Patent ID: 7012567

Claim:
An approach position input device, comprising: a plurality of first antennas arranged substantially in parallel with each other; a plurality of second antennas arranged substantially in parallel with each other, the second antennas being arranged in a direction to intersect the first antennas; an oscillator circuit for applying an alternating current voltage to the first and second antennas; a signal processing circuit for processing signals output from the first and second antennas, the signal processing circuit comprising: a high-pass filter for extracting signals having a frequency equal to or more than a predetermined frequency from the signals sent from the first and second antennas, a full-wave rectifier for conducting full-wave rectification for signals filtered by the high-pass filter, an integrating circuit for integrating a signal output from the full-wave rectifier, and an analog-to-digital (AD) converter for converting an analog signal integrated by the integrating circuit into a digital signal; a change-over switch for selectively sending the output signals from the first and second antennas to the signal processing circuit, the change-over switch sending the output signals from the first and second antennas to the signal processing circuit one at a time; and a computing device for outputting a signal causing the change-over switch to perform a change-over operation.