Signal-powered frequency-dividing transponder

Abstract From the Canadian patent

A batteryless, portable frequency divider such as used in presence detection, systems for article surveillance or as used for article-location determination includes a, series LC resonant circuit connected directed across a parallel LC resonant circuit. One circuit is resonant at a first frequency and the other circuit is resonant at a second frequency that is a plural-integer-divided quotient of the first frequency. In one class of embodiments, either or both of the series and parallel resonant circuits includes a variable capacitance element, such as a varactor in which the capacitance varies in accordance with the voltage across the variable capacitance element. The variation of the …