On human capital and economic development: some results for Africa

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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

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

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

Evaluation of a stacked-FET cell for high-frequency applications

This paper presents the design, electromagnetic simulation strategies and experimental characterisation of a two-stage stacked-FET cell in a 100 nm GaN on Si technology around 18.8 GHz, suited for Ka band satellite downlink applications. A good agreement is found between the electromagnetic simulations and the measured performance on the manufactured prototype, thus demonstrating that a successful voltage combining architecture can be obtained in the frequency range of interest with the selected topology, based on a symmetric fork-like connection between the transistors. This proves the effectiveness of an appropriate electromagnetic simulation set-up in correctly predicting the crosstalk, which typically affects this structure, leading to a correct stacking operation

A Novel Stacked Cell Layout for High Frequency Power Applications

This letter presents an innovative stacked cell, where the common source device is split in two smaller devices leading to a more compact and symmetric structure, with almost negligible parasitics associated to the transistors connection. This novel configuration is rigorously compared, for the first time, with the two classical approaches commonly adopted to physically connect the two devices. The three different layouts are fabricated in Gallium Nitride technology for high frequency power applications, and experimentally compared by means of an extensive measurement campaign performed on several loads and in different bias conditions, ranging from class AB to C. The proposed novel configuration outperforms the other two in all conditions, thanks to the advantages of adopting two smaller devices with reduced parasitics, higher gain and higher power density. These features are common to different technologies, thus making the novel topology widely applicable for the design of high frequency stacked cells

A 5-W GaN Doherty Amplifier for Ka-Band Satellite Downlink With 4-GHz Bandwidth and 17-dB NPR

This letter presents the design and experimental characterization of a GaN-Si monolithic Doherty power amplifier (PA) for the Ka-band satellite downlink. The fabricated amplifier favorably compares with the current state of the art, achieving from 16.3 to 20.3 GHz (4 GHz, 22% relative bandwidth), a record band to date, 36.6-37.7-dBm output power, 23%-31% power-added efficiency, 18-22-dB gain at saturation, and around 20% power-added efficiency at 6-dB output back-off. At 18.8 GHz, the amplifier shows a noise-to-power ratio higher than 17 dB at all power levels, making it suitable for satellite applications where additional linearization is usually unfeasible

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

Implementation and Validation of 3-D Ice Accretion Measurement Methodology

A research program has been implemented to develop and validate the use of a commercial 3-D laser scanning system to record ice accretion geometry in the NASA Icing Research Tunnel. A main component of the program was the geometric assessment of the 3- D laser scanning system on a 2-D (straight wing) and a 3-D (swept wing) airfoil geometries. This exercise consisted of comparison of scanned ice accretion to castings of the same ice accretion. The scan data were also used to create rapid prototype artificial ice shapes that were scanned and compared to the original ice accretion. The results from geometric comparisons on the straight wing showed that the ice shape models generated through the scan/rapid prototype process compared reasonably well with the cast shapes. Similar results were obtained with the geometric comparisons on the swept wing. It was difficult to precisely compare the scans of the cast shapes to the original ice accretion scans because the cast shapes appear to have shrunk during the mold/casting process by as much as 0.10-inch. However the comparison of the local ice-shape features were possible and produced better results. The rapid prototype manufacturing process was shown to reproduce the original ice accretion scan normally within 0.01-inch