Harmonic Included CSWPL Model for Broadband PA Design Based on GaN HEMTs

In this work, we present the development and the validation of a harmonic-included behavioral model based on the canonical section-wise piecewise linear (CSWPL) function. The validity of this new model is verified in terms of dc and RF behavior with both fundamental and harmonic load-pull simulation data of a 10-W gallium nitride (GaN) packaged transistor considering a wide range of input power. The proposed model can capture the harmonic behavior of the device under test (DUT) more accurately than the existing fundamental-only CSWPL model, which is very helpful for power amplifier (PA) designers. Furthermore, comparisons between the proposed model and the existing harmonic-included canonical piecewise linear function (CPL) based quadratic poly-harmonic distortion (QPHD) are also given. The input power interpolation and extrapolation capabilities of both models are tested and compared. According to the results, the proposed model provides more accurate predictions. The maximum interpolated prediction relative error is around 5%, which is 7% lower than the CPL-QPHD model; while its maximum extrapolated prediction relative error is about 8.7%, which is 9% lower than the CPL-QPHD model. Additionally, the proposed model is implemented in the Keysight advanced design system (ADS) simulator by using the frequency-domain defined device (FDD), and then used in a broadband PA design. According to the achieved results, the fabricated GaN-based PA has a power-added efficiency (PAE) greater than 60% and an output power of more than 40 dBm over the frequency range of 2 to 3 GHz. Simulation results of the proposed model match very well with the actual measurements of real PA. This demonstrates the suitability of the presented model for practical PA applications.