Source/Load-Pull Characterisation of GaN on Si HEMTs with Data Analysis Targeting Doherty Design

Abstract

This paper presents the source/load-pull characterisation of GaN HEMTs on Si substrate, with an analysis of the measurement data oriented to aid the design of Doherty power amplifiers for satellite communication applications in the 17-20 GHz band. In particular, fundamental load-pull, in both class AB and C, is used to identify the output power and efficiency contours and assess the scalability of the performance vs. device size. Second harmonic source/load-pull data is used to determine the harmonic impedance regions to avoid during matching network synthesis. The load-pull data allows to predict the optimum load modulation trajectory to be synthesised in the design phase and the associated performance in terms of efficiency, gain compression and phase distortion.

3–20-GHz GaN MMIC Power Amplifier Design Through a COUT Compensation Strategy

“…Table I shows that the results are comparable to the state of the art, while using a simple design approach and a small size MMIC. The measured results are in rather good agreement with the simulations, except for the discrepancy in the saturated efficiency, which can be justified both by the CW measurements being carried out on wafer directly on a room temperature chuck, without dedicated die attachment, and by the fact that load pull measurements on the same device have shown the large signal model to overestimate both saturated power and efficiency [10].…”

“…To achieve decade-bandwidth performance distributed PAs are typically used, normally in a non-uniform topology to improve output power and efficiency [1]- [4]. Other wideband GaN PAs have been proposed, relying for example on reactive matching [5] or on a reconfigurable dual-band operation [6], covering smaller bandwidths (6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18).…”

High-Gain and High-Linearity MMIC GaN Doherty Power Amplifier With 3-GHz Bandwidth for Ka-Band Satellite Communications

“…The design of a DPA is strongly based on a reliable large signal model, especially in a frequency range where the reactive parasitics of the transistors have a significant effect and contribute to power-and frequency-dependent signal dephasing. Therefore, the choice falls on the combination of four 8 × 100 µm devices in the final stage, for which the foundry provides a nonlinear and thermal model, and a load-pull measurement campaign is performed [7]. The output return loss requirement is rather critical in a DPA since it typically conflicts with the two-point matching requirements needed for the combiner to synthesize the desired load modulation.…”

Millimeter-Wave On-Wafer Large Signal Characterization System for Harmonic Source/Load Pull and Waveform Measurements

“…Harmonic load-pull systems have been reported at mm-wave, these use load diplexers to perform active injection to harmonically tune load impedance. This technique has been demonstrated up to 67 GHz [10].…”