Optimization of power-amplifier load impedance and waveform bandwidth for real-time reconfigurable radar

To create a reconfigurable radar transmitter, the power amplifier circuitry and waveform must be able to adjust in real time to changing operating frequencies and spectral requirements. For range radars, better range resolution can be accomplished by using waveforms of higher bandwidth. In this case it is desirable to maximize the chirp waveform bandwidth while maintaining spectral compliance and meeting power-added efficiency requirements. Based on the concept of the Smith Tube (presented in a recent conference article), this article describes a new intelligent, vector-based search for the load impedance and waveform bandwidth. The search provides the largest possible bandwidth while maintaining the power-added efficiency and adjacent-channel power ratio within specified requirements. The algorithm is demonstrated in measurement with multiple starting impedances and bandwidth search ranges, and consistently accurate and useful results are obtained. Multiple iterations of the two-part search can be performed for increased precision if the time needed to take additional measurements can be tolerated.