Non-contact, electromagnetically coupled transmission and receiving system for IC cards
US5418353A · kind A · utility
Assignees
Inventors
Key dates
| Filing date | Oct 19, 1994 |
| Grant date | May 23, 1995 |
| Priority date | — |
| Expiry date | Oct 19, 2014 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG06K7/0008
- WIPO fieldComputer technology
- WIPO sectorElectrical engineering
Abstract
A non-contact IC card communication in which power consumption of a driver of a reader/writer is reduced and the size of a power supply circuit for operating the driver is made small. The driver has a low output impedance. A current detecting circuit including a detecting coil magnetically coupled with a transceiver coil of the reader/writer through a magnetic coiling element and a resistor detects a current which flows through the transceiver coil. A voltage drop to be detected is small and is approximately constant for a variation of the transceiver coil current. When data is read from an IC card, a load of the driver is changed. The driver drives the transceiver coil in a constant voltage fashion even if a current flowing through the transceiver coil changes due to the change in load. Input voltages of a rectifying/smoothing circuit and a regulator in the IC card become approximately constant. As a result, the amplitude of a high frequency output voltage of the driver can be made small. Also, a high frequency signal current sent from a reader/writer is subjected to double modulation including amplitude modulation by card data and modulation by second information, such as informa…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.