(12) INTERNATIONAL APPLICATION PUBLISHED UNDER THE PATENT COOPERATION TREATY (PCT)
`
`9
`
`) Wo•ld I "1~~-;:;~~~n~n;::::.: o,....nh·.ation •
`
`(l
`
`11111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111
`
`(43) International Publication Date
`19 March 2009 (19.03.2009)
`
`PCT
`
`(10) International Publication Number
`WO 2009/035723 Al
`
`(51) International Patent Classification:
`HOIQ 3100 (2006.01)
`
`(21) International Application Number:
`PCT /US2008/05 8824
`
`(22) International Filing Date: 31 March 2008 (31.03.2008)
`
`(25) Filing Language:
`
`(26) Publication Language:
`
`English
`
`English
`
`(30) Priority Data:
`60/993,418
`
`11 September 2007 (11.09.2007) US
`
`(71) Applicant (for all designated States except US): RF CON(cid:173)
`TROLS, LLC [US/US]; 1141 S. 7th Street, St. Louis, Mis(cid:173)
`souri 63104-3623 (US).
`
`(72) Inventors; and
`(75) Inventors/Applicants (for US only): BLOY, Graham
`P. [US/US]; 4600 Chippewa St., Suite 301, St. Louis,
`Florida 63116 (US). PIERCE, Matthew E. [US/US];
`356 Old Homestead Drive, Troy, Illinois 62294 (US).
`
`HOFER, Russell [US/US]; 8928 Red Oak Drive, St.
`Louis, Missouri 63126 (US).
`(74) Agent: BABCOCK, Andrew; 4934 Wildwood Drive,
`P.O. Box 488, Bridgman, Michigan 49106 (US).
`(81) Designated States (unless otherwise indicated, for every
`kind of national protection available): AE, AG, AL, AM,
`AO, AT, AU, AZ, BA, BB, BG, BH, BR, BW, BY, BZ, CA,
`CH, CN, CO, CR, CU, CZ, DE, DK, DM, DO, DZ, EC, EE,
`EG, ES, Fl, GB, GD, GE, GH, GM, GT, HN, HR, HU, ID,
`IL, IN, IS, JP, KE, KG, KM, KN, KP, KR, KZ, LA, LC,
`LK, LR, LS, LT, LU, LY, MA, MD, ME, MG, MK, MN,
`MW, MX, MY, MZ, NA, NG, NI, NO, NZ, OM, PG, PH,
`PL, PT, RO, RS, RU, SC, SD, SE, SG, SK, SL, SM, SV,
`SY, TJ, TM, TN, TR, TT, TZ, UA, UG, US, UZ, VC, VN,
`ZA, ZM,ZW.
`(84) Designated States (unless otherwise indicated, for every
`kind of regional protection available): ARIPO (BW, GH,
`GM, KE, LS, MW, MZ, NA, SD, SL, SZ, TZ, UG, ZM,
`ZW), Eurasian (AM, AZ, BY, KG, KZ, MD, RU, TJ, TM),
`European (AT, BE, BG, CH, CY, CZ, DE, DK, EE, ES, Fl,
`FR, GB, GR, HR, HU, IE, IS, IT, LT, LU, LV, MC, MT, NL,
`
`[Continued on next page}
`
`---iiiiiiii
`
`iiiiiiii
`
`:::: ----------------------------------------------------------------------------------------------
`(54} Title: RADIO FREQUENCY SIGNAL ACQUISITION AND SOURCE LOCATION SYSTEM
`
`--------------------~--------------------------,
`
`10
`
`FIG.l
`
`(57) Abstract: A radio frequency
`signal acquisition and
`source
`location system, including a first
`signal acquisition and
`source
`location module comprising an
`RF
`transceiver coupled
`to an
`antenna,
`the antenna provided
`with a electronic steering circuit.
`The antenna operative to launch
`an
`interrogation
`signal,
`the
`interrogation signal steerable by
`an electronic steering circuit. A
`processor operatively
`coupled
`to
`the RF transceiver and the
`electronic steering circuit,
`the
`processor provided with a data
`storage for storing a signal data
`record for each of at least one
`received by
`response signal(s)
`the RF transceiver(s). The signal
`data record
`including a signal
`identification, a received signal
`strength indicator and an RF signal
`direction along which respective
`the
`received by
`signal(s) are
`antenna, the RF signal direction
`derived
`from
`the
`electronic
`steering circuit. A position logic
`operative upon the data record(s)
`deriving
`a
`three dimensional
`location of each
`signal origin
`response signal.
`
`- i
`
`iiiiiii
`
`---
`
`--i
`
`iiiiiii
`
`iiiiiiii ----
`
`RFC - Exhibit 1008
`
`1
`
`

`
`W 0 2009/0357 23 A 1
`
`lllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllllll
`
`NO, PL, PT, RO, SE, SI, SK, TR), OAPI (BF, BJ, CF, CG, Published:
`-
`CI, CM, GA, GN, GQ, GW, ML, MR, NE, SN, TD, TG).
`with international search report
`Declarations under Rule 4.17:
`as to the identity of the inventor (Rule 4.17(i))
`as to applicant's entitlement to apply for and be granted a
`patent (Rule 4.17(ii))
`as to the applicant's entitlement to claim the priority of the
`earlier application (Rule 4.17(iii))
`
`2
`
`

`
`wo 2009/035723
`
`PCT /US2008/058824
`
`RADIO FREQUENCY SIGNAL ACQUISITION AND SOURCE LOCATION
`
`SYSTEM
`
`CROSS REFERENCE TO RELATED APPLICATIONS
`
`This application claims the benefit of US Provisional Patent Application No.:
`
`60/993,418, titled "Steerable Phase Array Antenna RFI D Tag Locator and
`
`Tracking System", filed by Graham P. Bloy on September 11, 2007 and hereby
`
`incorporated by reference in its entirety.
`
`BACKGROUND
`
`Field of the Invention
`
`The invention generally relates to Radio Frequency (RF) signal acquisition and
`
`source location. More particularly, the invention relates to RF signal acquisition
`
`and source location in three dimensions.
`
`Description of Related Art
`
`Prior signal acquisition and source location systems, for example radio direction
`
`finding systems typically operate on a triangulation basis, where location
`
`accuracy is dependent upon the number of signal reception points and their
`
`relative distance away from each other and the signal source. Signal
`
`interference and false reflected or ghost signals frustrate the use of radio finding
`
`systems in smaller target areas. Radio direction finding systems may also apply
`
`flight timing as a component of a signal source location system. However,
`
`1 of 38
`
`3
`
`

`
`wo 2009/035723
`
`PCT /US2008/058824
`
`especially when applied to relatively short distances, the accurate measurement
`
`of the associated flight times with the required resolution may be cost prohibitive.
`
`Radio Frequency
`
`Identification
`
`(RFI D)
`
`technology
`
`is used,
`
`in multiple
`
`applications, to identify, track and trace physical objects. RFID tags also known
`
`as transponders or smart labels may be attached to objects, vehicles or people
`
`as a form of electronic label. These tags may contain unique identifiers (serial
`
`numbers) or may have a common identifier to identify a class of object such as a
`
`particular variety of a commodity.
`
`RFID tags may be read by readers (also known as interrogators) in order to
`
`collect the identity of the RFID tags and therefore by association the identity of
`
`the item to which the tag is attached. RFID readers may be portable, for close
`
`proximity reading of known position RFID tags and I or configured as portals or
`
`gateways scanning for the passage of RFID tags passing through, such as a
`
`pallet load of materials individually marked with RFI D tags entering or leaving a
`
`warehouse for inventory feedback and control, providing an entry, presence and
`
`or exit signal tracking. This does not provide a specific location and I or direction
`
`of travel, other than by transient association between the tags or tagged items
`
`and the location of the reader at the time of interrogation.
`
`Multiple gateways and or portals may be applied to improve the general location
`
`resolution, but the number of gateways and or portals required to obtain a
`
`2 of 38
`
`4
`
`

`
`wo 2009/035723
`
`PCT /US2008/058824
`
`worthwhile location accuracy renders a high resolution solution using large
`
`numbers of gateway installations cost prohibitive. Also, neighboring gateways
`
`create significant interrogation signal interference issues.
`
`A drawback of presence/passage gateways is that the residence time of the
`
`RFID tag(s) within the detection field may be relatively short and at the same
`
`time as large numbers of other RFID tags, such as where a pallet stacked with
`
`RFID tagged items moves past the gateway, during this short residence period it
`
`may be difficult to accurately interrogate and then differentiate between each of
`
`the resulting response signals and the full data content they each may transmit.
`
`Another signal generating electronic tag responsive to RF interrogation is an
`
`electronic article surveillance (EAS) tag. An EAS tag system indicates presence
`
`of an EAS tag within an interrogation field, but an EAS tag carries no data to
`
`identify the item to which it is attached. Widely used as theft protection systems,
`
`EAS tags have the drawback of alarming only as the EAS tag passes through a
`
`gateway, typically located at the door of a store.
`
`In many jurisdictions, the law
`
`does not permit challenging a person once beyond the store property, which
`
`frustrates shop-lifting enforcement I property recovery.
`
`Therefore, it is an object of the invention to provide a system and method(s) that
`
`overcomes deficiencies in the prior art.
`
`3 of 38
`
`5
`
`

`
`wo 2009/035723
`
`PCT /US2008/058824
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`The accompanying drawings, which are incorporated in and constitute a part of
`
`this specification, illustrate embodiments of the invention and, together with a
`
`general description of the invention given above, and the detailed description of
`
`the embodiments given below, serve to explain the principles of the invention.
`
`Figure 1 is a schematic block diagram of an exemplary embodiment of a signal
`
`acquisition and source location module.
`
`Figure 2 is a schematic diagram demonstrating possible signal position results
`
`and a related curve fitting function.
`
`Figure 3 is a schematic signal path diagram, demonstrating actual and ghost
`
`signals.
`
`Figure 4 is a flow chart diagram demonstrating a multi-path ambiguity resolution
`
`logic.
`
`Figure 5 is a block diagram of an RF signal intelligent tracking and control system
`
`embodiment with a plurality of signal acquisition and source location modules.
`
`Figure 6 is flow chart demonstrating an operations loop for an RF signal
`
`intelligent tracking and control system embodiment.
`
`4 of 38
`
`6
`
`

`
`wo 2009/035723
`
`PCT /US2008/058824
`
`DETAILED DESCRIPTION
`
`The inventors have analyzed presently available signal acquisition and source
`
`location technology and recognized that a cost effective solution was not
`
`available for three dimensional signal location within a defined zone. For
`
`example with respect to RFID signals, the inventors recognized that there was a
`
`collective mindset in the signal acquisition and source location technology space
`
`that RFID technology in particular is applicable only with respect to gateway type
`
`exit/entry and or general presence detection and reporting function(s).
`
`Further, the inventors have recognized that multiple gateway solutions for
`
`determining a general signal direction and or speed determination are
`
`unnecessarily complex, impractical and cost prohibitive.
`
`Therefore, the inventors have developed an RF signal intelligent tracking and
`
`control system (ITCS) 5 that utilizes one or more signal acquisition and source
`
`location (SASL) module(s) 10.
`
`As shown in Figure 1, an exemplary SASL module1 0 includes an RF transceiver
`
`12 operative to transmit an interrogation signal beam on a desired frequency or
`
`frequency band and to receive one or more response signals on a desired
`
`frequency or frequency band. The interrogation signal and response signal
`
`frequency(s) and or frequency band(s) may be configured to a common
`
`5 of 38
`
`7
`
`

`
`wo 2009/035723
`
`PCT /US2008/058824
`
`frequency or frequency band according to the signal parameters the system is
`
`configured for use with. For example, configured for use with ultra high
`
`frequency (UHF) RFID tag response signal(s), the RF transceiver 12 may
`
`operate in the 860-960 MHz frequency band. When optimized for RFID
`
`interrogation signal transmission and reception of backscatter modulation
`
`response signal(s) from one or more interrogation signal activated RFID tag(s),
`
`the RF transceiver 12 may also be known as an RFI D reader. The RF
`
`transceiver 12 is coupled to an antenna 14 provided with an electronic steering
`
`circuit 16 for directing the interrogation signal beam into a desired direction.
`
`As described herein below, it is highly advantageous for the antenna 14 to
`
`generate a narrow beam pattern. Although other types of narrow beam antenna
`
`14 may be applied, an exemplary antenna type, is the phased array antenna 14.
`
`Phased array antennas 14, for example including a power splitter 18 dividing an
`
`interrogation signal from the RF transceiver 12 between an array of antenna
`
`element(s) 20 such as dipole, patch or other form of radiator antenna element(s)
`
`20 may be formed as compact planar panels. To minimize interference and or
`
`for specific operating frequency requirements, the antenna 14 may be provided
`
`with a transmit antenna element 20 separate from a receive antenna element 20
`
`and or respective arrays of transmit and receive antenna element(s) 20.
`
`In addition to being configurable with a comparatively narrow beam
`
`characteristic, the phased array antenna 14 is also cost effectively directionally
`
`6 of 38
`
`8
`
`

`
`wo 2009/035723
`
`PCT /US2008/058824
`
`controllable by an electronic steering circuit 16 in the form of an array of phase
`
`shifter(s) 22, for example one phase shifter 22 for each antenna array element 20
`
`or group of antenna element(s) 20.
`
`Individual phase shifter 22 circuits, digitally controlled by a beam steering unit 24,
`
`may be formed for example as a series of varied reactances switchable in or out
`
`of line with the respective antenna element(s) 20 by varactors, the phase
`
`shifter(s) 22 operative to adjust the phase of the respective individual or group of
`
`antenna element(s) 20 coupled to the phase shifter 22. The beam steering unit
`
`24 may include processor, memory and communications capabilities such as the
`
`ability to store a pre-programmed zone beam sweep pattern, such as a linear,
`
`orthogonal, spiral raster scan, specific direction, or locate by coordinates,
`
`including desired exclusion areas such as areas of known interference, signal
`
`reflection surfaces or other areas where passage of the interrogation signal beam
`
`is not desired. Further attributes include the ability to receive control instructions
`
`and transmit beam position data to a remote processor 28 or other controller.
`
`The phase shifter(s) 22 and beam steering unit 24 controlling them together
`
`comprise the electronic steering circuit 16, which may be integrated partially or
`
`fully with the antenna 14. A power supply 30 converts mains power for use by
`
`SASL module 10 electrical power consumers, including the RF transceiver 12
`
`and controller 28. One skilled in the art will appreciate that, compared to
`
`mechanical and or electro-mechanical beam steering solutions, an electronic
`
`7 of 38
`
`9
`
`

`
`wo 2009/035723
`
`PCT /US2008/058824
`
`beam steering unit 24 provides significant improvements in sweep speed and
`
`has cost and reliability advantages.
`
`The beam steering unit 24 is operative, by discrete control of the phase shifter(s)
`
`22, to direct the antenna beam to a desired direction designated for example via
`
`theta and phi polar coordinates from a default beam direction normal to the
`
`antenna face. The beam driven by the electronic steering circuit 16 may
`
`preferably be directed from zero to 40 degrees from normal in any direction.
`
`Calibration of the electronic steering circuit 16 may be performed by placing
`
`response signal(s) at the zone periphery, instructing the electronic steering circuit
`
`16 to perform a sweep that includes the known response signals and then
`
`identifying same as the zone limits. Alternatively the electronic steering circuit 16
`
`may be manually adjusted until the known response signals are recognized, then
`
`designating same as the zone limits between which to perform the zone sweep.
`
`A processor 28, such as programmable personal, mini or hardwired computer,
`
`programmable controller, remotely or locally located, is operatively coupled to the
`
`RF transceiver 12 and the electronic steering circuit 16, for example by a direct
`
`digital data link 32 such as an Ethernet, FireWire, Universal Serial Bus, optical or
`
`other, for example parallel or serial wired or wireless data link. Alternatively, the
`
`RF transceiver 12 may be coupled to the electronic switching circuit 16 via a
`
`8 of 38
`
`10
`
`

`
`wo 2009/035723
`
`PCT /US2008/058824
`
`digital data link 32, and there through, along with the electronic switching circuit
`
`16 to the processor 28 by another digital data link 32.
`
`The processor 28 is preferably provided with a data storage 26, for example a
`
`hard drive, semi-conductor memory or network connected memory, for storing a
`
`signal data record for each of at least one response signal(s) received by the RF
`
`transceiver 12. The signal data record including at least a signal identification, a
`
`received signal strength indicator and an RF signal direction along which
`
`respective signal(s) are received by the antenna 14. The RF signal direction is
`
`derived from the electronic steering circuit 16 and a position logic operative upon
`
`the signal data record(s) is applied to derive a three dimensional signal origin
`
`location of each response signal.
`
`The signal identification is a unique identifier data for differentiating a response
`
`signal from other response signals. Where the response signal is from an RFI D
`
`tag, the signal identification can be the RFI D tag identification or item identity.
`
`The received signal strength indicator is a numeric value corresponding to a
`
`signal strength of the respective response signal received by the transceiver.
`
`The RF signal direction is the direction along which the corresponding
`
`interrogation beam was launched, according to the electronic steering circuit 16
`
`settings. The electronic steering circuit 16 may be calibrated, for example by
`
`9 of 38
`
`11
`
`

`
`wo 2009/035723
`
`PCT /US2008/058824
`
`scanning a zone for the direction that receives the strongest received signal
`
`strength indicator value from a response signal source at a known location with
`
`respect to the antenna 14.
`
`Where the response signal magnitude is a function of how fully the signal
`
`position is illuminated by the interrogation beam, or where the antenna 14 has
`
`sufficiently high directional gain, the position logic may be configured to identify a
`
`primary signal data record; the primary signal data record being the signal data
`
`record in which the received signal strength indicator is the highest among signal
`
`data record(s) having a common signal identification. Because the back scatter
`
`modulation generated response signal strength indicator will be maximized when
`
`the responding RFID tag is fully illuminated by the interrogation beam, the RF
`
`signal direction associated with the primary signal data record represents a
`
`vector along which the response signal is positioned. Further, the received
`
`signal strength indicator associated with the primary signal data record is
`
`proportional to a distance along the RF signal direction from the antenna,
`
`enabling generation of a three dimensional signal origin location. Depending
`
`upon the precision desired, and or a degree of confidence in the apparatus and
`
`position logic, the three dimensional signal origin location may be a designated
`
`point in three dimensional space, or a defined area of three dimensional space at
`
`or in which the respective response signal originates. Where a defined area is
`
`used as the three dimensional signal origin location, a further logic step may be
`
`applied to determine the center of the defined area, for example from a
`
`10 of 38
`
`12
`
`

`
`wo 2009/035723
`
`PCT /US2008/058824
`
`calculation based upon the beam cross-section dimension, and designate same
`
`as the three dimensional signal origin location.
`
`During the RF signal direction calibration procedures, the value of the received
`
`signal strength indicator from one or more response signals of known location
`
`may be used to similarly calibrate the return signal strength indicator
`
`proportionality factor and or function to apply to accurately convert the received
`
`signal strength indicator into a distance from the antenna to the response signal
`
`origin location along the RF signal direction specified beam.
`
`The accuracy of a position logic result relying only upon the RF direction and the
`
`received signal strength indicator is related to the interrogation beam cross
`
`section dimensions at the response signal location, the number of different
`
`response signal samples obtained and the size of the beam sweep position
`
`increment or granularity performed between sampling of the response signal(s).
`
`Ideally, the beam cross section should be as narrow as possible and the beam
`
`sweep increment size as small as possible. However, considerations for beam
`
`strength at near and far zone locations from the antenna, as well as electronic
`
`steering circuit and or available processing time limitations may result in an
`
`interrogation beam cross section and beam sweep increment size large enough
`
`to introduce a significant position error, for example if multiple response signals
`
`fail to fall upon evenly distributed areas within the beam cross section.
`
`11 of 38
`
`13
`
`

`
`wo 2009/035723
`
`PCT /US2008/058824
`
`As demonstrated in Figure 2, where at least three response signal samples P1,
`
`P2, and P3 proximate to one another have the same signal identification, as the
`
`RF direction Dis stepped around the same general area it can be assumed that
`
`the return signal strength indication(s) RSSI1, RSSI2 and RSSI3 associated with
`
`each of the three samples are proportional to a radar cross section of the actual
`
`signal source S, and that the resulting three dimensional signal origin locations
`
`associated therewith are each located on the face of the sphere closest to the
`
`antenna. Therefore, a position logic with enhanced accuracy can apply a curve
`
`fitting routine between the at least three points to define the sphere and there
`
`from a sphere center point. Testing by the inventors has shown that the position
`
`result accuracy is significantly improved by position logic that designates the
`
`calculated sphere center point as the three dimensional signal origin location.
`
`Less calculation intensive and or faster to derive alternative methods for handling
`
`multiple signal samples with the same signal identification but varying position
`
`results from successive scans of a local area include applying an average to
`
`define the three dimensional signal origin location for the respective signal
`
`identification and or application of a weighted average, where the scan data
`
`record with the highest received signal strength indicator is given an increased
`
`weight during averaging with the other scanned position results for a common
`
`signal identification.
`
`12 of 38
`
`14
`
`

`
`wo 2009/035723
`
`PCT /US2008/058824
`
`Metallic surfaces and the like within the zone may operate as reflectors of the
`
`various response signals, generating numerous ghost signals that can potentially
`
`result in erroneous three dimensional signal origin location designations. To
`
`improve signal discrimination, a discrimination logic may be applied by the
`
`processor to filter the signal data records between actual signal(s) and ghost
`
`signal(s).
`
`Figure 3 demonstrates how two signal(s) e1 and e2 can each generate multiple
`
`ghost signals received by the antenna, some of these different signals, from the
`
`antenna 14 frame of reference, appearing to originate from a common location
`
`r3. Reflectors in the reception zone of the antenna generate ghost signal(s)
`
`along paths p11, p12, p21 and p22. Checking the signal identification of the
`
`received signals can differentiate between separate signal sources. Because a
`
`reflected signal path will always be longer than the single direct path (P1 0 or
`
`P20) between the respective signal source (E1 or E2) and the antenna 14, a
`
`check of the received signal strength indicator of the response signals with a
`
`common signal identification can be used to identify an actual signal from a
`
`plurality of ghost signals, the response signal having the highest response signal
`
`strength indicator being the actual signal. Signals identified as ghost signals may
`
`be discarded, leaving a single signal data record for each actual signal
`
`identification.
`
`13 of 38
`
`15
`
`

`
`wo 2009/035723
`
`PCT /US2008/058824
`
`Alternatively, the discrimination logic may employ a multi-path ambiguity
`
`resolution logic (MPAL) as shown in Figure 4 (the notations following a"/\"
`
`representing superscript notations). The MPAL accesses a collection of received
`
`response signal(s) and converts each of them to a complex envelope, the
`
`collection represented as y(t), y(t-1 ), ... , y(t-K+ 1 ). A Blind-Identification Logic is
`
`then applied to identify signal components c/\k from N pseudo emitters d/\k(t):
`
`y(t)=c/\1 d/\1 (t)+ .. +c/\Nd/\N(t). Then, for each of k=1 to k=N, a Maximum
`
`Likelihood Logic is applied to c/\k to find Pk arrival angles (theta)/\kj for pseudo
`
`emitter d/\k(t), which can then be applied to a steering matrix: A/\k=[a((theta)/\k1 ))
`
`... a((theta)/\kPk)]. An origin determination logic upon c/\k then computes an
`
`alignment criterion g(c/\k) from A/\1, 1=1, .. , k-1, the origin determination logic
`
`continuing to increment k until g(c/\k) is larger than a predefined probability factor.
`
`When k=N, the angles (theta)/\kj are collected and the MPAL is completed.
`
`To obtain higher resolution points proximate a likely response signal location, the
`
`beam sweep rate and or increment may be adjusted to increase the residence
`
`time at a particular RF signal direction of interest. For example, when a
`
`response signal is detected, the next scan increment may be reduced and the
`
`residence time increased. Similarly, where no response signal has been
`
`detected, the scan increment may be increased and the dwell time reduced until
`
`a further response signal is detected. Further, as multiple scans are completed,
`
`the approach towards areas of the previous scan that had response signal
`
`activity may initiate similar sweep increment reductions and scan dwell time
`
`14 of 38
`
`16
`
`

`
`wo 2009/035723
`
`PCT /US2008/058824
`
`increases to attempt to identify with greater resolution the specific bounds of the
`
`scan that indicate specific signal identification response signal activity. By
`
`focusing on identified areas of signal activity and less upon areas of no or rare
`
`activity, the overall scan rate may be maximized. To reduce the load these types
`
`of logic operations may apply to the local processor and data storage bandwidth
`
`they may be placed at the edge server or master SASL 1 0, if present.
`
`The SASL 1 0 may be formed as an integral single assembly or arranged as
`
`separate sub-modules coupled by the respective digital data links. Where a
`
`single integral assembly is applied, installation requirements are significantly
`
`simplified.
`
`Although a single SASL 10 may be used to generate a three dimensional origin
`
`location of each response signal, the ITCS 5 system accuracy may be
`
`significantly improved, especially the distance from the respective antenna along
`
`the RF signal direction component based upon the received signal strength
`
`indicator, by applying a plurality of spatially separated SASL modules 1 0 each
`
`arranged facing the same zone and or zone portions of a larger area and
`
`communicating signal data over a digital data link to an edge server 34 or other
`
`processor resource. The edge server 34 is operable, for example, to perform a
`
`triangulation logic between the identified response signals to generate a higher
`
`order three dimensional signal origin location for each response signal. The
`
`edge server 34 may be separately located, for example as shown in Figure 5, or
`
`15 of 38
`
`17
`
`

`
`wo 2009/035723
`
`PCT /US2008/058824
`
`integrated into one of the SASL module1 0, to form a master SASL module1 0.
`
`Mounting the SASL module(s) 10 above the zone, for example proximate to the
`
`ceiling of a warehouse, store or auditorium provides the SASL module1 0
`
`isolation from accidental impact, vandalism and contaminants as well as
`
`providing a clear view of the desired zone below.
`
`Operating on the signal data from each of the SASL module(s) 10 reporting to
`
`the edge server 34, the triangulation logic is configured to select response
`
`signal(s) from each of the SASL module(s) 10 having a common signal
`
`identification. The RF signal direction of each of the common signal identification
`
`signal data is then applied as an input to an intersection calculation to determine
`
`an intersection point of each antenna beam. The resulting intersection defined
`
`area can then be processed to arrive at a center point in three dimensional
`
`space, which is the higher order three dimensional origin location for the
`
`respective response signal.
`
`Alternatively, the three dimensional signal origin location(s), for a common signal
`
`identification, reported by each SASL module1 0 may be averaged to obtain the
`
`higher order three dimensional origin location.
`
`Another effect of multiple SASL module(s) 10 directing their respective
`
`interrogation signal beam(s) through a common point of the zone is that the
`
`increased signal illumination of, for example, a passive RFID located at the
`
`16 of 38
`
`18
`
`

`
`wo 2009/035723
`
`PCT /US2008/058824
`
`interrogation signal beam(s) intersection point, will, where backscatter
`
`modulation is being utilized, increase the signal strength of the response signal
`
`activated, and thus the corresponding received signal strength indicator of same.
`
`The increase in the value of the return signal source indicator may be applied as
`
`a further higher order three dimensional signal origin refinement factor of the
`
`position and or triangulation logic.
`
`To obtain higher resolution points proximate a likely response signal location, the
`
`beam sweep rate and or increment may be adjusted to increase the residence
`
`time at a particular RF signal direction of interest. For example, when a
`
`response signal is detected, the next scan increment may be reduced and the
`
`residence time increased. Similarly, where no response signal has been
`
`detected, the scan increment may be increased and the dwell time reduced until
`
`a further response signal is detected. Further, as multiple scans are completed,
`
`the approach towards areas of the previous scan that had response signal
`
`activity may initiate similar sweep increment reductions and scan dwell time
`
`increases to attempt to identify with greater resolution the specific bounds of the
`
`scan that indicate specific signal identification response signal activity. By
`
`focusing on identified areas of signal activity and less upon areas of no or rare
`
`activity, the overall scan rate may be maximized. To reduce the load these types
`
`of logic operations may apply to the local processor 28 and data storage 26
`
`bandwidth they may be placed at the edge server 34 or master SASL module1 0,
`
`17 of 38
`
`19
`
`

`
`wo 2009/035723
`
`PCT /US2008/058824
`
`if present, and areas of the scan designated for higher or lower interest
`
`transmitted back to the respective electronic steering circuit.
`
`The edge server 34 and or processor 28 of each SASL module1 0 may also
`
`perform comparisons of changes between the three dimensional signal origin
`
`location resulting from successive interrogation signal sweeps of the zone and
`
`apply same as inputs to a velocity and or direction logic, to determine a speed
`
`and direction indication for each response signal. The velocity logic comparing
`
`the position change to the time elapsed between same and the direction logic
`
`applying a vector beginning at the previous three dimensional position and
`
`ending at the present three dimensional position to generate a direction of travel.
`
`The historic velocity and direction results may be used to direct the SASL
`
`module(s) 10 to anticipate future locations of a particular signal source and or
`
`steer the interrogation signal to remain upon a particular signal source of interest
`
`as it moves through the zone.
`
`In various embodiments, the several logical parameters that the various
`
`processor(s) may perform may be stored in the data storage as software code
`
`that may alternatively be loaded into the processor, coded into a complex
`
`programmable logic device (CPLD), field programmable gate array (FPGA) or
`
`permanent or rewritable static memories such as erasable programmable read(cid:173)
`
`only memory (EPROM).
`
`18 of 38
`
`20
`
`

`
`wo 2009/035723
`
`PCT /US2008/058824
`
`The SASL module(s) 10 and or edge server 34 if present are coupled to an
`
`operator interface such as computer display and or a user accessible web page
`
`for control and feedback.
`
`In an exemplary embodiment, for example a warehouse for products labeled with
`
`RFID tags, a SASL module1 0 is