Engineering and Technology Journal Vol. 38, Part A (2020), No. 02, Pages 211-225 Engineering and Technology Journal Journal homepage: engtechjournal.org 211 Publishing rights belongs to University of Technology’s Press, Baghdad, Iraq. An Analytic Design Approach to Inverse Class-F RF Power Amplifiers Firas M. Ali a* , Mahmuod H. Al-Muifraje b , Thamir R. Saeed c a Ph.D. Student, Dept. of Electrical Engineering, University of Technology, 30204@uotechnology.edu.iq b Assist. Prof., Dept. of Electrical Engineering, University of Technology, 30207@uotechnology.edu.iq c Professor, Dept. of Electrical Engineering, University of Technology, 50257@uotechnology.edu.iq *Corresponding author. Submitted: 12/05/2019 Accepted: 13/07/2019 Published: 25/2/2020 KEYWORDS ABSTRACT Class-F -1 , GaN HEMT, Harmonic Impedances, High Efficiency, RF Power Amplifier. The design of high efficiency inverse class-F (class-F -1 ) radio frequency (RF) power amplifiers includes extensive measurements to characterize the RF power device by means of the empirical load-pull test setup. This paper presents an alternative characterization approach based on evaluating the load impedances analytically at the desired harmonic frequencies for a high electron mobility transistor (HEMT) in terms of the internal and package elements of the active device. It additionally provides a method for extracting the parasitic elements of the power device as well as determining the optimum load-line resistance using the transistor manufacturer’s large signal model. A new topology for the output matching circuit is also proposed with its synthetic procedure to present the appropriate harmonic load impedances. To verify this methodology, a 900 MHz inverse class-F power amplifier circuit was designed and its performance was tested with the aid of the Keysight ADS software. The simulation results showed an output power of 38 dBm, a power gain of about 13 dB, DC-to-RF efficiency greater than 87%, and an acceptable level of linearity for both GSM and CDMA modulated signals. How to cite this article: F. M. Ali, M. H. Al-Muifraje and T. R. Saeed, “An Analytic Design Approach to Inverse Class-F RF Power Amplifiers,” Engineering and Technology Journal, Vol. 38, Part A, No. 02, pp. 211-225, 2020. DOI: https://doi.org/10.30684/etj.v38i2A.301 1. Introduction Highly efficient RF/microwave power amplifiers are being progressively used in contemporary solid- state radio transmitters to reduce power consumption and increase battery life [1]. The class-E, class- F, inverse class-F, and class-J are among the widely used modes of operation in high efficiency RF power amplifiers. In class-F/F -1 power amplifiers, the power transistor is operated as a non-linear current source with certain harmonic terminations at the transistor output. In ideal class F -1 power