Capacitance sensing method and assembly

A capacitance sensing assembly comprising:

• an op-amp;
• a first complex impedance circuit with a first terminal of the first complex impedance circuit connected to an inverting input of the op-amp;
• a second complex impedance circuit with a first terminal of the second complex impedance circuit connected to a second terminal of the first complex impedance circuit and a second terminal of the second complex impedance circuit connected to a non-inverting input of the op-amp;
• a third complex impedance circuit with a first terminal of the third complex impedance circuit connected to the inverting input of the op-amp and a second terminal of the third complex impedance circuit connected to an output of the op-amp;
• a fourth complex impedance circuit with a first terminal of the fourth complex impedance circuit connected to the non-inverting input of the op-amp;
• a sensing capacitor with:
• a first electrode of the sensing capacitor connected to a second terminal of the fourth complex impedance circuit and a second electrode of the sensing capacitor connected to a ground;
• or
• the first electrode of the sensing capacitor connected to the non-inverting input of the op-amp and the first terminal of the fourth complex impedance circuit and the second electrode of the sensing capacitor connected to the ground and the second terminal of the fourth complex impedance circuit, wherein the fourth complex impedance circuit is connected in parallel to the sensing capacitor;
• and
• wherein the complex impedance circuits are configured to increase a gradient of a phase to frequency response curve of the capacitance sensing assembly relative to that of an all-pass filter with a second electrode of a capacitor connected to the non-inverting input of the op-amp and the ground without the fourth complex impedance circuit.