Low phase nonlinearity is important criteria in power amplifier (PA) especially in ultra-wideband system so that the output will remain original identity. Up to date there is no analysis study have been established in achieving low group delay PA in UWB technology, therefore this paper is to examined the factors that affect low phase nonlinearity in 3.1-6.0 GHz PA using two-stage amplifier with shunt resistive feedback technique for UWB system. The proposed PA adopts two stages amplifier together with inter-stage circuit to obtain adequate flatness of the gain. The shunt resistive feedback topology is used to have very wide input matching. The inductive peaking technique and Class A amplifier is adopted to obtain high gain flatness, low phase nonlinearity and linearity simultaneously. The analysis shows that the dominant factor is identified for low phase nonlinearity in UWB PA. The proposed PA achieves the average gain of 10±1 dB, S11<-6dB, S22< -7 dB, and phase nonlinearity of ±195.5 ps. A good linearity and power consumption are obtained. Therefore, these key performance factors of low phase nonlinearity can be applied to facilitate other researchers working in the area of power amplifier circuit design.
