RFID技术原理.doc

General RD System model for Inductive ID systems Summary. A system model for inductive ID systems is presented which links parameters of ID tags and parameters of readers and antennas to reading ranges, including effects of external noise and interference sources. The presented model is a basic one and can be used as a guideline for testing and for comparison of systems. 0. Contents 1. Introduction 2 2. The loading effect on the tag antenna circuit by the power dissipation in the chipcircuit. 3 3. The minimum magnetic field strength. 5 4. The magnetic effective volume of the tag. 7 5. The tag conversion gain factor. 9 6. The magnetic dipole moment of the return signal. 12 7. The maximum antenna current in the reader antenna. 13 8. The maximum tag activation range. 14 9. The equivalent homogeneous magnetic field of the tag in the reader antenna. 14 10. The in the reader antenna induced voltage. 19 11. The external noise. 21 12. The transmitter noise. 22 13. The minimum signal to noise ratio of the receiver detector. 23 14. Reading range. 23 15. Calculation diagram. 25 16. Table of parameters. 26 Source: Nedap, Ir. T.W.H. Fockens 1. Introduction. Engineering inductive ID systems calls for an ability to calculate reading ranges for various combinations of readers, reader antennas, and tags. Also the risk of interference from external radio signals or from other readers in a system needs to be assessed. Such calculations can also be used for comparison of the system properties for different values of system parameters. For this purpose a simplified system model will be presented. First the loading effect on the tag antenna circuit by the power dissipation in the chipcircuit (2) is calculated and expressed in , the quality factor of the antenna circuit only loaded by the chip circuit. , the quality factor of the antenna circuit itself, is easilly measured. From both qua