Broadband SiGe HBT Gilbert downconverter with 1.8 to 36 GHz integrated dual Marchand balun

A broadband Gilbert downconverter with an integrated dual Marchand balun (balanced to unbalanced transformer) is demonstrated by using 0.35 m SiGe heterojunction bipolar transistor (HBT) technology. A dual Marchand balun consisting of a lower band balun and an upper band balun is employed in the LO stage of the downconverter to maintain balanced LO signals from 1.8 to 36 GHz. The broadband downconverter has peak conversion gain of 3 dB at RF 3 GHz and 3 dB bandwidth of 1.8 to 20 GHz at 3.3 V DC supply.