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.

/pdf/graphene-based-ambipolar-rf-mixers-2nn0z3phao.pdf

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.

/pdf/a-comprehensive-explanation-of-distortion-sideband-504dwqq4e4.pdf

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.

/pdf/prediction-of-imd-in-ldmos-transistor-amplifiers-using-a-new-2wzfrozcuy.pdf

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

In this paper, a novel highly linear circularly polarized active antenna with gain control is presented. In this approach, the antenna serves as a 90o hybrid and the active part has been implemented using a branch line coupler as the 90o input hybrid circuit, and two PHEMT based amplifiers. The amplifiers are based on a new strategy for gain control with low distortion.

/pdf/antena-polarizada-circularmente-con-control-de-ganancia-y-3v755ld73k.pdf

Antena polarizada circularmente con control de ganancia y alta linealidad

In this paper, a transmitting active array with spatial power combining concept for selective spatial linearization is implemented. The main nonlinearity of PHEMT device is used to describe some characteristics of its intermodulation distortion behaviour. An auxiliary branch is added for cancelling the third order intermodulation distortion (IMD3) of the main branch without diminishing its gain. A dual-feed series patch array was designed with a good input matching as well as acceptable portto-port isolation. Experimental characterization of the complete system has proved an important cancellation of the IMD3 appears on the pointing direction comparing with the class A operation. These results validate the proposed method.

/pdf/control-espacial-de-la-intermodulacion-en-un-transmisor-4z4i0z45sm.pdf

Control espacial de la intermodulación en un transmisor activo

A new set of pseudo -empirical equations are presented in order to simulate the optical and bias dependencies of GaAs MESFET junction capacitances, which is valid for the whole I-V plane. The variations induced in the small signal equivalent circuit by the optical illumination are extracted from on-wafer scattering parameter measurements. New linear and quasilogarithmic variations versus the incident optical power are shown for gate-to-drain and gate-to-source (Cgd and Cgs) capacitances. Furthermore, experimental results are in very good agreement with the simulated values for a wide range of optical power and bias conditions.

https://repositorio.unican.es/xmlui/bitstream/handle/10902/3553/Nuevo%20modelo%20capacidad.pdf;sequence=1

Nuevo modelo de capacidad de puerta para transistores MESFET de microondas incluyendo efectos ópticos

In accordance with the development that communication system have experimented in the last 30 years, it is expected that the fourth generation 4Gmobile will be able to offer a large variety of multimedia services. These services will range from the traditional service of voice to the transmission of high quality video, including the new IP service. Said systems will need higher transmission rates than nowaday equipment can currently offer. For this reason a new software radio platform is being developed. These platforms allow us to research into new interface technology that can be useful in the 4Gmobile systems. This article presents a brief summary of the stages in the design, simulation and elaboration of a 2.38 GHz receiver that will be part of the develop of one software radio platform.

Receptor de banda ancha para comunicaciones de alta velocidad

In this paper a new methodology for the extraction of parasitic elements of the small-signal models of GaAs MESFET and AlGaAs P-HEMTs is shown. The neurofuzzy algorithm used for the extraction allows the calculation of the values of access resistances, capacitances and inductances, with no especial cold FET measurements. Experimental results show very good agreement with the theoretical analysis. 1. INTRODUCCION

Ángel Mediavilla Sánchez

Papers

Antena polarizada circularmente con control de ganancia y alta linealidad

Control espacial de la intermodulación en un transmisor activo

Nuevo modelo de capacidad de puerta para transistores MESFET de microondas incluyendo efectos ópticos

Receptor de banda ancha para comunicaciones de alta velocidad

Método neurodifuso para la extracción de los elementos parásitos en MESFET y HEMT