An I/Q active balanced harmonic mixer with IM2 cancelers and a 45/spl deg/ phase shifter

An active I/Q harmonic mixer with IM2 cancelers and a 45/spl deg/ phase shifter for direct downconversion has two advantages. One is small self-mixing dc offset because of harmonic mixing, and the other is small and frequency insensitive 2/sup nd/ order intermodulation (IM2). The proposed 45/spl deg/ phase shifter has low element sensitivity. The measured 37 dBm IIPB and 3/spl deg/ phase error indicate that the integrated direct downconverter with harmonic mixers is applicable even for QPSK signals that have an amplitude modulation component.