Patent ID: 6167236
Filing Date: 2000-12-26
Classification: G06K

Abstract:
A damping modulation circuit within a transponder, wherein the transponder comprises a circuit having a fieldstrength voltage in dependence upon the transponder's proximity to an interrogator wherein the damping modulation circuit comprises:a high fieldstrength circuit comprising a plurality of voltage limiters, each of said voltage limiters comprising a modulation input for controlling the limiter voltage by conducting a large portion of transponder current to an electrical ground in response to said transponder circuit having a high fieldstrength voltage;a low fieldstrength circuit comprising a first plurality of transistors for conducting a small portion of transponder current to ground while leaving the remaining portion of transponder current for providing power for operating said transponder in response to said transponder circuit having a low fieldstrength voltage; anda medium fieldstrength circuit comprising a second plurality of transistors, said second plurality of transistors activated to establish a sufficient amount of current flow for a desired degree of modulation of energy within said transponder and in response to said transponder circuit having a medium fieldstrength voltage.