Patent ID: 8186358

Claim:
A closed system, comprising: an external device comprising: a first processor for generating a location interrogation signal; a first modulator for modulating a carrier signal by the location interrogation signal; a first antenna for transmitting the modulated location interrogation signal including a substantially constant external RF power signal; an internal device in wireless communication with the external device, the internal device comprising: a secondary antenna for receiving the modulated location interrogation signal including the external RF power signal from the external device and inducing an RF power signal therein; a converter for transforming the induced RF power signal to a DC induced voltage signal; a second processor for receiving as input the DC induced voltage signal and generating a location data signal including the DC induced voltage signal; a second modulator for modulating the location data signal prior to wireless transmission by the secondary antenna from the internal device to the external device; and the first processor receiving as input the modulated location data signal from the internal device and producing an indicator signal proportional to the intensity of the DC induced voltage signal induced in the secondary antenna of the internal device without calculating an absolute distance value.