Method and Apparatus for Energy Efficient Tacking of Resonant Devices
Patent application, Filed 10 Sep 1999
DEPARTMENT OF THE NAVY WASHINGTON DC
Pagination or Media Count:
A method and apparatus for interrogating a resonator to monitor its resonance characteristics e.g., resonant frequency in an especially energy efficient manner, particularly changes to the characteristics over time. The resonator is pulsed and the response thereto sampled. By comparison of samples of the response to sequential pulses, sampled at the same times after pulse initiation, one can infer phase changes between the responses, and hence infer changes in resonance characteristics. Preferably, one calibrates the resonators time response initially as a reference, which permits subsequent determination of the resonance state with only one digital sample per pulse. In one embodiment, the invention this detection scheme is used as a chemical detector. The resonator is an electo-acoustic device, having plural Bragg gratings, with a different adsorptive material atop each grating which adsorbs one selected chemical particularly well. Absorption causes the weight of material to increase, changing the resonance characteristics of the gratings. A single pulse launched into the SAW will cause reflections from each of the Bragg cells which are staggered in time, and hence separately detectable. The resonance of each grating is then tracked as above described, and changes thereto over time indicates the amount of material adsorbed.
- Electrical and Electronic Equipment
- Non-electrical Energy Conversion
- Radiofrequency Wave Propagation