Inductive coupling for imbalance improvement in a UWB balun employed in a folded cascode mixer

A folded cascode single-ended input, differential output Ultra Wideband (UWB) mixer circuit with active balun embedded in the transconductance (g_m) stage is proposed, analyzed and simulated in post layout level. The balun solution is based on differential topology. Significant improvement for phase and amplitude balance is observed by applying coupling between inductive loads, which is achieved in practice by centered tapped inductor used as load. The post layout simulation results for the mixer show a voltage conversion gain (CG) ranging from 10 to 18 dB, a double sideband Noise Figure (NF_dsb) less than 14dB while the linearity metrics are better than -12.5 and 1.6dB for the 1dB compression point and the IIP3 respectively for the frequency range between 3.1 and 10.6GHz. The chip area is compact and equal to 0.086mm² (core only), while the circuit draws 7mA from a 0.7V supply.