Dynamic, self consistent electro-thermal simulation of power microwave devices including the effect of surface metallizations

We present an efficient simulation technique to account for the thermal spreading effects of surface metallizations in the self-consistent dynamic electro-thermal analysis of power microwave devices. Electro-thermal self-consistency is achieved by solving the coupled nonlinear system made of a temperature dependent device electrical model, and of an approximate description of the device thermal behavior through a thermal impedance matrix. The numerical solution is pursued in the frequency domain by the Harmonic Balance technique. The approach is applied to the thermal stability analysis of power AlGaAs/GaAs HBTs and the results show that metallizations have a significant impact on the occurrence of the device thermal collapse

Generalized Symmetrical 3 dB Power Dividers with Complex Termination Impedances

The paper introduces a class of two-way, 3 dB narrowband power dividers (combiners), closed on complex termination impedances, that generalizes a number of topologies presented during past years as extensions of the traditional Wilkinson design. Adopting even-odd mode analysis, we demonstrate that, under very broad assumptions, any axially symmetric reactive 3-port can be designed to operate as a 3 dB two-way power divider, by connecting a properly designed isolation impedance across two symmetrically but arbitrarily located additional ports. We show that this isolation element can be evaluated by a single input impedance or admittance CAD simulation or measurement; moreover, an explicit expression is given for the isolation impedance. The theory is shown to lead to the same design as for already presented generalizations of the Wilkinson divider; further validation is provided through both simulated and experimental case studies, and an application of the theory to the design of broadband or multi-band couplers is suggested

Brill-Noether loci for divisors on irregular varieties

WetakeupthestudyoftheBrill–NoetherlociWr(L,X):={η∈Pic0(X)|h0(L⊗η) ≥ r + 1}, where X is a smooth projective variety of dimension > 1, L ∈ Pic(X), and r ≥ 0 is an integer. By studying the infinitesimal structure of these loci and the Petri map (defined in analogy with the case of curves), we obtain lower bounds for h0(KD), where D is a divisor that moves linearly on a smooth projective variety X of maximal Albanese dimension. In this way we sharpen the results of [Xi] and we generalize them to dimension > 2. In the 2-dimensional case we prove an existence theorem: we define a Brill–Noether number ρ(C, r) for a curve C on a smooth surface X of maximal Albanese dimension and we prove, under some mild additional assumptions, that if ρ(C,r) ≥ 0 then Wr(C,X) is nonempty of dimension ≥ ρ(C,r). Inequalities for the numerical invariants of curves that do not move linearly on a surface of maximal Albanese dimension are obtained as an application of the previous results

Compact GaN-based Stacked Cells for 5G Applications at 26 GHz

This work presents the development of two 2-FET stacked cells at 26 GHz in the WIN Semiconductors 150 nm power GaN/SiC technology. Two different compact layouts, based on the same circuit scheme, are designed targeting similar performance in the FR2 5G frequency band. One version favoring distance between components, to relieve electromagnetic cross-talk, and the other favoring instead symmetry. The cells have been conceived as basic building blocks for the development of high-power 5G amplifiers, rather than as stand-alone amplifiers, hence including only input matching and stabilization networks. Based on large-signal simulations on the optimum load, the cells are expected to deliver around 34 dBm with an efficiency higher than 35% at 26 GHz, and a linear gain of 10 dB. The output power performance is maintained from 24.5 GHz to 27.5 GHz, where the saturated efficiency is above 30 % for both cells. The small-signal experimental characterization results are in very good agreement with the simulations, proving the effectiveness of the electromagnetic simulation setup adopted for all the passive structures, despite the challenges posed by the compact layouts

Evaluation of In-Batch and In-Flow Synthetic Strategies towards the Stereoselective Synthesis of a Fluorinated Analogue of Retro-Thiorphan

A stereoselective synthetic strategy for the preparation of trifluoromethylamine mimics of retro-thiorphan, involving a diastereoselective, metal-free catalytic step, has been studied in batch and afforded the target molecule in good yields and high diastereoselectivity. A crucial point of the synthetic sequence was the catalytic reduction of a fluorinated enamine with trichlorosilane as reducing agent in the presence of a chiral Lewis base. The absolute configuration of the key intermediate was unambiguously assigned by X-ray analysis. The synthesis was also investigated exploiting continuous flow reactions; that is, an advanced intermediate of the target molecule was synthesized in only two in-flow synthetic modules, avoiding isolation and purifications of intermediates, leading to the isolation of the target chiral fluorinated amine in up to an 87:13 diastereoisomeric ratio

Studying oven technology towards the energy consumption optimisation for the baking process

A recent guideline from the European Commission declared that several highly energy consuming domestic equipment should be better regulated or avoided at all in the near future. Together with this, several EU nations are abandoning the gas ovens in favour of the electric ones, also due to the home energy rating regulations, that make impossible to get the highest rating with gas ovens. Due to this fact, the study of the technologies related to the energy efficiency in cooking is increasingly developing. The combination of several energy sources (e.g. forced convection, irradiation, microwave, etc.), as well as optimisation of each of them, is an emerging target for oven manufacturers, in matter of oven design and better use of the oven capabilities. Within this context, an energy consumption analysis and optimisation is targeted in this work, by the application of a bread baking model, validated on experimental data. Each source of energy is given the due importance and the practically applicable process solutions are compared. A basic quality standard is guaranteed by taking into account some quality markers, which are relevant on the basis of a consumer point of view. This work is a part of a more comprehensive study on oven cooking and energy integration, and could lead to practical applications in the design of energy efficient cooking programs