Analysis and Simulation of distributed nonlinearities in ferroelectrics and superconductors for microwave applications

Abstract

Abstract-This paper gives closed-form equations for the intermodulation and third harmonic signals generated in a nonlinear transmission line with distributed quadratic nonlinearities in the conductor and dielectric. Although the formulation developed is general, it is intended to be used in planar devices combining hightemperature superconductor (HTS) and oxide ferroelectrics. The analysis in this paper shows that the intermodulation and third harmonic signals produced by an HTS tend to cancel those of a ferroelectric, and that full cancellation is theoretically possible. This opens the way for using HTS/ferroelectric multilayers, not (only) for their tunable or phase-shifting properties, but for highly linear spurious-free planar HTS devices.

Measurements and Analysis of Microwave Nonlinearities in Ferroelectric Thin Film Transmission Lines

“…Although a decrease in the slope occurs at high powers due to heating effects, the third harmonic (on a logarithmic scale) follows a slope 3 …”

“…4. Detailed analysis of this circuit model, for matched transmission lines, is presented in [3], where closed-form expressions connecting the third harmonic (and also IMD) with the nonlinear distributed parameters (C(Vrf) in this case) can be found.…”

“…The combination of these materials with high temperature superconductors (HTS) is being considered to achieve lowloss filters with electronic frequency tuning/trimming features [2], or to reduce the nonlinear effects inherent to HTS components [3].…”

“…On one hand, by comparing C(Vrj) and C(VdC) we can evaluate the attainable time scales for tuning [5]. One the other hand, modeling the nonlinear effects in devices at these frequencies is important in order to assess their generation of passive IMD and other spurious signals, and evaluate the possible role of ferroelectric materials in the compensation of the nonlinear effects produced by HTS materials [3]. The full determination of the nonlinear behavior should include harmonic measurement for several frequencies of the fundamental tone and IMD measurements performed as a function of the spacing between the input tones.…”

Nonlinear characterisation for microstrip filters with low passive intermodulation

“…Signal impairments in printed circuits arising from the intrinsic electrical nonlinearities of conductors and substrate materials have been duly recognised and studied since the early 1990-s, particularly in application to superconducting microstrip lines [1][2][3], as well as tuneable microstrip circuits on ferroelectric [4] and liquid crystal substrates. The important aspect of previous studies is the use of deterministic models of the intrinsic nonlinearity, albeit phenomenological and subject to experimental characterization.…”