Fourier Transform Optical Beamformer Employing Spatial Light Modulator

Tomohiro AKIYAMA
Hideyuki OH-HASHI
Masahito SATO
Yoshihito HIRANO

IEICE TRANSACTIONS on Electronics   Vol.E90-C    No.2    pp.465-473
Publication Date: 2007/02/01
Online ISSN: 1745-1353
DOI: 10.1093/ietele/e90-c.2.465
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Section on Evolution of Microwave and Millimeter-Wave Photonics Technology)
optical beamformer,  optically controlled array antenna,  optical Fourier transform,  spatial light modulator,  microwave photonics,  

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Optically controlled beam forming techniques are effective for phased-array antenna control. We have developed the Fourier transform optical beamformer (FT-OBF). The antenna radiation pattern inputted into an amplitude spatial light modulator (A-SLM) is optically Fourier transformed to a specific phase-front light beam equivalent to an antenna excitation in the FT-OBF. Optical signal processing, used the Fourier transform optics, is effective to large-scale, two-dimensional, and high-speed signal processing. To implement a flexible and finer antenna beam pattern control, we use an A-SLM as input image formation of the FT optics. And, to realize a small-size FT-OBF, we use symmetric triplet lenses with convex, concave and convex lens. The total optical system becomes below 1/5 length compared with the length using single lens. Finally, we evaluated the developed FT-OBF with the generated amplitude and phase distributions, which excitation signal of an array antenna. We measured an antenna radiation beam pattern, beam steering and beam width control, in the C-band. Measurement results agreed with theoretical calculated results. These results show the feasibility of the spatial light modulator based FT-OBF.