In this paper, we study a high gain frequency tripler with high fundamental and harmonics rejection designed for K/Ka-band signal generation. To prove the concept, the circuit is implemented in a 130-nm SiGe-BiCMOS technology. It is based on a cascode class-A differential amplifier adopting an output bandpass filter to achieve high suppressions of fundamental and harmonics. At the input, an active balun converts the single-ended input signal to a differential signal and drives the frequency tripler into the non-linear region. To improve the conversion gain (CG), the proposed frequency tripler is followed by a buffer stage and a totem pole (TP) output stage. It offers a peak output power of −3 dBm at 26.7 GHz with a 3-dB output frequency range between 24 GHz to 34.5 GHz, and achieves a peak CG of 27.2 dB at an input power level of −33 dBm. Compared to the third harmonic, the fundamental frequency is suppressed by up to 32 dB while the second harmonic is reduced by a maximum of 45 dB.