US Patent 10928947 Pressure signal processing

A method includes receiving (S1), from a touch panel (1), force values (23) corresponding to a plurality of piezoelectric sensors (5,6, 7). Each piezoelectric sensor corresponds to a physical location (xm, yn) on the touch panel. The method also includes receiving (S2) an identification of which, if any, of the force values (23) are influenced by coupling to external electric fields. The method also includes, in response to one or more force values (23) being identified as influenced by coupling to external electric fields (S3), setting the corresponding force values (23) as excluded force values (S5), and setting the remaining force values (23) as valid force values (S5). The method also includes interpolating and/or extrapolating (S6), based on the valid force values, one or more reconstructed force values (25) corresponding to same physical locations (xm, yn) as the respective excluded force values (23).