Kinetic-inductance based superconducting microwave circuits: filters, couplers, and other components

It is pointed out that superconducting microstrip transmission lines operating in the kinetic-inductance limit have the potential to reduce the size and weight of microwave circuits by several orders of magnitude. Since the phase velocity of these guided wave structures is up to a hundred times less than in free space, the electrical length of distributed elements is similarly reduced. Simple transmission lines have been fabricated from both low- and high-transition-temperature superconductors while more complicated circuits, such as filters, with a good match to 50-Ω coax have been fabricated with the low-transition-temperature superconductors. Also, a novel coupled-line topology, compatible with these structures, has been studied analytically