Characterization of ceramic dielectrics for sub-GHz applications in nonlinear transmission lines

Low loss dielectric materials with high permittivity and nonlinear behavior are essential for use in capacitive non linear transmission lines (NLTLs) for RF generation. NLTLs have a great potential to generate solitons waves for high power microwave applications in mobile defense platforms and satellite communications. In this work the dielectric properties of a piezoelectric capacitor based on lead-zirconate-titanate (PZT) was characterized in a broadband frequency from 10 MHz to 1 GHz for use in NLTLs. Also three commercial ceramic capacitors made of barium titanate (BaTiO₃) were also assessed for comparison with the PZT capacitor. The characterization of materials consists of measuring the relative dielectric constant (real and imaginary parts) as function of the applied voltage and frequency to calculate the loss tangent of the material. The results showed that PZT material has a better performance for use in NLTLs than barium titanate because of its lower losses. As shown here, however, the use of PZT and barium titanate based materials in NLTLs are compromised by the self-resonant frequency of the capacitors due to the inherent parasitic inductance associated to the capacitor at high frequency.