A High Efficiency 25W Class-AB and Class-F GaN High Power Amplifier at 10 GHz for Satellite Applications

With the advent of GaN technology, the use of GaN based RF Solid State Power Amplifiers (SSPAs) has increased manifolds in satellite communications, radar applications and electronic warfare. But designing a highly efficient (e.g. Class-F) High Power Amplifier (HPA) at high frequencies (i.e. 10GHz and above) still remains a daunting task. Considerations such as an accurate device model, parasitic effects, device selection, load and source Pull analysis, circuit topology, biasing techniques, input and output matching networks and thermal management make SSPA design a challenging endeavor. At higher frequencies (i.e. C-Band and above), Class-F amplifiers are predominately developed using MMICs because transistor’s internal parasitics affect the Harmonic Control Networks (HCNs). Therefore, in order to use a packaged device for Class-F design at X-Band, transistor’s parasitics have to be extracted and embedded in the HCN design. This work presents the design and characterization of a 10 GHz GaN based 25W High Power Amplifier (in Class-AB and Class-F classes) for satellite and radar applications by embedding internal parasitics of Qorvos’s TGF2979 transistor in the HCN. The paper discusses design considerations, presents simulation results for Class-AB and Class-F classes, compares the results with existing literature and concludes with the performance evaluation of the power amplifier using Keysight’s Advanced Design System (ADS). The achieved efficiency for Class-F is 56% which is significantly greater than that achieved by Class-AB implementation in same transistor’s evaluation board (i.e. 31.25%), in datasheet (i.e. 40.8% max.) and in available reference design [3] (i.e. 42.3 at 5.8 GHz%).