Apple Inc.
System and method for multi-frequency projection scan for input device detection

Abstract:

In some examples, an input device includes a non-linear component, such as a diode. In response to a drive signal, such as a sinusoidal wave, the non-linear passive input device can produce a non-linear output that includes frequency content at the second and other higher harmonics of the fundamental frequency of the drive signal, for example. In some examples, drive electrodes can be driven with a drive signal having one of two fundamental frequencies such that the frequency of the drive signals are applied in an alternating pattern. The electronic device can sense the signal of the stylus to determine the coarse location of the stylus along the sense electrodes and, based on the frequency content of the received signal, a fine location along the axis of the drive electrodes.