The Impinj Indy R2000 and R500 RAIN reader chips are able to take advantage of the new ETSI (European) frequency band (CEPT REC 70 03 / EN 302 208). The new features in this band include:
- Doubling the maximum radiated power output to 4W ERP (from 2W ERP). This improves the link budget, most notably providing greater read range (distance between the reader antenna and tag).
- A frequency band common with FCC in North America, allowing for simplified global deployments that share the same tags.
- Faster communication between reader antenna and tag for improved tracking of moving items.
This article covers topics you will want to know when designing an embedded reader system to support the new upper frequency band using the Indy reader chips.
Disclaimer: Local regulations must be consulted to ensure regulatory compliance. Not all countries that permit EU Lower Band also permit EU Upper Band. In some cases, EU Upper Band is permitted but not at the higher transmit power (e.g. Russia).
ETSI Upper Frequency Band
The ETSI Upper frequency band has 3 channels, compared to 4 in the lower band. The radiated power is also doubled, to 4 watts ERP.
|Standard||Channel Center Frequency
|Maximum Radiated Power (Watts ERP)|
|ETSI Lower Band||865.7, 866.3, 866.9, 867.5||600||200||2|
|ETSI Upper Band||916.3, 917.5, 918.7||1200||400||4|
The Indy R2000 and R500 reference design has a single SAW filter in the transmit path, which limits out of band spurious emissions (shown below). In adapting the reference design, many users add switching capabilities so multiple SAW filters can be used, enabling multiple frequency bands. In order to support the new upper frequency band, one of the SAW filters must pass energy in all 3 channels, centered at 916.3, 917.5, and 918.7 MHz. These channels overlap with the FCC frequency band, so in many cases, an FCC SAW filter can be used.
Indy Reference Design Block Diagram
Achieving a higher transmit power output to reach 4 watts ERP may require modifications to the power amplifier circuit of a reader design. Increasing the transmit power will also introduce difficulties in meeting out of band emissions, so extra attention is required here.
RFID reader antennas are often designed for a specific frequency band, optimizing gain and reflection loss for that frequency range. Existing ETSI lower band antennas should be re-evaluated and potentially modified or replaced for operation in the upper band.
Any hardware change to a RAIN reader will require re-certification with regulatory bodies such as the FCC and ETSI.
Indy R2000 and R500's frequency hopping behaviors are governed by the configurable regulatory regions. These configurable regulatory regions are typically loaded into the non-volatile OEM configuration memory of the Atmel ARM7 embedded microcontroller in the radio circuit. Impinj has implemented an example of this regional configuration script, and it can be downloaded on the following support page: IndyMAC regional OEM configuration files.
The wider bandwidth of the ETSI upper frequency band also allows use of more aggressive link profiles. For example, Profile 3, the "very fast" profile which uses a 400 kHz FM0 backscatter link.
Achieving a higher transmit power output to reach 4 watts ERP may require modifications to the software and firmware running on the reader.