antenna circuit design for rfid applications(microchip)_AN710Antenna Circuit Design for RFID ApplicationsAuthor: Youbok Lee, Ph.D. Microchip Technology Inc.REVIEW OF A BASIC THEORY FOR RFID ANTENNA DESIGNCurrent and Magnetic FieldsAmpere’s law states that current flowing in a conductor produces a magnetic field around the conductor. The magnetic field produced by a current element, as shown in Figure 1, on a round conductor (wire) with a finite length is given by:INTRODUCTIONPassive RFID tags utilize an induced antenna coil voltage for operation. This induced AC voltage is rectified to provide a voltage source for the device. As the DC voltage reaches a certain level, the device starts operating. By providing an energizing RF signal, a reader can communicate with a remotely located device that has no external power source such as a bat……