A low-noise broadband SiGe mixer for 24GHz ultra-wideband automotive applications

The design and measured results for a broadband, miniature active mixer for use in a direct-down conversion I/Q receiver is presented. The high instantaneous bandwidth of a short-pulse radar system requires a broadband frequency domain response. In addition, the cost constraints and thermal demands require the RF front-end of the automotive radar system to be highly integrated, and energy efficient. The mixer displays a conversion gain of over 20 dB - including the contribution of the base band output stage - over the 3 GHz-35 GHz frequency range for an IF frequency of 500 MHz and an LO drive of 0 dBm. The double-side band (DSB) noise figure of the mixer is less than 8 dB at 24 GHz. The circuit occupies less than 0.075 mm/sup 2/. The entire mixer, including biasing circuitry, requires only 22 mA from a +5 V supply.