Reader
Transceiver. The RFID reader is a transceiver. The reader interrogates the RFID tag by transmitting a continuous carrier wave. As interrogation proceeds, the reader alternately transmits and receives. (Some readers transmit and receive at the same time.) The reader's output power partly determines its reliable reading range. For example, a toll road reader requires a longer range than a gas pump reader has. A reader can operate as a standalone unit, or it can connect to a data warehouse. The warehouse is probably the usual installation.
Authentication takes place after the reader captures and processes the ID from the RFID tag. If the tag ID matches a stored ID, and no exceptions prevent authentication, the control system performs an action. For instance, the system might...
| • Count stock | • Unlock a door | • Allow account access | • Debit a toll account |
Portable reader. Although built-in readers are common, an operator could authenticate tags with portable reader.
Data Warehouse
Server. A data warehouse is a database on a server, server bank or mainframe. The data warehouse stores and relates RFID data, such as door access history or purchases of some product. The data warehouse is optional for some applications, but can enhance security processes. A data warehouse is necessary for marketing that depends on purchase history. A typical warehouse uses common database applications: For example...
| • Oracle | • SQL Server | • DB2 |
Transmission Medium
ISM band operation. RFID tags for different purposes use very different radio frequencies. These radio frequencies are in the unlicensed ISM bands (Industrial, scientific and medical). An example of a low-frequency application is the gasoline credit tag. This tag uses a 125-kHz transponder. Typically, the coupling method for this tag is inductive. One of the most common frequencies is 13.56 MHz, just below the 20-meter shortwave band. Again, the coupling method is inductive. In such devices, the antenna is the largest part of the RFID device. As the frequency rises, antenna size shrinks. UHF RFID devices can be quite small. The smallest devices only require miniature antennas. These tiny devices operate as high as 2.4 GHz. The usual coupling method for microwave devices is backscatter transmission. These higher-frequency tags tend to have much higher read ranges than the lower-frequency tags do. The typical read range for a 13.56 MHz tag is under six feet. For a 2.4 GHz tag, the read range can exceed 90 feet.
| LF | HF | UHF-1 | UHF-2 | UHF-3 |
| 125 - 148 kHz | 13.56 MHz | 433 MHz | 850 - 930 MHz | 2.5 GHz |
Non-RF applications. Despite its name, RFID doesn't always rely on radio frequencies (RF). Besides radio frequencies, the transmission medium can be ultrasound, magnetic induction or infrared light. These other transmissions methods are useful in restricted RF environments. For example, infrared or ultrasound might be useful for RFID cards at blasting sites.
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