RFID

Radio Frequency Identification (RFID) is a technology in which a tiny chip of the size of sand grain is remotely powered by a reader, which then sends data back to the reader. Because this operation is passive, the cost of these chips are sub-dollars and very inexpensive.

  Frequency Allocation. RFID have frequency allocation called LF (100-130KHz), HF (13.56MHz) and UHF(800MHz-950MHz) and Microwave (2.5GHz).

            LF – or Low Frequency RFID is suited for high obstacle area including metals. LF RFID operates slowly but reliably. These are the oldest form of RFID and still being used extensively in ID Cards, Access Controls, and other close range environment. The range is limited to only 30cm. LF RFID may be read only or read write. Read Only type have chips like TK4100 and EM4200. Read/write have chips NXP HITAG, EM4305 or T5577. Special low frequency readers are used for Low Frequency use. LF readers are very inexpensive.

            HF or High Frequency tags are used where the environment is less noisy. The transmission speed is 13.56MHz, significantly higher than the LF range. HF RFID is used in theft control applications. Library tags use these tags extensively. Theft control tags, clothing tags, etc are other applications of HF RFID. ISO15963 is the most popular kind of HF RFID tag. This tag is used in EAS system, Library management (also called library tag) and retail. High Frequency readers/writers are required to read the tags. HF reader/writer price is higher than LF, but significantly less than UHF. HF based EAS system uses gate type readers for detection, which have a range of 1 meter.

UHF, or Ultra High Frequency RFID is fastest and longest range of RFID technology that exists today without going to active RFID. UHF tags can be detected from up to 30m range from the readers. Due to their speed of reading, a well designed reader may read 100s of these tags at the same time. UHF tags are used in inventory management to replace bar codes, automobile tracking, automobile access control, and many other long range detection applications. UHF tags are the most attractive due to their very low price, high speed, long range and reliability. In addition, modern readers are capable of reading multiple tags simultaneously (100s of tags together). This makes identification of inventory items very fast without needing to scan the barcode. UHF tags are replacing barcodes. While barcodes are not entirely gone, but most barcodes are printed on RFID stickers. UHF reader/writers are expensive. The price range from $200 to several thousand dollars. In addition, many unit is split into a reader part and antenna part. Reader part have co-axial port for antennas and many antennas can be attached to a single reader hardware. UHF antennas have directional polarization and a full planning is needed to put the antenna for best reading range and reliability. With high installation cost of UHF reader and antenna assembly, is supplemented by the ultra low price of the UHF RFID tags.

Types of Tags. Tags comes in the form of inlays, stickers, cards, wristband, plastic enclosures, etc. Inlays are the most basic form of tags. Inlays are used in stickers, cards, wristbands and other types. Inlays are wet and dry. Wet inlays have a sticky back. Dry inlays does not have any glue. Stickers are used to print labels or barcode. Wristbands are used in hospitals, ticketing, etc. where the band will be disposed off. PVC Cards are used as ID Cards and access controls.

       Tags can have not writable memory (just read only with a unique number). Read Only tags are cheaper, but tags with memory are getting to the same price range. Most of the tags today have some small memory for reading and writing. The memory is used by the application software for various categorizing purposes.

Active RFID

            Active RFID stands for RFID with some external power into to the tags to increase the range. The tag contain a tiny battery to increasing the range to about 100m. Most Active RFID have a range of over 30m. 2.5GHz Active RFID are very low power tags and the batteries last over 3 years. Active RFID tags are expensive starting from $3 per tag. They come in various forms inside plastic enclosures. PVC Card, wristbands, disc, keyring, etc are popular Active RFID types. Active RFID readers are small with omni-directional antenna.