An 8–10 GHz upconversion mixer, with a low-frequency calibration loop resulting in better than −73dBc in-band spurs

An 8–10 GHz X-band upconversion quadrature mixer stage implemented in 250 nm SiGe BiCMOS is presented. Orthogonality of the spurious responses caused by clock feed through, I/Q mismatch and baseband harmonics after self-mixing was exploited to realize a baseband calibration scheme reducing all in-band spurs down to below −73dBc, for baseband signals up to a bandwidth of 2MHz and with an IF center frequency up to 100MHz. Utilizing a low-frequency output spectrum analysis of an integrated self-mixer at the upconversion mixer output for calibration, eliminates the need for expensive microwave frequency spectrum analyzers.