Robustness Enhancement Technique and Fine-Tuning Technique of IIP3 for Wideband LNTA

Abstract

Wideband low noise transconductance amplifier(LNTA) is an essential part of current-mode SAW-less receivers, and its linearity design is the most challenging. Many low noise amplifier(LNA) linearization techniques(LT) are also applicable to LNTA, such as the famous derivative superposition(DS) and post-distortion(PD). But these techniques are not robust and are prone to failure. This paper is based on a noise canceling(NC) LNTA prototype and improves its performance in several aspects with some unique analysis. The robustness of the IIP3 of the original LNTA is enhanced by using a self-biasing network. By changing the connection of the DS MOSFETs, the sensitivity of the IIP3 to the load resistance is reduced. Finally, by adopting PD as a fine-tuning technique in the right place, the IIP3 of the LNTA is improved to more than 20dBm.