4H - SiC material and MESFET power device are analyzed according to the operating environment of the airborne phased array radar. A comparison between SiC and GaAs device shows that this novel device finds wide applications in the field of airbome phased array radar. An improved nonlinear large signal model of SiC MESFET for device CAD technology is also developed , which is a model based on experimental measurement. It is used to analyze the power performance of device through SPICE simulator. A good agreement between simulations and measurements is obtained.