A high IIP2 Gilbert mixer-based downconverter design for direct-conversion WiMAX receivers

A 2.6 GHz Gilbert mixer-based downconverter RFIC is designed and implemented in a 0.15 ¿m InGaAs pseudomorphic high electron mobility transistor (pHEMT) foundry process. A crucial goal for the design is to achieve high input second-order intercept point (IIP2) that is required in a direct-conversion WiMAX receiver. The adaptive biasing at the switching stage of this downconverter is used to compensate the unbalance of the input LO signals for improving the IIP₂. The technique presented here enhances the IIP₂ by 18.8 dBm without at the expense of reducing the conversion gain.