A Highly Linear Direct-Conversion Transmit Mixer Transconductance Stage with Local Oscillation Feedthrough and I/Q Imbalance Cancellation Scheme

Abstract

A linear transconductance stage with process insensitive gain control and gain insensitive output offset current is proposed. A calibration scheme to remove the LO feedthrough (LOFT) and I/Q imbalance is also introduced. The prototype achieves 3 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">rd</sup> -order IMD suppression better than 52dBc, LOF suppression better than 32dBc, and image rejection better than 46dBc for all gain settings. The transmit chain achieves an 802.11a EVM of < -40dB