125-PERCENT BANDWIDTH SUPERCONDUCTING CHIRP FILTERS

A previously-presented synthesis procedure is employed to design ultra -wide bandwidth linear chirp (quadratic phase) filters. The synthesis procedure eliminates the harmonic responses, theoretically permitting a bandwidth close to 200% (i.e. the frequency band zero to twice centr e frequency) without aliasing problems. It can also be configured so t hat the chirp Fresnel ripples are relegated to the time domain. (This avoids a large frequency domain ripple which in a low-loss device woul d create the inadmissible requirement that gain at the peak of the rip ple be greater than unity.) The design procedure is equally suitable f or single and dual delay line implementations. Measurements to be pres ented will be on superconducting single-track coplanar and microstrip filters, patterned from epitaxial YBCO films sputtered onto 2-inch dia meter LaAlO3 substrates. They have a centre frequency of 8 GHz, bandwi dth of 10 GHz (125%), and a TB product of 80.