A frequency doubler from 27 to 41 GHz fabricated in 0.13-µm SiGe BiCMOS technology with a maximum output power of 8 dBm and a power added efficiency (PAE) of 17.5% at dc power consumption of 35 mW is presented. It consists of a balun, a driver amplifier (DA), a common-base (CB) core and a medium power amplifier. The CB topology with balun is designed for wider bandwidth and better matching. The measured results showed that the doubler presents a gain of 16.8–19.8 dB, an output power of 1.3–4.3 dBm, and a fundamental rejection of better than 25.7 dB from 27 to 41 GHz with −15.5 dBm input power. The chip size is 0.75 × 0.45 mm2.