A 13.56 MHz localization system utilizing a switched injection locked transponder

In this paper a low-frequency local positioning system at 13.56 MHz is presented. The system is aiming at short range indoor localization problems, where a measurement through a crowd of people is required. Indoor navigation or information systems e.g. in museums, public buildings or fairs are possible applications. With a wavelength of approx. 22 m the system operates in the near field. Ranging is accomplished by measuring the phase shift between a transmitted CW base station signal and a response generated in the transponder with the use of the novel switched injection locked oscillator concept. First measurement results prove that the proposed concept allows for robust indoor ranging with an accuracy in the decimeter-range.