Numerical and Comparative Study of the Agility of Planar Transmission Lines printed on a Ferroelectric Thin Film
Résumé
In this paper, we report on simulation results at 10 GHz of planar transmission lines (TL) printed on a ferroelectric thin film deposited on sapphire and lanthanum aluminate substrates. The ferroelectric film permittivity is supposed to vary from 700 to 500. First, the main properties of microstrip (MS), coplanar waveguide (CPW) and coplanar strips (CS) namely their effective permittivity, characteristic impedance and insertion loss are computed as a function of the physical and electrical parameters. Then their tunability and figure of merit are defined and compared. CPW and CS lines present a tunability (eff/eff_max) of about 16 % for a gap value g = 30 μm. The MS lines show a much less tenability of 2%. Moreover, the figure of merit of CPW and CS configurations are of 6.3 and 12.2 %/dB for a gap value of 30 μm, respectively. By increasing the gap, these figures of merit can be improved up to the limiting values of 8.7 and 15.4 %/dB, respectively.
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