Case 6:21-cv-01101-ADA Document 25-14 Filed 04/14/22 Page 1 of 6
`Case 6:21-cv-01101-ADA Document 25-14 Filed 04/14/22 Page 1 of 6
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`EXHIBIT N
`EXHIBIT N
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`Ulllted States Patent [19]
`Watkins
`
`US006150948A
`[11] Patent Number:
`[45] Date of Patent:
`
`6,150,948
`Nov. 21, 2000
`
`[54] LOW-POWER RADIO FREQUENCY
`
`4,847,485
`
`7/1989 Koelsch
`
`.... .. 340/567 X
`
`IDENTIFICATION READER
`
`[75] Inventor: Randy W. Watkins, ChatsWorth, Calif.
`[73] Assigneez soundcraft’ Inc‘, Chatsworth, Calif‘
`
`[21] Appl' NO‘: 09/299’121
`[22]
`Filed;
`Apt; 24, 1999
`
`[51]
`
`7
`Int. Cl. ................................................... .. G08B 23/00
`U-S- Cl- ................ ..
`[58] Field of Search ............................ .. 340/5721, 573.1,
`340/105, 825.34, 505, 567, 522, 693.3
`
`[56]
`
`References Cited
`U.S. PATENT DOCUMENTS
`
`5,682,032 10/1997 Philipp . . . . . .
`. . . . . . . . .. 235/422
`6,040,773
`3/2000 Vega et a1. ......................... .. 340/5721
`Primary Examiner_Thomas Mullen
`Attorney, Agent, or Ftrm—Natan Epstein; Beehler & Pavitt
`[57]
`ABSTRACT
`Practical battery operation of radio-frequency proximity
`readers is made possible by monitoring activity in the RFID
`reader’s sensing ?eld With a secondary detector such as a
`passive infrared detector, and powering up the RFID reader
`only upon detection of activity
`the Secondary detector'
`The RFID reader is kept to a loW duty cycle relative to the
`secondary detector Which is chosen for relatively loW poWer
`consumption to achieve a net reduction in operating poWer
`requirements of the combined RFID reader and secondary
`detector'
`
`4,240,064 12/1980 DevChoudhury ................. .. 235/462 X
`
`10 Claims, 1 Drawing Sheet
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`Case 6:21-cv-01101-ADA Document 25-14 Filed 04/14/22 Page 2 of 6
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`U.S. Patent
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`Nov. 21, 2000
`
`6,150,948
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`Case 6:21-cv-01101-ADA Document 25-14 Filed 04/14/22 Page 3 of 6
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`

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`6,150,948
`
`1
`LOW-POWER RADIO FREQUENCY
`IDENTIFICATION READER
`
`BACKGROUND OF THE INVENTION
`
`1. Field of the Invention
`This invention relates to radio-frequency identi?cation
`readers used in conjunction With identi?cation tags in con
`trolled access systems, and more particularly is directed to
`loW poWer proximity readers suitable for battery poWered
`operation.
`2. State of the Prior Art
`Radio Frequency Identi?cation Systems (RFID) have
`come into Widespread usage and generally include a reader,
`typically installed in a ?xed location, and a population of
`portable identi?cation tags. Each ID tag contains a transpon
`der unit Which returns a coded response When interrogated
`by a radio-frequency transmission from the reader. The
`reader periodically sends out a transmission designed to
`evoke a radio-frequency response from any ID tags Within
`range of the reader. The tag response includes coded iden
`ti?cation data based on Which the reader makes a decision to
`grant or deny access to controlled facilities. RFID systems
`may use active tags Which carry their oWn source of poWer
`such as a battery, or passive tags Which contain no source of
`poWer and instead rely entirely on energy radiated by the
`reader unit. Passive tag readers continually or periodically
`search for the presence of passive tags in the vicinity of the
`reader by transmitting energy Which Will activate any tag
`present. Apassive tag does not announce is presence unless
`activated by the reader. Furthermore, the passive ID tag
`requires that is receive suf?cient radio-frequency poWer
`Which, When converted by the tag into the electrical current,
`Will support operation of the tag’s electronic circuits.
`Consequently, the operating range of the reader/tag system
`is to a large extent determined by the poWer transmitted by
`the reader, and the ID tag must come into suf?cient prox
`imity to the reader for the tag to be activated. For this reason
`passive tag readers as also knoWn as proximity readers.
`Proximity readers typically have substantially greater oper
`ating poWer requirements than active tag RFID readers of
`comparable range, and the development of portable battery
`poWered proximity readers has been hindered by excessive
`poWer drain on the batteries.
`A continuing need exists for RFID readers of reduced
`operating poWer requirements and, in particular, for a loW
`poWer proximity reader Which can be adequately poWered
`by batteries for portable use.
`
`SUMMARY OF THE INVENTION
`
`Case 6:21-cv-01101-ADA Document 25-14 Filed 04/14/22 Page 4 of 6
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`The present invention addresses the aforementioned need
`by providing a loW poWer radio-frequency identi?cation
`reader system Which includes a RFID tag reader operative
`for detecting and verifying the presence of identi?cation
`tags, and a secondary detector operative for detecting a
`change in the sensing ?eld of the RFID tag reader indicative
`of the possible entry of an identi?cation tag into the reader’s
`sensing ?eld and deriving an enabling signal responsive to
`such a change. By detecting such changes the secondary
`detector serves to detect the entry of an object into the
`sensing ?eld but by means other than evoking a radio
`frequency response from such an object.
`A poWer supply is provided for supplying operating
`poWer to the RFID tag reader and to the secondary detector.
`The detector and the reader each have an average operating
`poWer requirement, and the secondary detector is selected to
`
`2
`have a substantially smaller average operating poWer
`requirement than the reader. A poWer sWitching circuit
`normally limits or cuts of poWer from the poWer supply to
`the RFID tag reader While supplying the secondary detector.
`Full operating poWer to the RFID tag reader is enabled by
`the poWer sWitching circuit for a limited period of time in
`response to the enabling signal in order to verify the pres
`ence of an ID tag and, if so, to permit access to the controlled
`facilities. As a result, the RFID reader is relegated to a loW
`duty cycle relative to the secondary detector and the overall
`or average operating poWer of the reader system is con
`served by only operating the RFID tag reader brie?y upon
`detection of a physical change such as movement in the
`reader’s sensing ?eld indicative of the possible presence of
`an ID tag.
`Although the loW poWer RFID tag reader system of this
`invention is not limited to any particular type of RFID
`reader, it Will be found most useful With proximity or passive
`tag readers because of their relatively high operating poWer
`requirements. For this reason, in a preferred form of the
`invention, the RFID reader is a proximity reader designed to
`detect the presence of passive identi?cation tags.
`The secondary detector is not limited to any particular
`sensing technology. Rather, the secondary detector should
`be chosen to draW little poWer as compared to the RFID
`reader so that a signi?cant poWer savings can be realiZed by
`reducing the duty cycle of the RFID reader and relying
`instead on the secondary detector most of the time. The
`secondary detector may, for example and Without limitation,
`be selected from the group comprised of passive infrared,
`inductive, capacitive, microWave and ultrasound detectors.
`Generally the secondary detector operates as a motion
`detector since the changes to Which it responds are normally
`brought about by movement of objects Which are not nec
`essarily ID tags. A presently preferred secondary detector is
`a passive infrared sensor designed to sense changes in the
`infrared background in the reader’s sensing ?eld.
`PoWer savings may be optimiZed by limiting operation of
`the RFID reader to approximately the time period required
`to verify the presence of an ID tag, i.e., to transmit a
`radio-frequency interrogation signal, to receive and decode
`a response form an ID tag if present in the sensing ?eld, and
`if an ID tag is detected, to execute an access control function
`such as unlocking a door and then locking it again. Upon
`completion of the tag read function or access control
`function, the tag reader outputs a disabling or off control
`signal to the poWer control sWitch for returning the tag
`reader to a poWer limited Wait state.
`This invention also extends to a method of operating a
`radio-frequency identi?cation tag reader having a sensing
`?eld, comprising the steps of placing the RFID reader in a
`Wait state or sleep mode, detecting the introduction of an
`object into the sensing ?eld, activating or Waking the radio
`frequency reader for a relatively short period of time at least
`suf?cient for evoking a response from an identi?cation tag
`is present in the sensing ?eld; and returning the radio
`frequency proximity reader to the Wait state or sleep mode.
`The step of detecting may include sensing a change in a
`physical characteristic Within the sensing ?eld such as a
`change in position of an object not necessarily an ID tag
`Within the sensing ?eld of the RFID reader The change in
`position may be made by infrared, inductive, capacitive,
`ultrasound or microWave sensing.
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`BRIEF DESCRIPTION OF THE DRAWINGS
`FIG. 1 is a block diagram of a loW poWer consumption
`radio frequency identi?cation system according to this
`invention;
`
`

`

`3
`FIG. 2 depicts a loW-poWer RFID reader system accord
`ing to this invention featuring a passive infrared secondary
`detector; and
`FIG. 3 is a plan vieW diagram of the loW-poWer RFID
`reader system of FIG. 2 illustrating the RFID sensing ?eld
`and overlapping passive infrared ?eld of vieW.
`DETAILED DESCRIPTION OF THE
`PREFERRED EMBODIMENTS
`With reference to the accompanying draWing, FIG. 1
`shoWs in block diagram form a loW-poWer identi?cation tag
`reader system generally designated by numeral. Reader
`system 10 includes a radio frequency tag reader 12 Which
`may be any type of radio frequency reader, but for reasons
`given herein, this invention is particularly useful With proX
`imity or passive RFID tag readers because of their greater
`operating poWer consumption. The reader system 10 is
`supplied With operating poWer by electrical poWer supply 14
`connected to the reader 12 through a poWer control circuit or
`sWitch 16. PoWer supply 14 may be an AC. line poWer
`supply but Will normally be a battery poWer supply since a
`principal object of this invention is to enable practical
`battery operation of the reader system 10.
`The tag reader 12 has a radio frequency antenna 18,
`suggested in phantom lining in FIG. 2, Which emits an
`interrogation signal designed to evoke a response from ID
`tags in sufficient proximity to the reader 12, and to receive
`a radio frequency response signal from any such ID tags.
`The antenna or antenna system of the tag reader 12 has a
`sensing ?eld S, suggested b the concentric arcs in FIG. 3,
`Within Which the ID reader is capable of evoking a response
`from ID tags and also to receive the response signal from the
`tags. Outside of this sensing ?eld, the strength of the
`interrogation signal may be insuf?cient to evoke a response,
`or if a response is evoked, the strength of the response signal
`at the antenna 18 is too Weak to be read by the reader 12. Not
`only is the range of the tag reader 12 limited in terms of
`distance from the antenna, but the range may also vary With
`direction from the antenna, i.e., the antenna may be a
`directional pattern With greatest sensitivity in a particular
`direction and diminishing sensitivity aWay from that direc
`tion. Directionality of the tag reader may be further deter
`mined not only by the antenna radiation pattern but also by
`the physical environment around the reader. If the reader
`system 10 is mounted on a Wall W as in FIG. 3, then the
`effective sensing ?eld S is limited to the area in front of that
`Wall because ID tags Will be present only in that area and not
`behind the Wall, even though the tag reader’s radio fre
`quency ?eld may in fact eXtend through and behind the Wall.
`Consequently, the sensing ?eld of the tag reader 12 is limited
`in range and direction by its radio frequency signal radiation
`and reception patterns and by the physical environment
`around the reader system 10 as in FIGS. 2 and 3.
`According to this invention a secondary detector 20 is
`provided having a ?eld of vieW V Which generally overlaps
`the sensing ?eld S of the RFID tag reader 12. The presently
`preferred secondary detector 20 is a passive infrared (PIR)
`motion detector of the type commonly used in home security
`systems for turning on lights in response to changes in the
`infrared background in the detector’s ?eld of vieW, such as
`a person’s moving body in front of the PIR detector. PIR
`detectors of this type are noW commercially available at loW
`cost. In conventional applications the PIR detector derives
`an output signal Which is typically used to trigger a security
`alarm or to sWitch lights.
`When implemented according to this invention as the
`secondary detector 20, a PIR detector is arranged and
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`6,150,948
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`positioned as in FIGS. 2 and 3 relative to the RFID reader
`12 so as to detect, for example, the presence of a hand
`Waving an ID tag in front of the RFID tag reader 12. The
`output signal of the secondary detector is connected as an
`ON control signal to poWer control sWitching circuit 16.
`In an initial Wait state of the tag reader 12 the poWer
`control sWitch 16 is turned off to inactivate the RFID reader
`12. When a moving object such as an ID tag holder’s hand
`is detected by the PIR secondary detector 20, the resulting
`ON control signal of the secondary detector actuates poWer
`sWitch 16 for supplying electrical poWer to RFID reader 12
`from poWer supply 14, thereby activating the RFID reader.
`In its noW active state the tag reader 12 operates in a
`conventional manner and transmits a radio frequency signal
`designed to evoke a radio-frequency response from any ID
`tags Within range of the reader, and listens for any radio
`frequency response from the ID tags. Typically, the tag
`reader 12 Will remain turned on only for the length of time
`necessary to read an ID tag. If after an appropriate time no
`ID tag response is evoked by the reader’s transmission, the
`reader outputs an OFF control signal to the poWer control
`sWitch, thereby shutting doWn poWer and returning the
`reader to a Wait state. If the secondary detector in fact
`detected the entry of an ID tag into the sensing ?eld s, the
`tag reader 12 then also eXecutes an access control function
`to enable access to the protected facility, such as by opening
`an electric door lock and returning the facility to a locked
`condition. Upon completion of the access control cycle, the
`reader outputs the OFF control signal to the poWer control
`sWitch and is returned to a Wait state. The tag reader 12
`typically operates under control of a microprocessor, and the
`output of the OFF control signal at the appropriate time is
`accomplished by suitable programming of the microproces
`sor.
`The poWer control sWitch 16 may operate to suspend only
`some functions of the RFID reader rather than completely
`turning off poWer to the tag reader. It may be undesirable to
`entirely shut-doWn the tag reader 12 because certain initial
`iZation functions of the microprocessor Would require
`re-eXecution upon every poWer-up. For this reason, the ON
`control signal may instead operate to invoke certain func
`tions and subroutines of the microprocessor needed to
`actively sense and read ID tags, While keeping the micro
`processor in a loW poWer state in the Wait state of the tag
`reader. That is, the Wait state of the tag reader 12 is any state
`Where poWer consumption of the tag reader is limited to less
`than its normal operating requirements for detecting and
`reading ID tags.
`The on-time of the RFID reader per ID tag may be quite
`short, of the order of a feW seconds, depending on the type
`of access being controlled. By limiting the on-time of the
`RFID reader in this fashion, the RFID reader duty cycle, i.e.
`on-time of the RFID reader 12 relative to operating time of
`the reader system 10, can be made very small, thereby
`greatly reducing the poWer consumption of the combined
`RFID/PIR system 10 and making practical battery operation
`of such combined readers. The combined reader 10 may be
`packaged for either portable or stationary use, in any hous
`ing that may suit practical and esthetic considerations.
`Passive IR detectors consume little poWer as compared to
`passive RFID detectors because the PIR detector does not
`emit a signal but rather responds to the presence of radiation
`emitted by a Warm object or body. HoWever, the choice of
`secondary detector is not limited to infrared detectors. Other
`motion sensing technologies are available Which may be
`adapted for the purposes of this invention. For eXample,
`inductive or capacitive type sensors may be implemented as
`
`

`

`5
`the secondary detector 20 for detecting the entry of an object
`into the sensing ?eld of the RFID reader by detecting
`changes in inductance or capacitance in the environment
`near the reader. Similarly, ultrasound and microWave motion
`sensors are available and can be substituted for the passive
`infrared detector 20. Generally, a passive sensing technology
`such as inductive or capacitive Will normally be preferred to
`an active technology such as microWave or ultrasound
`motion sensing because passive detectors typically consume
`less electrical poWer. For greater sensitivity and reliability,
`multiple secondary detectors 20 may be installed and con
`nected in OR logic so that the RFID reader is turned on if
`either of multiple secondary detectors is activated. Multiple
`secondary detectors may also be connected in AND fashion
`so that the RFID readers turns on only if both secondary
`detectors are activated to reduce false activations of the
`reader.
`While a presently preferred embodiment of the invention
`has been described and illustrated for purposes of example
`and clarity it must be understood that many changes, sub
`stitutions and modi?cations to the described embodiment
`Will be apparent to those having only ordinary skill in the art
`Without thereby departing from the scope of the present
`invention as de?ned by the folloWing claims.
`What is claimed is:
`1. A loW-poWer radio-frequency proximity reader system
`comprising:
`a tag reader operative for detecting the presence of an
`identi?cation tag by evoking a radio-frequency
`response from identi?cation tags present Within a sens
`ing ?eld of said reader;
`secondary detector operative for detecting entry of an
`object including but not limited to identi?cation tags
`into said sensing ?eld by means other than evoking a
`radio-frequency response from said object and deriving
`an enabling control signal responsive to said detecting;
`poWer supply means for supplying operating poWer to
`said tag reader and to said secondary detector, said
`detector and said tag reader each having and average
`operating poWer requirement, said detector selected to
`have a substantially smaller average operating poWer
`requirement than said tag reader; and
`a poWer control sWitch normally limiting poWer from said
`poWer supply means to said tag reader and operative for
`enabling poWer to said tag reader for a limited period
`of time in response to said enabling control signal;
`such that operating poWer of the proximity reader system
`is conserved by operating the tag reader only upon
`entry of an object into the tag reader’s sensing ?eld.
`2. The reader of claim 1 Wherein said tag reader has a
`transmitter circuit and a receiver circuit connected to an
`antenna for transmitting a radio-frequency interrogation
`signal and decoding a response returned by identi?cation
`tags Within said sensing ?eld of the tag reader.
`3. The reader of claim 1 Wherein said secondary detector
`is a motion detector.
`4. The reader of claim 3 Wherein said motion detector is
`a passive infrared detector.
`5. The reader of claim 1 Wherein said secondary detector
`is selected from the group comprised of infrared, inductive,
`electrostatic, microWave and ultrasound detectors.
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`6. The reader of claim 1 Wherein said limited period of
`time is approximately the time period required to transmit a
`radio-frequency interrogation signal and receive and decode
`a response from an identi?cation tag present in said sensing
`?eld, and executing an access control function by said tag
`reader, so that the operating time of the tag reader is
`substantially minimiZed.
`7. The reader of claim 1 Wherein said tag reader provides
`an off control signal to said sWitch for returning said tag
`reader to a poWer limited state.
`8. A method of operating a radio-frequency proximity
`reader having a sensing ?eld, comprising the steps of:
`placing said radio-frequency proximity reader in a Wait
`state;
`detecting the introduction of an object into said sensing
`?eld; and
`activating said radio-frequency reader for a period of time
`generally suf?cient for evoking a response from an
`identi?cation tag is present in said sensing ?eld; and
`returning said radio-frequency proximity reader to said
`Wait state.
`9. The method of claim 8 Wherein said step of detecting
`comprises sensing a change in a characteristic of said
`sensing ?eld selected from the group comprised of infrared
`background, microWave re?ectivity, ultrasound re?ectivity,
`inductance and capacitance.
`10. AloW-poWer radio-frequency proximity reader system
`comprising:
`a proximity RFID tag reader operative for detecting the
`presence of an identi?cation tag by evoking a radio
`frequency response from identi?cation stages present
`Within a sensing ?eld of said reader;
`a passive infrared secondary detector oriented, arranged
`and positioned for vieWing said sensing ?eld thereby to
`detect entry of an object including but not limited to
`identi?cation tags into said sensing ?eld and deriving
`an on control signal responsive to said detecting;
`poWer supply means for supplying operating poWer to
`said tag reader and to said secondary detector, said
`detector and said tag reader each having an average
`operating poWer requirement, said secondary detector
`selected to have a substantially smaller operating poWer
`requirement than said tag reader; and
`a poWer control sWitch normally limiting poWer from said
`poWer supply means to said tag reader and operative for
`enabling poWer to said tag reader upon detecting entry
`of said object into the said sensing ?eld thereby to test
`for the presence of an identi?cation tag in said sensing
`?eld;
`said tag reader providing an off control signal to said
`sWitch for returning said tag reader to a poWer limited
`state upon completion of an access control function;
`such that operating poWer of the proximity reader system
`is conserved by operating the tag reader at a loW duty
`cycle relative to said secondary detector.
`
`