Untethered stylus empolying multiple reference frequency communication

A method implemented in an untethered stylus for use with a location sensor, comprising:

• receiving a drive signal by the stylus transmitted from the location sensor;
• energizing the stylus in response to receiving the drive signal;
• generating at the stylus a plurality of reference frequencies based on a source frequency of the drive signal, the plurality of reference frequencies indicative of a plurality of stylus states and synchronized to the source frequency of the drive signal;
• and
• mixing the plurality of reference frequencies with the stylus signal for reception by the location sensor.

An apparatus implemented in an untethered stylus for use with a location sensor, comprising:

• a receiver configured to receive a drive signal at the stylus transmitted from the location sensor;
• a power circuit provided at the stylus and energized in response to receiving the drive signal;
• means, coupled to the receiver and power circuit, for generating at the stylus a plurality of reference frequencies based on a source frequency of the drive signal, the plurality of reference frequencies indicative of a plurality of stylus states and synchronized to the source frequency of the drive signal;
• and
• a transmitter coupled to the generating means and configured to mix the plurality of reference frequencies with the stylus signal.