Coherent photonic true-time-delay beamforming system for a phased array antenna receiver

Photonic true-time-delay (TTD) beamformers, as a microwave photonic technique, provide solutions to some important drawbacks of broadband wireless communication systems, radar and satellite communications. However, scalability limitations may arise when increasing the number of antennas. In this paper, a new concept of a photonic TTD beamforming network for phased array antennas (PAAs) is presented and its control system described. This photonic TTD beamformer relies on tunable optical delay lines (TODLs) implemented by Mach-Zehnder delay interferometers (MZDIs) with tunable coupling ratio, thus allowing the continuous tuning of the TODLs. Results show that the proposed TTD beamforming is scalable up to a considerable number of PAAs. In addition, its architecture is directly implementable in photonic integrated circuits.