1,721,044 research outputs found
Microwave transistor modeling
No full textThe first chapter is meant to give a comprehensive overview of the fundamentals, state-of-the-art, challenges, and future trends in the field of high-frequency transistor modeling. Linear, as well as noise and nonlinear operations, are dealt with. The importance of microwave transistor modeling comes from the fact that the transistor is the key component in high-frequency circuits that are at the heart of modern wireless communication systems, such as mobile telephony. We are currently witnessing a proliferation of wireless communication applications and continuous progress in transistor technologies that make high-frequency transistor modeling a hot topic of great interest
Black-box noise modeling of GaAs HEMTs under illumination
No full textThe present work is focused on the modeling of the noise performance of GaAs HEMTs under laser illumination. The model is straightforwardly extracted by using a polynomial approximation of the noise correlation parameters without the need for determining an equivalent circuit representation. The validity of the model is confirmed by the observed good agreement between model simulations and noise measurements with and without light up to 26GHz
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Accurate Modeling of GaN HEMTs Oriented to Analysis of Kink Effects in S22and h21: An Effective Machine Learning Approach
No full textIn this work, for the first time, a machine learning behavioral modeling methodology based on gate recurrent unit (GRU) is developed and used to model and then analyze the kink effects (KEs) in the output reflection coefficient (S22) and the short-circuit current gain (h21) of an advanced microwave transistor. The device under test (DUT) is a 0.25-μ m gallium nitride (GaN) high electron mobility transistor (HEMT) on silicon carbide (SiC) substrate, which has a large gate periphery of 1.5 mm. The scattering (S-) parameters of the DUT are measured at a frequency up to 65 GHz and at an ambient temperature up to 200?C. The proposed model can accurately reproduce the KEs in S22 and in h21, enabling an effective analysis of their dependence on the operating conditions, bias point and ambient temperature. It is worth noticing that the proposed transistor model shows also good performance in both interpolation and extrapolation test
Theoretical and Experimental Analysis of a CSWPL Behavioral Model for Microwave GaN Transistors Including DC Bias Voltages
No full textIn this paper, a novel frequency domain behavioral modeling approach for gallium-nitride (GaN) devices is presented. The proposed technique is based on using the canonical section-wise piecewise linear (CSWPL) model framework to interpolate the dc input and output bias voltages by a two-dimensional polynomial function. The basic theory associated with the developed model is described in detail and experimentally verified. The model is implemented in a commercial software and, then, validated through both dc and radio frequency (RF) tests with measured load-pull data from 6-W GaN devices. The achieved results demonstrate an excellent prediction capability, thereby proving the accuracy of the developed modeling methodology. Compared with the standard CSWPL model, the proposed model is able to predict the transistor behavior at different bias voltages with one single set of parameters, which greatly reduces the model complexity as well as the required extraction time. Compared with existing bias included models, the proposed solution shows accurate predictions over a wide range of input power levels and bias conditions, simultaneously. Additionally, the proposed model is utilized for a broadband PA design for a further validation. The measurements carried out on the realized PA are compared with the simulations based on using the proposed model. The comparison is performed at four different bias conditions. The agreement between measurements and simulations confirms the extracted model’s validity
2-mm-gate-periphery GaN high electron mobility transistors on SiC and Si substrates: A comparative analysis from a small-signal standpoint
No full textIn this paper, a comparative analysis has been conducted on GaN high electron mobility transistor (HEMT) technology on Si and SiC substrates. Small-signal characteristics of 2-mm GaN-on-Si and GaN-on-SiC devices have been investigated. Both devices have the same gate length of 0.5 μm. Special emphasis has been put on the temperature dependence of the buffer/substrate loading effects arising from the Si substrate. As a matter of fact, the “cold” pinch-off admittance (Y-) parameter measurement showed significant loading effect for the Si-based device with respect to the SiC-based one. This has been clearly supported by the analysis of the extracted parameters of the small-signal equivalent-circuit model. The model was also validated by simulating active scattering (S-) parameters, which showed a very good agreement with the corresponding measurements. The results of this paper highlight the impact of buffer/substrate leakage currents on small-signal characteristics and the importance of taking this into account during the modeling phase of the GaN-on-Si HEMT technology. The lower thermal conductivity of this substrate increases the internal temperature, thus stimulating more leakage and reduction of the device power efficiency
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