NXP Semiconductors

SL3S1005

UCODE 9xm

9 Functional description

9.1 Air interface standards

The UCODE 9xm fully supports all parts of the "EPC™ Radio-Frequency Identity Protocols Generation-2 UHF

RFID, Specification for RFID Air Interface, Protocol for Communications at 860 MHz to 960 MHz, Version 2.1"

[1].

9.2 Power transfer

The interrogator provides an RF field that powers the tag, equipped with a UCODE 9xm. The antenna

transforms the impedance of free space to the chip input impedance in order to get the maximum power for the

UCODE 9xm on the tag.

The RF field, which is oscillating on the operating frequency provided by the interrogator, is rectified to provide a

smoothed DC voltage to the analog and digital modules of the IC.

The antenna that is attached to the chip may use a DC connection between the two antenna pads. Therefore

the UCODE 9xm also enables loop antenna design.

9.3 Data transfer

9.3.1 Interrogator to tag link

An interrogator transmits information to the UCODE 9xm by modulating an UHF RF signal. The UCODE 9xm

receives both information and operating energy from this RF signal. Tags are passive, meaning that they

receive all of their operating energy from the interrogator's RF waveform.

An interrogator is using a fixed modulation and data rate for the duration of at least one inventory round. It

communicates to the UCODE 9xm by modulating an RF carrier.

For further details, refer to [1].

9.3.2 Tag to interrogator link

Upon transmitting a valid command, an interrogator receives information from a UCODE 9xm tag by

transmitting an unmodulated RF carrier and listening for a backscattered reply. The UCODE 9xm backscatters

by switching the reflection coefficient of its antenna between two states in accordance with the data being sent.

For further details, refer to [1].

The UCODE 9xm communicates information by backscatter-modulating the amplitude and/or phase of the RF

carrier. Interrogators shall be capable of demodulating either demodulation type.

The encoding format, selected in response to interrogator commands, is either FM0 baseband or Miller-

modulated subcarrier.

SL3S1005

All information provided in this document is subject to legal disclaimers.

© 2025 NXP B.V. All rights reserved.

Product data sheet

Rev. 3.1 — 12 February 2025

Document feedback

10 / 33