Patent ID: 8618815

Claim:
A position detecting device comprising: a position indicator including a first receiver circuit operable to resonate at a first frequency so as to generate a resonance signal upon receipt of an excitation signal, an alternating-current-to-direct-current (AC-DC) converting circuit connected electrically to said first receiver circuit for receiving the resonance signal therefrom, and operable to perform AC-DC conversion upon the resonance signal so as to generate a direct current (DC) power signal, and a first transmitter circuit connected electrically to said AC-DC converting circuit for receiving the DC power signal therefrom, powered by the DC power signal to oscillate at a second frequency different from the first frequency so as to generate an oscillation signal, and operable to transmit the oscillation signal thus generated; and a position detector including a plurality of first antennas arranged along a first direction, a plurality of second antennas arranged along a second direction different from the first direction, a second transmitter circuit operable to generate the excitation signal, a second receiver circuit, a switching circuit connected electrically to said first and second antennas, said second transmitter circuit, and said second receiver circuit, and operable, according to a control signal, for switching between a first state, where said first antennas are connected electrically to said second transmitter circuit for transmitting the excitation signal to said first receiver circuit and where at least a portion of said second antennas is connected to said second receiver circuit for enabling said second receiver circuit to receive the oscillation signal from said first transmitter circuit, and a second state where said second antennas are connected electrically to said second transmitter circuit for transmitting the excitation signal to said first receiver circuit and where at least a portion of said first antennas is connected to said second receiver circuit for enabling said second receiver circuit to receive the oscillation signal from said first transmitter circuit, wherein said second receiver circuit is configured to perform band pass filtering and amplitude detection upon the oscillation signal to generate a processed signal, a frequency range of the band pass filtering including the second frequency and excluding the first frequency, and a processing circuit connected electrically to said switching circuit and said second receiver circuit, configured to provide the control signal to said switching circuit, and configured to obtain information corresponding to position of said position indicator relative to said position detector based on the processed signal from said second receiver circuit.