Three and four product surface-wave acousto-optic time integrating correlators

A device for obtaining a two-dimensional four product correlation by processing spread spectrum radar signals comprising:

• a source of a laser beam;
• beam splitting and shaping means for dividing and shaping the laser beam into first and second sheet beams, the plane of the second sheet beam being orthogonal to the plane of the first sheet beam;
• a first acousto-optic medium, having a planar surface extending between opposite first and second ends, which is disposed in the path of the first sheet beam such that the first sheet beam traverses the first medium intermediate the first medium ends along and parallel to the first medium surface;
• a second acousto-optic medium, having a planar surface extending between opposite first and second ends, which is disposed in the path of the second sheet beam such that the plane of the second medium surface is normal to the plane of the first medium surface and the second sheet beam traverses the second medium intermediate the second medium ends along and parallel to the second medium surface;
• transmitting means for transmitting a radar signal;
• signal sampling means for sampling and relaying the transmitted radar signal to the first acousto-optic medium;
• a first acoustic transducer, disposed at the first end of the first acousto-optic medium and supplied with the transmitted radar signal, for propagating the transmitted radar signal on the first medium surface in the direction of the second end of the first acousto-optic medium so as to cause a first diffraction of the first sheet beam with the transmitted radar signal;
• signal receiving means for receiving a reflected signal portion of the transmitted radar and relaying the reflected signal to the first acousto-optic medium;
• a second acoustic transducer, disposed at the second end of the first acousto-optic medium and supplied with the reflected signal, for propagating the reflected signal on the first medium surface in the direction of the first end of the first acousto-optic medium so as to cause a second diffraction of the first sheet beam with the reflected signal;
• a third acoustic transducer, disposed at the first end of the second acousto-optic medium and supplied with a first FM linear chirp signal, for propagating the first FM linear chirp signal on the second medium surface in the direction of the second end of the second acousto-optic medium so as to cause a first diffraction of the second sheet beam with the first FM linear chirp signal;
• a fourth acoustic transducer, disposed at the second end of the second acousto-optic medium and supplied with a second FM linear chirp signal, for propagating the second FM linear chirp signal on the second medium surface in the direction of the first end of the second acousto-optic medium so as to cause a second diffraction of the second sheet beam with the second FM linear chirp signal;
• beam shaping means for shaping the diffracted first and second sheet beams into respective square beams;
• and
• beam combining and directing means for combining and directing the square beams to a photodiode area array.

A method of processing spread-spectrum and other wideband communications and radar signals to obtain at least a three product, time integrated, correlated output signal, comprising the steps of:

• splitting a laser light beam into a first laser beam and a second laser beam;
• converting the first laser beam into a first sheet beam;
• converting the second laser beam into a second sheet beam, the plane of the second sheet beam being orthogonal to the plane of the first sheet beam;
• directing the first sheet beam to a first acousto-optic medium, having a planar surface extending between opposite ends, so that the first sheet beam traverses the first acousto-optic medium intermediate the first medium ends along and parallel to the planar surface of the first acousto-optic medium;
• directing the second sheet beam to a second acousto-optic medium, having a planar surface extending between opposite ends, so that the second sheet beam traverses the second acousto-optic medium intermediate the second medium ends along and parallel to the planar surface of the second acousto-optic medium, which is orthogonal to the planar surface of the first acousto-optic medium;
• propagating a first signal to be correlated on the planar surface of the first acousto-optic medium in a first direction toward one end of the first acousto-optic medium so as to cause a first diffraction of the first sheet beam with the first signal;
• propagating a second signal to be correlated on the planar surface of the first acousto-optic medium in a second direction toward the other end of the first acousto-optic medium so as to cause a second diffraction of the first sheet beam with the second signal;
• propagating a third signal to be correlated on the planar surface of the second acousto-optic medium in a third direction toward one end of the second acousto-optic medium so as to cause a first diffraction of the second sheet beam with the third signal;
• converting the diffracted first and second sheet beams into first and second rectangular beams, respectively;
• combining the first and second rectangular beams;
• and
• directing the combined beam to a time integrating photodetector for converting the combined beam to the at least three product, time integrated, correlated output signal.

A method of obtaining a two-dimensional four product correlating by processing spread spectrum radar signals comprising the steps of:

• dividing and shaping a laser beam into first and second sheet beams, the plane of the second sheet beam being orthogonal to the plane of the first sheet beam;
• directing the first sheet beam to a first acousto-optic medium, having a planar surface extending between opposite ends, so that the first sheet beam traverses the first acousto-optic medium intermediate the first medium ends along and parallel to the planar surface of the first acousto-optic medium;
• directing the second sheet beam to a second acousto-optic medium, having a planar surface extending between opposite ends, so that the second sheet beam traverses the second acousto-optic medium intermediate the second medium ends along and parallel to the planar surface of the second acousto-optic medium, which is orthogonal to the planar surface of the first acousto-optic medium;
• sampling a transmitted radar signal transmitted by a radar transmitter;
• propagating the sampled transmitted radar signal on the planar surface of the first acousto-optic medium in a first direction toward one end of the first acousto-optic medium so as to cause a first diffraction of the first sheet beam with the sampled transmitted radar signal;
• receiving a reflected signal portion of the transmitted radar signal reflected from a target;
• propagating the reflected signal on the planar surface of the first acousto-optic medium in a second direction toward the other end of the first acousto-optic medium so as to cause a second diffraction of the first sheet beam with the reflected signal;
• propagating a first linear FM chirp signal on the planar surface of the second acousto-optic medium in a third direction toward one end of the second acousto-optic medium so as to cause a first diffraction of the second sheet beam with the first linear FM chirp signal;
• propagating a second linear FM chirp signal on the planar surface of the second acousto-optic medium in a fourth direction toward the other end of the second acousto-optic medium so as to cause a second diffraction of the second sheet beam with the second linear FM chirp signal;
• shaping the diffracted first and second sheet beams into first and second square beams, respectively;
• combining the first and second square beams;
• and
• directing the combined square beams to a photodiode area array.