Key Aspects for Characterizing Device Inherent IMD in GaN HEMTs

The paper proposes an IMD characterization methodology representing a further refinement in the state-of-the-art of source-/load-pull for precise evaluation of intrinsic linearity in GaN HEMTs for 3G wideband applications. Presenting constant IF and RF load across wide modulation bandwidth is extremely difficult. By mimicking the amplifier environment, the RF bias tee which has significant influence on measured IMD products due to its IF and RF terminations, should be placed in the proximity of the device reference plane for acquiring true IMD characteristics of the active device. This has demonstrated means to mitigate IF harmonics at the baseband and IMD products at RF. As a consequence, a straightforward PA design guidelines are deduced through experimental optimization of bias and matching networks.