Patent ID: 7944216

Claim:
A capacitance sensor, comprising: a first electrode and a second electrode; a frequency spread signal generation circuit coupled to the first electrode and the second electrode to apply a first frequency spread signal based on a first spread sequence and a periodic signal with a frequency to the first electrode, and concurrently a second frequency spread signal based on a second spread sequence being orthogonal to the first spread sequence and the periodic signal to the second electrode; a frequency controller coupled to the frequency spread signal generation circuit to vary the frequency of the periodic signal; a receiver circuit coupled to the first electrode and the second electrode or a further electrode to receive a version of the first frequency spread signal which depends on a capacitance applied to the first electrode and a version of the second frequency spread signal that depends on a capacitance applied to the second electrode; and an evaluation circuit coupled to the receiver circuit to determine a capacitance value based on the received dependent versions of the first and second frequency spread signal.