A 10.2-12.6 GHz balanced heterojunction bipolar transistor (HBT)-high electron mobility transistor (HEMT) frequency tripler is presented. A pair of common-base/common-emitter HBTs is used to generate in-phase and out-of-phase harmonics. Two bandpass filters are utilised as matching networks to enhance the harmonic suppression. A common-gate/common-source HEMT active balun is employed to combine the third harmonic in-phase and provide conversion gain. The proposed frequency tripler shows a conversion gain of 2.8 dB, a fractional bandwidth of 21.2% and a fundamental suppression higher than 47 dB.