USOO7409291B2
`
`(12) Unlted States Patent
`(10) Patent No.:
`US 7,409,291 B2
`
`Pasolini et a].
`(45) Date of Patent:
`Aug. 5, 2008
`
`(54) DEVICE FOR AUTOMATIC DETECTION OF
`STATES OF MOTION AND REST, AND
`PORTABLE ELECTRONIC APPARATUS
`INCORPORATING IT
`
`(75)
`
`.
`.
`.
`Inventors: Fabio Pasolini, S. Martmo S1ccomano
`(IT); Ewes“) Lasalandms 3130113110
`M11anese(IT)
`
`(73) Assignee: STMicroelectronics 5.121., Agrate
`Brianza (IT)
`
`............ 74/5.34
`4/1989 Hartmann et al.
`4,823,626 A *
`............. 280/735
`8/1998 Jeenicke et al.
`5,788,273 A *
`6,320,822 B1* 11/2001 Okeya et 31.
`.................. 368/66
`6,463,347 B1
`10/2002 Nevruz et 31.
`6,463,357 B1 * 10/2002 An et al.
`..................... 700/245
`6,512,310 B1*
`1/2003
`307/121
`
`5/2004 Ishiyama et 31.
`.............. 360/75
`6,738,214 B2 *
`6,858,810 B2 *
`2/2005 Zerbini et 31.
`............ 200/61.08
`
`2002/0033047 A1 *
`
`3/2002 Oguchl et al.
`
`............ 73/514.l6
`
`( * ) Notice:
`
`Subject to any disclaimer, the term of this
`t
`t '
`t
`d d
`d'
`t d
`d
`35
`$1863? 1155:313:11);7321‘d:stuS e un er
`.
`i
`i
`.
`(21) APP]. No.: 10/789,240
`
`* cited by examiner
`Primary ExamineriKhoi H. Tran
`Assistant ExamineriMarie A Weiskopf
`(74) Attorney, Agent, 0}” FirmiLisa K. Jorgenson; Robert
`lannucci; Seed IP Law Group PLLC
`
`(22)
`
`Filed:
`
`Feb. 26, 2004
`
`(65)
`
`Prior Publication Data
`
`US 2004/0172167 A1
`
`Sep. 2, 2004
`
`(51)
`
`Int. Cl-
`(200601)
`G01C 21/00
`(52) US. Cl.
`.......................... 701/220; 700/245; 74/5 R
`(58) Field of Classification Search ................. 700/245,
`700/258, 108, 67; 701/220; 74/5 R, 5.34,
`74/5.46
`See application file for complete search history.
`_
`References Clted
`U.S. PATENT DOCUMENTS
`
`(56)
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`(57)
`
`ABSTRACT
`
`A device for automatic detection of states of motion and rest
`includes at least one inertial sensor, having at least one pref-
`erential detection axis, and a converter, which is coupled to
`the inertial sensor and supplies a first signal correlated to
`forces acting on the first inertial sensor according to the
`preferential detection axis; the device further includes at least
`one processing stage for processing the first signal, which
`supplies a second signal correlated to a dynamic component
`of the first signal, and at least one threshold comparator,
`which supplies a pulse when the second signal exceeds a
`pre-determined threshold.
`
`3,490,719 A *
`
`1/1970 Volpe et a1.
`
`................. 244/169
`
`28 Claims, 2 Drawing Sheets
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`
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`Page 1 of 13
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`SAMSUNG EXHIBIT 1003
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`SAMSUNG EXHIBIT 1003
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`Page 1 of 13
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`US. Patent
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`Aug. 5, 2008
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`Sheet 1 0f2
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`US 7,409,291 B2
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`Page 2 of 13
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`U.S. Patent
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`Aug. 5, 2008
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`Sheet 2 of 2
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`US 7,409,291 B2
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`US 7,409,291 B2
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`1
`DEVICE FOR AUTOMATIC DETECTION OF
`STATES OF MOTION AND REST, AND
`PORTABLE ELECTRONIC APPARATUS
`INCORPORATING IT
`
`BACKGROUND OF THE INVENTION
`
`1. Field of the Invention
`The present invention relates to a device for automatic
`detection of states of motion and rest and to a portable elec-
`tronic apparatus incorporating it.
`2. Description of the Related Art
`As is known, reduction of power consumption is one of the
`main objectives in any sector of modern microelectronics. In
`some fields, however, power consumption has an even deter-
`mining importance in the evaluation the quality of a product.
`Many widely used electronic devices, in fact, are provided
`with a stand-alone battery supply and are normally discon-
`nected from the mains supply; this is, for example, the case of
`cell phones and cordless phones, of palm-top computers and
`radio frequency pointer devices for computers (mouses and
`trackballs). It is clear that the reduction both of supply volt-
`ages and of currents advantageously involves an increase in
`the autonomy of the device and hence a greater convenience
`of use.
`Furthermore, frequently the cited above devices are effec-
`tively usedjust for briefperiods, whereas for most ofthe time
`in which they are on they remain inactive. Consider, for
`example, the ratio between the duration of a call from a cell
`phone and the average time between two successive calls. It is
`clear that, for almost the entire period of operation, the cell
`phone remains inactive, but is in any case supplied and thus
`absorbs a certain power. In effect, the autonomy of the device
`is heavily limited.
`Some devices, after a pre-determined interval of inactivity,
`can be automatically set in a wait state (stand-by), in which all
`the functions not immediately necessary are deactivated; for
`example, in a cell phone it is possible to turn offthe screen and
`all the circuitry that is not involved in identifying an incoming
`call.
`To reactivate the devices from stand-by, it is advantageous
`to exploit a signal linked to an event (such as, for example,
`reception ofa call signal, in the case ofcell phones). However,
`since it is not always possible to associate a signal to an event
`(for example, in the case where it is the user who wants to
`make a call), normally a reactivation key is provided, that the
`user can press for bringing back the device into a normal
`operative state.
`In this case, however, one drawback lies in that the device
`is not immediately ready for use: the user must in fact pick up
`the device, press the reactivation key and wait for the extinc-
`tion of a transient in which the functions previously deacti-
`vated are restored. Although this transient is relatively brief
`(at the most in the region of one second), it is not however
`negligible and in some cases can render the device altogether
`inefficient. For example, in a radio frequency mouse, the
`restore time would be so long that the advantage of having
`low consumption in stand-by would be basically nullified by
`the lower efficiency of use.
`It would, instead, be desirable to have available a device
`incorporated in an apparatus that is able to generate automati-
`cally a reactivation signal when the apparatus is to be used.
`
`BRIEF SUMMARY OF THE INVENTION
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`One embodiment ofthe present invention provides a device
`and an apparatus that enables the problem described above to
`be solved.
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`65
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`One embodiment of the present invention is a device for
`automatic detection of states of motion and rest. The device
`
`2
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`includes an inertial sensor having a preferential detection axis
`and a converter coupled to the inertial sensor and supplying a
`first signal correlated to forces acting on the first inertial
`sensor according to the preferential detection axis. The device
`also includes a processing stage structured to process the first
`signal and supply a second signal correlated to a dynamic
`component of the first signal; and a threshold comparator
`supplying a pulse when the second signal exceeds a pre-
`determined threshold.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`For a better understanding ofthe invention, an embodiment
`thereof is now described, purely by way of non-limiting
`example and with reference to the attached drawings,
`in
`which:
`FIG. 1 illustrates a simplified block diagram of an appara-
`tus incorporating a device made according to the present
`invention;
`FIG. 2 illustrates a more detailed circuit block diagram of
`the device according to the present invention; and
`FIG. 3 is a schematic plan view of a detail of the device of
`FIG. 2.
`
`DETAILED DESCRIPTION OF THE INVENTION
`
`With reference to FIG. 1, designated, as a whole, by the
`reference number 1 is a portable electronic apparatus, which,
`in the example illustrated herein, is a palm-top computer; this
`must not, however, be considered in any way limiting, in so
`far as the apparatus 1 could also be of a different type. The
`apparatus 1 comprises at least one battery 2, a control unit 3,
`a memory 4, an input/output (I/O) unit 5 (for example an
`infrared serial port), a screen 6, a counter 8 and an activation
`device 10.
`
`An output 2a of the battery 2, which supplies a supply
`voltage VDD, is connected to respective supply inputs of the
`control unit 3, the memory 4, the I/O unit 5, the screen 6, the
`counter 8 and the activation device 10.
`
`Furthermore, the control unit 3, the memory 4, the I/O unit
`5 and the screen 6 have: respective stand-by inputs connected
`to an output 8a of the counter 8, which supplies stand-by
`pulses STBY; and respective activation inputs, connected to
`an output 10a of the activation device 10, which supplies
`activation pulses WU (“Wake-Up”). Furthermore, the counter
`8 has a counting input connected to an output 3a ofthe control
`unit 3, which supplies a counting signal CT. In the presence of
`a first value of the counting signal CT, the counter 8 is dis-
`abled; when the counting signal CT switches from the first
`value to a second value, the counter 8 is reset and then incre-
`mented at each clock cycle. If the counter 8 reaches a pre-
`determined threshold counting value, a stand-by pulse STBY
`is generated.
`During normal operation of the apparatus 1 (active state),
`the control unit 3 maintains the counting signal CT at the first
`value, disabling the counter 8. When, instead, the control unit
`3 recognizes a condition in which the apparatus 1 is turned on,
`but is not used (for example, when the control unit 3 must
`execute only wait cycles), the counting signal is set at the
`second value, and the counter 8 is thus activated. After a
`pre-determined period of inactivity, the counter 8 reaches the
`threshold counting value and supplies at output a stand-by
`pulse STBY; in this way, the control unit 3, the screen 6, the
`I/O unit 5 and the memory 4 are set in a stand-by state, i.e., in
`an inoperative mode in which power consumption is mini-
`mized.
`The activation device 10, the structure of which will be
`described in detail hereinafter, detects the accelerations to
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`US 7,409,291 B2
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`3
`which the apparatus 1 is subjected, preferably along a first
`axis X, a second axis Y and a third axis Z orthogonal to one
`another and fixed to the apparatus 1. More precisely, the
`activation device 10 detects both the static accelerations (due
`to constant forces, like the force of gravity) and dynamic
`accelerations (due to non-constant forces) to which the appa-
`ratus 1 is subjected.
`When the apparatus 1 is not used, it usually remains sub-
`stantially immobile or in any case subjected to forces of
`negligible intensity, for example because it is resting on a
`shelf. As has been mentioned previously, after a pre-deter-
`mined time interval, the apparatus 1 goes into a stand-by state.
`In these conditions, the activation device 10 detects dynamic
`accelerations which are practically zero and maintains its
`output 10a constant at a resting logic value; the apparatus 1
`thus remains in stand-by.
`When the dynamic accelerations directed along at least one
`of the three axes X, Y, Z exceed a pre-determined threshold,
`the activation device 10 generates an activation pulse WU
`thus bringing its output 10a to an activation logic value. In the
`presence of an activation pulse WU, any possible standby
`pulses STBY are ignored, and the control unit 3, the screen 6,
`the I/O unit 5 and the memory 4 are set in the active state. The
`activation pulse WU terminates when all the dynamic accel-
`erations along the first axis X, the second axis Y and the third
`axis Z return below the pre-determined threshold.
`The activation device 10 is based upon capacitive-unbal-
`ance linear inertial sensors, made using MEMS (Micro-Elec-
`tro-Mechanical Systems) technology. For greater clarity,
`FIG. 2 illustrates a first inertial sensor 20, having a preferen-
`tial detection axis parallel to the first axis X.
`In detail, the first inertial sensor 20 comprises a stator 12
`and a moving element 13, connected to one another by means
`of springs 14 in such a way that the moving element 13 may
`translate parallel to the first axis X, whereas it is basically
`fixed with respect to the second axisY and the third axis Z (in
`FIG. 2, the third axis Z is orthogonal to the plane ofthe sheet).
`The stator 12 and the moving element 13 are provided with
`a plurality of first and second stator electrodes 15', 15" and,
`respectively, with a plurality of mobile electrodes 16, which
`extend basically parallel to the plane Y-Z. Each mobile elec-
`trode 16 is comprised between two respective stator elec-
`trodes 15', 15", which it partially faces; consequently, each
`mobile electrode 16 forms with the two adjacent fixed elec-
`trodes 15', 15" a first capacitor and, respectively, a second
`capacitor with plane and parallel faces. Furthermore, all the
`first stator electrodes 15' are connected to a first stator termi-
`nal 20a and all the second stator electrodes 15" are connected
`to a second stator terminal 20b, while the mobile electrodes
`16 are connected to ground. From the electrical standpoint,
`hence, the first inertial sensor 11 can be idealized by means of
`a first equivalent capacitor 18 and a second equivalent capaci-
`tor 19 (illustrated herein with a dashed line), having first
`terminals connected to the first stator terminal 20a and to the
`
`second stator terminal 20b, respectively, and second termi-
`nals connected to ground. Furthermore, the first and second
`equivalent capacitors 18, 19 have a variable capacitance cor-
`related to the relative position of the moving element 13 with
`respect to the rotor 12; in particular, the capacitances of the
`equivalent capacitors 18, 19 at rest are equal and are unbal-
`anced in the presence of an acceleration oriented according to
`the preferential detection axis (in this case, the first axis X).
`With reference to FIG. 3, the activation device 10 com-
`prises, in addition to the first inertial sensor 20, a second
`inertial sensor 21 and a third inertial sensor 22, identical to the
`first inertial sensor 20 and having preferential detection axes
`parallel to the second axis Y and to the third axis Z, respec-
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`tively. Moreover, the activation device 10 comprises: a mul-
`tiplexer 24; a capacitance-voltage (C-V) converter 25; a
`demultiplexer 26; a first detection line 28; a second detection
`line 29 and a third detection line 30, associated respectively to
`the first inertial sensor 20, to the second inertial sensor 21 and
`to the third inertial sensor 22; an output logic gate 31; and a
`phase generator 32.
`First stator terminals 20a, 21a, 22a and second stator ter-
`minals 20b, 21b, 22b respectively ofthe first, second and third
`inertial sensors 20, 21, 22 are selectively connectable in
`sequence to detection inputs 25a, 25b ofthe C-V converter 25
`via the multiplexer 24. For this purpose, a control input 24a of
`the multiplexer 24 is connected to a first output of the phase
`generator 32, which supplies a first selection signal SELl.
`The C-V converter 25 is based upon a differential charge-
`amplifier circuit, of a type in itself known, and has a timing
`input 250, connected to a second output ofthe phase generator
`32, which supplies timing signals CK, and an output 25d,
`which supplies, in sequence, sampled values of a first accel-
`eration signal AX, a second acceleration signal AYand a third
`acceleration signal AZ, correlated to the accelerations along
`the first, second and third axes X, Y, Z, respectively.
`The demultiplexer 26 connects the output of the C—V con-
`verter 25 selectively and in sequence to respective inputs of
`the first, second and third detection lines 28, 29, 30, which
`thus receive respectively the first, second and third accelera-
`tion signalsAX, AY, AZ. For this purpose, the demultiplexer 26
`has a control input 2611 connected to a second output of the
`phase generator 32, which supplies a second selection signal
`SEL2.
`
`Each of the detection lines 28, 29, 30 comprises a subtrac-
`tor node 34, a filter 35, of a low-pass type, and a threshold
`comparator 36. In greater detail, the input of each detection
`line 28, 29, 30 is directly connected to a non-inverting input
`34a of the adder node 34 and is moreover connected to an
`
`inverting input 34b of the adder node 34 itself through the
`respective filter 35.
`In practice, the filters 35 extract the dc. components ofthe
`acceleration signals AX, AY, AZ and supplies at output a first
`static-acceleration signal AXS, a second static-acceleration
`signal AYS and a third static-acceleration signal AZS, respec-
`tively. The subtractor nodes 34 subtract the static-acceleration
`signals AXS, AYS, A25 from the corresponding acceleration
`signals AX, AY, AZ. A first dynamic-acceleration signal AXD,
`a second dynamic-acceleration signal Am and a third
`dynamic-acceleration signal AZD, which are correlated exclu-
`sively to the accelerations due to variable forces, are thus
`provided on the outputs of the subtractor nodes 35 of the first,
`second and third detection lines 28, 29, 30, respectively.
`The threshold comparators 36 have inputs connected to the
`outputs of the respective subtractor nodes 34 and outputs
`connected to the logic gate 31, which in the embodiment
`described is an OR gate. Furthermore, the output of the logic
`gate 31 forms the output 10a of the activation device 10 and
`supplies the activation pulses WU. In particular, an activation
`pulse WU is generated when at least one of the dynamic-
`acceleration signals AXD, Am, AZD is higher than a pre-
`determined threshold accelerationATH stored in the threshold
`comparators 36; the activation pulses WU terminate when all
`the dynamic-acceleration signals AXD, AYD, AZD return below
`the threshold acceleration ATH. The threshold acceleration
`Am is moreover programmable and is preferably so selected
`as to be exceeded in the presence of the stresses that the user
`impresses on the apparatus 1 during normal use.
`In practice, the C-V converter 25 reads the capacitive
`unbalancing values ACX, ACY, ACZ of the inertial sensors 20,
`21, 22, to which it is sequentially connected and converts the
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`US 7,409,291 B2
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`5
`capacitive unbalancing values ACX, ACY, ACZ into a voltage
`signal VA, which is then sampled. The first, second and third
`acceleration signals AX, AY, AZ hence comprise respective
`sequences of sampled values of the voltage signal VA gener-
`ated when the C-V converter 25 is connected respectively to
`the first, the second and the third inertial sensor 20, 21, 22;
`moreover, the first, second and third acceleration signal AX,
`AY, AZ indicate the sum ofall the accelerations that act respec-
`tively along the first, second and third axes X, Y, Z.
`The static-acceleration signals AXS, AYS, A25 supplied by
`the filters 35, which basically correspond to the dc. compo-
`nents of the acceleration signals AX, AY, AZ, are correlated to
`the accelerations due to constant forces, such as for example
`the force of gravity. Note that, since the apparatus 1 can be
`variously oriented both during use and when it is not in use,
`not necessarily are the components of the force of gravity
`along the axes X, Y, Z always constant and they may be
`non-zero even when the apparatus 1 is not moved. However,
`as long as the apparatus 1 remains at rest, the force of gravity
`supplies constant contributions to the acceleration signalsAX,
`AY, AZ. The static-acceleration signals AXS, AYS, AZStake into
`account also all the causes that can determine, in the inertial
`sensors 20, 21, 22, a permanent displacement of the moving
`element 13 from the position of rest with respect to the stator
`12 (FIG. 2). Amongst these causes, for example, there are
`fabrication offsets and deviations that can be caused by the
`fatiguing of the materials, especially in the springs 14. Sub-
`traction of the static-acceleration signals AXS, AYS, A25 from
`the acceleration signals AX, AY, AZ advantageously enables
`compensation of said offsets.
`The dynamic-acceleration signals AXD, Am, AZD are
`exclusively correlated to the accelerations due to variable
`forces and, in practice, are different from zero only when the
`apparatus 1 is moved, i.e., when it is picked up to be used.
`Consequently, at the precise moment when the user picks up
`the apparatus 1, at least one of the dynamic-acceleration
`signals AXD, Am, AZD exceeds the threshold acceleration
`Am of the respective threshold comparator 36, and an activa-
`tion pulse WU is supplied, which brings the control unit 3, the
`memory 4, the 1/0 unit 5 and the screen 6 back into the active
`state. Note that, in this case, also the force of gravity can
`advantageously provide a contribution to the dynamic-accel-
`eration signals AXD, Am, AZD, as far as the apparatus 1 can be
`rotated by the user so as to change the orientation of the axes
`X, Y, Z with respect to the vertical direction (i.e., with respect
`to the direction of the force of gravity). Consequently, the
`movement due to the intervention of the user is more readily
`detected.
`
`Some advantages of the invention are evident from the
`foregoing description. In the first place, the activation device
`10 enables the apparatus 1 to be brought back automatically
`into the active state from the stand-by state, since it is based
`just upon the forces that are transmitted by the user when he
`picks up the apparatus 1 to use it. In practice, the activation
`device 10 is able to distinguish a condition of use from a
`condition of rest by simply detecting a state of motion from a
`state of substantial rest. Consequently, the apparatus 1 is
`reactivated as soon as it is picked up by the user and the
`transients of exit from the stand-by state are exhausted when
`the user is terminating the movement of picking up the appa-
`ratus 1. The troublesome delays, that can reduce or eliminate
`the advantages deriving from the use of portable apparatus
`with stand-alone supply, are thus prevented. Furthermore, the
`use of inertial sensors of the MEMS type, which are
`extremely sensitive, have small overall dimensions and canbe
`made at relatively low costs,
`is advantageous. Above all,
`however, the MEMS sensors have a virtually negligible con-
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`sumption: consequently, the energy accumulated in the bat-
`teries is almost entirely available for active use of the appa-
`ratus 1,
`the effective autonomy whereof is significantly
`increased.
`
`Finally, it is clear that modifications and variations can be
`made to the device described herein, without thereby depart-
`ing from the scope of the present invention. In particular, the
`activation device 10 could comprise two inertial sensors (for
`example, in the case of a radio frequency mouse, which in use
`is displaced just in one plane) or even just one inertial sensor;
`inertial sensors of a different type could also be used, for
`example rotational inertial sensors or else inertial sensors
`with more than one degree of freedom (i.e., having at least
`two preferential non-parallel detection axes). Furthermore,
`there can be provided a C-V converter for each inertial sensor
`used; in this case, use of the multiplexer and demultiplexer is
`not required.
`All of the above US. patents, US. patent application pub-
`lications, US. patent applications, foreign patents, foreign
`patent applications and non-patent publications referred to in
`this specification and/or listed in the Application Data Sheet,
`are incorporated herein by reference, in their entirety.
`From the foregoing it will be appreciated that, although
`specific embodiments of the invention have been described
`herein for purposes of illustration, various modifications may
`be made without deviating from the spirit and scope of the
`invention. Accordingly, the invention is not limited except as
`by the appended claims.
`The invention claimed is:
`1. A device for automatic detection of states of motion and
`
`rest, comprising:
`a first inertial sensor having a first preferential detection
`axis;
`a converter coupled to said first inertial sensor and supply-
`ing a first signal correlated to forces acting on said first
`inertial sensor according to said first preferential detec-
`tion axis;
`a first processing stage structured to process said first sig-
`nal and supply a second signal correlated to a dynamic
`component of said first signal wherein said first process-
`ing stage comprises a filter, supplying a third signal
`correlated to a static component of said first signal, and
`a subtractor element, for subtracting said third signal
`from said first signal; and
`a first threshold comparator supplying a pulse when said
`second signal exceeds a threshold.
`2. The device according to claim 1 wherein said first iner-
`tial sensor is a micro-electro-mechanical sensor with capaci-
`tive unbalancing.
`3. The device according to claim 1, further comprising a
`second inertial sensor having a second preferential detection
`axis, the first and second inertial sensors being of a micro-
`electro -mechanical type with capacitive unbalancing, the first
`preferential detection axis and the second preferential detec-
`tion axis being orthogonal to one another.
`4. The device according to claim 3 said first inertial sensor
`and said second inertial sensor are selectively connectable in
`sequence to said converter.
`5. The device according to claim 4, comprising a third
`inertial sensor of a micro-electro-mechanical
`type with
`capacitive unbalancing, having a third preferential detection
`axis, orthogonal to said first preferential detection axis and to
`said second preferential detection axis.
`6. The device according to claim 5, further comprising a
`switch device positioned to selectively connect said first iner-
`tial sensor, said second inertial sensor and said third inertial
`sensor in sequence to said converter.
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`7
`7. The device according to claim 1, further comprising a
`second inertial sensor having a second preferential detection
`axis that is transverse to the first preferential detection axis.
`8. The device according to claim 7, further comprising:
`a multiplexer connected between the inertial sensors and
`the converter to selectively electrically connect each of
`the inertial sensors to the converter, the converter sup-
`plying a third signal correlated to forces acting on said
`second inertial sensor according to said second prefer-
`ential detection axis;
`a second processing stage structured to process said third
`signal and supply a fourth signal correlated to a dynamic
`component of said third signal;
`a second threshold comparator supplying a pulse when said
`fourth signal exceeds the threshold; and
`a demultiplexer connected between the converter and the
`first and second processing stages to selectively supply
`the first and third signals to the first and second process-
`ing stages, respectively.
`9. The device according to claim 8, further comprising:
`a phase generator connected to the multiplexer, converter,
`and demultiplexer and structured to provide timing sig-
`nals that coordinate operations of the multiplexer, con-
`verter, and demultiplexer.
`10. A portable electronic apparatus, comprising:
`a supply source;
`a plurality of user devices alternatively connected to said
`supply source in a first operative state, and disconnected
`from said supply source in a second operative state;
`deactivation means connected to said user devices for set-
`
`ting said user devices in said second operative state; and
`activation means for setting the user devices in the first
`operative state, said activation means including:
`a first inertial sensor having a preferential detection axis,
`a converter coupled to said first inertial sensor and supply-
`ing a first signal correlated to forces acting on said first
`inertial sensor according to said preferential detection
`axis;
`a first processing stage structured to process said first sig-
`nal and supply a second signal correlated to a dynamic
`component of said first signal, and
`a first threshold comparator supplying an activation pulse
`when said second signal exceeds a threshold.
`11. An apparatus according to claim 10 wherein, in the
`presence of the activation pulse, said user devices are in said
`first operative state.
`12. The apparatus according to claim 10 wherein said first
`processing stage comprises a filter, supplying a third signal
`correlated to a static component of said first signal, and a
`subtractor element, for subtracting said third signal from said
`first signal.
`13. The apparatus according to claim 10 wherein said first
`inertial sensor is a micro-electro-mechanical sensor with
`
`5
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`40
`
`45
`
`50
`
`capacitive unbalancing.
`14. The apparatus according to claim 10, wherein said
`activation means further include a second inertial sensor hav-
`
`55
`
`ing a second preferential detection axis, the first and second
`inertial sensors being of a micro-electro-mechanical type
`with capacitive unbalancing, the first preferential detection
`axis and the second preferential detection axis being orthogo-
`nal to one another.
`
`15. The apparatus according to claim 14, wherein said
`activation means further include a third inertial sensor of a
`
`micro-electro-mechanical type with capacitive unbalancing,
`having a third preferential detection axis, orthogonal to said
`first preferential detection axis and to said second preferential
`detection axis.
`
`60
`
`65
`
`8
`16. The apparatus according to claim 10, wherein said
`activation means further include a second inertial sensor hav-
`
`ing a second preferential detection axis that is transverse to
`the first preferential detection axis.
`17. The apparatus according to claim 16, wherein said
`activation means further include:
`
`a multiplexer connected between the inertial sensors and
`the converter to selectively electrically connect each of
`the inertial sensors to the converter, the converter sup-
`plying a third signal correlated to forces acting on said
`second inertial sensor according to said second prefer-
`ential detection axis;
`a second processing stage structured to process said third
`signal and supply a fourth signal correlated to a dynamic
`component of said third signal;
`a second threshold comparator supplying a pulse when said
`fourth signal exceeds the threshold; and
`a demultiplexer connected between the converter and the
`first and second processing stages to selectively supply
`the first and third signals to the first and second process-
`ing stages, respectively.
`18. The apparatus according to claim 10, wherein said
`activation means further include:
`
`a phase generator connected to the multiplexer, converter,
`and demultiplexer and structured to provide timing sig-
`nals that coordinate operations of the multiplexer, con-
`verter, and demultiplexer.
`19. A method for automatic detection of motion of a por-
`table electronic device, comprising:
`sensing motion of the device along a first preferential
`detection axis;
`supplying a first signal correlated to forces acting on the
`device according to the preferential detection axis;
`processing the first signal and supplying a second signal
`correlated to a dynamic component of the first signal
`wherein the processing comprises filtering the first sig-
`nal to create a third signal correlated to a static compo-
`nent of the first signal, and subtracting the third signal
`from the first signal to create the second signal; and
`supplying an activation pulse when the second signal
`exceeds a first threshold.
`
`20. The method of claim 19, further comprising
`sensing motion of the device along a second preferential
`detection axis that is orthogonal to the first preferential
`detection axis;
`supplying a third signal correlated to forces acting on the
`device according to the second preferential detection
`axis;
`processing the third signal and supplying a fourth signal
`correlated to a dynamic component of the third signal;
`and
`
`supplying the activation pulse when the fourth signal
`exceeds a second threshold.
`
`21. The method of claim 19, further comprising:
`receiving the activation pulse at an operation circuit of the
`device, the operation circuit being in a stand-by condi-
`tion prior to receiving the activation pulse; and
`activating the operation circuit into an active condition in
`response to receiving the activation pulse.
`22. A device, comprising:
`a first inertial sensor having a first preferential detection
`axis;
`a converter coupled to the first inertial sensor and supply-
`ing a first signal correlated to forces acting on the first
`inertial sensor according to the first preferential detec-
`tion axis;
`
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`Page 7 of 13
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`US 7,409,291 B2
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`10
`sensing motion of the device along a second preferential
`detection axis that is orthogonal to the first preferential
`detection axis;
`supplying a third signal correlated to forces acting on the
`device according to the second preferential detection
`ax1s;
`processing the third signal and supplying a fourth signal
`correlated to a dynamic component of the third signal;
`and
`
`supplying the activation pulse when the fourth signal
`exceeds a second threshold.
`
`26. The method of claim 25, further comprising:
`sensing motion of the device along a third preferentia