High-power HTS microstrip filters for wireless communication

We report narrowband microstrip filters with low insertion loss and high power-handling capabilities made from high-temperature superconducting (HTS) films. One interdigital filter that uses HTS films for both the microstrip and ground plane has 0.6% bandwidth (BW), centered at 2 GHz, with an insertion loss of 0.4 dB. The third-order intercept of the filter is 35 dBm at 77 K and 40 dBm at 60 K. Another filter with 0.7% BW and wider linewidth for higher power handling has an insertion loss of 0.4 dB. The measured third-order intercept is 39 dBm at 77 K and 64 dBm at 56 K. We also report a more compact forward-coupled microstrip filter which consists of a parallel array of fully aligned half-wavelength resonators. The filter, which uses a YBCO microstrip and silver ground plane, has a 0.6% bandwidth centered at 2 GHz. The insertion loss is 4.5 dB, mainly caused by the silver ground plane.<>