The development of a high-efficiency, tunable ferrite frequency doubler operating at 17.0 GHz is described. The optimum efficiencies are from 30 to 40 percent, with incident power levels up to 10 kW peak, 3.0 watts average. The doubler consists of a yttrium-iron-garnet (YIG) disk located at the junction of

and K
u-band rectangular waveguides. Attempts to scale the doubler into the millimeter range are in progress.