Influence of the biasing scheme on the performance of Au/SrTiO3/LaAlO3 thin film conductor/ferroelectric tunable ring resonators

The performance of gold/SrTiO 3 /LaAlO 3 conductor/ferroelectric/dielectric sidecoupled, tunable ring resonators at Ku-band frequencies is presented. The tunability of these rings arises from the sensitivity of the relative dielectric constant (ε r ) of SrTiO 3 to changes in temperature and dc electric fields (E). We observed that the change in ε r which takes place by biasing the ring up to 450 V alters the effective dielectric constant (ε eff ) of the circuit resulting in a 3λ resonant frequency shift of nearly 12% at 77 K. By applying a separate dc bias between the microstrip line and the ring, one can optimize their coupling to obtain high Q bandstop resonators with δf n −1 = f 0 /Δf 3dB as high as 12,000. The 3λ resonance was tuned from 15.75 to 17.41 GHz while keeping δf n −1 above 768 over this range. The relevance of these results for practical microwave components will be discussed.