Capacitive sensor including resonant network

A combined seat heater and capacitive occupancy sensor, comprising:

• a heater network including a heating element connected between a first node and a second node to dissipate heat when a heating current is caused to flow between said first and second nodes, across said heating element,
• a capacitive sensing network connected to said heating element to use said heating element as an antenna electrode, said heating element being arranged for forming a capacitance with a counterelectrode, said capacitance being responsive to an electric-field-influencing property of an object or person proximate to said heating element, said capacitive sensing network being configured to apply an oscillating signal to said heating element and to determine said capacitance based upon characteristics of said oscillating signal;
• wherein said heater network comprises a common mode choke with at least two windings, said heating element being connected in series between a first and a second winding of said at least two windings so as to be operatively connectable to a power source via said common mode choke;
• and wherein said capacitive sensing network includes a plurality of reactive components, arranged to form a resonant network with at least one of said first and second winding and with said capacitance, said plurality of reactive components being activatable or deactivatable in such a way as to modify a resonance frequency of said resonant network.