Photonic Approach to Beam Steering of Phased Array Antenna

Beam steering of phased array antenna was achieved by changing the wavelengths of tunable light sources, where RF power was transmitted to the array antenna through optical fibers with finite chromatic dispersion. A concept of photonic approach to beam steering was first explained and then experimental demonstrations were shown for a 2 GHz array antenna with 4 patch antenna elements and for a 20 GHz array antenna with 2 patch antenna elements. The relationships between the phase shift of the RF signal and the fiber length, chromatic dispersion, and the wavelength tuning range were verified through the experiments. Transmission penalty caused by the phase difference between the upper and lower sidebands due to the chromatic dispersion was also studied together with the beam steering capability as a function of RF frequency. It has been shown that this method is viable up to millimeter wave band, if we choose a proper length of fiber and a wavelength tuning range.