An electronic apparatus for acquiring a frequency value of an electromagnetic signal emitted from a coordinate indicating device contacting a sensor pad, in response to an electric wave signal applied by the sensor pad to the coordinate indicating device, the electronic apparatus comprising: a signal receiving unit that receives the electromagnetic signal; characterised in that the apparatus further comprises: a band-pass filter unit comprising a first band-pass filter and a second band-pass filter; wherein the first band-pass filter receives the electromagnetic signal and filters a first frequency range to generate a first filtered signal; and wherein the second band-pass filter receives the electromagnetic signal and filters a second frequency range to generate a second filtered signal; wherein the band-pass filter unit comprises at least one pair of integrators (323, 324) that integrate the first filtered signal and the second filtered signal respectively; and a controller that calculates a ratio value between the first integrated signal and the second integrated signal and acquires the frequency value of the electromagnetic signal based on the ratio value and a predetermined frequency value; wherein the coordinate indicating device has n center frequencies, and the band-pass filter unit comprises n pairs of band-pass filters corresponding respectively to the n center frequencies. a signal receiving unit that receives the electromagnetic signal; characterised in that the apparatus further comprises: a band-pass filter unit comprising a first band-pass filter and a second band-pass filter; wherein the first band-pass filter receives the electromagnetic signal and filters a first frequency range to generate a first filtered signal; and wherein the second band-pass filter receives the electromagnetic signal and filters a second frequency range to generate a second filtered signal; wherein the band-pass filter unit comprises at least one pair of integrators (323, 324) that integrate the first filtered signal and the second filtered signal respectively; and a controller that calculates a ratio value between the first integrated signal and the second integrated signal and acquires the frequency value of the electromagnetic signal based on the ratio value and a predetermined frequency value; wherein the coordinate indicating device has n center frequencies, and the band-pass filter unit comprises n pairs of band-pass filters corresponding respectively to the n center frequencies. a band-pass filter unit comprising a first band-pass filter and a second band-pass filter; wherein the first band-pass filter receives the electromagnetic signal and filters a first frequency range to generate a first filtered signal; and wherein the second band-pass filter receives the electromagnetic signal and filters a second frequency range to generate a second filtered signal; wherein the band-pass filter unit comprises at least one pair of integrators (323, 324) that integrate the first filtered signal and the second filtered signal respectively; and a controller that calculates a ratio value between the first integrated signal and the second integrated signal and acquires the frequency value of the electromagnetic signal based on the ratio value and a predetermined frequency value; wherein the coordinate indicating device has n center frequencies, and the band-pass filter unit comprises n pairs of band-pass filters corresponding respectively to the n center frequencies.