Optical adaptive filter

• US 4,579,421 A
• Filed: 10/05/1983
• Issued: 04/01/1986
• Est. Priority Date: 10/05/1983
• Status: Expired due to Fees

• Current Assignee: The United States of America As Represented By The Director National Security Agency
• Original Assignee: The United States of America As Represented By The Director National Security Agency
• Inventors: Brown, Douglas E., Rhodes, Joanne F.
• Primary Examiner(s): Corbin, John K.
• Assistant Examiner(s): Ben, Loha
• Application Number:
  US06/539,270
• Time in Patent Office: 909 Days
• Field of Search: 350/311, 350/162.12, 350/162.13, 350/356, 350/342, 364/822, 364/825
• US Class Current: 359/259
• CPC Class Codes: G06E 3/005 using electro-optical or opto-electronic means

Abstract

An electrooptic apparatus is disclosed for linear predictive adaptive filtering. The apparatus combines the desirable filtering effects of a correlation cancellation loop method of linear prediction with the parallelism and large bandwidth capabilities of optical processing.

Claims

1. An electrooptic signal processing apparatus, comprising:

a source of an electrical information signal;

a first source of coherent light;

first modulating means for intensity modulating the output of said first light source in response to an electrical signal to produce a first intermediate optical signal;

second modulating means for modulating said first intermediate optical signal in response to delayed samples of said information signal to produce a second intermediate optical signal;

means for integrating said second intermediate optical signal;

a second source of coherent light;

third modulating means for modulating the output of said second light source in accordance with the integrated values of said second intermediate optical signal to produce a third intermediate optical signal proportional to the integrated signals;

fourth modulating means for modulating said third intermediate optical signal in response to delayed samples of said information signal to provide a fourth intermediate optical signal comprising a plurality of weighted samples;

means for converting said fourth intermediate optical signal into an electrical output representative of the sum of said weighted samples;

means for producing an electrical signal representing the difference of said electrical output and said information signal; and

means for providing said difference signal to said first modulating means.

2. The apparatus of claim 1 wherein said first and second light sources are lasers.

3. The apparatus of claim 2 wherein said first modulating means is an electrooptic modulator.

4. The apparatus of claim 3 wherein said second modulating means is a Bragg cell.

5. The apparatus of claim 4 wherein said integrating means is the photodetector side of a liquid crystal light valve.

6. The apparatus of claim 5 wherein the third modulating means is the liquid crystal side of a liquid crystal light valve.

7. The apparatus of claim 6 wherein said fourth modulating means is a Bragg cell.

8. The apparatus of claim 7 wherein said converting means is a photomultiplier tube.

9. The apparatus of claim 8 wherein said difference producing means is a differential amplifier.