An optically controlled array antenna with a beam-forming network (BFN) using two laser sources

With respect to the optically controlled array antenna in which the optical Fourier transform and the O/E conversion are used for generation and control of the microwave excitation distribution in the optical region, the excitation amplitude and phase distribution and the radiation characteristics are studied theoretically and experimentally for a two‐laser system in which two laser sources with their oscillation frequency difference set at the desired microwave frequency are used. First, the excitation distribution and the radiation pattern are expressed theoretically in the case where a circular aperture image mask is used and the relationship between the image mask aperture diameter and the element antenna spacing is derived. Next, a two‐laser experimental system is shown which uses LD pumped Nd: YAG lasers as the laser sources. an excitation distribution experiment was carried out at 1.54 GHz. From the experimental results, it is found that a stable excitation distribution corresponding to the theoretical value can be obtained in the experimental system in the two‐laser system as in the one‐laser system. 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 aperture diameter can be obtained.