| GaN HEMTs will likely become the solid-state device of choice for power in microwave and millimeter-wave circuits. These products, such as base stations and other communication systems, tend to be space-constrained. Hence solutions continuously move from a hybrid (circuit board plus components) approach to a microwave monolithic integrated circuit (MMIC). To be successful in a MMIC design, GaN will have to perform well in other areas besides power. One of the most crucial metrics of a system is its noise. The noise of GaN devices and circuits has only been critically examined in the last five years.; This work will investigate several aspects of the noise performance of GaN HEMTs. Measurements of noise figure (NF) and low-frequency noise (LFN) are used to characterize devices. Modeling useful for calculations and circuit simulation are applied, with some introduced. Several studies of NF and LFN are presented. Some confirm or challenge previous publications while others are new observations. Two differential oscillators were built to characterize the phase noise. As it is believed that GaN HEMTs will replace GaAs HEMTs in various applications, the NF, LFN, and phase noise of the two are compared. |
