A wide-bandwidth Si/SiGe HBT direct conversion sub-harmonic mixer/downconverter

A wideband sub-harmonic mixer/direct-conversion downconverter is implemente d in a Si/SiGe HBT technology, with improved rejection of the local oscilla tor (LO), high input intercept point, and low current requirements, The cir cuit utilizes a combination of phase shifters operating at 45 degrees and 9 0 degrees to achieve better than 33-dB input-referred rejection of the LO, The measured third-order input intercept point (IIP3) was approximately -3 dBm and the second-order input intercept point (IIP2) was roughly 35 dBm, w ith a measured double sideband (DSB) noise figure of 7.8 dB, A comparison w as made between devices of differing germanium concentration in the base, a nd the devices with higher Ge content exhibited improved noise figure and g ain. Each mixer required approximately 2.8 mA from a 3.3-V supply.