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.

A highly accurate measurement method of parameters of MZ-type LN optical intensity modulators is presented. In this method, a CW optical signal is input to an optical terminal and small CW RF signal is applied to an electrode of the modulator. Then sideband levels of an output optical signal at different bias points are measured by using optical spectrum analyzer. By using 1st order sideband levels which are measured at two different bias conditions, and using a compensation method to measured levels, we can obtain accurate chirp parameter even when very small power of RF signal is applied to the modulator. In this method, the chirp parameter can be obtained in good accuracy when the input RF voltage is only 3% of the halfwave voltage.

A matched load for post-wall waveguide (SIW; Substrate Integrated Waveguide) is presented. It consists of an electrically-shorted post-wall waveguide and a rectangular thin-film resistor sheet on the surface of the waveguide, resulting in a quite compact structure without three-dimensional bulky absorber as in conventional waveguide matched loads. A fabricated X-band matched load has achieved less than -20 dB reflection in more than 20% relative bandwidth.