduce the signal on 104 even further.
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`shown by 402. It should be self-evident to the practitioner
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`The difference in signal shift polarity between the above
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`that the charge integrator 402 can be an opamp-based
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`two scenarios of FIGS. 2a and 3a is significant and can be
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`30 integrator to integrate the charge flowing through the Y lines.
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`taken advantage of to create a robust sense element which
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`Such integrators also use capacitors to store the charge. It
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`can detect and discriminate between surface films and bulk
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`may be noted that although integrators add circuit complex­
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`materials or human fingers. In one case (e.g., FIG. 2a) the
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`ity they provide a more ideal summing-junction load for Y
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`detected material causes a rise in signal, while in the case of
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`sense currents and more dynamic range. If a slow speed
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`FIG. 3a, the detected material causes a decrease in signal.
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`35 integrator is employed, it may be necessary to use a separate
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`It is preferred in most embodiments to use a solid panel
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`capacitor in the position of 402 to temporarily store the
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`material 103 as an intervening layer between the electrodes
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`charge at high speed until the integrator can absorb it in due
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`and the material or object to be sensed. This is not only for
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`time, but the value of such a capacitor becomes relatively
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`purposes of concealment of the electrodes 100 and 104 and
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`non-critical compared to the value of the integration capaci-
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`associated wiring, but also to allow the fields to 'mix' within
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`40 tor incorporated into the opamp-based integrator.
`
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`the panel prior to exiting into free space. An overlying
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`The circuit shown in FIG. 4a provides an important
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`dielectric panel provides an efficient means of creating
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`electrical feature, that of a 'virtual ground' node on the Y
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`coupling capacitances 105, 301 and 302, the latter two being
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`line, which is sampled during the closure of 401 to position
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`set up when sensing an object, finger, or other substance.
`
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`1.The charge integrator, whether a simple ground-
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`In another embodiment, 103 of FIG. lb is actually the
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`45 referenced capacitor or an opamp-based integrator, provides
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`substance to be sensed, such as a dielectric fluid ( e.g. oil,
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`a summing-junction attribute which, as discussed above , is
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`petrol), or a moving solid ( e.g. a plastic encoder vane) that
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`invaluable for keeping the effects of interference and stray
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`is directly contacting or very close to the electrodes. The
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`capacitance of the Y connections low.
`
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`presence of this fluid or solid adjacent to 100 and 104 creates
`
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`Switch 401 should preferably connect Y lines 112 to
`
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`additional coupling 110 between the electrodes and
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`50 ground when not actually sampling charge to create an
`RF
`
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`increases signal strength, resulting in a higher level of
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`artificial ground plane on the matrix, thus reducing
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`CElOS, which can be readily detected. In this case the
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`emissions, and also permitting the coupled charge of oppo­
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`electrodes are mechanically affixed in space or bonded to a
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`site polarity to that being sensed by the charge integrator 402
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`non-critical dielectric substrate for mechanical stability (not
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`to properly dissipate and neutralize. If one were to omit
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`shown in the context of FIG. lb).
`
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`55 grounding the Y lines between sample pulses the system
`
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`Turning now to FIG. 4a, one finds a circuit based in part
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`would be purely AC coupled and would quickly cease to
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`on the charge-transfer ("QT") apparatus and methods dis­
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`function, because charge would be both pulled and pushed
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`closed in the inventor's U.S. Pat. No. 5,730,165. This circuit
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`across 105 with no DC restoration. It is also possible to use
`
`
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`shows an implementation of a sensor comprising electrodes
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`a resistor to ground on the Y lines to accomplish the same
`
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`
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`100,104, and processing circuitry 400. The exemplar pro­
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`60 effect between transitions of voltage sources 101. As an
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`cessing circuitry 400 depicted in FIG. 4a comprises a
`
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`alternative to a single SPDT switch 401, two independent
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`sampling switch 401, a charge integrator 402 (shown here as
`
`
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`switches can be used if timed in an appropriate manner.
`
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`a simple capacitor), an amplifier 403 and a reset switch 404,
`
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`Although there are many alternative approaches possible, it
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`and may also comprise optional charge cancellation means
`
`
`should be clear that an important feature of a preferred
`
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`405.The timing relationships between the electrode drive
`
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`65 embodiment of the invention is the provision of means for
`
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`signal from the voltage source 101 and the sample timing of
`
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`restoring charge on the receiving plate 104 after each
`
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`switch 401, as shown in FIG. by a suitable4b, are provided
`
`sampling.
`
`IPR2020-00778
`Apple EX1014 Page 11
`
`

`

`
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`US 6,452,514 Bl
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`7
`8
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`As explained in the inventor's U.S. Pat. No. 5,730,165,
`signal controlling switch 401. The switch 401 connects to
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`there are many signal processing options possible for the
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`position 1 of the controlling switch 401 before, during, and
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`manipulation and determination of a detection or measure­
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`after the rising portion of drive signal 100. It is during the
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`ment of signal amplitude. The aforesaid patent also
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`rising portion of 100, slew 109, that the charge is transferred
`
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`describes the gain relationship of the arrangement depicted
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`5 across the coupling capacitance 105. However, if water or
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`in FIG. 4a, albeit in terms of a single electrode system. The
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`other conductive films are present on the touch surface,
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`gain relationship in the present case is the same. The utility
`
`
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`some of the coupled energy will lag in phase with respect to
`
`
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`of a signal cancellation means 405 is described in the
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`
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`the edges 109. This is due to the distributed RC nature of
`
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`inventor's U.S. Pat. No. 4,879,461 as well as the U.S. Pat.
`
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`such films. That is, the film receives an induced charge from
`
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`No. 5,730,165 patent. The disclosure of U.S. Pat. No.
`
`
`
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`10 the drive electrode 100 and the resulting induced currents
`
`
`
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`4,879,461 is herein incorporated by reference. The purpose
`
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`flow through the resistive fluid sheet in two dimensions, and
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`of signal cancellation is to reduce the voltage (i.e. charge)
`
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`
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`charge the parasitic capacitances associated therewith. If the
`
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`
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`buildup on the charge integrator 402 concurrently with the
`
`
`
`sampling switch 401 is held in position 1 for a relatively
`
`
`generation of each burst, so as to permit a higher coupling
`
`
`long time after the rising slew 109 on the drive electrode 100
`
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`between the driven 100 and receiving 104 electrodes. One
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`15 has ended, the film will couple back to the receive electrode
`
`
`
`benefit of this approach is to allow a large sensing area that
`
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`104 and thence through the sampling switch 401 any
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`is sensitive to small deviations in coupling between 100 and
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`
`changes in charge due to the current distribution in the sheet.
`
`
`104 at a low cost. Such large sense couplings are present in
`
`
`
`The conductive sheet will therefore increase the sampled
`
`physically large, highly interdigitated electrodes used in
`
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`signal the longer 401 is held in position 1 after the rising
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`human touch sensing pads. Charge cancellation permits
`
`
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`20 slew of 100 is complete. This effect is also described in my
`measurement of the amount of coupling with greater
`
`
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`
`
`U.S. Pat. No. 5,730,165 with regard to water films around a
`
`
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`
`
`linearity, because linearity is dependent on the ability of the
`
`
`
`
`water spout. It is better, in the presence of fluids, to discon­
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`
`
`coupled charge from the driven 100 to the receiving 104
`
`
`
`
`nect switch 401 very quickly from position 1 so as to limit
`
`
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`electrode to be sunk into a 'virtual ground' node over the
`
`
`
`
`the recovery of charge from the distributed capacitance of
`
`
`
`
`
`course of a burst. If the voltage on the charge integrator 402
`
`
`25 the fluid film. For example, it has been noted experimentally
`
`
`
`
`were allowed to rise appreciably during the course of a burst,
`
`
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`
`that if the lag time between the cessation of the positive slew
`
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`
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`the voltage would rise in inverse exponential fashion. This
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`of 100 and the opening of 401 is less than 200 ns, moisture
`
`
`
`exponential component has a deleterious effect on linearity
`
`
`films will be strongly suppressed; at 50 ns lag time the
`
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`and hence on available dynamic range. There are numerous
`
`
`suppression effect is almost complete.
`
`
`
`
`possible circuits disclosed in the inventor's previous capaci­
`
`
`It may be noted that Ca