Algorithm for Fast Simultaneous Harmonic and Fundamental Impedance Tuning in Reconfigurable Radar Transmitter Power Amplifiers

Strategic choice of harmonic load impedances for a radar transmitter power amplifier can increase both the power efficiency and range of the transmitter. With the advent of high-power tunable circuitry, possibilities exist for real-time reconfiguration of the power amplifier fundamental and harmonic impedances to maximize output power and efficiency over changes in frequency and array scan angle. We present, for the first time, a search algorithm that performs simultaneous, fast tuning of the power amplifier fundamental- and harmonic-frequency load impedances. Simulation results demonstrate a 20% PAE increase for the transistor model examined over fundamental tuning alone. In addition, re-tuning after changing frequencies from 500 MHz to 300 MHz is shown to provide a 30% PAE improvement at the second frequency compared to using the same reflection coefficient as the first frequency. These improvements demonstrate the need and benefits of a fundamental and harmonic frequency reconfigurable radar transmitter amplifier in increasing the efficiency and radar range of the transmitter.