Epitaxially grown large area YBCO films are essential for superconducting h
igh frequency devices ag. microstrip filters for telecommunications. Theref
ore, c-axis oriented, 250 to 500 nm thick YBCO films were simultaneously de
posited by sputtering from hollow cylindrical targets on both sides of CeO2
buffered 3 " sapphire wafers. The lateral homogeneity was analyzed by mapp
ing the surface resistance, R, at 145 GHz and 75K. Values of R, below 50m O
mega were reached over the whole area The HF power handling capability was
demonstrated by a break down field higher than 10 mT at 8.5 GHz and 77 K.
In order to demonstrate the quality of our sputtered films with respect to
large area high frequency applications, simple microstrip resonators were p
atterned by UV photo lithography end wet chemical etching. At a circulating
power of up to 1 W, very high unloaded quality factors, Q(0), of up to 320
00 at 4 GHz and 77 K were achieved Above 5 W, Q(0) decreased due to the fie
ld dependence of R, The operation of complex structures was demonstrated by
3 pole and 7 pole bandpass filters operated at 77 K and 2 GHz and 6 GHz, r
espectively. The filters, tuned by brass tuning elements, showed transmissi
on losses of less than -0.3 dB and reflection losses of more than -17 dB.