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Frequency Operation (frequency + operation)

Distribution by Scientific Domains
Engineering60%

Selected Abstracts

Textured Microstructure and Dielectric Properties Relationship of BaNd2Ti5O14 Thick Films Prepared by Electrophoretic Deposition

ADVANCED FUNCTIONAL MATERIALS, Issue 7 2009
Zhi Fu
Abstract An alternative approach to tailor the temperature coefficient of permittivity (TC,r) of high Q dielectric BaO,Re2O3,TiO2 (Re: rare earth elements) thick films is presented. 10- to 80-µm-thick BaNd2Ti5O14 (BNT) films are fabricated by electrophoretic deposition on Pt foils under different processing conditions. Observed anisotropic grain growth is facilitated by constrained sintering. The increase of the sintering temperature increases markedly the aspect ratio of the grains, decreases the dielectric permittivity and TC,r changes from ,114 to +12,ppm °C,1. By controlling the sintering temperature, near-zero TC,r, high Q thick films can be fabricated with 45,<,,r,<,70. These findings are of technological relevance since they demonstrate that control of substrate constraint and sintering conditions can be used to control grain anisotropy and thus microwave properties of the BaO,Re2O3,TiO2. The thick films facilitate scaling to small device sizes for high frequency operation. Similar observations are expected in other microwave systems thus opening further technological opportunities. [source]

Compact dual-mode bandpass filter using arrow-shaped slot resonator

MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 12 2009
Youngje Sung
Abstract A novel design of a compact bandpass ring slot filter for achieving dual-mode operation is proposed and experimentally studied. By using an arrow-shaped slot structure as a resonator, the resonant frequency of the proposed filter is significantly lowered, which can lead to a large filter size reduction for a fixed frequency operation. Two degenerate modes are achieved by loading with proper asymmetry, which can be placed at the corner of diagonals. A prototype of the proposed design is implemented and measured. From the measured results, the proposed filter has about 5.2% bandwidth at the center frequency of 0.97 GHz and a minimum insertion loss of 1.07 dB within passband. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 2989,2991, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24809 [source]

Dielectric resonator antenna: Operation of the magnetodielectric composites Cr0.75Fe1.25O3 (CRFO)/Fe0.5Cu0.75Ti0.75O3 (FCTO)

MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 2 2007
H. H. B. Rocha
Abstract The probe-feed cylindrical dielectric resonator antennas (DRA) based on a new magnetodielectric composites Cr0.75Fe1.25O3 (CRFO)/Fe0.5Cu0.75Ti0.75O3 (FCTO) are investigated. The experimental and theoretical characteristics of the antenna like return loss, bandwidth, input impedance, and radiation patterns are in good agreement. Numerical validation is done, tacking into account the air gaps between the dielectric resonator and the metallic conductors. Frequency response bandwidth in the range of 6.6,11.8% was obtained for frequency operation around 4 GHz. The CRFO-FCTO present a dielectric constant in the range of 8,13 with loss around 10,3. To summarize, the performance of a cylindrical DRA based in a new matrix CRFO/FCTO was examined. These measurements confirm the potential use of such materials for small DRA. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 409,413, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22160 [source]

Optimization of AlGaN/GaN HEMTs for high frequency operation

PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 7 2006
T. Palacios
In the article [1] featured at Editor's Choice, the structure and processing of AlGaN/GaN high electron mobility transistors (HEMTs) have been optimized for maximum small signal gain at high frequencies. The cover picture combines the sample structure , shown schematically and in a scanning electron microscopy image , with the band diagram of the sample with an InGaN back-barrier used to increase the electron confinement in comparison to a standard HEMT. The first author, Tomás Palacios, is currently a Project Scientist at UCSB. His research interest focuses on the search of novel GaN-based transistors for mm-wave applications and biological sensors. He is one of the winners of the physica status solidi Young Researcher Awards for his outstanding presentation at the 6th International Conference on Nitride Semiconductors held in Bremen, Germany, in 2005. Further articles from ICNS-6 will also be published in phys. stat. sol. (b) 243, No. 7 (2006) and phys. stat. sol. (c) 3, No. 6 (2006). The present issue of phys. stat. sol. (a) as well as phys. stat. sol. (c) 3, No. 5 (2006) also contain papers presented at the International Conference on Nanoscale Magnetism (ICNM-2005) in Gebze, Turkey. [source]

Petri nets based FPGA controller of PDP sustainer with half-voltage energy recovery circuit,

ASIAN JOURNAL OF CONTROL, Issue 3 2010
Jian-Long Kuo
Abstract This paper proposes a FPGA controller design of a driver circuit based Petri nets for the Plasma Display Panel (PDP). In such a driver circuit, complicated control logic is required in the PDP sustainer circuit to implement the sustaining voltage waveform. The control logic has the zero-switching behaviour for the driver circuit to provide better efficiency for the driving circuit. Conventionally, the VHDL programmer does not have a systematic way to program the control logic. Time delay problem of logic components in logic controller may occur under high frequency operation. With the help of the proposed Petri nets approach, the VHDL programming for the PDP driver circuit can be easier in a systematic way. Also, this paper illustrates three types of sustainers with Petri nets based FPGA controller. The basic full-bridge and full-voltage sustainers are used to compare the performance with the proposed half-voltage sustainer. Details of the circuit operation are described. From the experimental results, the performance such as efficiency, luminance, and gamma curve are assessed to show the effectiveness of the proposed half-voltage sustainer. It is believed that the proposed Petri nets based control circuit is very powerful for the practical application of the PDP sustainer circuit. Copyright © 2010 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society [source]