Demodulation System and Method for Recovering a Signal of Interest from an Undersampled Modulated Carrier
Patent, Filed 10 Nov 97, patented 16 Mar 99
DEPARTMENT OF THE NAVY WASHINGTON DC
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A demodulation system and method is used in a sensor system such as a fiber optic sensor system, that senses optical signals and modulates a phase generated carrier having a carrier frequency Wc to form a modulated carrier. The modulated carrier is preferably undersampled at three times the carrier frequency 3Wc, thereby maximizing the sensors demodulated bandwidth relative to the sensors sampling frequency. The undersampled modulated carrier is orthogonally demodulated by multiplying the undersampled, modulated carrier by cosWcT0 and sinWcT0 to extract even and odd harmonic components of the signal of interest. The even and odd harmonic components of the signal of interest are further demodulated by taking the square root of the sum of squares of the even and odd harmonic components, normalizing the even and odd harmonic components, and differentiating, cross-multiplying and differencing the normalizer even and odd harmonic components to recover the signal of interest.
- Optical Detection and Detectors
- Fiber Optics and Integrated Optics