Birefringent photonic integrated circuit for beam forming network of independently steerable multibeam antenna

We report on the development of a beam forming network (BFN) for three independently steerable beams by a five-element array antenna integrated on a birefringent photonic integrated circuit (PIC) chip and measured phase shift characteristics of the BFN by optical wavelength tuning. In a coherent optical signal processing system transmitting an RF signal as the frequency difference of two lightwaves, the phase of the regenerated RF signal from the lightwaves is controlled by changing the relative phase difference between the two lightwaves, which requires only a small optical path control on the order of micrometers. The operating principle of the BFN is based on the combination of an optical Rotman lens technique for multibeam formation and an optical wavelength scanning technique to steer each beam independently.