Abstract

The theory of multidither adaptive optical radar phased arrays is briefly reviewed as an introduction to the experimental results obtained with seven-element linear and three-element triangular array systems operating at 0.6328 μm. Atmospheric turbulence compensation and adaptive tracking capabilities are demonstrated.

© 1974 Optical Society of America

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References

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  1. D. L. Margerum, “Self-phased Arrays,” in Microwave Scanning Antennas, R. L. Hansen et al. , Eds. (Academic Press, New York, 1964), Chap. 5, pp. 341–407.
  2. A. Ksienski, “A Survey of Signal Processing Arrays,” in Signal Processing Arrays, W. T. Blackband, Ed. (Technivision Services, England, 1968), pp. 1–43.
  3. R. T. Adams, IEEE Trans. Anten. Propagat. AP-12, 224 (1964).
    [Crossref]
  4. Various authors, IEEE Trans. Anten. Propagat. AP-12 (1964).
  5. W. T. Cathey, C. L. Hayes, W. C. Davis, “Coherent Optical Adaptive Techniques,” North American Rockwell Corp. Tech Rep. RADC-TR-68-190 (July1968); Appl. Opt. 9, 701 (1970).
    [PubMed]
  6. T. R. O’Meara et al., “Coherent Optical Adaptive Techniques,” Hughes Research Laboratories, Malibu, California Tech. Rep. RADC-TR (Dec.1970).
  7. R. P. Futrelle, G. E. Mevers, C. L. Hayes, “Coherent Optical Adaptive Techniques,” Contract F30602-70-C-0298 (Apr.1971).
  8. “Laser Technology Identification Study (U),” ARPA Order No. 1279, Contract F30602-71-C-0085 (Dec.1971).
  9. T. R. O’Meara, “Classification of Adaptive Arrays,” unpublished.
  10. We should note that the closed-loop bandwidth depends not only on the low-pass filter bandwidth but also on the open-loop gain. The closed-loop bandwidth will generally be much greater than the filter 3-dB bandwidth, which was the case here.

1964 (2)

R. T. Adams, IEEE Trans. Anten. Propagat. AP-12, 224 (1964).
[Crossref]

Various authors, IEEE Trans. Anten. Propagat. AP-12 (1964).

Adams, R. T.

R. T. Adams, IEEE Trans. Anten. Propagat. AP-12, 224 (1964).
[Crossref]

Cathey, W. T.

W. T. Cathey, C. L. Hayes, W. C. Davis, “Coherent Optical Adaptive Techniques,” North American Rockwell Corp. Tech Rep. RADC-TR-68-190 (July1968); Appl. Opt. 9, 701 (1970).
[PubMed]

Davis, W. C.

W. T. Cathey, C. L. Hayes, W. C. Davis, “Coherent Optical Adaptive Techniques,” North American Rockwell Corp. Tech Rep. RADC-TR-68-190 (July1968); Appl. Opt. 9, 701 (1970).
[PubMed]

Futrelle, R. P.

R. P. Futrelle, G. E. Mevers, C. L. Hayes, “Coherent Optical Adaptive Techniques,” Contract F30602-70-C-0298 (Apr.1971).

Hayes, C. L.

W. T. Cathey, C. L. Hayes, W. C. Davis, “Coherent Optical Adaptive Techniques,” North American Rockwell Corp. Tech Rep. RADC-TR-68-190 (July1968); Appl. Opt. 9, 701 (1970).
[PubMed]

R. P. Futrelle, G. E. Mevers, C. L. Hayes, “Coherent Optical Adaptive Techniques,” Contract F30602-70-C-0298 (Apr.1971).

Ksienski, A.

A. Ksienski, “A Survey of Signal Processing Arrays,” in Signal Processing Arrays, W. T. Blackband, Ed. (Technivision Services, England, 1968), pp. 1–43.

Margerum, D. L.

D. L. Margerum, “Self-phased Arrays,” in Microwave Scanning Antennas, R. L. Hansen et al. , Eds. (Academic Press, New York, 1964), Chap. 5, pp. 341–407.

Mevers, G. E.

R. P. Futrelle, G. E. Mevers, C. L. Hayes, “Coherent Optical Adaptive Techniques,” Contract F30602-70-C-0298 (Apr.1971).

O’Meara, T. R.

T. R. O’Meara et al., “Coherent Optical Adaptive Techniques,” Hughes Research Laboratories, Malibu, California Tech. Rep. RADC-TR (Dec.1970).

T. R. O’Meara, “Classification of Adaptive Arrays,” unpublished.

IEEE Trans. Anten. Propagat. (2)

R. T. Adams, IEEE Trans. Anten. Propagat. AP-12, 224 (1964).
[Crossref]

Various authors, IEEE Trans. Anten. Propagat. AP-12 (1964).

Other (8)

W. T. Cathey, C. L. Hayes, W. C. Davis, “Coherent Optical Adaptive Techniques,” North American Rockwell Corp. Tech Rep. RADC-TR-68-190 (July1968); Appl. Opt. 9, 701 (1970).
[PubMed]

T. R. O’Meara et al., “Coherent Optical Adaptive Techniques,” Hughes Research Laboratories, Malibu, California Tech. Rep. RADC-TR (Dec.1970).

R. P. Futrelle, G. E. Mevers, C. L. Hayes, “Coherent Optical Adaptive Techniques,” Contract F30602-70-C-0298 (Apr.1971).

“Laser Technology Identification Study (U),” ARPA Order No. 1279, Contract F30602-71-C-0085 (Dec.1971).

T. R. O’Meara, “Classification of Adaptive Arrays,” unpublished.

We should note that the closed-loop bandwidth depends not only on the low-pass filter bandwidth but also on the open-loop gain. The closed-loop bandwidth will generally be much greater than the filter 3-dB bandwidth, which was the case here.

D. L. Margerum, “Self-phased Arrays,” in Microwave Scanning Antennas, R. L. Hansen et al. , Eds. (Academic Press, New York, 1964), Chap. 5, pp. 341–407.

A. Ksienski, “A Survey of Signal Processing Arrays,” in Signal Processing Arrays, W. T. Blackband, Ed. (Technivision Services, England, 1968), pp. 1–43.

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Figures (13)

Fig. 1
Fig. 1

Schematic representation of: A, a phased array focused on a distant target through an ideal propagation medium; B, array defocusing caused by atmospheric turbulence; and C, adaptive refocusing by proper predistortion of the radiated wavefront.

Fig. 2
Fig. 2

Schematic drawing of a two-element dithered COAT system.

Fig. 3
Fig. 3

Phasor diagram showing how phase modulation at ω5 is converted to amplitude modulation of the resultant at ω5 when elemental phasor 5 is added to the other elemental phasors.

Fig. 4
Fig. 4

Schematic layout of the components and optical path for the seven-element COAT experiment.

Fig. 5
Fig. 5

Phasor matrix used in the seven-element COAT experiment. A, photograph; B, schematic drawing showing optical paths.

Fig. 6
Fig. 6

Target board showing a dual glint mounted on the black velvet backboard with a viewing slot just below. The scanning detector is mounted in the small box riding on the traveling cross arm of the x-y recorder.

Fig. 7
Fig. 7

(A) Experimental trace of the seven-element COAT system converged on a 2-mm wide glint. (B) Theoretical calculation of an ideally phased seven-element array of Gaussian beams.

Fig. 8
Fig. 8

Oscilloscope trace of the power incident on the glint (upper trace) and the signal returned to the photomultiplier (lower trace). A mechanical shutter begins to open at the time marked by the white arrow. Sweep speed is 10 msec/cm.

Fig. 9
Fig. 9

Seven-element COAT convergence on a single glint in the presence of artificial turbulence. Traces (a) and (b) were taken with the system off and show the washout of the array pattern at the target. Traces (c) and (d) show the recovery of the array pattern with the COAT system on. Scan time was 100 sec/trace; recorder time constant was 20 msec for (a) and (d), 1 sec for (b) and (c).

Fig. 10
Fig. 10

A, Schematic drawing of the two glint target. A set of masks with H1 + H2 constant were made to keep the total signal return constant. B, Scans of the converged beam (central lobe only is shown) for increasing glint strength ratio H1/H2. The central lobe moves completely and apparently discontinuously from G1 to G2 in changing masks from (c) to (d).

Fig. 11
Fig. 11

Peak intensity on a single glint target moving at 0.72 cm/sec (1.8 mrad/sec) for a three-element linear and six-element linear array COAT system in still laboratory air.

Fig. 12
Fig. 12

A, Schematic representation of three-element triangular array radiation pattern. B, Schematic representation of the far field pattern. C, Experimental profile of the far field pattern taken by superposing all the scan lines of a video frame with a camera view as in B.

Fig. 13
Fig. 13

Side-on (upper) and end-on (lower) views of the far-field pattern with the COAT system on (left) and off (right). The amplitude scale in the upper traces is not linear; an approximate dB scale has been drawn in.

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