Accession Number : ADD018369

Title :   Method and Aparatus for Signal Filtering.

Descriptive Note : Patent, Filed 29 Aug 94, patented 24 Dec 96,

Corporate Author : DEPARTMENT OF THE NAVY WASHINGTON DC

Personal Author(s) : Alexander, Edward M ; Spezio, Anthony E

Report Date : 24 Dec 1996

Pagination or Media Count : 9

Abstract : A signal filter, and method of signal filtering, in which an optical signal is spatially dispersed according to frequency, and undesired frequencies blocked out. In an embodiment, a Bragg cell receives a (typically microwave) signal, and transduces it to an acoustic signal. A light source, e.g. a laser diode, directs light through the acoustic signal in a known manner so as to produce an optical output which is spatially dispersed according to frequency. A programmable spatial light modulator blocks out unwanted frequency components. Upon removal of the optical carrier, e.g. by heterodyning the spatial light modulator's output with a reference signal from the light source, the components can be recombined into a resultant filtered signal. The invention can be used as a repeater, a military electronic countermeasure, in environments which have large amounts of electromagnetic clutter but in which one does not want the clutter repeated. The spatial light modulator can be programmed to pass only frequency components in which one is interested, thus blocking the clutter from the repeated signal.

Descriptors :   *SPATIAL FILTERING, *LIGHT MODULATORS, *PATENTS, HETERODYNING, ELECTRONIC COUNTERMEASURES, ACOUSTOOPTICS, REPEATERS, BRAGG ANGLE

Subject Categories : Electrooptical and Optoelectronic Devices
      Acoustooptic and Optoacoustic Devices

Distribution Statement : APPROVED FOR PUBLIC RELEASE