Fast radar power amplifier optimization for bandwidth, efficiency, and spectral confinement using the Smith Tube

The Smith Tube, a three-dimensional cylindrical extension of the Smith Chart, provides a mechanism to simultaneously optimize power amplifier circuit and waveform parameters for radar transmitters. A direct, vector-based search algorithm is presented to find the optimum combination of bandwidth and load impedance for a power amplifier to maximize the waveform bandwidth while meeting requirements on the power-added efficiency and the adjacent-channel power ratio. For this optimization, waveform bandwidth is represented on the vertical axis of the Smith Tube, with the complex load reflection coefficient represented in the horizontal plane. Excellent correspondence is obtained in measurement testing of the algorithm from multiple starting combinations of load reflection coefficient and bandwidth. The results of this work are expected to be useful in real-time optimization of power amplifiers for radar and communications. The algorithm is expected to be useful in optimizing the range resolution of radar transmissions.