AN OPTICALLY CONTROLLED ARRAY ANTENNA WITH A BEAM-FORMING NETWORK (BFN) USING 2 LASER SOURCES

With respect to the optically controlled array antenna in which the op tical Fourier transform and the O/E conversion are used for generation and control of the microwave excitation distribution in the optical r egion, the excitation amplitude and phase distribution and the radiati on characteristics are studied theoretically and experimentally for a two-laser system in which two laser sources with their oscillation fre quency difference set at the desired microwave frequency are used. Fir st, the excitation distribution and the radiation pattern are expresse d theoretically in the case where a circular aperture image mask is us ed and the relationship between the image mask aperture diameter and t he element antenna spacing is derived. Next, a two-laser experimental system is shown which uses LD pumped Nd:YAG lasers as the laser source s. An excitation distribution experiment was carried out at 1.54 GHz. From the experimental results, it is found that a stable excitation di stribution corresponding to the theoretical value can be obtained in t he experimental system in the two-laser system as in the one-laser sys tem. Further, by using the measured excitation distribution, the array radiation pattern is computed. In this way, it is confirmed that the radiation pattern in a beam shape corresponding to the image mask aper ture diameter can be obtained.