RFID Backscatter Cancellation Using Time-Offset Reference Signals

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Solution Overview

Problem

Interference between RFID reader device signals and backscattered signals from RFID tags, as well as environmental signals, hampers accurate time-of-arrival estimation and positioning accuracy in RFID-based systems.

Innovation Solution

Implementing interference cancellation techniques using known time offsets between consecutive backscattered signals, indicated by the RFID reader, to reduce or eliminate interference in RFID backscattered signals.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If interference cancellation is performed using a second backscattered signal, then positioning accuracy and time-of-arrival estimation are improved, but device complexity increases due to additional signal processing requirements

Engineering Contradiction:

Improvetime-of-arrival estimation accuracyVSAvoidsignal processing complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The RFID reader device transmits a second interrogation signal before the first one, causing the RFID tag to transmit a second backscattered signal that serves as a reference for interference cancellation. This preliminary action creates a known reference signal that characterizes the interference environment, which is then used to cancel interference from the first backscattered signal used for positioning measurements

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The second backscattered signal acts as an intermediary reference signal that mediates between the interference environment and the first backscattered signal. By using this intermediate reference signal, the system can characterize and cancel interference without directly manipulating the primary positioning signal, thus improving measurement precision while managing processing complexity

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If multiple backscattered signals are transmitted for interference cancellation, then signal reliability is improved, but loss of time increases due to additional transmission cycles

Engineering Contradiction:

Improvesignal qualityVSAvoidpositioning time

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The system uses periodic transmission of interrogation signals in a structured sequence: a second interrogation signal is transmitted first to generate a reference backscattered signal, followed by a first interrogation signal to generate the positioning backscattered signal. This periodic pattern with known time offsets allows interference cancellation while maintaining efficient timing

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The system changes the temporal parameter of signal transmission by introducing a known time offset between the second (reference) backscattered signal and the first (positioning) backscattered signal. This parameter change allows the receiver to distinguish between reference and positioning signals while using the time-offset relationship for interference cancellation, thereby improving reliability without excessive time loss

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS12456022B2Interference cancellation for backscattered reference signals

Publication Date: 2025.10.28 QUALCOMM INC

AI summary

Disclosed are Techniques for wireless communication are provided. In an aspect, a radio frequency identification (RFID) device receives, from an RFID tag, a first backscattered signal, receives, from the RFID tag, a second backscattered signal having a known time offset relative to the first backscattered signal, and performs interference cancellation on the first backscattered signal based on the second backscattered signal.