US 2002/0158752 A1 · Multi-level RF identification system

Abstract

A radio frequency identification system having a radio frequency transceiver for generating a continuous wave RF interrogation signal that impinges upon a RF identification tag. An oscillation circuit in the RF identification tag modulates the interrogation signal with a subcarrier of a predetermined frequency and modulates the frequency-modulated signal back to the transmitting interrogator. The interrogator recovers and analyzes the subcarrier signal and determines its frequency. According to one aspect of the invention, the interrogator generates an output indicative of the frequency of the subcarrier frequency, thereby identifying the responding RFID tag as one of a “class” of RFID tags configured to respond with a subcarrier signal of a predetermined frequency.

Claims24

Dependent claims

A radio frequency identification tag, comprising:

an antenna configured to receive a radio frequency signal;
a rectification circuit having a first input coupled to the antenna, a second input, and an output;
and
a tag oscillator having an input coupled to the output of the rectification circuit and an output coupled to the second input of the rectification circuit, the tag oscillator being structured to modulate the radio frequency signal received at the antenna and to apply the modulated radio frequency signal to the antenna.

1 more element

Dependencies are inferred from the claim text.

Multi-level RF identification system

Life of this patent

Multi-level RF identification system

Life of this patent

Abstract

Claims24