An electromagnetic encoding switch and a method for calculating rotation information of a runner. The electromagnetic encoding switch (10) comprises: a runner assembly (11), wherein the runner assembly (11) comprises an LC resonant circuit (111), the LC resonant circuit (111) comprising an inductor L and a capacitor C connected to the inductor L, the inductor L having a magnetic core, and the inductor L being used for receiving and transmitting electromagnetic waves; a runner (112), the LC resonant circuit (111) being disposed on the runner (112); a transceiver unit (12), the transceiver unit (12) comprising an antenna (121) disposed below the runner (112) and used for transmitting electromagnetic waves at a preset frequency in a transmitting period, so that the LC resonant circuit (111) receives energy in the transmitting period; and an antenna selection switch (122) connected to the antenna (121). The electromagnetic encoding switch (10) has no mechanical noise and is low-cost.

Front-end circuits that combine inductive and capacitive sensing are described. In one embodiment, an apparatus includes a plurality of inductive elements, an inductive measurement circuit, and a frequency divider circuit. The inductive measurement circuit is to output a first signal with a first frequency. The first signal is associated with an inductance change of one of the inductive elements. A feedback circuit can maintain the sinusoidal operation of the first signal. The frequency divider circuit can generate a second signal with a second frequency that is lower than the first frequency.