Characterization of nonlinear behavior in a tunable phase shifter using ferroelectric PZT thin-film capacitors and its effect on system performance

In this paper, the nonlinear behavior in a tunable phase shifter using ferroelectric lead zirconate titanate (PZT) thin-film capacitors is described. The phase shifter is of reflection-type consisting of a coplanar waveguide Lange coupler and two ferroelectric PZT varactors on high resistivity silicon substrate. The nonlinearity is characterized by measuring the AM/AM and AM/PM transfer curves of the device, a technique that is commonly used to characterize power amplifiers. The responses of the device to two-tone and quadrature-amplitude-modulation waveforms are then estimated according to the measured transfer curves.