High IIP2 CMOS doubly balanced quadrature sub-harmonic mixer for 5 GHz direct conversion receiver

by 1978- Upadhyaya, Parag

by Parag Upadhyaya, M.S. Washington State University May 2005 Chair: Deukhyoun Heo This thesis presents a new low power and high IIP2 0.25-µm CMOS doubly balanced sub-harmonic mixer for 5 GHz Industrial Scientific Medical (ISM) band direct conversion - zero IF receiver. Using a ½X LO frequency generation scheme the sub-harmonic mixer overcomes LO self-mixing problem common in conventional direct conversion receivers (DCR). Measurement shows the sub-harmonic mixer is able to achieve voltage conversion gain of 8.2 dB, input compression P1dB of –8 dBm, IIP3 of –2.5 dBm and IIP2 of 36 dBm while consuming only 1.35 mA of DC current. Measured results correlate well with simulated results where the mixer is able to achieve high IIP2 of 55.3 dBm, IIP3 of –6.5 dBm, P1dB of –12 dBm and voltage conversion gain of 8 dB including 1% gm mismatch, 0.5% load mismatch and 2º LO phase error. The mixer takes up less than 1mm2 of silicon real estate including test die pads. This work also gives an overview of direct conversion RF transceiver architecture and its design challenges and potential solutions for addressing 1/f noise, DC offset, 3rd order intermodulation products and more importantly 2nd order intermodulation in the mixer. Two novel CMOS doubly balanced quadrature sub-harmonic mixer architectures, which have high v immunity to 2nd order intermodulation products and achieves high IIP2 needed for DCR applications, are presented. While sub-harmonic are generally associated with microwave frequency design in 10s and 100s of gigahertz, a novel topology shows its viability for 5 GHz ISM band applications, which includes IEEE 802.11a and Hiperlan2 wireless LAN standards in the US and Europe, respectively. The design emphasizes trifecta of low power, low voltage, and low cost sub-harmonic mixer design that can be applied to CMOS and SiGe technologies. The mixer theory and design methodology presented can be also be followed as a design guide for developing high performance mixer circuits for many applications including superheterodyne transceivers and are not just limited to homodyne transceivers. vi