Analysis of a PLL-based down converter and phase detection circuit for self-tracking arrays

In this paper we analyze a down conversion and phase detection circuit for a self-tracking receiving antenna array which uses a nested phase-locked loop (PLL) architecture. Analytic expressions for the system model are derived and stability is checked using the Hurwitz criterion. The results lead to design constraints for the employed loop filters, ensuring stability of the proposed circuit. The general influence of parameter choice on system bandwidth and adaption speed is evaluated.