614 research outputs found
2009 Index IEEE Antennas and Wireless Propagation Letters Vol. 8
This index covers all technical items - papers, correspondence, reviews, etc. - that appeared in this periodical during the year, and items from previous years that were commented upon or corrected in this year. Departments and other items may also be covered if they have been judged to have archival value. The Author Index contains the primary entry for each item, listed under the first author\u27s name. The primary entry includes the coauthors\u27 names, the title of the paper or other item, and its location, specified by the publication abbreviation, year, month, and inclusive pagination. The Subject Index contains entries describing the item under all appropriate subject headings, plus the first author\u27s name, the publication abbreviation, month, and year, and inclusive pages. Note that the item title is found only under the primary entry in the Author Index
2008 Index IEEE Transactions on Control Systems Technology Vol. 16
This index covers all technical items - papers, correspondence, reviews, etc. - that appeared in this periodical during the year, and items from previous years that were commented upon or corrected in this year. Departments and other items may also be covered if they have been judged to have archival value. The Author Index contains the primary entry for each item, listed under the first author\u27s name. The primary entry includes the coauthors\u27 names, the title of the paper or other item, and its location, specified by the publication abbreviation, year, month, and inclusive pagination. The Subject Index contains entries describing the item under all appropriate subject headings, plus the first author\u27s name, the publication abbreviation, month, and year, and inclusive pages. Note that the item title is found only under the primary entry in the Author Index
Novel Dual Band Frequency Selective Surface and its Applications on the Gain Improvements of Compact UWB Monopole Antenna
In this work, a highly directional ultra-wideband (UWB) microstrip patch antenna as a single-element is suggested. The proposed antennaâs gain is enhanced with a novel dual-band frequency selective surface (FSS) placed beneath it. The FSS design has a hexagonal structure with meander line inductances and a capacitance-like structure connecting all of the corners to the middle. There is no metallic layer on the other side of the substrate, which shows transmission zeros at 4.95 GHz and 12.7 GHz, and a modified U-shaped monopole antenna is developed. First, the performance characteristics of the antenna and FSS are analyzed from the simulation results, and they are validated experimentally after fabrication, followed by measurement. The compact configuration comprises an antenna loaded with the proposed FSS results S11 less than -10 dB from 3.15 GHz to 22.65 GHz, covering the UWB band together with the X, Ku-band with a bandwidth of 19.5 GHz (151.16% FBW). The antennaâs overall physical dimensions would be 38.8 mmĂ38.8 mmĂ25.2 mm (0.407λoĂ0.407λoĂ0.265λo), with λo denoting the lowest frequencyâs free-space wavelength. The FSS loading results in a 9.9 dBi maximum gain at 10 GHz. The antennaâs small size increases bandwidth, and its high peak gain makes it ideal for use in real-time applications
Ultra-wideband tightly coupled phased array antenna for low-frequency radio telescope
This paper introduces a novel approach to a broadband array design for a low frequency radio telescope. It presents a low profile ultra-wideband tightly coupled phased array antenna with integrated feedlines. The approach consists of applying broadband techniques to an array of capacitively coupled planar element pairs with an octagonal fractal geometry, backed by a ground plane. Designed as a low cost, low loss, dual-polarized wideband array, this antenna is optimised for operation between 50 and 250 MHz. Simulations have shown that the antenna has a wide-scanning ability with a low cross-polarisation level, over the operational broad frequency range.peer-reviewe
Time-Scale Domain Characterization of Time-Varying Ultrawideband Infostation Channel
The time-scale domain geometrical-based method for the characterization of the time varying ultrawideband (UWB) channel typical of an infostation channel is presented. Compared to methods that use Doppler shift as a measure of time-variation in the channel this model provides a more reliable measure of frequency dispersion caused by terminal mobility in the UWB infostation channel. Particularly, it offers carrier frequency independent method of computing wideband channel responses and parameters which are important for ultrawideband systems. Results show that the frequency dispersion of the channel depends on the frequency and not on the choice of bandwidth. And time dispersion depends on bandwidth and not on the frequency. It is also shown that for time-varying UWB, frame length defined over the coherence time obtained with reference to the carrier frequency results in an error margin which can be reduced by using the coherence time defined with respect to the maximum frequency in a given frequency band. And the estimation of the frequency offset using the time-scale domain (wideband) model presented here (especially in the case of multiband UWB frequency synchronization) is more accurate than using frequency offset estimate obtained from narrowband models
Acoustic excitation on flame properties caused by two sound sources
Research and development in understanding the responses of acoustic excitation as a
meant to influence flame behavior have become one of the significant issues in
combustion instability. This interaction can be found in most processing, power
generating, and propulsion application. Some of the responses that can be seen from
the interaction are lift-off phenomenon, changes of flame macroscopic structure, and
production of emission that contribute to the environment. However, it seems there
are insufficient data that were focusing mainly on the change of flame properties and
how it's being affected by the increase of acoustic excitation. The need to publish
some of the significant results and helps improve the understanding of combustion
instabilities became the major motivational in conducting the research. This study
adopted experimental research and understanding the change of flame behavior by
differentiates two number of speakers (source of acoustic) excited to the flame. For
data collection, it employs a direct imaging technique using a DSLR camera. The
data obtained were analyzed using image processing software, Image J. This
experiment focuses on the change of flame properties based on the number of the
speaker (source of acoustic) used with the increased number of frequencies. The
flame shape obtain in this experiment is divided into disturbances and un-disturbance
categories, and each shape is then thoroughly discussed by focusing on the change of
its length, width, and angle. The results from this experiment shows that the response
of flame is significantly affected by the configuration of speakers (sound source) and
the magnitude of amplitude used. It indicated that for dual speakers and higher
amplitude in terms of its flame characteristic shows a promising flame response
compare with a single speaker and lower amplitud
Backscatter Transponder Based on Frequency Selective Surface for FMCW Radar Applications
This paper describes an actively-controlled frequency selective surface (FSS) to implement a backscatter transponder. The FSS is composed by dipoles loaded with switching PIN diodes. The transponder exploits the change in the radar cross section (RCS) of the FSS with the bias of the diodes to modulate the backscattered response of the tag to the FMCW radar. The basic operation theory of the system is explained here. An experimental setup based on a commercial X-band FMCW radar working as a reader is proposed to measure the transponders. The transponder response can be distinguished from the interference of non-modulated clutter, modulating the transponderâs RCS. Some FSS with different number of dipoles are studied, as a proof of concept. Experimental results at several distances are provided
Uneven-Layered Coding Metamaterial Tile for Ultrawideband RCS Reduction and Diffuse Scattering
In this paper, a novel uneven-layered coding metamaterial tile is proposed for ultra-wideband radar cross section (RCS) reduction and diffuse scattering. The metamaterial tile is composed of two kinds of square ring unit cells with different layer thickness. The reflection phase difference of 180° (±37°) between two unit cells covers an ultra-wide frequency range. Due to the phase cancellation between two unit cells, the metamaterial tile has the scattering pattern of four strong lobes deviating from normal direction. The metamaterial tile and its 90-degree rotation can be encoded as the â0â and â1â elements to cover an object, and diffuse scattering pattern can be realized by optimizing phase distribution, leading to reductions of the monostatic and bi-static RCSs simultaneously. The metamaterial tile can achieve â10 dB RCS reduction from 6.2 GHz to 25.7 GHz with the ratio bandwidth of 4.15:1 at normal incidence. The measured and simulated results are in good agreement and validate the proposed uneven-layered coding metamaterial tile can greatly expanding the bandwidth for RCS reduction and diffuse scattering
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