Fast reconfiguration in real-time transmitter amplifier impedance optimization using S-parameters

Reconfigurable devices in cognitive and adaptive radio and radar transmitters must be able to reconfigure power amplifier load impedance quickly in real-time to accommodate changes in operating frequency and spectral performance. This paper focuses on the use of small-signal S-parameters, which provide the optimum small-signal gain load termination, to calculate an intelligent starting point for the real-time impedance search. Use of the S-parameter calculated starting point is shown to produce good results for optimizing the power-added efficiency of the power amplifier device in its nonlinear operating regime. As such, using only the S-parameters of the device, the search can be initiated at an impedance close to the optimum, reducing the number of measurements necessary for reconfiguration and maintaining high-efficiency device performance during the search.