Battery-Assisted Passive (BAP) RFID Tag

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Battery Assisted Passive (BAP) RFID or "BAP" as it’s often referred to in the industry, combines features of both Passive RFID Tags and Active RFID Tags.

Traditional Passive RFID Tags rely on gathering energy from the RFID Reader's signal to wake up the integrated circuit (IC) and provide the backscatter required for identification. BAP RFID tags contain their own integrated power source, which is most commonly a battery. It’s very important not to confuse BAP tags with Active RFID Tags. Active tags transmit a beacon at a defined interval. BAP tags do not transmit. The range is improved because no energy needs to be harvested from the RFID Reader to power the integrated circuit and all of the captured energy can be used for backscatter.

The ISO/IEC 18000-6:2010 Standard was approved by the ISO Committee and published in November 2010. Building on the successful EPC C1G2 passive RFID Standard’s relatively simple, low power communications protocol, the new BAP Class 3 Standard enables capabilities previously only available with Active RFID Tag: long read ranges in excess of 100 meters, reliable performance in RF challenging environments, and support for sensors.

Support for Sensors

Battery assisted passive tags contain a battery to power the RFID Tag Integrated Circuit when there is not enough RF power present. The battery can also be used to power other electronic circuits such as sensors to monitor environmental conditions and time. There already exists UHF BAP RFID Tags that contain multiple sensors, as well as simple controllers to manage and log sensor readings. The most common being a temperature sensing / data logging tag.

How Battery-Assisted Passive (BAP) RFID Tags Work

Using a “reader-talks-first” approach, the batteries on BAP tags are activated only when scanned by a reader. Once activated, it uses the power of the battery. Once read, the tag goes back to “sleep”, which helps extend the tag’s battery life. The battery also enables the option of attaching sensors to monitor and log temperatures or other conditions and maintain accurate time.

BAP RFID is fundamentally different than Active RFID Tags because it utilizes the “reader-talks-first” principle. The tags do not actively transmit signals to the reader, they instead reflect back (or backscatter) the reader signal. With the BAP technology, the tag is always ready to respond to a reader query and the reader can implement the appropriate business logic to determine when and how often tags should be read. In addition, the ISO/IEC 18000-6:2010 BAP RFID Standard implements sophisticated tag selection capabilities, allowing readers to only request responses from tags meeting certain selection criteria. Using the “reader-talks-first” principle, combined with the sophisticated tag selection capabilities, readers can inventory all tags on a programmable periodic basis while also constantly inventory tags based on certain selection criteria (e.g. only read tags that have alarm events). For example, a reader in a hospital nursery can perform an inventory of all infant tags every seven seconds. In between this seven second interval, the reader can constantly inventory tags selecting only tags that have an alarm event present. This provides sub-second response time for alarm event recognition. In addition, when a tag is not read during a regular inventory round, the system does not have to wait for the tag’s next beacon interval to find the tag (as with Active RFID systems), the system can take immediate proactive action to command the expected reader, and all other relevant readers, to “search” for the missing tag.

The reader-talks-first principle also simplifies portal uses cases (exits, elevators, etc.) where the reader can inventory all tags in the designated read zone. Tags within this read zone will reply to the reader and the system can then take the appropriate actions.

One other important benefit of ISO/IEC 18000-6:2010 BAP RFID Standard based technology, is the frequency range over which the tag and reader communicate. Single channel systems are subject to interference, whether accidental or intentional (jamming). Sophisticated tags with multiple security sensors become worthless if the reader to tag communication can be easily jammed. Class 3 readers and tags implement a frequency hopping communication protocol which minimizes interference and the threat of jamming the RF signal. This frequency hopping capability, combined with the ability to repeatedly search for specific tags, allows the system to find the optimum frequency to communicate with the tag even in difficult RF environments. Furthermore, if an interference or jamming event does occur, our readers can detect the event, identify the affected reader(s) and notify the system to take immediate and appropriate actions.

Getting Maximum Performance from Battery-Assisted Passive (BAP) RFID Tags & Labels

Obviously, some RFID readers perform better than others, but this is especially true when working with BAP tags. Because of the high sensitivity of the BAP tag, the RFID reader's receiver sensitivity also should be high to be able to receive this signal. Keep in mind that high sensitivity does not help the performance of standard passive labels because performance in this case is limited by the reader-to-tag link. Lower sensitivity readers will still work, but they will provide shorter read distances.

With handhelds RFID readers, BAP tags will still outperform most passive tags but the difference in read range will be less significant. The reason for degradation is that the small size of the handheld limits the size of the antenna which in turn limits the gain and beam width of the antenna.

Other Related RFID Wikipedia Articles

RFID Tags
Components of an RFID Tag
RFID Tag Form Factors

External Links

Intelleflex BAP Tags Shatter Read Distance Records with 120+ Meters
PowerID Battery Assisted Passive RFID Tags Read at 160+ Feet
Passive UHF RFID Tags

Subject Matter Experts Contributing to this Article

User:Mrrfid, Louis Sirico