RFID Side-Lobe Blocking Antennas for Stray Tag Reads

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Solution Overview

Problem

RFID systems face issues with stray RFID tags being unintentionally read due to side-lobe radiation from directional antennas, which cannot distinguish the direction of these tags, leading to inefficiencies and processing bandwidth consumption.

Innovation Solution

A side-lobe blocking (SLB) system that modifies an RF signal to prevent stray RFID tags from decoding the RFID reader's data by superimposing a blocking signal on the transmission or backscattered communication, using a secondary directional antenna to radiate a blocking signal in the direction of stray tags, thereby reducing or preventing their reads.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If a directional antenna is used to read RFID tags in a specific direction, then the reading accuracy in the intended area is improved, but stray tags in side-lobe directions are unintentionally read

Engineering Contradiction:

Improvereading accuracyVSAvoidstray tag interference

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The patent divides the antenna system into two separate directional antennas: a first directional antenna for reading intended RFID tags and a second directional antenna for blocking side-lobe reads. This segmentation allows each antenna to be optimized for its specific function, resolving the contradiction between maintaining reading accuracy and preventing stray tag interference.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent introduces a blocking signal as an intermediary element that is superimposed on the RFID communication signal. This blocking signal is transmitted through the second directional antenna specifically targeted at stray tags, acting as a mediator to prevent unintended reads without affecting the primary reading function.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Area of stationary object

If the RFID interrogator is installed to limit the visible field to the main lobe area, then the intended area coverage is optimized, but side-lobes still allow communication with tags outside the intended area

Engineering Contradiction:

Improveintended area coverageVSAvoidside-lobe radiation

Core Design Contradiction:

Area of stationary objectVSObject-affected harmful factors

Solution Approach 1:

The patent converts the harmful side-lobe radiation into a beneficial blocking mechanism. By using the second directional antenna to transmit a blocking signal in the side-lobe directions, the previously problematic radiation pattern is transformed into a useful tool for preventing stray tag reads while maintaining intended area coverage.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

The patent applies different signal qualities to different spatial regions: the primary reading signal is concentrated in the main lobe direction for intended tags, while a blocking signal is applied in the side-lobe directions for stray tags. This local differentiation of signal quality resolves the contradiction between area coverage and stray tag prevention.

Inventive Principle:

Principle #3Local quality

3Measurement precision

If a blocking signal is superimposed on the RFID signal to prevent stray tag reads, then the accuracy in intended areas is improved, but processing bandwidth is consumed

Engineering Contradiction:

Improvereading accuracyVSAvoidprocessing bandwidth

Core Design Contradiction:

Measurement precisionVSProductivity

Solution Approach 1:

The patent segments the signal processing into two independent channels: the primary RFID communication channel for intended tags and the blocking signal channel for stray tags. This segmentation allows the blocking function to operate independently without consuming processing bandwidth in the main RFID communication path, thus maintaining both accuracy and productivity.

Inventive Principle:

Principle #1Segmentation

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

Effectively reduces or prevents the reading of stray RFID tags by preventing them from decoding the RFID reader's signals, thus minimizing processing bandwidth consumption and improving the system's accuracy in intended reading areas.

Implementation Method 1

providing the modified signal as an input signal to a secondary directional antenna having a second main lobe extending in a second direction different than the first direction to radiate a second signal toward one or more stray RFID tags

Methodology Applied

Scientific EffectElectromagnetic radiation: Electromagnetic Induction

Data Source

PatentUS11907779B2Passive-radio frequency blocking of side-lobe reads

Publication Date: 2024.02.20 SENSORMATIC ELECTRONICS CORP

AI summary

A radio-frequency (RF) identification (RFID) system provides side-lobe blocking (SLB) functionality. The RFID system modifies a first RF signal to provide a modified signal. The first RF signal has an RF carrier frequency according to an RFID protocol, and a main directional antenna in the RFID system has a first main lobe extending in a first direction and is configured to radiate a first signal for reading one or more RFID tags according to the RFID protocol. The RFID system then provides the modified signal as an SLB signal to a secondary directional antenna having a second main lobe extending in a second direction different than the first direction to radiate a second signal toward one or more stray RFID tags.