Theoretical and experimental implementation of microwave active filters using automatic frequency control techniques

Abstract

This paper discusses phase-locked loop (PLL) and magnitude-locked loop (MLL) techniques based on a voltage-controlled filter (VCF) for the automatic frequency control (AFC) of active filters. Applications to a microwave planar filter are considered. Theoretical analysis and simulated and measured results are presented for both phase and magnitude control circuits, enabling the filter to accurately track a reference signal. © 2000 John Wiley & Sons, Inc. Microwave Opt Technol Lett 27: 23–27, 2000.