Arrays of Josephson junctions coupled by distributed circuits

Both the linewidth reduction and the gain in output power have been analyzed for Josephson-junction arrays with distributed coupling circuits. Different ways of Josephson junction connection to the distributed circuits, as well as both the nonlinear interaction effect and the crucial role of high frequency losses have been studied. It has been found that the contradictory requirements to the junctions as nonlinear active elements on (i) low wave reflection and (ii) high total power produced can be fulfilled by an increase in number of Josephson junctions with a proper impedance value. The first condition is necessary to provide the most reduction in the linewidth, and the second one is needed to compensate for the power output. An array of biased in parallel bicrystal Josephson HTSC junctions coupled by a microstrip circuit has been fabricated and preliminary tested.