A balanced push-push frequency doubler has been demonstrated in 0.25-µm SOI (Silicon on Insulator) SiGe BiCMOS technology operating from 22GHz to 29GHz with high fundamental frequency suppression and high conversion gain. A series LC resonator circuit is connected in parallel with the differential outputs of the doubler core circuit. The LC resonator is effective to improve the fundamental frequency suppression. In addition, the LC resonator works as a matching circuit between the output of the doubler core and the input of the output buffer amplifier, which increases the conversion gain of the whole circuit. A measured fundamental frequency suppression of greater than 46dBc is achieved at an input power of -10dBm in the output frequency band of 22-29GHz. Moreover, maximum fundamental frequency suppression of 66dBc is achieved at an input frequency of 13GHz and an input power of -10dBm. The frequency doubler works at a supply voltage of 3.3V.