UMPS: Ultrasound-Microwave-Fused Phase Synchronization for UAV-Based Phased Arrays

A wireless ultrasound-microwave-fused phase synchronization (UMPS) method for antenna elements in a UAV-based phased array is presented in this paper. The UMPS includes multiple non-connected modules that follow a leader-follower scheme for positioning and phase synchronization. The only leader is the reference point, to which followers locate their relative position by Time-of-Flight of ultrasound calibrated with microwave signal and synchronize its phase by on-board phase shifters. With a synchronized phase, the UMPS modules can form a phased array with a variable spatial arrangement of antenna elements. In this work, the prototype UMPS exhibits a root-mean-square (RMS) positioning error at 14 mm and a 7.5° RMS phase error for synchronizing a 433 MHz continuous wave RF signal, which is satisfactory for forming a UAV-based phased array.