There are two types of RFID devices: Active and Passive. Active devices have power source built in which supplies the transmitter. The transmitter is triggered by sending the signal to RFID device. These devices have their own code and can transmit signal in desired time intervals. Active RFID devices are good in defining locations of objects or sending some information about particular place (RFID-based location determination). Active RFID devices use high frequencies (455MHz, 2,45GHz or 5,8GHz) – working range about 20 – 100 meters.

The most common are passive RFID. They don’t need power source. Passive RFID devices are low frequency(124 – 135kHz – low) and high(13,56MHz – 960KHz – high; 2,45GHz - UHF). The working principal of low and high frequency devices differ. While low frequency readers generates magnetic field which induces current in RFID device antenna. The chip inside RFID device modifies this magnetic field which is read again by reader. The working distance of such device is about 35cm.

High frequency RFID labels works a little different. There is no magnetic field between reader and RFID label. Reader sends radio signal which energy is used to power inside chip which changes RFID label antenna charge – this modulates reflected wave. Modulation can be done by amplitude or phase. With high frequency passive RFID devices working distance may reach 3 meters. In some passive RFID devices there may be power supply used to increase working distance.

RFID labels carry some informations which can be like 32kB. For instance using frequency 13,56MHz reading speed is about 3kB/s.

RFID isn’t new technology. It is successfully used in many industries like road taxes where RFID label is located inside a car. You don’t even need to lower your speed – reading is done automatically. Now in USA car numbers have such labels built in. Other widely used are is markets, where all items are labelled with RFID labels. This is for theft prevention. Also same method is used in vehicles where RFID key is used to unblock the engine.

RFID labels are successfully used in passports. In USA are used passports with 64kB memory where are person data (biometric data, blood type, and other identification data) stored. This type of passports is almost impossible to fake.

Even money are labelled with RFID chips. From 2001 USD and EURO have small (less than 1 square mm) chips are pressed in bills(near security strip). These chips are so called “smart dust”. If you put such bill in microwave the chip burns leaving a hole in a bill. Don put your money in microwave…

Well RFID technologies affects my life two. I have a card with passive RFID which I use everyday at my work as ID to enter to facilities. I don’t even need to take it out of my wallet - I wave near the reader and my door opens…

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This entry was posted on Monday, July 10th, 2006 at 2:03 pm and is filed under Electronics. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.