A ring electrode to determine the orientation of the stylus relative to the surface. The stylus can include a ring electrode configuration which can improve capacitive coupling between the ring electrode and the touch panel. The ring electrode configuration can include a ring electrode and ground ring, and ground plate. By varying the lengths of ring electrode, ground ring, ground plate, and the distance between these elements, the electric field emanating from the ring electrode can be tuned to optimize the capacitive coupling between the ring electrode and surface. In some examples, the ring electrode can include multiple sub-rings. In some examples, the ring electrode can comprise a crown shape including projections, each having a width that tapers to a minimum width along the length of the ring electrode.

A capacitance value fast-placing vacuum capacitor includes: a housing, a first electrode group and a second electrode group. A vacuum chamber is provided in the housing. The first electrode group and the second electrode group are mutually coupled and accommodated in the vacuum chamber. An electromagnetic drive mechanism is mounted on the outer side of one end of the housing. The electromagnetic drive mechanism is capable of driving the first electrode group to shift relative to the second electrode group, the vacuum capacitor is switched between two capacitance value states. In the capacitance value rapid-switching vacuum capacitor, the electromagnetic drive mechanism is configured for rapidly adjusting and switching capacitance values of the vacuum capacitor, the capacitance value switching time of the vacuum capacitor is within one hundred milliseconds, thus meeting the requirement of an application device of the vacuum capacitor for rapid matching of an impedance matcher.