The combination of the unique properties of graphene with new device concepts and nanotechnology can overcome some of the main limitations of traditional electronics in terms of maximum frequency, linearity, and power dissipation. In this letter, we demonstrate the use of the ambipolar-transport properties of graphene for the fabrication of a new kind of RF mixer device. Due to the symmetrical ambipolar conduction in graphene, graphene-based mixers can effectively suppress odd-order intermodulations and lead to lower spurious emissions in the circuit. The mixer operation was demonstrated at a frequency of 10 MHz using graphene grown by chemical vapor deposition on a Ni film and then transferred to an insulating substrate. The maximum operating frequency was limited by the device geometry and the measurement setup, and a high-quality factor was observed with a third-order intercept point of +13.8 dBm.

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Graphene-Based Ambipolar RF Mixers

This paper presents a comprehensive study of intermodulation-distortion response asymmetries often observed in microwave nonlinear systems subject to a two-tone or multitone test. The reasons for the different amplitudes of the two adjacent tones are first investigated under small- and large-signal regimes, using a general circuit with frequency-dependent embedding impedances and resistive and reactive nonlinearities. It is shown that this intriguing phenomenon can be mainly attributed to the terminating impedances at the baseband or difference frequencies. Multitone behavior is also addressed and its main differences from the two-tone case explained. Those theoretical conclusions are then extrapolated for real circuits and validated by measured results obtained from microwave power amplifiers of two different technologies, i.e., a GaAs MESFET and an Si bipolar junction transistor.

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A comprehensive explanation of distortion sideband asymmetries

The currency of the research consists in the necessity if rethinking of the notion of culture in Russian contemporary thought in order to present more adequately the process of development of culture in a future. The paper aims to elucidate political origins of the movement of Proletarian culture that play the leading role in a creation of a new conception of culture. As a materials were used documents and archives, scientific paper of Russian and foreign researchers. As a maim method was used problematicanalytical reconstruction, explored in the framework of an enactive approach that allows to envelop the subject in its evolvement and to concentrate on concrete practical situations of its realization. Such reconstruction permits to accomplish the original interpretation of the problem. The authors focus in the pre-history of the movement. Analyzing the social-political context of the origin of the movement, the authors come to the conclusion about artificially created necessity of political enlightenment of the society by the revolutionaries. The paper demonstrates how agents of proletarian working circles manipulate by the public opinion of working class. As a result, the paper shows the process of formation the ideology of cultural movement revolutionary period and evaluates significance of ideological function in its realization. The authors produce critical evaluation of the history of the movement in original judgment about political grounding of culture.

Индикаторы качества светодиодных осветительных систем, применяемых в стоматологической практике для местного освещения операционного поля

Wireless power transmission (WPT) is an emerging technology that is gaining increased visibility in recent years. Efficient WPT circuits, systems and strategies can address a large group of applications spanning from batteryless systems, battery-free sensors, passive RF identification, near-field communications, and many others. WPT is a fundamental enabling technology of the Internet of Things concept, as well as machine-to-machine communications, since it minimizes the use of batteries and eliminates wired power connections. WPT technology brings together RF and dc circuit and system designers with different backgrounds on circuit design, novel materials and applications, and regulatory issues, forming a cross disciplinary team in order to achieve an efficient transmission of power over the air interface. This paper aims to present WPT technology in an integrated way, addressing state-of-the-art and challenges, and to discuss future R&D perspectives summarizing recent activities in Europe.

Wireless Power Transmission: R&D Activities Within Europe

In this paper, the intermodulation distortion (IMD) behavior of LDMOS transistors is treated. First, an analysis is performed to explain measured IMD characteristics in different classes of operation. It is shown that the turn-on region plays an important role in explaining measured IMD behavior, which may also give a clue to the excellent linearity of LDMOS transistors. Thereafter, with this knowledge, a new empirical large-signal model with improved capability of predicting IMD in LDMOS amplifiers is presented. The model is verified against various measurements at low as well as high frequency in a class-AB power amplifier circuit.

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Prediction of IMD in LDMOS transistor amplifiers using a new large-signal model

This paper presents the design of new compact printed broadband antennas for Ultra Wide Band applications. The antenna structures are based on the CPW-fed combined with a slot and a stub line to increase the bandwidth. The proposed antennas have been successfully designed, optimized and simulated by using Momentum software integrated into ADS “Advanced Design System” and CST Microwave Studio. The measured input impedance bandwidth of the final broadband antennas ranging from 2.17.3 GHz and 2.1-11 GHz. The design considerations for achieving broadband antennas and both simulated, experimental results are presented and discussed.

New compact antenna structures with a slot shaped and a stub tuning for ultra wide band applications

In this paper a novel compact planar monopole antenna with a T-shaped coupling feed for LTE/GSM/UMTS operation in the mobile phone is presented and studied. The proposed antenna has a simple structure, a planar configuration and can be directly printed on the system circuit board of the mobile phone. The antenna size is 40 × 20 mm2 it consisting of T-shaped driven strip and a coupled radiating structure. In addition two wide bands can be generated by the designed antenna for the LTE/GSM/UMTS operation in the mobile phone. The proposed antenna is validated by using two electromagnetic softwares CST-MWS and Ansoft HFSS. Operating principle of this antenna and details of the various antenna parameters are also studied and discussed in this paper. The simulated results including return loss, radiation patterns and current distributions are presented for the proposed antenna.

A Compact Planar Monopole Antenna with a T-Shaped Coupling Feed for LTE/GSM/UMTS Operation in the Mobile Phone

El gran avance tecnologico producido en los ultimos anos en el ambito de las comunicaciones, ha incrementado la complejidad de los dispositivos de RF y microondas. Todo ello ha ido acompanado de un refinamiento de las herramientas CAD de alta frecuencia utilizadas en simulacion, exigiendoles que muestren la maxima fidelidad posible a la realidad de su funcionamiento con la seguridad de que el prototipo funcione a la primera. Por esta razon, grandes empresas han invertido en el desarrollo de software de simulacion de RF y microondas como pueden ser Agilent ADS, GENESYS, HSPICE o AWR Microwave Office, y en el caso de los tres primeros, soportan la utilizacion de Verilog-A, un completo lenguaje de programacion que permite definir cualquier tipo de circuito para su posterior simulacion. Este ultimo punto es de gran importancia debido a que como norma general la creacion continua de nuevos modelos y la necesidad de trabajar con ellos hace imprescindible una herramienta que simplifique su modelado. A raiz de la participacion nuestro grupo de investigacion en la red de excelencia Europea TARGET [1], se adopto Verilog-A como lenguaje para la descripcion de aquellos modelos compactos de dispositivos activos de RF y microondas que habitualmente no aparecen en librerias comerciales. En esta comunicacion se mostrara la flexibilidad, potencia y transportabilidad entre plataformas de este lenguaje en la descripcion de modelos de dispositivos de RF y microondas. Para ello se presentaran, simulaciones de dispositivos de microondas en dos plataformas distintas disponibles en el Dpto. de Ingenieria de Comunicaciones de la Universidad de Cantabria: ADS y GENESYS ambas de Agilent Technologies. Figura 1. Proceso de creacion del modelo basado en lenguaje Verilog-A, y su portabilidad a diferente plataformas.

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Modelado de dispositivos activos de microondas utilizando código Verilog-A

This paper presents the development of a new miniaturized and compact GCPW-fed slotted rectangular antenna structure reader for wideband UHF RFID applications. The optimized proposed antenna is suitable to operate a large frequency-band range from 0.8GHz to 1.3GHz with a bandwidth of 500MHz with a return loss less than -10dB. The antenna is based on a 1.6mm thickness FR4 epoxy substrate with a reduce dimensions compared to the simple rectangular antenna and size of proposed antenna is 47*40mm2. The new design consists of a compact rectangular patch with symmetric U-shaped slots and I-shaped include a partial ground plan and fed by 50 Grounded coplanar line. The antenna parameters have been investigated and optimized by   using   CST Microwave Studio. To validate the CST Microwave Studio results before the   antenna achievement,   we   have   conducted another study by using ADS. The   final circuit   achieved, measured and validated. Experimental results show that the proposed antenna has good radiation characteristics and operating in UHF-RFID applications.

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A New Compact and Miniaturized GCPW-fed Slotted Rectangular antenna for Wideband UHF FIRD Applications

In this paper, we propose a dual band Radio Frequency Identification (RFID) reader antenna. The reader antenna operates at 2.45GHz and 5.8GHz. It has two resonances, the first one in the radiation patch, and the second one in the protruding stub located at the ground plane. The radiating patch of the present compact antenna has the dimensions of 15.6mm x 8.8mm. The matching techniques using stub tuning are adopted in this work. A good impedance bandwidth of 148.48MHz and 204.85MHz has been achieved for 2.45GHz and 5.8GHz respectively while the return loss S11 < −10dB. The proposed antenna is simple and compact in size, providing broadband impedance matching and an appropriate gain, 1.92dBi and 3.385dBi for the lower and upper bands respectively. The comparison between measured and simulated results shows a good agreement, which validates the proposed concept.

Ángel Mediavilla Sánchez

Papers

New compact antenna structures with a slot shaped and a stub tuning for ultra wide band applications

A Compact Planar Monopole Antenna with a T-Shaped Coupling Feed for LTE/GSM/UMTS Operation in the Mobile Phone

Modelado de dispositivos activos de microondas utilizando código Verilog-A

A New Compact and Miniaturized GCPW-fed Slotted Rectangular antenna for Wideband UHF FIRD Applications

Design of a compact dual-band microstrip RFID reader antenna