Modified Green´s Function and Spectral-Domain Approach for Analyzing Anisotropic and Multidielectric Layer Coplanar Waveguide Ferroelectric Phase Shifters

Phase-shifter design based on ferroelectric materials technology has shown promising performance characteristics and the potential for achieving the long standing goal of realizing high performance, low-cost microwave phase shifters, and phased-array antennas. In this paper, we present a unifying spectral-domain approach and a newly derived Green\´s function that provide a "first principles" method for the design and analysis of ferroelectric material based coplanar waveguide phase shifters. The modified Green\´s function not only accounts for the finite thickness of the conductors, but also for the "current crowding" phenomena that results from using the very high dielectric constant ferroelectric film. Both isotropic and anisotropic effects were analyzed and the developed theoretical results were in excellent agreement with measured data. It is also shown that the multidielectric layer-based design of these phase shifters may provide nearly threefold increase in the figure-of-merit compared with the direct metallization case. A new biasing approach is proposed to achieve effective biasing of the ferroelectric layer and without excessive field concentration in the overlaying low dielectric layer. The formulation, procedure for the calculation of the current and charge distributions, and comparison between simulation and experimental results are described and presented in detail