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

Abstract

-This work evaluates the microwave nonlinear properties of ferroelectric BaSrTiO thin films by measuring the frequency response of several coplanar transmission lines and interdigital capacitor structures as a function of the applied electric field from 150 Hz to 40 GHz. From these measurements, we obtain the distributed nonlinear capacitance C(VdC) as a function of dc bias. We also measure the harmonic generation at microwave frequencies in ferroelectric transmission lines, and use an accurate circuit model to obtain C(Vrf), the nonlinear capacitance as a function of rf bias. Information about the tuning speed of the film is obtained from a comparison between the two nonlinear capacitances. Characterization of this mechanism is also required to assess the spurious signal generation in ferroelectric-based devices.

Intermodulation Distortion in Coupled-Resonator Filters With Nonuniformly Distributed Nonlinear Properties—Use in HTS IMD Compensation

“…Assuming a power law dependence of the circuit parameters in Fig. 1 Although the procedure described henceforth might be applied for any power dependence, we will use a quadratic nonlinear dependence , which agrees with many results found in the literature for both HTS [10], [11] and ferroelectric thin films [7]- [9]. Details on how to apply this procedure for a given type of power dependence in superconductors may be found in [12].…”

“…By using (5) and (6) and considering the propagation of the IMD and fundamental signals along the structure of Fig. 2(a), the resulting IMD is (7) where is the characteristic impedance of the line and is the real part of . Since the nonlinear effects for the HTS and ferroelectric are in opposite phase [8], [13], we find the condition for IMD cancellation as (8)…”

Nonlinear effects in thin-film ferroelectric transmission lines at microwave frequencies

“…We demonstrate in [3] how different geometry devices can be described by the same function for the case of the dependence of the nonlinear capacitance on dc voltage. This is accomplished by calculating the change in film permittivity as a function of electric field from the measured capacitance per unit length.…”

Passive Intermodulation Due to Self-Heating in Printed Transmission Lines

“…As a result of the above-described process, measurements of the third-order intermodulation signals at different separations between tones might be used to unveil the low-pass filter shape of the thermal impedance [10] since (2) where is the third-order intermodulation distortion power.…”

“…Such is the case for transmission lines made of superconductors [1] or ferroelectric materials [2]. However, several papers have shown the existence of third-order intermodulation distortion, even in transmission lines made of inherently linear materials, such as copper on commercial substrates [3], [4].…”