Electronic identification system with improved sensitivity
US6472975B1 · kind B1 · utility
Assignee
Inventors
Key dates
| Filing date | Jun 20, 1994 |
| Grant date | Oct 29, 2002 |
| Priority date | — |
| Expiry date | Jun 20, 2014 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG06K19/0723
- WIPO fieldComputer technology
- WIPO sectorElectrical engineering
Abstract
The coil in the reader that is used to establish an alternating magnetic field is transformer-coupled through capacitors to a push-pull driving circuit consisting of four field-effect transistors connected in a bridge arrangement. The coil, capacitors, 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 utilizes a coil to couple with the reader's alternating magnetic field and a capacitor to resonate the coil, thereby extracting power from the field more efficiently. Transformer coupling of the coil and capacitor is utilized for improved impedance matching. The coil, capacitor, and coupling circuitry can be maintained in a tuned condition by continually adjusting either the coil inductance, or the capacitor capacitance during communications. Certain configurations of the system may require that tuning maintenance be discontinued during the transmission of data.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.