Designing a broadband amplifier without loadpull

The design of a broadband amplifier without using loadpull is described. This approach relies on a coarse model of the power amplifier, in which matching networks are represented by rational polynomials and the device by its large-signal model. A simultaneous search of the impedance space and possible matching networks via particle swarm optimization can identify the design solution. The prototype amplifier demonstrates an outstanding gain of 12.8 – 14.9 dB with ±1 dB gain flatness, output power greater than 40 dBm, and efficiency between 51-70% over a target frequency range of 2.4-4.6 GHz, the highest frequency range using the CGH40010 to date. The measured two-tone third-order intermodulation (IMD3) is lower than -20 dBc up to an average output power of 38.7 dBm for frequencies less than 4.2 GHz. The impedances obtained by our approach converge within the high-efficiency region identified by the conventional load-pull approach.