The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Jun. 23, 1992
Filed:
Jan. 15, 1991
Jason Hoendervoogt, Phoenix, AZ (US);
James Watson, Phoenix, AZ (US);
Calcomp, Inc., Anaheim, CA (US);
Abstract
A battery powered oscillator in a freely movable pointer drives a coil and a divider. A grid of spaced conductors in a base unit is inductively coupled to the coil. A conductive plate that lies parallel to the conductor grid capacitively couples the signal from the divider to a phase locked loop to provide a reference signal that has a constant phase in relation to the oscillator. Detection circuitry uses the signals induced in selected grid conductors and the phase reference signal to determine the location of the pointer relative to the conductors. As an alternative to the phase locked loop, the signal induced in an idle reference conductor can be combined with the capacitively coupled reference signal to aid in demodulating the induced signals. As an alternative to an oscillator in the pointer, the coil may be driven by a signal capacitively coupled from the base unit.