The UHF tag antennas are usually made of a copper, aluminum, or silver deposited on the substrate. UHF interrogators are usually costlier than HF interrogators, but UHF tags are becoming more economical. The new Gen 2 protocol for UHF tags is designed for reading several hundred tags per second. All the protocols in the UHF range have some type of anti-collision capability, allowing multiple tags to be read simultaneously in the IZ. The UHF tags have a read range of about 15 to 20 feet. The passive and the semi-passive tags in this frequency range use far-field radiative coupling, or backscatter coupling. Tags and interrogators in this range are called UHF tags and UHF interrogators. The frequency range of 860–960 MHz is often referred to by a single frequency of 900 or 915 MHz.
The 433 MHz frequency is used for active tags, while the 860–960 MHz range is used mostly for passive tags and some semi-passive tags. The ultra high frequency range includes frequencies from 300 to 1000 MHz, but only two frequency ranges, 433 MHz and 860–960 MHz, are used for RFID applications. If the ID is incorrect or no tag is found, the car cannot be started. If the tag ID is correct, the car can be started. When that key is used to start the car, an RFID interrogator placed around the key slot reads the tag ID. For example, in an automobile vehicle immobilizer system, an LF tag is embedded inside the ignition key. The automotive industry is the largest user of LF tags. They are used in access control, asset tracking, animal identification, automotive control, as vehicle immobilizers, healthcare, and various point-of-sale applications (such as Mobil/Exxon SpeedPass). The LF tags can be easily read while attached to objects containing water, animal tissues, metal, wood, and liquids. They are expensive to manufacture, and tags using them are thicker than others at higher frequencies. The tag antennas are usually made of a copper coil with hundreds of turns wound around a ferrous core. The LF tags have no or limited anti-collision capabilities therefore, reading multiple tags simultaneously in the IZ is impossible or very difficult. They have the lowest data transfer rate among all the RFID frequencies and usually store a small amount of data. The LF tags are passive tags (no battery and transmitter on the tag) and have a short read range of a few inches. They use near-field inductive coupling to obtain power and to communicate with the interrogator. The tags in this range are generally called LF tags. It is available for RFID use all over the world. This range has been in use for RFID tags for animal tracking since 1979 and is the most mature range in use. Applications include the identification of cases/pallets, products, work-in-process, specimens and laboratory tests.Low frequency range includes frequencies from 30 to 300 KHz but only 125 KHz and 134 KHz (actually, 134.2 KHz) are used for RFID. Inlays that offer improved read ranges with off-axis placement, on diverse materials, densely packed items, with overhead readers, as well as when extended read ranges are required. Cost-effective inlays designed for use with most standard applications, such as the identification of cases/pallets, products, work-in-process, specimens, laboratory tests and patients.
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