* Question

How is energy obtained in an inductive coupling system, such as RFID tags?

* Answer

In an inductive coupling system, the energy is obtained through the interaction between the reader’s magnetic field and the electronic tag (transponder). When the reader coil generates an alternating magnetic field, it induces a voltage in the tag’s coil by electromagnetic induction.

This induced voltage provides the energy required to power the tag’s integrated circuit. In mathematical terms, the magnetic energy stored in the reader coil is:

E=1/2LI²

where L is the inductance of the reader coil and I is the current flowing through it. The tag captures part of this energy via inductive coupling.

Reader side: Generates a time-varying magnetic field.

Tag side: A resonant coil harvests the induced energy, rectifies it, and powers the chip.

Application: This is the principle behind RFID systems, contactless smart cards, and wireless charging.

Summary:
The energy of the inductive coupling system is not stored in the tag itself but is dynamically supplied by the reader’s magnetic field. The electronic tag harvests this magnetic energy through induction, which powers its circuitry and enables communication without a battery.