Active pen, touch controller, and method of operating active pen

Abstract

An active pen adapted for use with a touch pad includes: a receiving circuit configured to generate an internal signal in response to modulating a received uplink signal, a first filter configured to generate a first sampling signal by sampling the internal signal at a first frequency, a second filter configured to generate a second sampling signal by sampling the internal signal at a second frequency unequal to the first frequency, and a timing information generating circuit configured to generate timing information associated with the uplink signal from the internal signal. The receiving circuit is also configured to receive the uplink signal at the first frequency in a first frame, and at the second frequency in a second frame. A noise power calculating circuit is also provided to calculate a noise power level of the uplink signal at each of the first and second frequencies, in response to the first and second sampling signals.