A Systematic Technique for Designing Wideband RF Power Amplifiers

The objective of this article is the design and implementation of wideband RF power amplifiers that can be used in different solid-state wireless transmitting systems. A systematic technique has been devised and confirmed. This technique uses the RF power transistor´s optimum load and source impedances, obtained from the load-pull procedure, to characterize the RF power device at the required output power level and operating frequency band. The input and output device impedances are taken as the complex conjugates of the optimum source and load terminations and are stored in external data files as one-port networks. The input and output matching networks can then be optimized separately, using a suitable microwave circuit optimization program, to achieve the required matching between the stored impedance data and the terminal 50-Omega impedances across the frequency band of interest. The microwave CAD program Touchstone has been utilized to implement this technique. As a practical implementation to the proposed design procedure, a 1-W class-C power amplifier circuit was designed and built to operate within the communication band 225-400 MHz and to achieve a power gain of 10-dB