1. A method comprising: obtaining measures of a signal feature from a proximity sensor at times, respectively, while an object is sufficiently close to the proximity sensor to affect the measures of the signal feature, wherein the proximity sensor comprises, in order of stack arrangement: a conductively isolated patch filter, a first substrate, a strip filter, and a ground plane, wherein a driving signal drives the strip filter and the signal feature measures are obtained from the strip filter; and determining distances of the object from the proximity sensor corresponding to the times, respectively, according to the respective measures of the signal feature.