Hilbert fractal curves for HTS miniaturized filters

This work presents compact high temperature superconductor microstrip resonators based on Hilbert fractal curves. Their miniaturization performance has been investigated, emphasizing the parameters which allow to obtain a good trade off between compact size and quality factor. Hilbert resonators with different arrangements have been designed and assessed by using full wave simulators. In order to experimentally verify our analysis, a four pole quasi elliptic filter, in the cascade quadrupled configuration, with f₀ close to 2.45 GHz, have been fabricated by patterning a 10×10 mm² YBCO film on MgO substrates. Minimum insertion losses of the order of (0.1-0.2) dB have been measured.