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

This paper describes the design of a new configuration of a low pass filter (LPF). This filter structure is based on a ring topology. The proposed LPF is miniature and low cost because it is mounted on FR4 substrate. The validation of this circuit into simulation was based on many optimization methods integrated in ADS "Advanced Design System" and some tuning methods. At the end, the fabrication and the test of the final circuit permits to have a good agreement between simulation and measurement results reaching a low pass behavior. The proposed filter has an area of 25x25 mm, with a cutoff frequency of 2GHz and good performances in term of insertion losses, which are around -0.127 dB in the whole bandwidth and a high stopband.

A novel microstrip low pass filter based on ring topology

This paper presents a novel structure of low pass filter designed by using microstrip technology. The proposed filter consists of a modified ring resonator with open stubs and two input/output feed lines. Based on series of optimization and a specific design method, a compact low pass filter with good electrical performances is obtained. In order to characterize the frequency response of the proposed filter, the simulations are carried out using two different solvers (ADS Agilent and CST-MWS). Furthermore, to validate the conception approach the circuit is manufactured and measured. The experimental results shows a wide attenuation band with a good rejection level up to 6 GHz, a cutoff frequency of 2.66 GHz and a reduced insertion loss level. In addition, a good agreement between the simulation and the measured results is achieved.

A Novel Design of a Ring Resonator Low Pass Filter

As an extension of our previous works in the opticalmicrowave interaction field, this paper shows the result of the research on large signal dynamic behavior (pulsed I/V curves) of AlGaAs P-HEMT (pseudomorphic high electron mobility transistor) devices, in the overall I/V plane, when the incident optical input power is changed. A complete bias and optical power dependent of the large signal model for a P-HEMT is determined from experimental scattering parameters, DC and pulsed measurements. All derivatives of the model shown here are continuous for a realistic description of circuit distortion and intermodulation. Experimental results show very good agreement with the theoretical analysis.

Modelo de gran-señal para transistores p-hemt y mesfet de microondas incluyendo efectos opticos

A Microwave Measurement Method for Complex Permittivity Determination of Dielectric Materials at Ku-Band

This paper shows the results of research on the optical control of a GaAs chip monolithic amplifier, and is an extension of previous work by our group in the field of optical-microwave interaction [1-3]. The amplifier was originally for the transmitter stage of an indoor mobile communications system in the 2.4 GHz band. The possibilities of optical control of this amplifier are evidenced as follows: if the amplifier operates with the same biasing, the gain can be optically controlled from a condition of almost isolation, (gain less than 5 dB), up to an active condition, (gain greater than 10 dB), which gives a range of optical control of about 15 dB. At the same time, the optical control provides an improvement of the input and output matching in a range of 12dB and 6dB, respectively. This optical control promises an interesting control of gain and matching for other microwave FET based active devices.

Ángel Mediavilla Sánchez

Papers

A novel microstrip low pass filter based on ring topology

A Novel Design of a Ring Resonator Low Pass Filter

Modelo de gran-señal para transistores p-hemt y mesfet de microondas incluyendo efectos opticos

A Microwave Measurement Method for Complex Permittivity Determination of Dielectric Materials at Ku-Band

Control óptico de un amplificador MMIC de AsGa en banda S