An Optimized-Load-Impedance Calculation and Mining Method Based on I–V Curves: Using Broadband Class-E Power Amplifier as Example

Broadband power amplifier (PA) designs are usually based on optimized-load-impedance (Zopt) searching, which can be guided by PA theories or a load-pull method. After practical devices' internal dc I-V curves and package parasitics are known, a direct impedance calculation method is realized in this paper to offer an alternate option. This method can offer relatively accurate Zopt solutions, which can satisfy both operation-mode and performance requirements for a practical device. Following this large-signal impedance calculation method, waveform regulations can be added to the design steps to realize a specific PA operation-mode through a robust and fast small-signal S-parameter simulator. A waveform-guided perturbation and selection process is introduced to expand the impedance space further. A broadband quasi-class-E PA example, across 1.4 to 2.4 GHz, is given to demonstrate this method. Its output matching network is designed accordingly to fit into the expanded impedance space, and its theoretical performances are verified by harmonic balance simulations and measurements. Finally, this PA is fabricated and measured to offer 39.0 to 40.9 dBm power, 11.6 to 14.0 dB gain, and 73% to 83% drain efficiency in its frequency band.