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In-phase/quadrature (I/Q) mismatch is a key problem in zero intermediate frequency (ZIF) receiver architectures. Although integration and careful layout can alleviate I/Q mismatch, circuit and system level calibrations are also needed due to process variations and variable operating conditions. The amplitude im- balance between I/Q channels was calibrated using a modified R-2R ladder to achieve fine linear-in-dB variable gain. A downconversion mixer working in the 2.4-GHz band was developed for a wireless local area network (WLAN) ZIF receiver using 0.25-μm complementary metal-oxide semiconductor (CMOS). The two- stage mixer configuration relaxes the tradeoff between noise and linearity. Experimental results verify the fine linear-in-dB variable conversion gain of the mixer, which can also be used as part of an automatic gain control (AGC) loop.
In-phase / quadrature (I / Q) mismatch is a key problem in zero intermediate frequency (ZIF) receiver architectures. Although integration and careful layout can alleviate I / Q mismatch, circuit and system level calibrations are also needed due to process variations and variable operating conditions. The amplitude im- balance between I / Q channels was calibrated using a modified R-2R ladder to achieve fine linear-in-dB variable gain. A downconversion mixer working in the 2.4-GHz band was developed for wireless local area network (WLAN) ZIF receiver using 0.25-μm complementary metal-oxide semiconductor (CMOS). The two-stage mixer configuration relaxes the tradeoff between noise and linearity. Experimental results verify the fine linear-in-dB variable conversion gain of the mixer , which can also be used as part of an automatic gain control (AGC) loop.