Passive remote programmer for induction type RFID readers

A hand held passive remote programmer for Radio Frequency Identification readers has a keyboard for turning on any one of several RFID transponder tags in the programmer. Each transponder of the programmer is recognizable by the RFID reader as a program instruction which modifies the operation of the reader, rather than one of a second population of transponder tags which are recognized simply by proximity to the reader, such as tags provided in key cards. In a broader sense, the invention provides a method for wireless linkage of a keypad to an induction type RFID reader.

BACKGROUND OF THE INVENTION
 1. Field of the Invention
 This invention relates generally of the field of radio frequency
 identification (RFID) systems and devices intended to sense the presence
 of a transponder tag within a sensing field of a reader unit and to read
 an identification code unique to each such tag thereby to identify a
 person or object associated with the tag. More particularly this invention
 is directed to a passive remote programmer for reprogramming
 microprocessor controlled induction type RFID readers.
 2. State of the Prior Art
 Radio frequency identification systems have come into widespread usage in a
 wide range of applications. One such application is controlling access to
 restricted areas of buildings or plant facilities by authorized personnel
 while excluding those lacking the necessary authorization. Most such
 proximity systems consist of a transponder, a reader and a host computer.
 The reader generates a radio frequency (usually in the 125 kHz or 13.5 MHz
 range). The transponder usually consists of an antenna circuit (tuned to
 the same frequency as the output of the reader) and an integrated circuit
 (IC). Sufficient energy to activate the IC is obtained via induction when
 the transponder is placed within the field of the reader. The frequency of
 the reader is also used as a clock for the IC. When energized, the
 transponder IC loads the antenna circuit of the transponder in a pattern
 determined by the design and programming of the IC. The loading of the
 transponder antenna is detected as a pattern of voltage changes on the
 reader's antenna circuit. The changes are converted into logical data bits
 using standard decoding methods and the data is then interpreted by the
 host and appropriate action (such as opening the door) is taken.
 The topology of the various systems can range from a stand alone single
 door unit that contains the reader and the host in one small box mounted
 adjacent to a passageway to a complex system consisting of thousands of
 readers and other input/output devices connected to a communications
 network controlled by hundreds of host computers (running specialize
 software) that control access, personnel and property movement, lighting,
 HVAC, fuel dispensing and other functions. In stand alone, single door,
 products and in some systems with distributed intelligence, the reader and
 host are often combined into a single entity.
 SecuraKey, a division of Soundcraft, Inc., the assignee of this invention
 sells a reader under the name Radio Key.RTM. 600 or RK600, described in
 their commercial literature as a "stand alone proximity/keypad access
 control system" which has a built-in programmer. This reader is of the
 inductive type and is intended to function in conjunction with key tags,
 also sold by the same assignee, which are passive bi-directional
 transponders in that power for the key tag is derived from the
 electromagnetic field generated by the reader. Each transponder consists
 of an integrated circuit and an antenna coil, both embedded in a small
 plastic token or tag. The integrated circuit of the transponder tag is a
 TEMIC e5550 contactless R/W-Identification IC (IDIC.RTM.) device sold by
 the semiconductor division of TEMIC TELEFUNKEN microelectronic GmbH,
 P.O.B. 3535, D-74025 Heilbronn, Germany.
 There is a need for periodically reprogramming such proximity systems as
 authorized personnel and access control requirements change. For example,
 as newly authorized individuals are issued transponder tags, the new tags
 must be entered into the reader's programmed data base in order to be
 recognized when presented to the reader. Likewise, tags need to be removed
 from the data base as personnel leaves or is reassigned. In large RFID
 systems such reprogramming is typically done through the host computer
 linked to multiple readers. In smaller systems or those lacking
 centralized control, reprogramming may need to be done at each reader.
 Conventionally, this may be achieved through a keyboard provided on the
 reader unit itself, as in the aforementioned RK600 reader. It is often
 desirable to provide means for remotely programming the reader for
 convenience or security reasons. Radio frequency linked hand held remote
 programmers are available for this purpose. Such units typically include a
 keyboard connected to a microprocessor which delivers programming data
 transmitted via a low power radio frequency carrier generated by the
 programmer unit. Also available are passive programmers which draw their
 operating power from the electromagnetic field emitted by the reader.
 Existing passive programmers, however, are based on microprocessors or
 other complex circuitry . Also, the power requirements of these existing
 units is relatively large which results in a rather short operating range
 because the programmer must be brought sufficiently close to the reader
 where the field strength is adequate for powering the programmer. A
 continuing need exists for simpler, lower cost passive programmers,
 particularly for use with small or stand alone RFID installations.
 SUMMARY OF THE INVENTION
 This invention addresses the aforementioned need by providing a simpler
 passive remote programmer for induction type RFID readers. The novel
 remote programmer is of economical design, requiring only three main
 components: a keypad, an antenna and a number of commercially available,
 low cost transponder tag integrated circuits. Each of the transponder tag
 ICs, when connected to the antenna by actuation of a key on the keypad,
 communicates with the RFID reader by loading down the magnetic field in
 the vicinity of the transmitter antenna of the reader in a pattern which
 the reader interprets and decodes as digital data.
 More specifically, the passive remote programmer system of this invention
 is intended for use with an induction type RFID reader having radio
 frequency (RF) sensing means operatively connected to a digital processor,
 such as a microprocessor, for reading tag identification data of RFID
 transponder tags powered by a sensing field of the reader and for
 verifying the identification data against stored identification data
 thereby to recognize the presence of authorized tags.
 The programmer which may be a hand held unit houses an antenna, such as a
 loop antenna, a number of dedicated RFID transponder tag integrated
 circuits each having a unique tag code, and a keyboard having a plurality
 of keys each selectively operable for connecting a corresponding one of
 the dedicated RFID transponder tag integrated circuits to the antenna
 thereby to inductively power the selected tag IC in the reader's sensing
 field and enable the unique tag code of the selected tag IC to be read by
 the RFID reader. The remote programmer operates in conjunction with
 programming of the reader's microprocessor for recognizing the unique tag
 codes of the dedicated tag ICs as new reader programming instructions. In
 most cases the reader program is also operative for retaining or storing
 in microprocessor memory the new program instructions for subsequent
 execution by the microprocessor. The new program instructions may, for
 example, comprise data for modifying a transponder tag data base
 accessible to the reader microprocessor for use in executing decision
 making algorithms such as granting or denying access upon reading a
 particular tag code.
 In a broader sense, the present invention may be understood as a method for
 wireless linkage of a keypad to an induction type RFID reader, comprising
 the steps of providing a keyboard having one or more individually
 actuatable normally open switch keys, connecting each of the switch keys
 to a corresponding RFID transponder tag IC and an antenna such that
 closing a particular switch key places a corresponding transponder tag IC
 in operative connection with the antenna for inductively communicating a
 unique identification code of the tag IC to the RFID reader; and program
 means executable by a microprocessor in the RFID reader for recognizing
 the unique identification code of each tag IC connected to the keyboard
 thereby to recognize the reading of those tag ICs as representing the
 actuation of a key or switch rather than the conventional presentation of
 a proximity key tag to the reader. The reading of the unique
 identification code may be interpreted as a new program instruction for
 the microprocessor modifying existing programming, but in general elicits
 a response from the reader which is different from the response elicited
 by the reading of a conventionally presented access key tag such that the
 response of the RFID reader to conventionally presented RFID tags may be
 modified by actuation of keys of the remote programmer keyboard.
 These and other features, improvements and advantages of the present
 invention will be better appreciated and understood by reference to the
 following detailed description taken in conjunction with the accompanying
 drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
 With reference to the accompanying drawings wherein similar elements are
 designated by similar numerals. FIG. 1 depicts a typical proximity RFID
 reader unit 10 contained in a reader housing 12 which is mounted on a wall
 surface 14. For purposes of this description the reader 10 may be an RK600
 sold by SecuraKey equipped with an exteriorly mounted keypad 16 which
 provides an interface for accessing the reader's microprocessor control
 system. In most installations such access requires entry of an authorized
 passcode before the keyboard is enabled for reprogramming the reader unit.
 The keypad may also be used for entering a personal identification number
 (PIN) as an alternative to presentation of a key tag.
 A passive remote programmer 18 according to this invention is shown having
 a housing 20 on which is mounted a keypad 22. The housing 20 may be a
 small enclosure sized for convenient hand held operation. The remote
 programmer's keypad may be a duplicate of the reader keypad 16, or may be
 configured differently.
 Turn now to FIG. 2 which shows a circuit diagram of the passive remote
 programmer 18. It will be appreciated that this circuit is quite simple
 and with few components. Switches S1 through S16 are normally open
 switches corresponding to sixteen keys arranged in a four-by-four matrix
 on the keypad 22. Integrated circuits IC1 through IC16 are sixteen similar
 transponder tag ICs each programmed to transmit a unique identification
 code when activated by the inductive sensing field of a proximity reader.
 The transponder IC's may be TEMIC e5550 devices which operate with the
 RK600 reader. Antenna coil L1 and capacitor C1 form an antenna tank
 circuit which is resonant at the transmitter frequency of the proximity
 reader. For example, L1 may be a 1.62 mH coil and C1 may have a value of
 1000 pF. Each tag IC has two active terminals, one of which is connected
 directly to one side of the antenna tank circuit by means of bus line 24.
 The other active terminal of each tag IC is connected through a
 corresponding normally open switch S1-S16 to the other side of the antenna
 tank circuit by means of bus line 26. In a normal condition of the
 programmer all switches S1-S16 are open and none of IC1-IC16 are connected
 to the antenna circuit. Consequently, if the remote programmer unit 18 is
 placed in this condition within the sensing field of the reader unit 10,
 the programmer unit will not respond to the reader's sensing field. If,
 however any one of the keys on the keypad is pressed, closing one of
 switches S1-S16, the corresponding one of IC1-IC16 will have both of its
 active terminals operatively connected across the antenna tank circuit. In
 this condition, the operative IC will be powered up by energy inductively
 coupled from the reader to the antenna coil 1, and will transmit its
 unique tag code to the reader. The transponder IC may be in the form of
 surface mount dies and the entire circuit of FIG. 2 can be easily
 implemented on a single circuit board which can also carry the keypad and
 antenna coil. The resulting package is lightweight and rugged. The passive
 programmer disclosed herein improves over prior passive programmers not
 only in terms of greater simplicity and economy, but also in extended
 operating range from the proximity reader because the transponder tag ICs
 have lower power requirements than more complex passive programmers.
 The program executed by the reader's microprocessor is written to recognize
 the unique tag codes of the programmer's transponder tag ICs IC1-IC16 as
 dedicated to a function other than ordinary access key tag data. In
 particular, the reader's program should recognize the reading of the
 dedicated tag codes as representing the actuation of a key rather than the
 presentation of a conventional key tag to the proximity reader. This
 recognition may be exploited by the programmer of the reader for any
 desired purpose. For example, keys corresponding to the digits 0 through 9
 may each be represented by a particular and unique tag code, so that
 numerical data may be entered into the reader by pressing a sequence of
 keys. Logic function keys such as ADD or DELETE may be similarly
 represented by corresponding unique tag codes. Still other control
 functions, such as an ENTER key on the keyboard, may also be assigned
 corresponding tag codes. For example, the remote programmer may be used to
 add to or delete authorized key tags in the reader's data base, as by
 pressing a sequence of digits followed by pressing an ENTER key, or to
 enter PIN codes into the reader as an alternative to using the keypad 16
 on the reader unit 10. In fact, the remote programmer can replace
 altogether the keypad on the reader with no sacrifice in programmability
 of the reader, resulting in a more secure installation since the keypad is
 no longer accessible on the reader. Also, elimination of the keypad makes
 it possible to better seal the reader enclosure or housing for better
 weather proofing and resistance to environmental contaminants.
 The manner of programming the reader's microprocessor to accomplish such
 recognition will be apparent to those having ordinary knowledge of such
 systems and need not be described in greater detail here, particularly in
 view of the many ways in which proximity reader systems can be programmed
 both for conventional purposes and for purposes of implementing this
 invention. The programming which controls operation of the reader's
 microprocessor may be installed as firmware in non-volatile memory
 provided on the processor chip. Of course, other program storage devices
 may be provided for this purpose. For purposes of this invention, the
 reader control program should contain information to enable the reader to
 identify the unique ID code transmitted by the transponder tag ICs in the
 remote programmer so that these are distinguishable from other transponder
 tags not enabled by actuation of a key or switch, such as conventional key
 tags. This information is distinct from the data base which the
 microprocessor accesses in order to identify conventional key tags
 authorized for access. Recognition of key enabled transponder ICs permits
 programming of the reader to take special action in response to such tag
 IC readings, different from action taken in response to conventional tags
 which are enabled simply by sufficient proximity to the reader. From the
 preceding paragraph and the description generally it will be understood
 that this invention contemplates two distinct sets, groups or populations
 of transponder tags: a first population of dedicated tags associated with
 the remote programmer which to be enabled for recognition by the reader
 require both proximity to the reader as well as actuation of a key on the
 remote programmer, and a second population which are enabled by mere
 proximity to the reader. The transponder tags of the second population are
 recognized by the reader in a conventional manner, i.e. simply by being
 brought into sufficient proximity to the reader, and as explained earlier
 in the paragraph, the ID codes of these tags are recognizable from a data
 base accessible by the reader's microprocessor. The transponder tags of
 the first populations have ID codes which are different from those in the
 first population data base and are instead recognized by the reader's
 microprocessor as programming instructions which in some way control or
 modify the way in which the RFID reader responds to transponder tags of
 the second population. That is, the reader recognizes two different
 populations of tags and responds differently to tags from the two
 populations.
 The number and functions of keypad keys which can be encoded and wirelessly
 linked to a reader in this fashion is virtually unlimited. As a practical
 matter, however, it may be found that this approach to passive remote
 programming is best suited to smaller keypads, while programmer units
 requiring large and complex keyboards are better implemented with
 microprocessor driven circuits or the like.
 It should be understood that this invention is not restricted to any
 particular manufacturer's proximity systems, and is generally useful with
 any induction type proximity readers, provided that the tag ICs used in
 the remote programmer unit can be read by the target proximity reader.
 While a particular embodiment of the invention has been described and
 illustrated for purposes of clarity and example, many changes,
 substitutions and modifications to the described embodiment will be
 apparent to those having ordinary skill in this technology without thereby
 departing from the scope of this invention as defined by the following
 claims.