Inter-Satellite Phase and Frequency Synchronization for Software-Defined CubeSat Radio Subsystems

In this work, an approach towards wireless syntonization (i.e., frequency) and carrier-phase synchronization using CubeSat software-defined radio subsystems is shown. Therefore, a previously published approach which utilizes the two-way time transfer (TWTT) principle for ranging and timing synchronization is extended towards carrier phase and frequency difference estimation. By adaptively tuning the digitally controlled crystal oscillator (DCXO) of the used commercial frontend, carrier phase and frequency synchronization is achieved between two nodes. Experimental results obtained in a laboratory setup show a standard deviation of 0.21 rad of the relative carrier phase difference at a carrier frequency of 2 GHz.