ELECTRONIC IDENTIFICATION SYSTEM WITH IMPROVED SENSITIVITY

摘要

The electronic identification system provides two-way communications between reader (1) and tags (3) using alternating magnetic fields established by the reader (1) and tag (3). Communications is accomplished by utilizing either a one-step or a two-step modulation process in which the information to be communicated either modulates an alternating magnetic field directly or modulates a periodic signal which modulates an alternating magnet field. The coil (5), capacitors (9), and coupling circuitry are maintained in a tuned condition by continually adjusting either the driving frequency, the coil inductance, or the capacitor capacitance during communications. A tag (3) utilizes a coil (50) to couple with the reader's alternating magnetic field and a capacitor (55) to resonate the coil (50), thereby extracting power from the field more efficiently. The coil (50), capacitor (55), and coupling circuitry can be maintained in a turned condition by continually adjusting either the coil inductance, or the capacitor capacitance during communications.