Microwave Electronics Research Articles

Study of Structural and Dielectric Properties of Ba<sub>0.6</sub>Sr<sub>0.4</sub>(Zr<sub>X</sub>Ti<sub>1-X</sub>)O<sub>3</sub> Ceramic

BaxSr1-xTiO3[(BST), 0£x£1] is a solid solution ferroelectric material exhibiting a large dielectric constant non-linear change with an applied DC electric field. And Ba(ZrxTi1-x)O3solid solution also has received much attention because of the good tunbality. In this paper, Ba0.6Sr0.4(ZrxTi1-x)O3(x=0.15,0.20,0.25,0.30,) ceramic was obtained by traditional ceramic processing. The structural, surface morphological, dielectric properties, tunable properties of this material as well as the mechanism of their nonlinear dielectric constant under DC electric field were systematically examined. The Zr ions substitution of Ti ions has a strong effect on the grain sizes and the dielectric property. The results show that Ba0.6Sr0.4(ZrxTi1-x)O3(x = 0.2, 0.25,0.3) ceramic is a promising candidate for the DC electric field tunable materials for microwave electronics application, because they exhibit high relative tunability (44%, 48%, 35%, respectively) as the strength of electric field is up to 1.5 kV/mm, and low dielectric loss (0.0026, 0.00044, 0.0015, respectively) at 100 kHz at room temperature. X-ray diffraction analyses indicated that the samples present perovskite phase. Scanning electron microscopy micrograph of sample indicated that the grain size decreased and density increased with Zr concentration increasing.

Nanoscale microwave microscopy using shielded cantilever probes

Quantitative dielectric and conductivity mapping in the nanoscale is highly desirable for many research disciplines, but difficult to achieve through conventional transport or established microscopy techniques. Taking advantage of the micro-fabrication technology, we have developed cantilever-based near-field microwave probes with shielded structures. Sensitive microwave electronics and finite-element analysis modeling are also utilized for quantitative electrical imaging. The system is fully compatible with atomic force microscope platforms for convenient operation and easy integration of other modes and functions. The microscope is ideal for interdisciplinary research, with demonstrated examples in nano electronics, physics, material science, and biology.

Features of active stand-alone repeaters for synchronous DVB - T broadcasting networks

The work describes the results of analysis and approaches to creating a national network of digital terrestrial television broadcasting standard DVB-T stand-alone repeater with an output power 25 watts, which can provide highquality TV signal in populated areas of an uncertain reception or in areas of radioshadow. Using the new circuit solutions in the field of microwave electronics and telecommunications, as well as solar energy can be achieved by maintenance of individual settlements with minimal performance and energy consumption. These active transponders will create conditions to cover the entire territory of Ukraine by multichannel television services of acceptable

High-power microwave LDMOS transistors for wireless data transmission technologies (Review)

The fields of the application, structure, fabrication, and packaging technology of high-power microwave LDMOS transistors and the main advantages of these devices were analyzed. Basic physical parameters and some technology factors were matched for optimum device operation. Solid-state microwave electronics has been actively developed for the last 10–15 years. Simultaneously with improvement of old devices, new devices and structures are actively being adopted and developed and new semiconductor materials are being commercialized. Microwave LDMOS technology is in demand in such fields as avionics, civil and military radars, repeaters, base stations of cellular communication systems, television and broadcasting transmitters, and transceivers for high-speed wireless computer networks (promising Wi-Fi and Wi-Max standards).

How grain boundaries limit supercurrents in high-temperature superconductors

The interface properties of high-temperature cuprate superconductors have been of interest for many years, and play an essential role in Josephson junctions, superconducting cables, and microwave electronics. In particular, the maximum critical current achievable in high-Tc wires and tapes is well known to be limited by the presence of grain boundaries, regions of mismatch between crystallites with misoriented crystalline axes. In studies of single, artificially fabricated grain boundaries the striking observation has been made that the critical current Jc of a grain boundary junction depends exponentially on the misorientation angle. Until now microscopic understanding of this apparently universal behavior has been lacking. We present here the results of a microscopic evaluation based on a construction of fully 3D YBCO grain boundaries by molecular dynamics. With these structures, we calculate an effective tight-binding Hamiltonian for the d-wave superconductor with a grain boundary. The critical current is then shown to follow an exponential suppression with grain boundary angle. We identify the buildup of charge inhomogeneities as the dominant mechanism for the suppression of the supercurrent.

Monolithically integrated solid-state terahertz transceivers

Recent advances in microfabricated terahertz quantum cascade lasers have achieved coherent power and frequency performance previously possible only with much larger gas- or vacuum-tube sources. A significant advantage offered by terahertz quantum cascade lasers lies in the potential to integrate them with other components on the same chip. Such terahertz photonic integrated circuits would help close the terahertz technology gap between microwave electronics and infrared photonics. Here, we describe the first successful monolithic integration of a terahertz quantum cascade laser and diode mixer to form a simple but generically useful terahertz photonic integrated circuit—a microelectronic terahertz transceiver. We show that this terahertz photonic integrated circuit performs all the basic functions (for example, transmission of a coherent carrier, heterodyne reception of an external signal, frequency locking and tuning) of discrete-component terahertz photonic systems, but at a small fraction of the size and in a robust platform scalable to semiconductor fabrication production. A terahertz quantum cascade laser and diode mixer are monolithically integrated to form a simple microelectronic terahertz transceiver. The performance of this system — the transmission of a coherent carrier, heterodyne reception of an external signal, frequency locking and tuning — is as efficient as that of discrete component terahertz photonic systems.

GaN for space application: almost ready for flight

On the last years, gallium nitride (GaN) technology has made a remarked breakthrough in the world of microwave electronics. Power transistors are now available. How this GaN technology would impact space-borne units is now a priority concern. Although the power capability of GaN technology is the first obvious profit, GaN could also be used for other applications like low noise amplifiers, mixers, and probably more. The high sustainable temperature of GaN transistors is most striking advantage for in-flight use. This is connected to packaging design which is also experiencing a lot of activities and quick progresses. Of course, space application is dependent upon the full demonstration of reliability and this constitutes another field of investigation. Finally, after 8 years of GaN studies, experimental results are presented: they open wide the road a revolution inside space-borne electronics: the rise of GaN.

ELBARA II, an L-Band Radiometer System for Soil Moisture Research

L-band (1–2 GHz) microwave radiometry is a remote sensing technique that can be used to monitor soil moisture, and is deployed in the Soil Moisture and Ocean Salinity (SMOS) Mission of the European Space Agency (ESA). Performing ground-based radiometer campaigns before launch, during the commissioning phase and during the operative SMOS mission is important for validating the satellite data and for the further improvement of the radiative transfer models used in the soil-moisture retrieval algorithms. To address these needs, three identical L-band radiometer systems were ordered by ESA. They rely on the proven architecture of the ETH L-Band radiometer for soil moisture research (ELBARA) with major improvements in the microwave electronics, the internal calibration sources, the data acquisition, the user interface, and the mechanics. The purpose of this paper is to describe the design of the instruments and the main characteristics that are relevant for the user.

Double-locked semiconductor laser for radio-over-fiber uplink transmission

The nonlinear dynamics of an optically injected semiconductor laser are explored for radio-over-fiber uplink transmission. Under optical injection locking, the laser at the base station is operated in the period-one oscillation state, where its intensity oscillates at a tunable microwave frequency. When the oscillation is tuned to the subcarrier frequency, it is further locked by the uplink microwave signal. By simply using an ordinary 2.5-Gbps-grade semiconductor laser, uplink transmission of the phase-shift keying (PSK) signal at a subcarrier of 16 GHz with bit-error rate of less than 10(-11) is demonstrated experimentally. Microwave PSK to optical PSK is achieved at the double-locked laser, which allows all-optical demodulation without any high-speed microwave electronics.

Microwave and Radio Electronics Week 2010

Microwave and Radio Electronics Week 2010

Nanoelectromagnetics: Circuit and Electromagnetic Properties of Carbon Nanotubes

This Review presents a discussion of the electromagnetic properties of nanoscale electrical conductors, which are quantum mechanical one-dimensional systems. Of these, carbon nanotubes are the most technologically advanced example, and are discussed mainly in this paper. The properties of such systems as transmission electron microscopy waveguides for on-chip signal propagation and also the radiation properties of such systems are discussed. This work is primarily aimed at microwave, nanometer-wave, and THz electronics. However, the use of nanotubes as antennas in the IR and optical frequency range is not precluded on first principles and remains an open research area.

The Czech and Slovak Microwave and radio Electronics Week 2010

The Czech and Slovak Microwave and radio Electronics Week 2010

Microwave Resonant Transmission in a Superconducting Fabry–Perot Bilayer

Microwave resonant transmission properties in a superconducting Fabry–Perot bilayer made of a high-temperature superconductor (YBa2Cu3O7−x) and a nearly ferroelectric superconductor (n-SrTiO3) are theoretically investigated. The effect of high-temperature superconducting layer on the unusual resonant transmittance existing in a nearly ferroelectric superconductor is investigated. It is shown that a frequency-agile two-layer coating can be obtained with the addition of the high-temperature superconducting coating. Resonant frequencies can be shifted by varying the thickness of this coating. In addition, the ultra-narrow filtering feature makes such a bilayer resonator useful in the superconducting microwave electronics, such as a frequency sampler or spectrum analyzer in the signal processing.

Non-linear graphene optics for terahertz applications

The linear electrodynamic properties of graphene—the frequency-dependent conductivity, the transmission spectra and collective excitations—are briefly outlined. The non-linear frequency multiplication effects in graphene are studied, taking into account the influence of the self-consistent-field effects and of the magnetic field. The predicted phenomena can be used for creation of new devices for microwave and terahertz optics and electronics.

Student high efficiency power amplifier design competition [Education News

In 2005, the MTT-S High Power Amplifier Technical Coordinating Committee (MTT-5) decided to sponsor a Student High Efficiency Power Amplifier Design Competition with measurements and awards taking place at the International Microwave Symposium. The reasoning behind the contest was to attract students to the study of microwave electronics by providing them with an exciting challenge, make them aware of the importance of RF and microwave technology in our lives, and to encourage its study thus providing graduates with the skills needed by the job market and our society.

First Results of Experimental Tests of the Newly Developed NARL Phased-Array Doppler Sodar

Abstract A multifrequency phased-array Doppler sodar system has been installed recently at the National Atmospheric Research Laboratory (NARL) for the continuous observation of the lower atmosphere from near ground to the atmospheric boundary layer (ABL). The NARL sodar, developed in technical collaboration with the Society for Applied Microwave Electronics Engineering and Research (SAMEER), was built using piezoceramic tweeters, which are capable of generating 100-W acoustic power. In favorable atmospheric conditions, the sodar gives wind profiles up to 1 km. The performance evaluation is one of the most important aspects for quality assurance of sodar operations. This paper presents the first results of experimental observations of the NARL sodar system and its scientific validation. The NARL sodar has been validated using the simultaneous observation of another sodar system (Scintec model MFAS64). Various physical parameters of the atmosphere are derived using the results obtained from both of the systems. Comparison of simultaneous measurements by both of the sodars, located about 100 m apart, shows good agreement on wind speed, wind direction, and vertical wind variance. The correlation coefficient of more than 0.80 in wind speed and direction between the sodars shows the usefulness of the system for observing the atmosphere and deriving physical parameters below the ABL.

Modeling and characterization of a cantilever-based near-field scanning microwave impedance microscope

This paper presents a detailed modeling and characterization of a microfabricated cantilever-based scanning microwave probe with separated excitation and sensing electrodes. Using finite-element analysis, we model the tip-sample interaction as small impedance changes between the tip electrode and the ground at our working frequencies near 1 GHz. The equivalent lumped elements of the cantilever can be determined by transmission line simulation of the matching network, which routes the cantilever signals to 50 Omega feed lines. In the microwave electronics, the background common-mode signal is canceled before the amplifier stage so that high sensitivity (below 1 aF capacitance changes) is obtained. Experimental characterization of the microwave microscope was performed on ion-implanted Si wafers and patterned semiconductor samples. Pure electrical or topographical signals can be obtained from different reflection modes of the probe.

Two-surface wave decay: Controlling power transfer in plasma-surface interactions

Controlled interaction of high-power pulsed electromagnetic radiation with plasma-exposed solid surfaces is a major challenge in applications spanning from electron beam accelerators in microwave electronics to pulsed laser ablation-assisted synthesis of nanomaterials. It is shown that the efficiency of such interaction can be potentially improved via an additional channel of wave power dissipation due to nonlinear excitation of two counterpropagating surface waves, resonant excitations of the plasma-solid system.

Radar Interferometric Measurements With a Planar Patch Antenna Array

A planar patch antenna array has been made for radar interferometry. The antenna array consists of 32 rectangular patches on a ceramic loaded teflon substrate. The patches are individually coupled to the microwave electronics in two orthogonal circular polarizations. The radar interferometer is intended for topographic imaging in industrial environment, in this case, a blast furnace producing hot metal for the steel and metal industry. Ordinary imaging techniques with IR or visible radiation are not possible to use due to high temperatures, scattering from dust and particles. A model of blast furnace burden material surface was measured and detected.

RETRACTED: Synthesis and properties of Ba(Zn1/3Ta2/3)O3 for microwave and millimeter wave applications

High dielectric materials have gained an important position in microwave electronics by reducing the size and cost of components for a wide range of applications from mobile telephony to spatial communications. Ba(Zn 1/3 Ta 2/3 )O 3 (BZT) is an A(B'B)O 3 type perovskite material, showing ultra high values of the quality factor Q. Ceramic-based BZT dielectric materials were prepared by solid state reaction. The samples were sintered at temperatures in the range 1400÷1600 °C for 4 h. Compositional, structural and morphological characterization were performed by using XRD, SEM and EDX analysis. The dielectric properties were measured in the microwave range (6÷7 GHz). An additional annealing at 1400 °C for 10 h has improved some dielectric parameters. For samples sintered at temperatures higher than 1500 °C, the permittivity values were obtained in the interval 30-35 and almost do not change the value after the annealing. The Q×f product substantially increases up to about 135,000 GHz, exhibiting a low temperature coefficient of the resonant frequency (τ f ) in microwaves. The best parameters were obtained for the samples sintered at 1600 °C with additional annealing. The achieved high values of the Q×f product recommend these materials for microwave and millimeter wave applications.