RFID Test and Measurement Solutions

Similar to a barcode, Radio Frequency Identification or RFID (also known as Dedicated Short Range Communication or DSRC) allows a user to identify an object by retrieving information stored on a remote unit called an RFID tag or transponder without requiring line-of-sight. RFID tags respond to amplitude shift keyed (ASK) commands sent by modulating them around a specific frequency. The command signal induces a current activating the tag, which gives it enough energy to power the circuit and transmit a frequency shift keyed (FSK) response at the same frequency. The response from the tag could be a simple ID number or more detailed data from an EEPROM chip embedded in the RFID tag.

Technology Background

RFID systems have existed since the 1960s and take advantage of technology developed by the Soviet Union in the 1920s for covert military operations. Each system consists of three main parts, including an antenna to generate a command signal, a RFID tag or transponder to transmit data, and another antenna to receive the response. RFID systems fall into three different categories depending on their operational bandwidth - low frequency (LF - 30 KHz to 500 KHz), high frequency (HF - 500 KHz to 900 MHz), or ultra high frequency (UHF - 900 MHz to 2.5 GHz).

There are three types of RFID tags in mainstream use. Passive tags (which cost under 10 cents when ordered in bulk) require no internal power source and have an unlimited lifespan. Its circuitry is powered by the electrical current induced by an external signal. Semi-passive tags are similar except they are equiped with a battery and do not require stimulation from the carrier and have faster response time. Active tags serve as beacons operating on fixed intervals. They typically have a battery life of ten years and are capable of storing more information and broadcasting over a larger range. Most RFID tags are extremely small (typically .4mm by .4mm) and can be embedded into virtually any object, including animals and humans. Low frequency passive RFID systems have shorter transmission ranges (less than 3 feet) while high frequency active systems can reach over 100 feet.

RFID technology can be used for virtually anything, especially in systems concerned with supply chain management. There are countless examples of companies who have integrated RFID into their business model. Walmart recently implemented a new tracking system to be used in their stores where all products will be outfitted with RFID tags (in all shipping, receiving, etc). Goodyear and Michelin are using RFID tags in tires to monitor tread depth and tire pressure. Chevy and Toyota have begun to use RFID transponders with keys in the ignition systems of their automobiles (they even use the tags on the assembly line to help track what parts go on specific cars). Many pharmacies use RFID drug prescriptions to eliminate the possibility of mismatching the patient to the medicine. The US Transportation System has used RFID technology for years to create ExpressPay toll tags for cars on the highway. The government also uses the technology in prisons to help track the movement of inmates. Credit cards like American Express Blue use RFID tags to help make them more secure.

VI Service Networks RFID Solutions

VI Service Network offers RF air interface test solutions for high frequency (13.56MHz) and UHF (860M – 960MHz) RFID equipments. This solution uses NI-5671 RF source to simulate the RFID reader (interrogator) with ASK and frequency hopping functionalities, and NI-5660 RF analyzer to capture and analysis the RF signals from both the reader and the tag. VISN proprietary modulation and demodulation algorithms are used in both RF signal generation and analysis. The following pictures are the analysis of a captured UHF RFID signal, which includes 8 rounds of queries and responses. The lowest picture shows the joint-timefrequency analysis of the signal, which is frequency hopping. The middle picture is the power versus time plot, which shows large query signals from the RF source and small positive reflected signals from the tag right after each query. The top plot shows the instantaneous spectrum at the cursor position. The HF RFID is specified by ISO 18000-3, and the UHF RFID is specified by ISO 18000-6.

VI Service Network Webpage >>

17 ratings | 4.06 out of 5

Print

Reader Comments | Submit a comment »