Chip card with field strength detector having a switch and load to limit damping to the measurement cycle
US5418358A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jul 28, 1993 |
| Grant date | May 23, 1995 |
| Priority date | — |
| Expiry date | Jul 28, 2013 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG06K19/0723
- WIPO fieldComputer technology
- WIPO sectorElectrical engineering
Abstract
The invention relates to a contactless and batteryless chip card having an antenna coil, a transmission and reception stage which via an electromagnetic alternating field generated by a write/read unit on the one hand supplies the chip card with energy and on the other hand ensures bidirectional data transmission to the write/read unit. The chip card in accordance with the invention has a detector for determining the field strength of the electromagnetic alternating field transmitting energy to said chip card. The functions of the user part, which have a high energy requirement to implement them, are only implemented advantageously when the detector has detected a sufficient field strength. This prevents defective or incomplete implementation of energy-consuming functions of the chip card before they are begun. The field strength detector consists of a switch and load in parallel to the coil with the switch controlled by a control circuit to cause the switch to be on only during a measurement cycle. By having the switch on only during the measurement cycle damping of the coil is prevented and the range of the card is extended compared to a card where the load is always in parallel …
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.