Comparison of 24 GHz low-noise mixers in CMOS and SiGe:C technologies

This paper presents a comparison of two low-noise mixers designed in Infineon´s 0.13 mum CMOS and 0.35 mum SiGe:C processes. The mixers have been optimized for low-noise performance for narrow-band 24 GHz applications. Both circuits are based on the Gilbert cell and have similar topology. The chips are designed to fulfill high robustness requirements for industrial and automotive applications. The CMOS mixer provides a conversion gain of 7 dB and a double-sideband (DSB) noise figure of 7.5 dB . To the authors´ knowledge, this is the lowest reported to date CMOS noise-figure in this frequency range. The SiGe mixer offers a higher gain of 10.5 dB and a lower DSB noise figure of 4.7 dB . Furthermore, it has better linearity of -7.2 dBm compared to -12 dBm input-referred 1dB compression point, measured for the CMOS circuit. The CMOS and SiGe circuits consume 2.8 mA from 1.5 V and 12 mA from a 3.3 V supply, respectively. Performance variation of key parameters has been analyzed in measurement over a wide range of temperatures from -40degC to 12 degC. The SiGe chip offers better performance stability over temperature.