Low frequency bidirectional communication transponder for security and automotive applications

A microcontroller-based passive keyless entry (PKE) transponder can be used for smart bi-directional communications. The transponder can detect low-frequency signals as low as 1 mVpp, and respond to the base station unit (reader) by using its internal backscattering modulators for proximity range or via an external high-frequency transmitter for long-range applications. This transponder device has three input channels to detect signals from x, y and z directions. The device´s versatile low frequency front-end functions are dynamically controlled by the microcontroller firmware. The device can be used for smart keyless-entry systems in high volume low cost security and automotive applications. This paper describes the feasibility of the smart transponder for various hands-free access control applications.