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:
Jan. 29, 2013
Filed:
May. 01, 2009
Paul L. Kebabian, Acton, MA (US);
Paul L. Kebabian, Acton, MA (US);
Aerodyne Research, Inc., Billerica, MA (US);
Abstract
In one embodiment, a frequency generator produces an excitation signal, a local oscillator signal, and a reference signal at a difference frequency of the excitation signal and local oscillator signal. The excitation signal is applied to a physical system to produce a response signal, which is mixed with the local oscillator signal. A filter selects a difference frequency component. The frequencies of the excitation signal and/or local oscillator signal are varied, such that the magnitude of the difference frequency is constant, but a sign of the difference frequency changes from positive to negative. The phase shift of the difference frequency component, with respect to the reference signal, at each of the two signs of the difference frequency, is measured. The measured phase shift at the negative sign is subtracted from the measured phase shift at the positive sign, and the difference is divided in half, to produce a result.