Test Your RFID Knowledge

1. What does RFID stand for?

1. Radio Frequency Identification
2. Remote Field Identity Device
3. Radio Field Integrated Data
4. Rapid Frequency Identification Detection

RFID stands for Radio Frequency Identification - identifying objects automatically using radio waves exchanged between a reader and a tag.

2. Where does a passive RFID tag get the energy to operate?

1. From a small built-in coin battery
2. From the radio frequency field transmitted by the reader
3. From a tiny solar cell on the label
4. From static electricity built up during handling

A passive tag has no battery. It harvests energy from the reader's RF field, which powers the chip long enough to reply. That is why passive tags are cheap, thin and long-lasting.

3. How does a passive UHF tag send its data back to the reader?

1. It switches on its own radio transmitter
2. It sends an infrared pulse
3. By backscatter - changing how much of the reader's signal it reflects
4. By storing the data until the reader physically touches it

Passive UHF tags use backscatter: the chip switches its antenna impedance so that the reflected carrier is modulated with data. LF and HF tags use a related technique called load modulation.

4. Which is a key advantage of RFID over barcodes?

1. RFID labels are always cheaper than barcode labels
2. RFID is completely unaffected by metal and liquids
3. RFID tags never need any software to be useful
4. RFID does not need line of sight and can read many items at once

RFID can read tags inside cartons and read hundreds of items in seconds without line of sight. It is usually more expensive per label than a barcode, and metal and liquids do affect it - especially at UHF.

5. In RFID standards, what is an "interrogator"?

1. A tag with a built-in battery
2. The chip and antenna assembly on a film
3. The formal term for an RFID reader
4. Software that filters duplicate reads

Interrogator is the formal standards term for a reader - the device that sends commands to tags and receives their replies. A chip and antenna on a film is an inlay, and filtering software is middleware.

6. What is the standard operating frequency of HF RFID and NFC?

1. 125 kHz
2. 13.56 MHz
3. 866 MHz
4. 2.45 GHz

HF RFID, including NFC, ISO 14443 and ISO 15693, operates at 13.56 MHz. 125 kHz is LF, 866 MHz is UHF and 2.45 GHz is microwave.

7. Which UHF frequency band is permitted for RFID in India?

1. 902-928 MHz
2. 920-925 MHz
3. 2400-2483.5 MHz
4. 865-867 MHz

India has delicensed 865-867 MHz for UHF RFID, with up to 4 W EIRP, regulated by WPC. 902-928 MHz is the US band and 2.4 GHz is not used for passive UHF RFID.

8. Which frequency band is traditionally used for animal identification because it works well near water and body tissue?

1. LF (125-134.2 kHz)
2. HF (13.56 MHz)
3. UHF (865-867 MHz)
4. Microwave (5.8 GHz)

LF RFID is least affected by water and tissue, which is why ISO 11784/11785 animal tags use 134.2 kHz. The trade-off is short range and slow data rates.

9. What best describes a battery-assisted passive (BAP) tag?

1. A tag that must be recharged every day
2. A tag with a battery that powers its own active transmitter
3. A tag whose battery powers the chip, but which still replies by backscatter
4. A passive tag that stores a battery's serial number

A BAP (semi-passive) tag uses its battery to run the chip and often a sensor, making it more sensitive, but it still communicates by backscatter. A tag with its own transmitter is an active tag.

10. What usually happens when an ordinary UHF paper label is stuck directly onto a metal surface?

1. The read range increases because metal acts as a reflector
2. Performance drops sharply because the metal detunes the antenna
3. Nothing changes, because UHF ignores metal
4. The tag turns into an active tag

Metal right behind a standard inlay detunes its antenna and disrupts the field, so it may not read at all. Use purpose-designed on-metal tags, which include a spacer or ground plane.

11. Which ISO/IEC standard is aligned with the EPC Gen2 UHF air interface?

1. ISO/IEC 14443
2. ISO/IEC 15693
3. ISO/IEC 18000-63
4. ISO 11785

ISO/IEC 18000-63 (formerly 18000-6C) is the ISO version of EPC Gen2. ISO 14443 and 15693 are HF standards, and ISO 11785 covers LF animal identification.

12. Which Gen2 memory bank contains the chip maker's identification, written and locked at the factory?

1. TID
2. EPC
3. User
4. Reserved

The TID (Tag Identifier) bank identifies the chip manufacturer and model and, in most modern chips, a unique serial number. It is locked at the factory and cannot be changed.

13. What is stored in the Reserved memory bank of a Gen2 tag?

1. The product's GTIN
2. Extra user data such as batch numbers
3. The StoredCRC and PC bits
4. The kill password and the access password

Bank 00 (Reserved) holds the 32-bit kill password and the 32-bit access password. The StoredCRC, PC bits and EPC live in the EPC bank; extra data goes in User memory.

14. NFC is built on which family of technologies?

1. UHF EPC Gen2 at 865-867 MHz
2. 13.56 MHz HF standards such as ISO 14443 and ISO 15693
3. LF 125 kHz proximity standards
4. Bluetooth Low Energy at 2.4 GHz

NFC works at 13.56 MHz and builds on ISO 14443, ISO 15693 and FeliCa. That is why phones can read many HF cards and NFC tags but cannot read UHF tags.

15. What does an SGTIN identify?

1. A logistic unit such as a pallet
2. A returnable asset such as a crate
3. An individual trade item - a GTIN plus a unique serial number
4. A physical location such as a warehouse

SGTIN (Serialised Global Trade Item Number) combines the product's GTIN with a serial number so each item is unique. Pallets use SSCC, returnable assets use GRAI and locations use GLN/SGLN.

16. A reader output of 30 dBm is equal to how much power?

1. 100 mW
2. 1 W
3. 2 W
4. 4 W

dBm is referenced to 1 mW: 0 dBm = 1 mW, 20 dBm = 100 mW and 30 dBm = 1 W. Every extra 3 dB roughly doubles the power, so 33 dBm is about 2 W and 36 dBm about 4 W.

17. Why are circularly polarised reader antennas so widely used?

1. They read tags reliably even when tag orientation varies
2. They always give longer range than linear antennas
3. They work without a reader
4. They are required by law in India

Circular polarisation reads tags at any rotation around the beam axis, ideal when items arrive in random orientations. The trade-off is about 3 dB less than a perfectly aligned linear antenna.

18. Which of these situations will usually reduce passive UHF read range the most?

1. Applying the tag to a dry cardboard carton
2. Printing text and a barcode on the RFID label
3. Reading the tag through a thin plastic crate
4. Mounting the tag directly on a water-filled bottle

Water absorbs UHF energy and detunes the tag, which can reduce range dramatically. Cardboard, printing and thin plastic have little effect.

19. What is the purpose of the Q algorithm in EPC Gen2?

1. To encrypt the EPC stored on the tag
2. To set the reader's transmit power
3. To manage anti-collision by having tags reply in random time slots
4. To choose which frequency channel to use

The reader sets Q, each tag picks a random slot from 0 to 2^Q - 1, and the reader adjusts Q depending on collisions and empty slots. This lets it singulate hundreds of tags quickly.

20. What is the relationship between EIRP and ERP?

1. EIRP = ERP + 2.15 dB
2. EIRP = ERP - 2.15 dB
3. EIRP = ERP x 10
4. They are always exactly equal

ERP is referenced to a half-wave dipole, which has 2.15 dBi of gain, while EIRP is referenced to an isotropic antenna. So EIRP is 2.15 dB higher than ERP for the same transmission - 4 W ERP is about 6.6 W EIRP.

21. What technology does India's FASTag use?

1. NFC, tapped against a toll booth reader
2. Active 2.45 GHz tags with a battery
3. Passive UHF RFID tags on the windscreen
4. LF 125 kHz key fobs

FASTag is a passive UHF RFID windscreen sticker read by overhead readers in toll lanes, with tolls deducted through the NETC system. It is designed to break if removed.

22. What is the best first step in an RFID project?

1. Buy the cheapest tags in bulk to lower the unit price
2. Define the business problem, then test tags on real items in a pilot
3. Install the most powerful readers available
4. Tag every item in the company at once

Successful projects start with a clear, measurable problem and a pilot that tests tags on the actual items in the actual environment. Buying hardware first is the most common route to failure.

23. Which GS1 standard is used to capture and share visibility events (what, when, where and why) between trading partners?

1. LLRP
2. NDEF
3. Tari
4. EPCIS

EPCIS (Electronic Product Code Information Services) defines a common event format so partners can share RFID and barcode visibility data. LLRP controls readers, NDEF is the NFC data format and Tari is a Gen2 timing parameter.

24. Which standard lets software control fixed UHF readers from different manufacturers over a network?

1. LLRP (Low Level Reader Protocol)
2. ISO 11784
3. SSCC
4. FM0

LLRP is the GS1/EPCglobal protocol for configuring readers and receiving tag reports. ISO 11784 is an LF animal code structure, SSCC identifies logistic units and FM0 is a tag encoding.

25. Which application normally uses HF/NFC rather than UHF RFID?

1. Tracking pallets through a dock door
2. Electronic toll collection on highways
3. Bulk stock counting of a warehouse aisle
4. Contactless payment and access cards

Payment and access cards use HF (ISO 14443) for deliberate, short-range, secure transactions. Dock doors, tolling and bulk counting need the longer range and fast multi-tag reading of UHF.