A monolithic 6 GHz quadrature frequency doubler with adjustable phase offset

A 6 GHz frequency doubler with quadrature outputs generated from a differential single phase input is presented. The phase offset between the in-phase and quadrature outputs can be digitally controlled in linear steps for use in an automated calibration algorithm. The design nominally achieves standard deviations in quadrature phase error and amplitude balance of 0.4° and 0.1dB, respectively. This is demonstrated with a single sideband (SSB) mixer that realizes an average uncalibrated sideband rejection of 48.2 dB which improves to 55.8 dB post-calibration under nominal conditions.