This article describes a simple and accurate behavioral model of the radio frequency metal oxide semiconductor field effect transistor (RF MOSFET) to accurately describe the higher-order derivatives of the transconductance of the RF MOSFET using short channel I-V equation based on unified charge control model and improved mobility model. Based on this model; a simple procedure for extracting the model parameters from the measured data is proposed and implemented. The extracted results are physically meaningful and good agreement has been obtained between the model and measured data of distortion characteristics. Also, the proposed behavioral model accurately describes the transconductance reduction with improved mobility model.