A 215~230 GHz Schottky varactor-based frequency doubler utilizing novel four-port balanced configuration has been developed with improved conversion efficiency and power-handling capability. The proposed doubler， featuring doubled number of anodes in conventional balanced ones， could inhibit the odd- and fourth-order harmonics. Thus， better conversion efficiency and doubled power handling capability could be achieved. At room temperature， the fabricated doubler exhibits a ~39.5% peak conversion efficiency （@218 GHz） for an input power of 196~340 mW， which is proved to be a perfect solution for the generation of high power terahertz waves even at higher frequencies.