This paper focuses on the determination and analysis of an accurate small-signal equivalent circuit for gallium-nitride high electron-mobility transistors under different bias conditions. Our experimental results show that a channel capacitance has to be added to the conventional forward "cold" model for modeling the device-under-test. The validity of the proposed extraction procedure has been verified by the very good agreement between simulated and measured scattering parameters up to 50 GHz

This paper presents a new modeling approach accounting for the nonlinear description of low-frequency dispersive effects (due to thermal phenomena and traps) affecting electron devices. The theoretical formulation is quite general and includes as particular cases different models proposed in the literature. A large set of experimental results, oriented to microwave GaN power amplifier design, is provided to give an exhaustive validation under realistic device operation.

This article presents a novel technique to remove the radar self-motion effects (RSMs) for an accurate detection of human vital signs. As opposed to the commonly used techniques, the proposed approach does not require any additional sensor, and instead, it extracts the RSM from the signals reflected by stationary clutters. Since the proposed technique requires to accurately identify the clutter range, two procedures for its automatic identification are proposed, aimed to detect both small and large radar motions. Besides allowing precise and reliable vital sign detection, it provides a compact, lightweight, comfortable, and cost-effective solution since potentially intrusive additional sensors are not required. Simulations have been carried out for validating the proposed approach, with an insight on the influence of different clutter radar cross sections on the sensitivity. Moreover, the effectiveness of the RSM cancellation has been experimentally demonstrated, showing its suitability for different applications, e.g., radar on moving platforms, vibrating tools, handheld devices, unmanned aerial vehicles, and cars.

The purpose of this letter is to present an experimental analysis of the temperature effects on the small-signal equivalent circuit of a GaN HEMT. With the aim of contributing to the exploration and advancement of this technology for high-power and high-temperature applications, the major intrinsic RF figures of merit together with the positive derivative of the real parts of the impedance parameters versus frequency are deeply investigated versus ambient temperature.