Cheat Sheet – What is RFID

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Main Objectives

  1. Define RFID technology, what it is and its working principles.
  1. Recognize main types of RFID systems based on communication:
  • Passive (no power source but derives its power from the reader’s transmission)
  • Battery Assisted or Semi-Passive (tag has a battery to assist with transmitting response to the reader but relies on the reader transmission to initiate action or wake up, does not beacon)
  • Active (tag has a battery and does not rely on reader transmission for any power needs) 
  1. Know characteristics of these categories and how they impact:
  • Data Transfer Rate
  • Read Range
  • Cost
  • Typical Applications
  • Frequencies normally used
  • Behavior around water based liquids and metals
  • Regulations
  • Modes of operations (inductive/capacitive)
  • Types of antennas used

Passive RFID Systems use passive RFID tags or labels.

Passive RFID Tag

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Passive RFID

The passive RFID tag has no power source but derives its power from the reader’s transmission. It often comes in form of a flat inlay or a label and is the simplest type of RFID tag.

Frequencies normally used

  • Low Frequency (LF) – 120 – 150 kHz
  • High Frequency (HF) – 13.56 MHz
  • Ultra-High Frequency (UHF) – 860 – 960 MHz
  • Microwave Frequency 2.45 GHz

Data Transfer Rate – depends on frequency and is function of the wave

  • LF – very slow
  • HF – slow
  • UHF – fast
  • Microwave – ultrafast

Read Range – shortest, up to 30 ft, depends on frequency

  • LF – up to few inches
  • HF – up to 3 feet, most often 3- 5 inches
  • UHF – up to 30 ft
  • Microwave – few inches max.

Cost – lowest, starting at 5 cents per tag in high volumes

Typical Applications

  • Inventory tracking
  • Asset tracking, access control
  • Warehouse, hospital, office, events

Behavior around water based liquids and metals – depends on frequency:

  • LF, HF – can read through aqueous liquids
  • UHF, Microwave – cannot read through aqueous liquids
  • No frequencies can read through metal and tags get detuned when placed on or near metal objects.

Regulations

  • FCC Part 15.247 – governs UHF allowed transmitted power from the reader/interrogator (maximum 4 W EIRP), frequency hopping channels (50) and the channel width (500 kHz).
    • For systems using digital modulation in the 902-928 MHz, 2400-2483.5 MHz, and 5725-5850 MHz bands, the maximum peak conducted output power of intentional radiators is 1 watt. 
  • ETSI 302 208 (newer)
    • 865.0 – 868.0 MHz
    • 15 channels – 200 kHz each
    • Three sub-bands
    • Up to 2 W ERP in subband 865.6 – 877.6 MHz (10 channels)
    • Required LBT
  • ETSI 300-220 (older, restrictive)

Standards (air interface)

  • LF – ISO/IEC 18000-2
  • HF – ISO/IEC 18000-3, ISO/IEC 15693, ISO/IEC 14443
  • UHF – ISO/IEC 18000-6 (A, B, C), EPC Global/GS1 Class 1 Gen 2 (ratified into ISO 18000-6C)
  • Microwave – ISO/IEC 18000-4 for 2.45 GHz, (ISO/IEC 18000-5 for 5.8 GHz (withdrawn due to lack of use)

Modes of operation – based on frequency

  • LF, HF – Inductive coupling – based on changes in the magnetic field
  • UHF, Microwave – Capacitive coupling also called passive backscatter – based on changes in the electric field

Types of antennas used

  • LF, HF – coil antenna
  • UHF, Microwave – dipole antenna

Battery Assisted Passive RFID (BAP) or Semi-Passive RFID

The battery assisted passive RFID tag (also called BAP or semi-passive tag) relies on the initial transmission from the reader and then uses a battery to assist with transmitting response to the reader. This allows for longer read ranges. The BAP tags have often integrated sensors.

Frequencies normally used

  • Ultra-High Frequency (UHF) – 860 – 960 MHz
  • Microwave Frequency 2.45 GHz

Data Transfer Rate – depends on frequency and is function of the wave

  • UHF – fast
  • Microwave – ultrafast

Read Range – medium, up to 100 ft, depends on frequency and technology

  • UHF – usually up to 100 ft (depends on technology)
  • Microwave – usually up to 30 ft (depends on technology)

Cost – high, starting at several dollars per tag

 

Typical Applications – applications with sensors – temperature tracking for inventory, transportation, assets; regular and returnable asset tracking where long read ranges are necessary

Behavior around water based liquids and metals – depends on frequency:

  • UHF, Microwave – cannot read through aqueous liquids
  • No frequencies can read through metal.
  • Tags are encapsulated and can be tuned to perform well on metal.

Regulations

  • FCC Part 15 – governs UHF allowed transmitted power from the reader/interrogator (maximum 4 W EIRP), frequency hopping channels (50) and the channel width (500 kHz).

Standards (air interface) – compatible with passive readers if compliant with the same standards as below:

  • UHF – ISO/IEC 18000-6 (A, B, C), EPC Global/GS1 Class 1 Gen 2 (ratified into ISO 18000-6C)
  • Microwave – ISO/IEC 18000-4 for 2.45 GHz, (ISO/IEC 18000-5 for 5.8 GHz (withdrawn due to lack of use)

Modes of operations – based on frequency

  • UHF, Microwave – passive backscatter – based on changes in electric field – aided by the battery

Types of antennas used

  • UHF, Microwave – dipole antenna

Active RFID

The active RFID tag has a battery and does not rely on reader transmission for any power needs. It can beacon and have integrated sensors.

Frequencies normally used

  • Ultra-High Frequency (UHF) – 433 MHz
  • Microwave Frequency – 2.45 GHz
  • Ultra Wide Band (UWB) Frequency 3.2 – 10 GHz

Data Transfer Rate – depends on frequency and is function of the wave

  • UHF – fast
  • Microwave – ultrafast
  • UWB Frequency – fastest

Read Range – longest

  • UHF up to 1000’s of feet (depends on technology and power source)
  • Zigbee – about 30 – 300 ft (10 – 100 m)
  • WiFi IEEE 802.11n – up to 820 ft (250 m)

Cost – highest, starting around $20 per tag (ballpark price)

Typical Applications

  • Applications with sensors – temperature tracking for inventory, transportation, assets; tamper sensors;
  • Long range tracking – cars, rail cars, containers for transportation and control in depots, docks, shipyards, military, etc.,
  • Real-time location systems (RTLS) – Both Wi-Fi and UWB technology is often used for RTLS and UWB is one of the most accurate technologies for location.

Behavior around water based liquids and metals – depends on frequency:

  • Cannot read through aqueous liquids.
  • No frequencies can read through metal.
  • Tags are encapsulated and can be tuned to perform well on/around metal.
  • Due to the tag having a battery and transmitter and therefore stronger signal, the signal can bounce/bend around metal objects, which means that active RFID has usually better performance in metal environments.

Regulations

  • FCC Part 15 – governs allowed transmitted power from the reader/interrogator (maximum 4 W EIRP), frequency hopping channels (50) and the channel width (500 kHz).

Standards (air interface):

  • UHF – ISO/IEC 18000-7 for 433 MHz
  • Microwave – ISO/IEC 18000-4 for 2.45 GHz
  • DASH7 (2nd gen of ISO 18000-7) for 433 MHz
  • Wi-Fi IEEE 802.11n – 2.45 GHz
  • Zigbee IEEE 802.15.4 for 868/915 MHz or 2.45 GHz

Modes of operations

  • Active transmission

Types of antennas used

  • Dipole or monopole antenna

Active RFID Systems utilize active RFID tags and readers and provide much longer read ranges than passive systems.

Active RFID Tag