The 0.35‐μm SiGe BiCMOS high linearity Gilbert upconverters are demonstrated in this article by utilizing NMOS and PMOS transconductance amplifiers (TCAs), respectively. To improve the linearity of a Gilbert upconverter, the IF input TCA is replaced by a bias‐offset differential pair. A reactive LC current combiner is used as the load of the Gilbert mixer to double the output current. The upconverter with an NMOS TCA achieves the conversion gain of −4 dB, the OP1dB of −11 dBm, and the OIP3 of 5.5 dBm, whereas the other one with a PMOS TCA has the conversion gain, OP1dB, and OIP3 of −6 dB, −11 dBm, and 9.5 dBm, respectively. Furthermore, the LC current combiner can be extended to a dual‐band version. The 2.4/5.7 GHz dual‐band upconverter is also demonstrated in this work. The conversion gain at 2.4/5.7 GHz is −3/−3.5 dB with the OP1dB of −15.5/−15 dBm and the OIP3 of −2.5/−3 dBm, respectively. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1718–1722, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24433