Neural-Based Nonlinear Device Models for Intermodulation Analysis

A new procedure to learn a nonlinear model together with its derivative parameters using a composite neural network is presented.So far neural networks have never been used to extract large-signal device model accounting for distortion parameters.Applying this method to FET devices leads to nonlinear models for current- voltage functions which allow improved prediction of weak and mildly device nonlinearities in the whole bias region. The resulting models have demonstrated to be suitable for both small-signal and large-signal analyses,including intermodulation distortion prediction

An approach to harmonic load- and source-pull measurements for high-efficiency PA design

High-efficiency power-amplifier design requires numerous efforts to investigate both input and output harmonic terminations effects. A simplified theoretical approach to clarify the relevance of such terminations is presented here, and design criteria to improve efficiency for high-frequency applications are briefly discussed. An advanced active load/source-pull test-bench has been used to validate theoretical harmonic tuning techniques, characterizing an active device. The adopted optimization strategy is presented, together with measured results obtained with a medium-power 1-mm MESFET at 1 GHz. Input second harmonic impedances effects are stressed, showing a drain efficiency spread between 37%-49% for a fixed input power level, corresponding to 1-dB compression. Finally, as predicted by the presented theory, after input second harmonic tuning, further improvements are obtained, increasing fundamental output load resistive part, demonstrating an additional drain efficiency enhancement, which reaches a level of 55% at 1-dB compression

Theoretical and experimental assessment of the non-linear scattering functions for the cad of non-linear microwave circuits

The Non-Linear Scattering Functions have been theoretically defined and experimentally measured for the linear-equivalent design of non-linear circuits in arbitrary large signal conditions. Non-linear measures and simulations have been compared, with good agreement. Linear CAD concepts can therefore be extended to non-linear circuits in a rigorous way

Использование щелевых резонаторов для проектирования усилителя мощности с манипуляцией гармоник

Предложена и экспериментально проверена схема усилителя мощности инверсного класса F (F⁻¹) на основе GaN-транзистора NPTB00004, работающего на частоте 1,7 ГГц. Новым при этом является использование в схеме трехслойной структуры на основе щелевых резонаторов прямоугольной формы в заземляющей плоскости микрополосковой линии передачи в качестве фильтра высших гармоник. Для контроля уровней второй и третьей гармоник в спектре выходного сигнала и одновременно для согласования с 50-омной нагрузкой на рабочей частоте усилителя используется планарная периодическая структура, состоящая из двух щелевых резонаторов различной длины. КПД по добавленной мощности экспериментального макета усилителя составил 60% при выходной мощности 3,9 Вт и коэффициенте усиления 13 дБ.Запропоновано та експериментально перевірено схему підсилювача потужності на базі GaN-транзистору інверсного класу F (F⁻¹), що працює на частоті 1,7 ГГц. Новим при цьому є використання в схемі тришарової структури, що складається з щілинних резонаторів прямокутної форми у заземлювальній площині мікросмужкової лінії передачі для фільтрації вищих гармонік основного сигналу. Зокрема, періодична планарна структура, що складається з двох пар щілинних резонаторів різної довжини, використовується для контролю рівня другої та третьої гармонік у спектрі вихідного сигналу та одночасно для узгодження із 50-омною навантагою на робочій частоті підсилювача. Стоковий ККД експериментального макета підсилювача склав 60% при вихідній потужності 3,9 Вт та коефіцієнті підсилення 13 дБ.The authors proposed and experimentally verified the power amplifier circuit of inverse class F (F⁻¹) based on GaN transistor NPTB00004, operating at 1,7 GHz. The novelty of this scheme is the application of a three-layer structure based on slot rectangular shaped resonators in the ground plane of the microstrip transmission line as a filter of higher harmonics. To control the levels of the second and third harmonics in the output signal spectrum and simultaneously to match the 50 ohm load at the operating frequency of the amplifier, a planar periodic structure is used, consisting of two slot resonators of different lengths. Power added efficiency for experimental model of the amplifier is 60% at an output power of 3.9 W and a gain factor of 13 dB

Can Ptilinopus greyii (Columbidae) Disperse Seeds in New Caledonia’s Dry Forests?

v. ill. 23 cm.QuarterlyConservation of endangered habitats of South Pacific islands is partially dependent on activity of seed dispersers. In consuming fruits, animals can spread seeds from parent plants to distant sites, thus contributing to plant regeneration and colonization of new sites. In the dry forests of New Caledonia, the red-bellied fruit-dove, Ptilinopus greyii, is a potential disperser of many fleshyfruited species. Trials with a captive bird showed that gut passage enhanced seed germination for Diospyros fasciculosa and Mimusops elengi but not for Vitex cf. collina, compared with whole fruits. Gut passage did not shorten duration of seed dormancy, which is consistent with evidence of a simple deinhibition effect for D. fasciculosa and M. elengi. Minimum Retention Time (MRT) of seeds in the gut differed significantly between the three tree species, from a mean of 17.4 min for D. fasciculosa to a mean of 52.4 min for M. elengi. These times are longer than observed foraging times in fruiting trees, potentially making this fruit-dove an effective seed disperser

High efficiency and high linearity power amplifier design

The optimum high-frequency Class-F loading conditions are inferred, accounting for the effects of actual output device behavior, and deriving useful charts for an effective design. The important role of the biasing point selection is stressed, demonstrating that it must be different from the Class-B theoretical one to get the expected improvement. The IMD behavior of the Class-F amplifier is presented and the large-signal sweet-spot origin in the IMD output characteristics is discussed, together with possible strategies to improve intermodulation distortion performances. The control of the sweet spot position is demonstrated via proper terminating impedances, both at fundamental and harmonic frequencies and low frequencies

Evaluating GaN Doherty architectures for 4G Picocells, WiMax and microwave backhaul links

This paper evaluates the Doherty power amplifier architecture in terms of linearity, efficiency and design solutions. As case study four different prototypes are presented, one for 4G Picocells at 2.1 GHz, one for WiMax applications at 3.5 GHz and two for point-to-point microwave backhaul radiolinks at 7 GHz. Experimental results together with design guidelines are discussed addressing strengths and weaknesses of the Doherty architectur

Generic flow profiles induced by a beating cilium

We describe a multipole expansion for the low Reynolds number fluid flows generated by a localized source embedded in a plane with a no-slip boundary condition. It contains 3 independent terms that fall quadratically with the distance and 6 terms that fall with the third power. Within this framework we discuss the flows induced by a beating cilium described in different ways: a small particle circling on an elliptical trajectory, a thin rod and a general ciliary beating pattern. We identify the flow modes present based on the symmetry properties of the ciliary beat.Comment: 12 pages, 6 figures, to appear in EPJ

A high efficiency 10W MMIC PA for K-b and satellite communications

This paper discusses the design steps and experimental characterization of a monolithic microwave integrated circuit (MMIC) power amplifier developed for the next generation of K-band 17.3–20.2 GHz very high throughput satellites. The technology used is a commercially available 100-nm gate length gallium nitride on silicon process. The chip was developed taking into account the demanding constraints of the spacecraft and, in particular, carefully considering the thermal constraints of such technology, in order to keep the junction temperature in all devices below 160°C in the worst-case condition (i.e., maximum environmental temperature of 85°C). The realized MMIC, based on a three-stage architecture, was first characterized on-wafer in pulsed regime and, subsequently, mounted in a test-jig and characterized under continuous wave operating conditions. In 17.3–20.2 GHz operating bandwidth, the built amplifier provides an output power >40 dBm with a power added efficiency close to 30% (peak >40%) and 22 dB of power gain

Low-Bias-Complexity Ku-band GaN MMIC Doherty Power Amplifier

This paper present a two-stage Doherty power amplifier designed to maximize the efficiency at 6 dB back-off while minimizing the complexity in terms of bias voltages. The amplifier has been manufactured on a GaN-SiC 150 nm monolithic microwave integrated circuit technology. The fabricated chip, measured in continuous wave conditions, maintains a linear gain higher than 13 dB, a saturated output power in excess of 34 dBm, with a power-added efficiency higher than 20% both at saturation and at 6 dB output back-off, over the 14.5 GHz-17.25 GHz band, favorably comparing with the present state of the art for similar applications