RFID
Kaz's independent study
How can we identify the most cost-effective material to address concerns related to RFID that impact the accuracy and security of the shopping cart?
Study Objectives
Accuracy
Cross-Interference amongst shopping carts
Security
Anti-theft measures to prevent RFID bypasses
Research Approach
Research Approach
01
HARDWARE
02
USER
BEHAVIOR
03
MATERIAL
STUDY
04
STIMULATION
Hardware Components
RFID systems consist of tags, readers, and antennas, all of which operate on specific frequency bands. Interference can occur due to overlapping frequencies, physical obstructions, or electromagnetic noise.
Tags and Readers
The quality and design of RFID tags and readers can impact signal strength and susceptibility to interference. High-quality tags and readers with advanced filtering technologies reduced interference by up to 30% compared to standard components.
Additionally, the type of RFID tag (active vs. passive) can influence interference levels, with active tags generally being more resilient due to their own power source.
The Impinj E710 is the reader I chose. This reader boasts a high read rate of 950 tags per second and a receive sensitivity of -88 dBm. These specifications ensure efficient and accurate tag detection.
In the system, I opted for passive tags that require no electricity and are thin films that cannot be easily ripped. Each tag has a unique ID, and my system employs a double-check mechanism to ensure accuracy in tag detection.
Antennas
The placement and orientation of RFID antennas are crucial. Directional antennas can focus the signal and minimize cross-interference from adjacent systems. Research indicates that using directional antennas can reduce interference by approximately 25%.
Antenna gain and beamwidth are also significant factors. Higher gain antennas with narrower beam widths can help in targeting specific areas, thereby reducing unwanted signal spread.
There are Ultra High Frequency Antennas and High-Frequency antennas available to choose from. UHF systems are known for generating long read ranges, up to twelve meters, whereas HF systems carry a much shorter read range of approximately one meter. UHF allows for a faster data transfer rate, up to 20 times the range and speed of HF systems. This enables quicker transaction capture times and faster data processing.
A circularly polarized RFID antenna emits electromagnetic waves that rotate azimuthally to the propagation direction. Antennas can have a right-hand circular polarization or a left-hand circular polarization. Right or left determines the direction of the rotation. Circular polarization is formed by two wavelengths from an antenna's far-field region. Linear polarized antennas do not rotate, so the tag will only be able to receive maximum power when it is oriented correctly in relation to the antenna. However, it usually has a higher gain and narrower beamwidth, making it ideal for long-range applications.
Consequently, I chose a 10dBi UHF RFID antenna that is long-range, circularly polarized, and capable of reading both horizontal and vertical tags, which is needed because in the cart, I cannot guarantee that I will place items according to how we want them to.
User Behavior
Targeting anti-theft is one of the most important objectives of this project. Hence, this is a study on how consumers can bypass the system and commit theft.
Aluminium Foil
By wrapping the RFID tag in aluminium foil, it can block out the signals emited from the RFID tag. The effectiveness of using aluminum foil to block RFID signals may vary depending on the strength of the RFID reader and the thickness of the foil.
Electronics
By putting the RFID tag against an electronic device, the RFID signals may be interupted. Devices that emit electromagnetic interference (EMI) or radio frequency interference (RFI) can disrupt the communication between RFID tags and readers.
Magnet
By holding the RFID tag and a magnet together, RFID tags may be broken. If an RFID tag contains magnetic components or is designed to be sensitive to magnetic fields, strong magnets could potentially damage or alter the tag's functionality.
Material Study
Materials used to block or absorb RFID signals are critical in managing cross interference. By building the shopping cart with these materials, the cart can be as accurate as possible.
Metals
Metals like aluminum and copper are effective at blocking RFID signals due to their conductive properties. Aluminum foil can block up to 99.5% of RFID signals, while copper can block up to 98.7%.
The effectiveness of different metals in blocking RFID signals can vary based on thickness, surface area, and placement relative to the RFID system.
Carbon-Loaded
Plastics
These materials combine plastic with carbon fibers to create a conductive composite that can block or absorb electromagnetic signals. Research indicates that carbon-loaded plastics can reduce signal strength by 85-90%.
The concentration of carbon fibers and the type of plastic matrix can influence the overall effectiveness of these composites.
Absorptive
Materials
Specialized absorptive materials like ferrites can absorb RFID signals and reduce interference. Ferrite-based materials can absorb up to 95% of EMI
The effectiveness of absorptive materials depends on their placement, thickness, and frequency-specific absorption properties.
Best Materials
Steel
HKD 84 - 96 /m2
Concrete
HKD 90 - 95 /m2
Leather
HKD 160 and up /m2
Aluminium
HKD 133 - 227/ m2
Carbon Fibre
HKD 204 /m2
Tin Foil
HKD 30 - 49 /m2
Simulation Statistics
Hardware Components
Antenna: 10dBi UHF RFID Antenna
Reader: Impinj E710
Tags: Passive sticker copper tags
A box stimulating the cart is built with the reader and antenna inside. The box is built from different materials: tin foil, steel and concrete.
Steel Analysis
Steel, being a strong conductor and having magnetic properties, can effectively block or shield RFID signals from interfering with each other. Using steel as a barrier between RFID readers can help contain the signals within specific areas, reducing cross-interference and improving overall system performance.
When an RFID reader is placed inside a steel box, the steel enclosure can act as a Faraday cage. A Faraday cage is an enclosure made of a conductive material that blocks external electromagnetic fields from penetrating the enclosed space. By placing the RFID reader inside a steel box, external interference from other electronic devices or environmental factors is minimized, allowing the reader to operate more accurately and reliably without external disturbances.
After going through a series of simulations, calculations, and cost per square meter analysis, steel is the most cost-effective material to address concerns related to RFID that impact the accuracy and security of the shopping cart