Abstract:
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.

Description:
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&#39;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® 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®) 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&#39;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&#39;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&#39;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. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view illustrating a typical wall mounted RFID reader equipped with a keypad and a remote programmer according to this invention packaged as a hand held unit; and 
     FIG. 2 is a circuit diagram of the novel remote programmer. 
    
    
     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&#39;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&#39;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 S 1  through S 16  are normally open switches corresponding to sixteen keys arranged in a four-by-four matrix on the keypad  22 . Integrated circuits IC 1  through IC 16  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&#39;s may be TEMIC e5550 devices which operate with the RK600 reader. Antenna coil L 1  and capacitor C 1  form an antenna tank circuit which is resonant at the transmitter frequency of the proximity reader. For example, L 1  may be a 1.62 mH coil and C 1  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 S 1 -S 16  to the other side of the antenna tank circuit by means of bus line  26 . In a normal condition of the programmer all switches S 1 -S 16  are open and none of IC 1 -IC 16  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&#39;s sensing field. If, however any one of the keys on the keypad is pressed, closing one of switches S 1 -S 16 , the corresponding one of IC 1 -IC 16  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&#39;s microprocessor is written to recognize the unique tag codes of the programmer&#39;s transponder tag ICs IC 1 -IC 16  as dedicated to a function other than ordinary access key tag data. In particular, the reader&#39;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&#39;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&#39;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&#39;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&#39;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&#39;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&#39;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.