De-hierarchization, trans-linearity and intersubjective participation in ethnographic research through interactive media representations: www.laviedurail.net

This article reflects on the advantages as well as the challenges of interactive media productions as a form of (re-)presentation for ethnographic and anthropological research. It draws upon the example of the interactive website www.laviedurail.net, which retraces the Malian part of the former Dakar-Niger Express train track. The website invites users to take stops at different stations where mutual influence with the train determines life along the rail. By choosing an order in which media elements such as photos, videos, sound recordings and texts are addressed, the recipient creates a subjective path of knowledge. While a multimedia presentation offers a de-hierarchized and trans-linear approach, at the same time it cannot avoid the selective character of the material. Therefore, it becomes necessary to perceive and reflect recipient, informants as well as researcher as subjects of the project.Este artículo reflexiona sobre las ventajas así como sobre los retos de los nuevos medios interactivos como forma de (re-)presentación para la investigación etnográfica y antropológica. Me baso en el ejemplo de la web interactiva www.laviedurail.net, que pone de relieve el aporte maliano en la construcción de la antigua línea férrea entre Dakar y Níger. La página web invita a los usuarios a detenerse en diferentes estaciones donde la relación que se establece con el tren va determinando el devenir de la vida a lo largo del viaje por la vía férrea. Escogiendo el orden en el que fotos, vídeos, gravaciones sonoras y textos son presentados, el usuario crea un itinerario de conocimiento subjetivo. Mientras que una presentación multimedia ofrece una perspectiva desjerarquizada y trans-lineal, no puede evitar sin embargo el carácter selectivo del material. En consecuencia, resulta necesario percibir y considerar el receptor, los informantes así como el investigador como sujetos del proyecto.Cet article aborde les avantages et les enjeux des media interactifs comme forme possible de (re)présentation pour les recherches ethnographiques et anthropologiques. Ces réflexions s’appuient sur l’exemple d’un site web interactif www.laviedurail.net qui décrit la partie malienne de ce qui était au paravent le train Express Dakar-Niger. Le site web invite les utilisateurs à s’arrêter à différentes stations où des interactions, provoquées par le passage du train, influent sur la vie le long des voies de chemin de fer. En choisissant l’ordre dans lequel les éléments audio visuels, photos, enregistrements sonores, vidéos, textes sont présents, le spectateur crée un accès subjectif au savoir. Alors que la présentation multimédia offre une approche sans hiérarchie et trans-linéaire, en même temps cela ne permet pas d’éviter le caractère sélectif du support. Ainsi il devient nécessaire de percevoir et de concevoir comme sujets à part entière du projet les destinataires, les informateurs et les chercheurs

Electro-magnetic Crosstalk Effects in a Millimeter-wave MMIC Stacked Cell

This work discusses the design of a 2-stacked cell at 36 GHz, analyzing the large discrepancies found between circuit-level and electro-magnetic (EM) simulations due to crosstalk (gate power leakage). At millimeter-wave frequencies, EM optimization of the inter-stage matching is crucial, however, its layout compactness poses several issues on the selection of the EM set-up, thus simulations reliability was put in doubt. To dispel this doubt the cell was fabricated and tested, demonstrating the effectiveness of EM predictions and the actual presence of gate power leakage. This required a deep re-design of the cell, currently on-going, based on a completely different inter-stage matching approach

A Balanced Stacked GaN MMIC Power Amplifier for 26-GHz 5G applications

This work reports the design and experimental characterization of a 4 W Ka-band MMIC power amplifier in GaN/SiC technology, featuring a balanced stacked architecture. The proposed amplifier is composed of a pair of 2-stage amplifier branches, each including a single-transistor driver stage and a 2-stacked-transistor power stage. Small-signal characterization exhibits very good agreement between measurements and simulations, while system-level characterization, employing a 50 MHz instantaneous bandwidth, 10 dB PAPR 5G FR2 signal, demonstrates the very promising linearity performance of the proposed amplifier. The measured minimum ACPR is better than -27 dBc up to an average output power of 24 dBm, from 25 GHz to 27 GHz

Electro-magnetic Crosstalk Effects in a Millimeter-wave MMIC Stacked Cell

This work discusses the design of a 2-stacked cell at 36 GHz, analyzing the large discrepancies found between circuit-level and electro-magnetic (EM) simulations due to crosstalk (gate power leakage). At millimeter-wave frequencies, EM optimization of the inter-stage matching is crucial, however, its layout compactness poses several issues on the selection of the EM set-up, thus simulations reliability was put in doubt. To dispel this doubt the cell was fabricated and tested, demonstrating the effectiveness of EM predictions and the actual presence of gate power leakage. This required a deep re-design of the cell, currently on-going, based on a completely different inter-stage matching approach

High efficiency power amplifiers for modern mobile communications: The load-modulation approach

Modern mobile communication signals require power amplifiers able to maintain very high efficiency in a wide range of output power levels, which is a major issue for classical power amplifier architectures. Following the load-modulation approach, efficiency enhancement is achieved by dynamically changing the amplifier load impedance as a function of the input power. In this paper, a review of the widely-adopted Doherty power amplifier and of the other load-modulation efficiency enhancement techniques is presented. The main theoretical aspects behind each method are introduced, and the most relevant practical implementations available in recent literature are reported and discussed

3.1-3.6 GHz 22 W GaN Doherty Power Amplifier

This paper presents a Doherty power amplifier working from 3.1 GHz to 3.6 GHz. It adopts 10 W packaged GaN HEMTs from Cree/Wolfspeed and achieves a saturated output power in excess of 43.4 dBm. Saturated efficiency ranges from 57.7 % to 75.2 %, while efficiency at 6 dB back-off is between 44.2 % and 59.8 %. System-level simulations at 3.5 GHz adopting a 16QAM signal with 5 MHz bandwidth and 4 dB peak to average power ratio showed an adjacent channel power ratio of -28 dBc/Hz without pre-distortion, at an average output power of 43 dBm and with an average efficiency of 71 %

Design strategy of a 2.8–3.6 GHz 20W GaN Doherty power amplifier

This paper presents the design of a 20W GaN Doherty Power Amplifier working in the range 2.8 GHz–3.6 GHz. The design strategy adopted for the design of the Doherty output combiner is discussed, which consists in embedding the device parasitics into the latter, implemented as a multi-stage quarter-wavelength transformer, in order to achieve wideband behaviour. The saturated output power ranges from 42dBm to 44 dBm, with a corresponding drain efficiency in excess of 47%. The efficiency at 6 dB of output back-off is higher than 42% over the whole frequency band, and the small-signal gain is higher than 10 dB. Due to the discrepancies of the measured scattering parameters compared to the simulated ones, which could not be corrected with post-tuning, a redesign of the prototype is ongoing

A 3-3.8 GHz Class-J GaN HEMT Power Amplifier

This paper presents a wideband class J power amplifier (PA) based on a packaged 10 W GaN HEMT device covering the 3 GHz to 3.8 GHz frequency range. A good trade-off between efficiency and gain has been pursued in synthesizing the second harmonic output termination. The achieved output power is in excess of 41 dBm with drain efficiency ranging from 59 % to 65.5 % and a small signal gain above 14 dB. Preliminary large signal measurements at 3.3 GHz confirm the proper behavior of the PA

Broadband Class-J GaN Doherty Power Amplifier

This paper presents a broadband 3 GHz–3.7GHz class-J Doherty power amplifier exploiting second harmonic tuning in the output network. Furthermore, the output impedance inverter is eliminated and its effect is embedded in the main device’s output matching network, thus trading off among bandwidth, efficiency, and gain. The proposed amplifier adopts two 10W packaged GaN transistors, and it achieves in measurement 60–74%, and 46–50% drain efficiency at saturation and 6 dB output back-off, respectively, with a saturated output power of 43 dBm–44.2dBm and a small-signal gain of 10 dB–13 dB. The proposed DPA exhibits a simulated adjacent channel power ratio less than 30 dBc at 36dBm average output power when a 16-QAM modulation with 5 MHz bandwidth is applied to the 3.5 GHz carrier

Watt-level 21-25 GHz integrated Doherty power amplifier in GaAs technology

This paper presents the design and characterization of a Doherty power amplifier for K-band applications based on the GaAs 150nm pHEMT technology of Qorvo. For the output power combiner, a wideband design approach, based on embedding the output capacitance of the active devices in the combiner, is applied. A state-of-the-art bandwidth of 4 GHz is achieved: in the 21 GHz-25 GHz range, the output power is above 29.5 dBm, with an associated PAE higher than 30 %. At 6 dB output back-off, the PAE is above 19% while the corresponding gain is higher than 10 dB