A Systematic Approach for the Design of Broadband, High Efficiency, High Power RF Amplifiers.

This paper demonstrates a systematic approach for the design of broadband, high efficiency, high power, Class-AB RF amplifiers with high gain flatness. It is usually difficult to simultaneously achieve high gain flatness and high efficiency in a broadband RF power amplifier, especially in a high power design. As a result, the use of computer-aided simulation is most often the best option to achieve these goals, but a systematic approach with an appropriate initial value is necessary to rapidly converge the simulation results. In this way, the above objectives can be achieved with minimum trial and error. Signal gain variations are reduced over a wide bandwidth using a proper pre-matching network. Source and load impedances are satisfactorily obtained from small-signal and load-pull simulations, respectively. Two high-order Chebyshev low-pass filters are employed to provide optimum input and output impedance matching networks over 100-500 MHz. The resulting power amplifier yields good performance over an octave of bandwidth, 44.2-44.8 dBm output power at the 1-dB gain compression point, 16.5 ± 0.3 dB gain, and greater than 52% power-added efficiency throughout the band. Using a non-linear model of the transistor and an EM simulation for the substrate, it is observed that the simulated results are in close agreement with measured results. [ABSTRACT FROM AUTHOR]