Patent ID: 6472975
Filing Date: 2002-10-29
Classification: G06K

Abstract:
A reader for use with a tag, the reader comprising:a coil; at least one capacitor; a means for coupling the capacitor(s) to the coil and coupling the coil to at least one other means, the signal(s) provided to the other means as a result of the coupling being called coupling-means signal(s), the combination of the coil, the capacitors and the coupling means being called the resonating circuit, the resonating circuit having a resonant frequency; a means for driving the coil through the capacitor(s) with a driving signal; a means for generating the driving signal; a resonating means for automatically maintaining the resonating circuit in a tuned condition, a tuned condition being the condition where the difference between the resonant frequency and the driving frequency is a predetermined value in the range from a negative predetermined value to a positive predetermined value.