RFID Reader Basics
RFID tags contain a unique identification number which is read by RFID readers. Tags can also be equipped with sensors which are able to transmit data back to the reader, making it possible to go beyond simple item tracking.
The Clicker 2 for STM32 development board is used here for the demonstration.
Detection
The RFID reader emits a radio frequency signal that the chip or transponder responds to by sending its own back, containing information on the tag. The chip or transponder is either active (with a battery to power the circuit and antenna) or passive (no battery).
When an RFID tag is detected by a fixed reader, it may be associated with a specific room. However, a mobile RFID reader can scan assets in a wide range of positions and angles. This results in the possibility that the same RFID tags are scanned from adjacent rooms. This is called cross read and is a major problem for inventory tracking.
To avoid this, some solution providers use RFID media and readers that are locked and can only be read by their own devices. These devices are sold to software developers who can create their own applications that use them, or integrate the device into a current offering. These devices typically come with a Software Development Kit, or SDK, that includes documentation, samples and API access to the RFID reader.
The RFID reader can also detect a collision of multiple signals, or tag collision, which occurs when too many RFID tags confuse an RFID reader by transmitting their data at the same time. This can reduce the reading distance and limit the reliability of the data gathered by the reader. Choosing an RFID reader that gathers tag info one at a time can prevent this issue.
Transmission
The RFID reader sends an RF signal to a tag, activating it and prompting it to transmit its own return signal. This RFID Reader process is called backscatter. The RFID tag’s circuit and antenna combine to broadcast or receive a signal, depending on whether the tag is passive (no battery) or active (has a battery and circuit that provide energy when it comes in contact with an RF field).
A passive RFID system can detect tags within a few meters of the reader. Its range increases to hundreds of feet with an active tag. The RF signals are encoded with unique electronic IDs, which the reader can translate into information. The reader then stores the data, or transmits it to another system for processing.
RFID technology enables a variety of applications, such as reducing management times and lowering operational costs. For example, a company that manages a supply chain can benefit from RFID systems that optimize product identification and data capture throughout a manufacturing process.
To get the most out of an RFID system, it’s important to ensure that the polarity of the reader and tag match up. The polarity of an antenna is either horizontal or vertical, and a mismatch can significantly reduce a system’s read range. This is why some companies prefer to use only COTS readers that support a specific polarity or opt for a reader-agnostic solution.
Decoding
RF signals have to be converted into a form that the access control system can understand. This process is called decoding. The RFID reader has to determine the format of the desfire ev1 data sent by the tag and translate that into commands. It also has to figure out what type of wiring is needed between the reader and the access control system. The communication protocol specifies how the reader and card/tag communicate with each other and the coding format that is used. The word Wiegand is often used to describe the coding format and the physical connection between a reader and an access control system. The protocol also defines a standard for how the wires are configured in a cable.
Passive tags use electromagnetic energy from the RF signal to power their circuits and antennas. This allows the tags to send their data back to the reader without using a battery. The conductive material of the tag is struck with the electromagnetic field and generates an electric current that turns on the internal circuit of the tag.
When multiple RFID tags are within the detection range of an RFID reader, they will all try to transmit their data at once. This is a known problem as tag collision and can cause confusion for the RFID reader. To prevent this, RFID readers are programmed with anti-collision protocols that take the time to gather each tag’s information one at a time. There are two common methods: probabalistic and deterministic detection.
Storage
RFID technology is useful for a lot of use cases. It’s used to track inventory, assets, people, and more. It also enables a number of omnichannel features, like buy online, pickup in store. The ability to track items makes them more attractive to customers who want to have control over when they pick up their purchases in-store.
Adding an RFID solution to a retail environment is an easy way to improve accuracy and lower labor costs. RFID antennas don’t need line of sight, so it’s much faster to scan products than it is with barcode scanners. This reduces cycle count time and helps automate reordering at safety stock levels.
Aside from the benefits mentioned above, RFID is valuable for improving security. RFID readers can monitor item-level data, which is useful for monitoring employee actions and preventing theft. The data that is transmitted can also help retailers keep a closer eye on their supply chain partners, which is important for compliance with FDA regulations related to adverse event reporting.
Our current RFID reader management software, MotionWorks Enterprise, provides a suite of tools for deploying and configuring readers. This includes the ability to configure readers’ operation and radio settings, as well as forward RFID read data and reader management alerts to customer or partner backend systems via REST webhook or MQTT.
