Radio frequency identification (RFID) systems allow for the identification of objects at a distance and out of line of sight. Radio frequency identification (RFID) systems generally consist of one or more RFID readers (also called RFID interrogators) and a plurality of RFID transponders, which are commonly termed RFID tags. RFID systems utilize an RFID transmitter-receiver unit (a base station or interrogator) to query an RFID transponder or tag which maybe located within a maximum distance from the interrogator unit. The RFID tag detects the interrogating signal and transmits a response signal containing encoded data back to the receiver. In principle, RFID techniques entail using an RFID reader to interrogate one or more RFID tags. The reader transmitting a radio frequency (RF) wave performs the interrogation. A tag that senses the interrogating RF wave responds by transmitting back another RF wave. The tag generates the transmitted back RF wave either originally, or by reflecting back a portion of the interrogating RF wave in a process known as backscatter. The RFID devices generally utilize an antenna structure that is operatively coupled to electrical or electronic components, in the form of a chip or a strap, to communicate with a receiver or transceiver device such as a detector or reader. The antenna structure utilizes conductive material arranged on a dielectric substrate in a suitable array. When a RFID reading device broadcasts a radio frequency signal, this signal interacts with the RFID transponder antenna. The transponder antenna converts part of the received RF signal energy into an electrical current. This electrical current, in turn, is detected by the integrated circuit and, in many applications, actually powers the integrated circuit. The integrated circuit then modulates this electrical current in the transponder antenna to thereby create a return RF signal. This return RF signal is then detected by the antenna in the RFID reading device. The antenna is coupled to the chip or strap to allow communication between the RFID device and the reader and the detector. The RF electromagnetic field induces an alternating current in the transponder antenna that can be rectified by a RF diode of the transponder. The rectified current can be used for a power supply for the electronic components of the transponder, and enables the transponder to broadcast a return signal without itself having a self-contained power supply. RFID systems can be used in many ways for locating and identifying objects to which the tags are attached. RFID systems are particularly useful in product-related and service-related industries for tracking large numbers of objects being processed, inventoried, or handled.

Radio frequency identification (RFID) tags or transponders are electronic devices generally composed of an antenna and an integrated circuit. The antenna is used for sending and receiving data as radio-frequency signals. The integrated circuit contains non-volatile memory, modulation circuitry (for facilitating radio communication), and control logic. An RFID tag emits radio frequency signals containing information stored on the RFID tag when excited by an RFID reader. RFID readers typically operate to read the RFID tag as an item is transported past the stationary reader. Radio frequency identification (RFID) tags are used as a replacement for barcodes. RFID tags are capable of providing significantly greater information than barcodes and are capable of being read irrespective of the orientation of the item bearing the RFID tag. RFID tags can be passive, active or hybrid devices. RFID tags with a power storage device are known as active tags. Advances in semiconductor technology have miniaturized the electronics so much that an RFID tag can be powered solely by the RF signal it receives. Such RFID tags do not include a power storage device, and are called passive tags. Passive devices do not contain a discrete power source, but derive their energy from an RF signal used to interrogate the RFID tag. Passive RFID tags usually include an analog circuit that detects and decodes the interrogating RF signal and that provides power from the RF field to a digital circuit in the tag. The digital circuit generally executes all of the data functions of the RFID tag, such as retrieving stored data from memory and causing the analog circuit to modulate the RF signal to transmit the retrieved data. In addition to retrieving and transmitting data previously stored in the memory, the RFID tag can permit new or additional information to be stored in the RFID tag's memory, or can permit the RFID tag to manipulate data or perform some additional functions. RFID transponders or tags, either active or passive, are typically used with the RFID reader to read information from the RFID tag embedded in a label. RFID smart tags can be embedded in or attached to product packaging, or incorporated directly into the product, and may convey conventional "bar code" information, as well as other more detailed information.

RFID tags can retain and transmit enough information to uniquely identify individuals, packages, inventory and the like. The information received from an RFID tag is specific to the particular application, but often provides an identification for an article to which the tag is fixed. The powered up RFID TAG communicates with the RFID reader by generating transponder data signals within the circuitry of the RFID transponder and transmitting the transponder data signals in the form of electromagnetic waves into the surrounding space occupied by the RFID reader. The RFID reader contains its own circuitry as well as its own reader programming, which are cooperatively designed to "read" the data contained in the transponder data signals received from the RFID transponder. The powered up transponder transmits communication signals in the form of electromagnetic waves into the surrounding space which are received by the reader. Accordingly, all of the transponders and readers each have a transmitting function and a receiving function. In general an RFID tag system allows for objects to be labeled with tags such that when the tag is passed through the electromagnetic field of a reader/interrogator the object can be identified by reading the tag that is attached to the object. The operational distance between the transponder and the reader depends on the configuration of the reader and tag used, as well as the frequency and power of the transmitted signals. RFID tags are attached in a wide variety of methods including being bolted to the item or simply glued to the inside of existing packaging or labeling. They can be encoded with a user-defined data at time of use, or pre-coded at time of tag manufacture numbering system or even a combination of both. RFID labels can be produced by placing an RFID tag in a label, programming information into the tag, such as from a host computer, and based on the information, printing the label with a proper bar code and/or other printable information using a thermal printer. RFID labels can also be produced in a thermal printer by first printing on the label and then programming or encoding the RFID tag on the label.

Radio frequency identification (RFID) tags and labels are widely used to associate an object with an identification code. Radio frequency identification tags are used in a multiplicity of ways. They may be used in locating and identifying accompanying objects, as well as for transmitting information about the state of an object. Radio frequency identification systems provide a number of advantages over paper and ink labels, such as bar code systems in that a much greater degree of automation is permitted; clear line of sight is not required, tags can be obscured by dirt, paper, even other objects or packaging; reading distances can be greater; tags can be hidden either to protect the tag from damage in use or for security reasons. Moreover, in the case of read/write tags incremental information can be stored on the tags such as PO#, expiry date, destination, confirmation of an applied process, etc. Various commercial applications have been suggested for smart tags, particularly in the area of retail marketing and sales. RFID technology may be used to gather information related to consumer trends, purchasing habits, consumption rates, etc. It has also been suggested that RFID technology has promise in the areas of inventory control, manufacturing process and control, product accountability and tracking systems, etc. Transfer of data via RFID technology may be used, for example, in indicating the presence of the object, such as in electronic article surveillance (EAS), for obtaining data associated with the object or for identifying the object. RFID systems may have a variety of forms and configurations for different applications. They can be a handheld device (e.g., wand), a free standing structure (e.g., theft detection devices in retail stores), a fixed structure attached to or extending from a building, or a toll tag reader structure above a toll road, for example.