Wireless tags and wireless tag system

Patent metadata

Field	Value
Publication number	US-12333372-B2
Application number	US-202218276840-A
Country	US
Kind code	B2
Filing date	Jan 26, 2022
Priority date	Feb 16, 2021
Publication date	Jun 17, 2025
Grant date	Jun 17, 2025

Abstract

A passive wireless tag to identify a given command which has been received, even while responding to a wireless tag communication device. In this wireless tag, radio waves serving as a predetermined command are received from a wireless tag communication device via an antenna and an RF switch. Signal components are detected from the received radio waves by the detection circuit. The detected signal components are sampled by the sampling circuit in accordance with the timing when the RF switch is controlled to its ON state by a predetermined control signal. The time interval of the ON state is set to be sufficiently shorter than a transfer cycle of the received radio waves. The control circuit thus identifies the foregoing predetermined command according to the sampling results obtained from the sampling circuit.

First claim

What is claimed is:

1. A radio tag system comprising:
a radio tag communication device; and
a passive radio tag transmitting a response signal to the radio tag communication device according to a backscatter method and a subcarrier method,
wherein the passive radio tag comprises:
an antenna,
an RF switch connected to the antenna and controlled to be turned ON/OFF such that the antenna is controlled to two states, turning ON the RF switch corresponding to an impedance matched state of the antenna when transmitting the response signal,
a control circuit that controls the RF switch such that the response signal is transmitted via the antenna by outputting a predetermined control signal to the RF switch,
a detection circuit that detects signal components from the received radio wave received as a predetermined command from the radio tag communication device via the antenna and the RF switch, and
a sampling circuit that samples the signal components detected by the detection circuit in accordance with timing at which the RF switch is controlled to the matched state by the predetermined control signal,

wherein a time interval of the matched state is set to be shorter than a symbol duration of the received radio wave, and
the control circuit identifies the predetermined command based on a sampling result of the sampling circuit.

2. A passive radio tag that transmits a response signal to a radio tag communication device using a backscatter method and a subcarrier, wherein the passive radio tag comprises:
an antenna,
an RF switch connected to the antenna and controlled to be turned ON/OFF such that the antenna is controlled to two states, turning ON the RF switch corresponding to is an impedance matched state of the antenna when transmitting the response signal,
a control circuit that controls the RF switch such that the response signal is transmitted via the antenna by outputting a predetermined control signal to the RF switch,
a detection circuit that detects signal components from the received radio wave received as a predetermined command from the radio tag communication device via the antenna and the RF switch, and
a sampling circuit that samples the signal components detected by the detection circuit in accordance with timing at which the RF switch is controlled to the matched state by the predetermined control signal,
wherein a time interval of the matched state is set to be shorter than a symbol duration of the received radio wave, and
the control circuit identifies the predetermined command based on a sampling result of the sampling circuit.

3. The radio tag system according to claim 1 ,
wherein the time interval of the matched state is set to be ⅛ or less compared to the symbol duration of the received radio waves.

4. The radio tag system according to claim 1 ,
wherein the time interval of the matched state is set to be 1/10 or less compared to the symbol duration of the received radio waves.

5. The passive radio tag according to claim 2 ,
wherein the time interval of the matched state is set to be ⅛ or less compared to the symbol duration of the received radio waves.

6. The passive radio tag according to claim 2 ,
wherein the time interval of the matched state is set to be 1/10 or less compared to the symbol duration of the received radio waves.

Assignees

• Univ Keio
• Denso Wave Inc

Inventors

• Mitsugi Jin
• Sakabe Haruki

Classifications

• H04B5/45

  Transponders · CPC title

• G06K19/07773 Primary

  Antenna details (antennas for wireless devices, e.g. RFID tags, in general H01Q1/22) · CPC title

• G06K19/0723 Primary

  the record carrier comprising an arrangement for non-contact communication, e.g. wireless communication circuits on transponder cards, non-contact smart cards or RFIDs · CPC title