Integrated optical beamformers

Microwave photonics (MWP) is an emerging field in which the radio signals are generated, distributed, processed and analysed using the strength of photonics. It is a disruptive technology which enables various functionalities which are not feasible in only the microwave or electronic domain. A particular aspect that has gained a significant interest recently is the use of photonic integrated circuit (PIC) technology in this field, i.e., integrated microwave photonics (IMWP) [1, 2, 3]. A field where IMWP can have a strong impact is the one of phased array antennas (PAA) for next generation mobile (5G) and Satcom networks. Such arrays offer a number of attractive characteristics, including a conformal array profile, beamforming (beam shaping and beam steering), interference nulling and the capability to generate multiple antenna beams simultaneously. In many cases, however, the performance of a phased array is limited by the static characteristics of the beamforming network (BFN) used. It is generally desired to realize beamformers with broad instantaneous bandwidth, continuous amplitude and delay tunability and, at the same time, capable of feeding large arrays. This, however, is very challenging to achieve using electronics only.