A new approach for ultra-wideband continuous class B/J power amplifier design and fabrication based on increasing efficiency in power loss-less case

A new theoretical approach to designing an ultra-wideband continuous class B/J power amplifier is presented. In the conventional design of continuous class J, the maximum accessible bandwidth is limited to one octave, which is equivalent to 66 % fractional bandwidth. In this paper, it will be shown by reforming the voltage expression of resistive-reactive class J, high efficiency continuous class B/J power amplifier design can be realized sothat the output power level maintains across more than one octave. Using a new defined correction factor in the output voltage of resistive-reactive class J while the third harmonic element with a proper coefficient is added to it, not only could help to decrease the compromise between the design space and efficiency but also improve the PA output power than conventional one. To check the feasibility of the suggested approach and validate the theoretical and simulation results, a broadband PA using CGH40010F GaN transistor in 0.5-2 GHz is designed and fabricated on RO4003c substrate with 20 mil thickness. The measured 39.8-42.2 dBm output power with 63.68 % average drain efficiency over more than 120 % fractional bandwidth confirmed both the theoretical and simulation results.