BEAM SCANNING CHARACTERISTICS OF AN OPTICALLY CONTROLLED ARRAY ANTENNA FED BY A FIBER OPTIC ARRAY

For an optically controlled array antenna in which the microwave excit ation distribution is generated and controlled in the optical domain b y means of the optical Fourier transform and the optical/electrical (O /E) conversion, element antenna excitation, and the radiation characte ristics are theoretically and experimentally studied in the case in wh ich the image mask is shifted from the optical axis of the Fourier tra nsforming lens for an intended beam scanning. A planar fiber optic arr ay was constructed and the excitation profile and the radiation patter n were experimentally investigated by means of a fiber optic array. Fi rst, the excitation profile and the beam scan angle were theoretically expressed in the case in which the circular aperture image mask shift and beam scan angle is derived. From the excitation profile experimen t using a type of two-laser optically controlled array system, it is s hown that the excitation profile necessary for the beam scanning can b e obtained. From the calculation of the radiation pattern, the beam sc anning corresponding to the computed value is possible. A 61-element f iber optic array was then designed for trial. By using the excitation profile experiment with this array, it is shown that the excitation pr ofile and the beam scanning characteristics can be obtained with the f iber optic array if the transmission loss of the fiber optic array is compensated for.