Patent Publication Number: US-2009231138-A1

Title: RFID Technology

Description:
This invention relates to various improvements in and relating to RFID (radio-frequency identification) technology. 
     BACKGROUND OF THE INVENTION 
     Radio-frequency identification (RFID) is an automatic identification method, relying on storing and remotely retrieving data using devices called RFID tags or transponders. An RFID tag is an object that can be applied to or incorporated into a product, animal or person for the purpose of identification using radio waves. Most RFID tags contain at least two parts, namely (a) an integrated circuit (IC) for storing and processing information, modulating and demodulating a radio-frequency (RF) signal, which may also be used for other specialized functions, and (b) an antenna for receiving and transmitting the signal. 
     In recent years, there have been significant developments in the field of RFID technology. However, there still exist various shortcomings associated with the present RFID tags and RFID readers. For example, a batch of goods are in transit and all such goods are associated with RFID tags which are in sleeping mode in transit. A user may then wish to wake up certain RFID tags associated with a certain kind of such goods but not others. Conventionally, the user would have no choice but to transmit a wakeup beacon onto the batch of goods, and wake up all RFID tags. The available energy of some of the RFID tags is thus wasted, and thus their usable life is shortened. 
     In addition, an object embedded, implanted or inserted with one type of RFID tag will only respond to queries from one type of RFID reader, which is not versatile in use. 
     These are just some examples of the existing shortcomings of the existing RFID technology. It is thus an object of the present invention to provide various improvements in and relating to RFID technology with a view to mitigating the present shortcomings associated with the RFID technology, or to at least provide useful alternatives to the public 
     SUMMARY OF THE INVENTION 
     According to a first aspect of this invention, there is provided a method of selectively waking up at least two RFID tags, including steps of (a) providing a first RFID tag: (b) programming said first RFID tag to respond to and wake up only to signals with a first characteristic; (c) providing a second RFID tag; and (d) programming said second RFID tag to respond to and wake up to only to signals with a second characteristic. 
     According to a second aspect of the present invention, there is provided a dual-mode active RFID tag, wherein said tag is adapted to be in a real time location system (RTLS) mode for a first pre-determined period of time and in an inventory mode for a second pre-determined period of time. 
     According to a third aspect of the present invention, there is provided a signal transmission apparatus for transmitting wakeup signals to RFID tags, said apparatus being adapted to transmit signals with information indicative of the cumulative period of time which has lapsed since transmission of the first wakeup signal. 
     According to a fourth aspect of the present invention, there is provided a method of transmitting wakeup signals to RFID tags, including transmitting signals with information indicative of the cumulative period of time which has lapsed since transmission of the first wakeup signal. 
     According to a fifth aspect of the present invention, there is provided an RFID tag assembly with at least an active RFID tag and at least a passive RFID tag. 
     According to a sixth aspect of the present invention, there is provided a portable RFID reader containing a real time location tracking RFID tag. 
     According to a seventh aspect of the present invention, there is provided a portable RFID reader containing a global positioning system (GPS) receiver. 
     According to an eighth aspect of the present invention, there is provided an active RFID tag with at least two electric power sources, wherein at least one of said electric power sources is rechargeable. 
     According to a ninth aspect of the present invention, there is provided an active RFID tag reader with at least two electric power sources, wherein at least one of said electric power sources is rechargeable. 
     According to a tenth aspect of the present invention, there is provided a method of calibrating an RFID tag positioning system with at least a first and a second real time location tracking active RFID readers, including the steps of (a) positioning said at least two real time location tracking active RFID readers in two respective locations in an environment; (b) positioning a first calibrating RFID tag at a fixed and known position in said environment; (c) moving a second calibrating RFID tag along a pre-determined path in said environment; (d) obtaining said first RFID reader&#39;s readings of location-related information of said first and second calibrating RFID tags at a point in time; (e) obtaining said second RFID reader&#39;s readings of location-related information of said first and second calibrating RFID tags at said point in time; and (f) comparing said readings of said first RFID reader and of said second RFID reader with said known positions of said first and second calibrating tags. 
     According to an eleventh aspect of the present invention, there is provided an RFID tag including an RFID tag integrated circuit; a high dielectric constant plastic layer with two major surfaces; a first layer of printed-circuit-board material fixedly secured on a first major surface of said plastic layer; a second layer of printed-circuit-board material fixedly secured on a second major surface of said plastic layer; and antenna formed on said first layer of printed-circuit-board material. 
     According to a twelfth aspect of the present invention, there is provided an RFID reader including a high dielectric constant plastic layer with two major surfaces; a first layer of printed-circuit-board material fixedly secured on a first major surface of said plastic layer; a second layer of printed-circuit-board material fixedly secured on a second major surface of said plastic layer; and an antenna formed on said first layer of printed-circuit-board material. 
     According to a thirteenth aspect of the present invention, there is provided an RFID system including a remote controller of an electrical appliance, said remote controller having at least one RFID reader adapted to receive at least identity (ID) data from at least one RFID tag; a data processing apparatus adapted to receive at least said ID data from said remote controller; and a visual display unit adapted to visually show at least said ID data of said RFID tag. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Preferred embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which: 
         FIG. 1  is graph showing the multi-subcarrier wakeup concept according to an aspect of the present invention; 
         FIG. 2  are graphs showing the multi-code wakeup concept according to a further aspect of the present invention; 
         FIG. 3  is a flow chart showing the modes which a dual-mode active RFID tag according to a yet further aspect of the present invention may be in; 
         FIG. 4  is a graph showing schematically a pattern of signals of a wakeup beacon of a method of transmitting wakeup signals to RFID tags according to a still further aspect of the present invention; 
         FIG. 5  is a schematic view of an RFID tag with both an active RFID tag module and a passive RFID tag module according to an aspect of this invention, 
         FIG. 6  shows further capabilities of the RFID tag shown in  FIG. 5 ; 
         FIG. 7  shows a schematic circuit arrangement of the RFID tag of  FIG. 5 ; 
         FIG. 8  shows interaction of the circuit arrangement of  FIG. 7  with queries from an active RFID reader; 
         FIG. 9  shows further capabilities of the circuit arrangement of  FIG. 7 ; 
         FIG. 10  shows schematically a portable RFID reader with a real time location (RTLS) RFID tag, according to a further aspect of the present invention: 
         FIG. 11  shows schematically a portable RFID reader with a global positioning system (GPS) receiver, according to a still further aspect of the present invention; 
         FIG. 12  shows schematically a portable RFID reader with both an real time location (RTLS) RFID tag and a global positioning system (GPS) receiver, according to a yet further aspect of the present invention; 
         FIG. 13  shows schematically an active RFID tag with energy harvesting system and multiple battery banks, according to an aspect of the present invention; 
         FIG. 14  shows schematically an active RFID reader with energy harvesting system and multiple battery banks, according to a further aspect of the present invention; 
         FIG. 15  shows schematically the arrangement for calibrating a plurality of RTLS RFID readers in an environment, according to a still further aspect of the present invention; 
         FIG. 16  shows the structure of an RFID reader antenna according to a yet further aspect of the present invention; 
         FIG. 17  shows schematically the arrangement of an RFID system according to an aspect of the present invention; 
         FIG. 18  shows a variant arrangement to the RFID system shown in  FIG. 17 ; 
         FIG. 19  shows a further variant arrangement to the RFID system shown in  FIG. 17 ; 
         FIG. 20  shows a still further variant arrangement to the RFID system shown in  FIG. 17 ; 
         FIG. 21  shows a yet further variant arrangement to the RFID system shown in  FIG. 17 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A first aspect of this invention relates to ways of selectively waking up certain of a number of RFID tags but not others. Take as an example the situation with two RFID tags, say Tag A 1  and Tag A 2 . Tag A 1  is embedded, implanted or inserted in an Object O 1 , and Tag A 2  is embedded, implanted or inserted in an Object O 2 , which is transported together with Object O 1 , say in a same truck. Both Tag A 1  and Tag A 2 . are in sleeping mode, and it is now desired to identify whether the truck contains Object O 1  In the conventional method, a wakeup beacon is transmitted into the truck, and wake&#39; up both Tag A 1  and Tag A 2 , thus wasting the energy stored in Tag A 2 . 
     The underlying concept of the new scheme is to program the RFID tags differently, so that they respond to and wakeup to wakeup signals with different characteristics.  FIG. 1  shows a multi-subcarrier wakeup scheme according to an aspect of the present invention. In this multi-subcarrier wakeup scheme, selective wakeup of RFID tags can be achieved. A subcarrier is a separate analogue or digital signal carried on a main radio transmission. 
     An RFID reader is constructed to be capable of wirelessly transmitting wakeup signals/messages at different frequency subcarriers, and that the relevant RFID tags are programmed to respond to and wake up only to wakeup signals with different subcarriers. For example, and a shown in  FIG. 1 , the RFID reader is capable of selectively wirelessly transmitting wakeup signals/messages with subcarrier  1  at f 1  and with subcarrier at f 2 . Again take the example of two RFID tags, Tag B 1  and Tag B 2 . Tag B 1  is software configured to respond to and wake up only to wakeup signals/messages transmitted with a subcarrier at a frequency of f 1 , and Tag B 2  is software configured to respond to and wake up only to wakeup signals/messages transmitted with a subcarrier at a frequency of f 2 . 
     Thus, it is possible to selectively waking up Tag B 1  (without simultaneously waking up Tag B 2 ) by operating the RFID reader to wirelessly transmit wakeup signals/messages with a subcarrier at frequency f 1 . Such an arrangement allows partitioning of the RFID tags without having to wake up all RFID tags in response to all wakeup calls to wait for summoning, and the energy stored in Tag B 2  is thus not wasted. 
     It is envisaged that the RFID tags may be re-configured so as to allow more convenience and versatility in use. For example, after Tag B 1  and Tag B 2  have moved from one zone to another zone (be it the logistics trail waypoint or work-in-progress stage), where it is no longer necessary to differentiate these two tags vis-á-vis their response to wakeup calls, Tag B 2  may be re-configured to respond to wakeup signals/messages transmitted with a subcarrier at a frequency of f l  (as is Tag B 1 ), or to any wakeup calls. 
     It is also possible to software configure Tag B 1  such that it responds to and wakes up only to wakeup signals/messages transmitted with a subcarrier at a frequency of f 1  for a pre-determined period of time T 1 , after which it will charge to respond to and wake up only to wakeup signals/messages transmitted with a subcarrier at a frequency of f 2  for a determined period of time T 2 , after which it will change to respond to and wake up only to wakeup signals/messages transmitted with a subcarrier at a frequency of f 3  for a determined period of time T 3 , and so on. All these periods of time T 1 , T 2  and T 3  are configurable and field-programmable and re-configurable. 
     A second possible scheme allowing selective waking up of RFID tags is a multi-code scheme as shown in the two graphs of  FIG. 2 . In this multi-code scheme, an RFID reader is constructed to be capable of wirelessly transmitting wakeup signals/messages with different codes, and that the relevant RFID tags are programmed to respond to and wake up only to wakeup signals with different codes. For example, and as shown in  FIG. 2 , the RFID reader is capable of selectively wirelessly transmitting wakeup signals/messages with Code A and with Code B. Take the example of two RFID tags, Tag C 1  and Tag C 2 . Tag C 1  is software configured to respond to and wake up only to wakeup signals/messages transmitted with Code A, and Tag C 2  is software configured to respond to and wake up only to wakeup signals/messages transmitted with Code B. It can be seen that, as in the case of the multi-subcarrier scheme discussed above, it is possible to selectively wake up Tag C 1  and not Tag C 2 , or vice versa. 
     Similarly, it is possible to re-configure Tag C 1  so that after it has moved from one zone to another zone, it will respond to wakeup signals/messages transmitted with Code B, or to any wakeup calls. It is also possible to software configure Tag C 1  such that it responds to and wakes up only to wakeup signals/messages transmitted with Code A for a determined period of time T 4 , after which it will change to respond to and wake up only to wakeup signals/messages transmitted with Code B for a determined period of time T 5 , after which it will change to respond to and wake up only to wakeup signals/messages transmitted with Code C for a determined period of time T 6 , and so on. All these periods of time T 4 , T 5  and T 6  are configurable and field-programmable and re-configurable. 
     According to a further aspect of the present invention, a dual-mode active RFID tag is provided, which may operate either in a real time location system (RTLS) mode or an inventory mode. As shown in the flow chart of  FIG. 3 , which shows an exemplary sequence of mode states of a dual-mode active RFID tag according to this aspect of the invention. As shown in  FIG. 3 , such a dual-mode active RFID tag may be software configured to be in one of the RTLS mode or inventory mode in the following order: 
     remains in RTLS mode for six hours, in which the tag is of real time position awareness, with high battery drain. When queried by an RFD reader, the tag will provide real time data of its location. This is required when the RFID tag (as well as the article with which the tag is associated) is at an embarkation container port (e.g. Hong Kong Container Port) for rapid loading; 
     then remains in inventory mode for fifteen days, in which the RFID tag is only of ID responding awareness, with low battery drain. When queried by an RFID reader, the tag will only provide data showing its own identity. This may be the time duration for which the tag (as well as the article with which the tag is associated) is on a cross-ocean container vessel; 
     then remains in RTLS mode for one day, in which the tag is of real time position awareness, with high battery drain. When queried by an RFID reader, the tag will provide real time data showing its location. This is required when the tag (as well as the article with which the tag is associated) is at an disembarking container port (e.g. San Diego Container Port) for unloading and custom clearing; and 
     then remains in inventory mode for eighteen hours, in which the RFID tag is only of ID responding awareness, with low battery drain, when the tag (as well as the article with which the tag is associated) is in a container truck on an interstate highway. When queried by an RFID reader, the tag will only provide data showing its own identity. 
     It can be seen that the RFID tag may alternate between RTLS mode and inventory mode to suit different needs and environments. 
     With such a dual-mode active RFID tag, a signal transmission apparatus is constructed to wirelessly transmit wakeup beacon/signals with time information of the cumulative period of time which has elapsed since transmission of the first wakeup signal up till the then current moment. As shown in  FIG. 4 , the wakeup beacon contains time slots with time index. This is useful in cases where a tag is software configured to Remain in sleeping mode for a long time. The RFID tag can calculate, on the basis of such time-related information, still how long it has to wait before the relevant wakeup signal will be transmitted. The tag may then go back to sleeping mode, wakeup just before the calculated time of transmission of the relevant wakeup beacon/signals, and start communication with the RFID reader transmitting the wakeup signals. 
     As a means of ensuring identification of an RFID tag even in case of battery failure, and according to a further aspect of this invention, an RFID tag assembly is shown in  FIG. 5 , and generally designated as  10 , as including both an active RFID tag  12  and a passive RFID tag  14 . The passive RFID tag  14  is stored with a unique identification (ID) code, such as that of the active RFID tag  12 . In normal operation, the active RFID tag  12  may respond to queries transmitted by an active RFID reader. Even in case of battery failure, an operator may use a passive RFID reader to query the tag assembly  10 . Although the active RFID tag  12  cannot function in case of battery failure, the minute electrical current induced in the antenna of the passive RFID tag  14  by the incoming radio frequency query signals from a passive RFID reader provides just enough power for the integrated circuit in the passive RFID tag  14  to power up and transmit a response. The passive RFID tag  14  may then transmit the unique ID code to the passive RFID reader in response to a query from it. 
     As shown in  FIG. 6 , the active RFID tag  12  may b software-configured to respond to and wakeup to wakeup signals with a specific characteristic, such as according to the multi-subcarrier wakeup scheme or the multi-code wake p scheme discussed above. Thus, while the passive RFID tag  14  can respond to queries from passive RFID reader (without expending any energy source in the RFID tag assembly  10 ), the battery life of the tag assembly  10  can be further preserved by configuring the active RFID tag  12  to only respond and wakeup to wakeup signals of a pre-determined characteristic, e.g. of a pre-determined frequency carrier or with a pre-determined code. 
       FIG. 7  shows a circuit arrangement of the RFID tag assembly  10  with the active RFID tag  12  and the passive RFID tag  14 . The tag assembly  10  has an internal baseband coupling circuit to read from and write data to the radio frequency (RF) terminal of the passive RFID  14 , so that critical information can be stored in a non-volatile memory of the passive RFID tag  14 . Such critical information may then be read back by a passive RFID reader even in cases where there is a battery failure or the battery life has run out. 
     According to the circuit arrangement shown in  FIG. 7 , a baseband pulse from the output terminal (Output Pin  1 ) of an integrated circuit (IC)  16  of the active RFID tag  12  in the proper command format is directly coupled to an RF antenna terminal (RF Antenna In) of the passive RFID tag  14 , and the same connector from the passive RFID tag  14  is connected to a comparator  18  and then finally to an input terminal (Input Pin  1 ) of the IC  16  of the active RFID tag  12 . Each of the “RF Antenna In” port and “RF Ground” port of an IC  20  of the passive RFID tag  14  is separately connected to a respective matching circuit  22 ,  24  and then to a respective antenna  26 ,  28 . Such an arrangement optimizes sensitivity when the tag assembly  10  is independently read by a passive RFID tag reader, while allowing the tag assembly  10  to be read by an active RFID tag reader. 
     As discussed above, and as shown in  FIG. 8 , the active RFID tag  12  may be software-configured to respond to and wakeup to wakeup signals with a specific characteristic, such as according to the multi-subcarrier wakeup scheme or the multi-code wakeup scheme discuss above, so as to conserve battery power. 
     As a further alternative to this arrangement, and as shown in  FIG. 9 , the active RFID tag  12  may be one with passive RFID tag protocol responding capability, so that it can respond to both short-range backscatter mode passive RFID protocol reader and long-range 2-way communication mode passive RFID protocol reader. As the data (in particular critical data) can be stored in and transferred between the active RFID tag  12  and the passive RFID tag  14  (as discussed above), the stored data can be transferred among all three modes of RFID operation, namely active RFID reader, 2-way communication mode passive RFID reader, and traditional backscatter mode passive RFID reader. This is therefore a triple connectivity tag. 
     To further enhance the function of the existing RFID system, a handheld/portable RFID reader is shown in  FIG. 10  and generally designated as  30 . The portable RFID reader  30  contains a real time location tracking (RTLS) RFID tag  32  so that the exact location (for example as represented in an x, y, z, location on earth) of the reader  30  can be ascertained by neighboring RTLS readers  34 , whether indoor or outdoor. Thus all read/write operations carried out by the reader  30  will have a x, y, z, location on earth as a position reference, and clock information obtained from a network clock server with which the reader  30  is associated, as a time reference. The reader  30  will thus have both an absolute spatial reference and absolute temporal reference for each of its read/write operation, even if the reader  30  may be a passive RFID reader for obtaining responses from passive RFID tags. 
     As an alternative, a handheld/portable RFID reader shown in  FIG. 11  and generally designated as  40  may include a global positioning system (GPS) receiver  42  for receiving position signals from GPS satellites, so that the exact location or the reader  40  is known outdoor and to some extent, indoor. Thus, all read/write operations carried out by the reader  40  will have a x, y, z location on earth as a position reference, and clock information obtained from a network clock server, as a time reference. The reader  40  will thus have both an absolute spatial reference and an absolute temporal reference for each of its read/write operations, even if the reader  40  may be a passive RFID reader for obtaining responses from passive RFID tags. 
     To provide a higher degree of redundant absolute positional reference and time reference that will enable location tracking both indoor and outdoor (even in outdoor areas with no neighboring RTLS readers), and as shown in  FIG. 12 , a handheld/portable RFID reader generally designated as  50  includes both an RTLS RFID tag and a GPS receiver, which provide it with both an absolute spatial reference and an absolute temporal reference for each of its read/write operations, even if the reader  50  may be a passive RFID reader for obtaining responses from passive RFID tags, and even if with no RTLS readers in the vicinity. 
     An active RFID tag according to a still further aspect of the present invention is shown in  FIG. 13  and generally designated as  60 . With a view to prolonging the usable life of the tag  60 , the tag  60  includes a number of rechargeable electric batteries  62   a ,  62   b ,  62   c , a smart power and recharge system  64 , and energy harvesting means, here being represented as both a stationary device energy harvesting system  66  and a mobile device energy harvesting system  68 . Generally speaking, an energy harvesting system captures and stores energy. The stationary device energy harvesting system  66  and the mobile device energy harvesting system  68  may be a solar cell, piezoelectric cell, thermoelectric cell, or kinetic power harvesting device. The recharge system  64  will recharge the batteries not currently in use. For example, if the battery  62   a  is being used, the recharge system  64  will recharge the batteries  62   b  and/or  62   c  with the electrical energy harvested by the energy harvesting systems  66 ,  68 . 
     Adopting the same basic principle, an active RFID reader generally designated as  70  and shown in  FIG. 14  includes a number of rechargeable electric batteries  72   a ,  72   b ,  72   c , a smart power and recharge system  74 , and energy harvesting means, here including both a stationary device energy harvesting system  76  and a mobile device energy harvesting system  78 . The stationary device energy harvesting system  76  and the mobile device energy harvesting system  78  may be a solar cell, piezoelectric cell, thermoelectric cell, or kinetic power harvesting device. The recharge system  74  will recharge the batteries not current in use. For example, if the battery  72   a  is being used, the recharge system  74  will recharge the batteries  72   b  and/or  72   c  with the electrical energy harvested by the energy harvesting systems  76 ,  78 . 
       FIG. 15  shows an arrangement of a method for calibrating a number of RTLS RFID readers in an environment, for locating RFID tags in the environment. Calibrator Tags  82   a ,  82   b ,  82   c  are each positioned in a fixed and known position in the environment. RTLS RFID readers  84   a ,  84   b ,  84   c ,  84   d  to be calibrated are placed in the environment. A movable Calibrator Tag  82   d  is moved, during the calibration process, along a pre-determined path in the environment, such that the position of the Calibrator Tag  82   d  at any point of time during the calibration process is also pre-determined. 
     The movable Calibrator Tag  82   d  should be fixedly associated with an optical barcode, optical descriptor or a passive RFID tag for simultaneous movement. Each of the fixed calibrating positions occupied by the Calibrator Tags  82   a ,  82   b ,  82   c  should have a landing pattern to allow the calibrator, with a camera, to allow optical alignment. 
     A data processing apparatus (e.g. a so called “location engine”) associated with the four RTLS RFID readers  84   a ,  84   b ,  84   c ,  84   d  may then obtain readings of location-related information relating to the various Calibrator Tags  82   a ,  82   b ,  82   c ,  82   d  as obtained by each of the four RTLS RFID readers  84   a ,  84   b ,  84   c ,  84   d  at a same point of time. The location engine then compares such readings with the actual known positions of the Calibrator Tags  82   a ,  82   b ,  82   c ,  82   d  at that point of time, so as to assess the ranging performance of each of the RTLS RFID readers  84   a ,  84   b ,  84   c ,  84   d . The location engine may then decide whether to use or discard ranging information from one or more of the RTLS RFID readers  84   a ,  84   b ,  84   c ,  84   d , or whether to assign different weights on the readings from different RTLS RFID readers  84   a ,  84   b ,  84   c ,  84   d.    
     An RFID tag and reader antenna or integrated reader circuit may be fabricated by a new method as schematically shown in  FIG. 16 . The RFID tag, generally shown as  90  in  FIG. 16 , is formed of an inner slab  92  of a high dielectric constant plastic material with upper and lower major surfaces. In particular, the slab  92  of plastic material is of a dielectric constant of at least 6.5. The high dielectric constant plastic material may be one traded by Saudi Basic Industries Corp. under Model No. Sabic Innovative Plastics™ ZX06323 or RX06324. Onto each of the major surfaces of the slab  92  is fixedly secured (e.g. by lamination) an outer single- or multi-layered material  94   a ,  94   b  suitable for fabricating a printed circuit board (PCB). An appropriate material is one called “FR-4”. FR-4 is an abbreviation for “Flame Retardant  4 ”. It is a composite of a resin epoxy reinforced with a woven fiberglass mat, and is a material from the class of epoxy resin bonded glass fabric. Metal pins (of which only one, designated as  96 , is shown in  FIG. 16 ) are provided to electrically connect the two layers of PCB material  94   a ,  94   b , for signal/power/ground connection purposes. An antenna may be formed on the outer surface of the layer of PCB material  94   a , while allowing circuitry to form, thus creating an all-in-one tag and antenna assembly. When assembled, an integrated circuit (IC) is also provided to be in electrical connection with the antenna, to form an RFID tag. 
     The same technique can be used for the formation of an RF antenna arrangement of an RFID reader, i.e. an RFID reader may also include, for its RF antenna arrangement, an inner high dielectric constant plastic layer with two major surfaces, two outer layers of PCB materials (e.g. FR-4) laminated each on a respective major surface of the inner plastic layer, with an antenna formed on the outer surface of one of the two outer PCB material layers. Metal pins are provided to electrically connect the two layers of PCB material for signal/power/ground connection purposes. 
     In an RFID system according to a yet further aspect of the present invention, and as shown in  FIG. 17 , a remote controller  100  is in a data communicable relationship, on a first hand, with a number of RTLS RFID tags  102  and, on a second hand, with a data processing apparatus, which is associated with an electrical appliance, e.g. a television set  106 , a DVD player  108 , a blu-ray player, a high-definition (HD) DVD player, a digital media player, a set top box, or a personal computer (PC). The remote controller  100  contains an active RTLS RFID reader  104 . The RTLS RFID tags  102  may be tagged on assets, people, pets or vehicles. 
     In use, the RTLS RFID reader  104  in the remote controller  100  can wirelessly obtain data relating to the RTLS RFID tags  102  (such as their respective unique ID, range, etc.) and transmit such data wirelessly to the data processing apparatus. Upon reception and possible further manipulation of the data (upon execution of a computer program in the data processing apparatus), the data processing apparatus transmits such (manipulated) data to a visual display unit (e.g. the television set  106 , or the monitor of the PC) for visual display. Such data may be displayed as text information or in the form of a radial map showing distances of the tags  102  (and thus the tagged items) with respect to the remote controller  100  (which contains the RFID reader  104 ). The tag ID information and range information as obtained by the RFID reader  104  of the controller  100  and transmitted to the data processing apparatus may be used for other purposes. 
     As an alternative arrangement, and as shown in  FIG. 18 , an RFID system includes a number of RTLS RFID readers  120  positioned in strategic positions in an environment (e.g. a house), and a remote controller  122  including an RTLS RFID reader or tag  124  which can communicate with the RTLS RFID readers  120  to initiate an inventory and/or ranging query on a number of RTLS RFID tags  126 . Data obtained by the RTLS RFID readers  120  are transmitted to the RTLS RFID reader or tag  124  of the remote controller  122 , and then subsequently transmitted wirelessly by the remote controller  122  to a data processing apparatus (not shown) of an electrical appliance (e.g. a television set  128 , a DVD player  130  or set top box), for subsequent visual display by a visual display unit. 
     As a number of RFID readers  120  are used, multiple range information relating to a same RFID tag  126  may be obtained. It is possible to obtain the x, y coordinates of the tag  126  by triangulation. The x, y location of the tag  126  may then be shown on the visual display unit with an x, y coordinated map. 
     As a further alternative RFID system, and as shown in  FIG. 19 , a remote controller  140  transmits information to a personal computer (PC)  142  via a wireless USB dongle or bridge. A dongle is a small hardware device that connects to a computer, often to authenticate a piece of software. When the dongle is not present, the software runs in a restricted mode or refuses to run. The data are then transmitted to a computer monitor  144  for visual display. The information may likewise be text based, on a radial map, or on an x, y coordinated map. 
     As a yet further alternative RFID system, and as shown in  FIG. 20 , a remote controller  150  includes a passive RFID reader  152  which reads identity (ID) data from a number of passive RFID tags  154 . As in the previous RFID systems, data obtained by the remote controller  150  are transmitted to a data processing apparatus of an electrical appliance  156  for display on a visual display unit. 
     As a still further alternative RFID system, and as shown in  FIG. 21 , a remote controller  160  includes both an RTLS reader or tag  162  and a passive RFID reader  164 . By way of such an arrangement, it is possible to go around the house with the remote controller  160  and read passive RFID tags  166  tagged on all kinds of assets. The RTLS reader/tag  162  in the remote controller  160  will give the x, y (and maybe even z) coordinates of the tags  166 . Such information is then sent either to a memory in an electrical appliance (e.g. a television set  168 ) for storage, or to a personal computer  170  for storage. Such data may later be displayed on the television set  168  or a monitor of the personal computer  170 . 
     It should be understood that the above only illustrates examples whereby the present invention may be carried out, and that various modifications and/or alterations may be made thereto without departing from the spirit of the invention. 
     It should also be understood that certain features of the invention, which are, for clarity, described in the context of separate embodiments, may be provided in combination in a single embodiment. Conversely, various features of the invention which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any appropriate sub-combinations.