The use of a resistive shunt is one of the simplest and most used methods for measuring current in an electronic device. Many researchers use this method to measure drain current during short-circuiting of fast devices such as GaN HEMTs. However, the high switching speed of these devices together with the non-ideality of the shunt resistors produces an overestimation of the current in the initial phases of the transient. In this paper, a passive compensation network is proposed, which is formed by adding an inductor to the voltage measurement circuit and allows an accurate measurement of the current using the resistive shunt even in the presence of very fast devices. The proposed method is validated by simulations and experimental measurements.

Commutations of power IGBT modules used in power converters cause high voltage and current gradients in the collector waveforms, which can generate and irradiate very high electromagnetic noise levels. An innovative experimental-simulative method is presented, which is able to predict irradiated noise levels during converter operation: such method allows power electronics designer to have a proper and simple method to predict spectrum and amplitude of irradiated noise during converter operation, in order to ensure a direct compliance with the enforce normative. The irradiated noise is generated by high frequency conducted current flowing in IGBT module and in the converter. Frequency and amplitude of the internal oscillating currents are simulated by means of a suitable IGBT module model proposed in the past and now optimized for irradiation simulation. The irradiated field during converter operation can be calculated by means of a preliminary static measure executed in anechoic chamber, where the diagram of irradiation of the system is measured at different frequencies, connecting IGBT gate to a radiofrequency generator. Presented results are precise within 3dB limit.

Sharp voltage gradients act as a stimulus for high power IGBT modules, which can exhibit a potentially instable high frequency behaviour. In effect, they can act as a radio frequency (RF) amplifier and under certain operating conditions the interaction between the device and the control or the external circuit can cause self-sustaining oscillations or the enhancement of the unevenness in current distribution inside a power module and that can have a significant impact on the reliability of the power converter. Moreover, this RF amplification worsen the generated EMI (Electro Magnetic Interference). This paper presents an extensive experimental investigation about the high frequency behaviour of IGBT high power modules. Measurements were performed by an original experimental set-up that was specifically conceived and constructed. Data were analysed with the help of a theoretical small signal model which was able to describe RF behaviour of high power IGBT modules.

Multi-baseline interferometric SyntheticAperture Radar (In-SAR) systems can be exploited to estimate the Digital Elevation Model (DEM) of the observed scene without ambiguities and with an increased accuracy, even in the case of high sloped ground regions. The techniques usually used exploit only the interferometric phase information and they are based on Maximum Likelihood (ML) estimation. An important problem to be taken into account is the mutual correlation of the (complex) interferometric images which impedes the closed form evaluation of the interferometric phases likelihood function. Moreover the statistical independence approximation of the phase interferograms is usually adopted. In this paper we present a method exploiting both amplitude and phase of the interferometric images, with the purpose of expressing the multi-baseline likelihood function in closed form, and we show that, when the number of baselines increases, to achieve an higher estimation accuracy the images mutual correlation cannot be neglected. We also show that to obtain a full resolution speckle reduced intensity image from several full resolution multi-baseline interferometric (complex) images, a phase compensation and a whitening operation have to be performed before averaging the data intensities.

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