Radio frequency identification (RFID) is a technology that incorporates the use of electromagnetic or electrostatic coupling in the radio frequency (RF) portion of the electromagnetic spectrum to uniquely identify an object, animal, or person. RFID is coming into increasing use in industry as an alternative to the bar code. The advantage of RFID is that it does not require direct contact or line-of-sight scanning. RFID is sometimes also called dedicated short range communication (DSRC).
In an RFID system, multiple wireless tags are interrogated by sending information from an interrogating transmitter to the tags and having information transmitted by the tag in response. This is commonly accomplished by having the tag listen for an interrogation and for it to respond with a unique serial number and/or other information. However, it is desirable to extend the range of wireless tags so that it is not necessary to bring each tag close to a reader for reading. Two problems are evident when extending the range of the reading system. One of the problems is that there is limited power available for transmission from the wireless tag, and that if the range is significant, it is possible that many tags will be within range of the interrogating system and their replies may corrupt each other.
There are a number of methods and apparatuses that address these problems and enable the fabrication of wireless tags with longer ranges and an ability of the system to handle many tags in the sensitive range.
In one application, RFID tags can be used to identify items for purchase, inventory, etc. And, as outlined, there are known methods that enable one specific tag in a group of many tags to be interrogated without corruption by other tags of information sent by that one particular tag to the reader and without accidental transmission of data or commands to other tags of information sent to that particular tag.
The least expensive tags usually have read only memory. This is adequate for identifying a tag and for executing a purchase. However, at times, the purchaser might require privacy after the purchase so that another party cannot perform a scan and learn the contents of that purchaser's purse, car or home. Further, the tags may need to be disabled to allow the product to be taken through a security device that recognizes intact tags.
Thus, there are times when it is desirable to disable or destroy an RFID tag after purchase. This disablement may be either partial or complete and may be accomplished by data erasure, modification, etc. However, tags with destructible memory may be susceptible to thievery, in that a thief with the proper equipment could potentially disable a tag. Thus, it is desirable to require some type of validation of authority to disable a tag. Furthermore, when a tag is destroyed it is desirable that other tags within range of the disabling device, typically a reader, are not also destroyed.