Abstract: This paper presents the design of high efficient w-band doubler, the doubler was built with a GaAs schottky diode. The input and output signal of the compact doubler were fed by finline. For the input power of 100mw, the maximal output power of 3.3mw was obtained at 91.8GHz. From 83GHz to 98GHz, the conversion efficiency was greater than 2%.This doubler can be used to extend U-band signal source to W-band.