Patent ID: 7164358
Filing Date: 2007-01-16
Classification: G08B

Abstract:
1. A marker, comprising: a first resonant circuit comprising a first planarized coil having a pair of terminals and a capacitor connected to said pair of terminals, said first resonant circuit to generate a first resonant signal in response to an interrogation signal; and a second resonant circuit comprising a second planarized coil having a pair of terminals and a variable capacitor connected to said pair of terminals, with a portion of said second planarized coil to overlap a portion of said first planarized coil, said second resonant circuit to receive said first resonant signal and generate a second resonant signal having a second resonant frequency; wherein said variable capacitor comprises a metal-oxide semiconductor device, said metal-oxide semiconductor device to operate as a non-linear capacitor having varying amounts of capacitance corresponding to varying amounts of voltage received by said metal-oxide semiconductor device; and wherein said metal-oxide semiconductor device comprises a lamination of an insulation material and a semiconductor material disposed between metal terminals, and as said voltage applied across said terminals varies, a concentration of charge carriers in a region of said semiconductor material adjacent to said insulation material also varies to thereby vary said capacitance.