Showing papers in "Microwave and Optical Technology Letters in 1999"
TL;DR: The proposed single-channel color image encryption method is more compact and robust than the multichannels methods and since color information is added to the shape information, better verification performance can be achieved in optical security systems.
Abstract: A new encryption technique is proposed to encrypt color images using existing optical encryption systems for gray-scale images. The color images are converted to their indexed image formats before they are encoded. At the decryption end, the color images are recovered by converting the decrypted indexed images back to their RGB formats. The proposed single-channel color image encryption method is more compact and robust than the multichannels methods. Since color information is added to the shape information, better verification performance can be achieved in optical security systems. ©1999 John Wiley & Sons, Inc. Microwave Opt Technol Lett 21: 318–323, 1999.
144 citations
TL;DR: In this article, 2D photonic bandgap reflectors in microstrip technology have been proposed and simulations and measurements have been realized, giving very similar performance for both 1-D and 2-D structures.
Abstract: Recently, 2-D photonic bandgap reflectors in microstrip technology have been proposed. Finite-element 3-D electromagnetic simulation shows negligible values of the fields outside the central row of the periodic pattern. This suggests the use of 1-D patterns to reduce the transversal size of the reflectors. Simulations and measurements have been realized, giving very similar performance for both 1-D and 2-D structures. ©1999 John Wiley & Sons, Inc. Microwave Opt Technol Lett 22: 411–412, 1999
118 citations
TL;DR: In this paper, a new design of a rectangular microstrip antenna with a directly coupled patch and two gap-coupled parasitic patches for achieving broadband operation is proposed and experimentally studied.
Abstract: A new design of a rectangular microstrip antenna with a directly coupled patch and two gap-coupled parasitic patches for achieving broadband operation is proposed and experimentally studied. The proposed broadband antenna has a compact configuration such that the required realty space for implementing the antenna is minimized. Experimental results show that the proposed antenna can have an antenna bandwidth greater than six times that of a single rectangular microstrip antenna. Details of the proposed antenna are described, and experimental results of the broadband performance are presented and discussed. ©1999 John Wiley & Sons, Inc. Microwave Opt Technol Lett 22: 348–349, 1999.
77 citations
TL;DR: In this paper, the authors present the LEMA-ARTICLE-1999-010, which is the current state-of-the-art in the field of computer vision.
Abstract: Reference LEMA-ARTICLE-1999-010doi:10.1002/(SICI)1098-2760(19990805)22:3 3.0.CO;2-2 Record created on 2006-11-30, modified on 2016-08-08
63 citations
TL;DR: In this paper, the intrinsic properties of a two-dimensional rectangular and three-dimensional parallelepipedic lattice photonic bandgap (PBG) material were used to design a cover antenna.
Abstract: In this paper, we use the intrinsic properties of a two-dimensional rectangular and three-dimensional parallelepipedic lattice photonic bandgap (PBG) material to design a cover antenna. We demonstrate the interest in such a device for increasing the directivity of a patch antenna. ©1999 John Wiley & Sons, Inc. Microwave Opt Technol Lett 22: 136–139, 1999.
60 citations
TL;DR: In this article, the impedance bandwidth and cross-polarization characteristics of shorted patch antennas were investigated experimentally, and it was found that, for a square quarter-wave patch on foam substrate of thickness 5.8% of wavelength, the bandwidth is 18.54%, which is more than three times that of the half-wave patches.
Abstract: The impedance bandwidth and cross-polarization characteristics of quarter-wave shorted patch antennas are investigated experimentally. It is found that, for a square quarter-wave patch on foam substrate of thickness 5.8% of wavelength, the bandwidth is 18.54%, which is more than three times that of the half-wave patch. The cross polarization in the H-plane is very large at oblique angles, even if a think substrate is used. ©1999 John Wiley & Sons, Inc. Microwave Opt Technol Lett 22: 101–103, 1997.
57 citations
56 citations
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TL;DR: In this paper, a planar antenna with a dipole-like radiation pattern has been proposed, which is suitable for phased-array applications, and the analysis is carried out both theoretically and experimentally, and very good agreement is observed.
Abstract: In this letter, a new design for a planar antenna is introduced. The antenna is built using coplanar technology. It has dual-frequency operation: the first and second resonances are in the X- and Ku-bands, respectively. The proposed antenna has wideband behavior around both resonance frequencies. It has a dipole-like radiation pattern, which makes it suitable for phased-array applications. The analysis is carried out both theoretically and experimentally, and very good agreement is observed. The results include the return loss, the current distribution, the radiation patterns, and the antenna gain. ©1999 John Wiley & Sons, Inc. Microwave Opt Technol Lett 22: 288–290, 1999.
53 citations
52 citations
TL;DR: This letter presents a complete equivalent circuit of a receive antenna in terms of the radiation field function of the element and of the amplitude and phase of the incoming wave.
Abstract: This letter presents a complete equivalent circuit of a receive antenna. The induced voltage or current in this equivalent circuit is expressed in terms of the radiation field function of the element and of the amplitude and phase of the incoming wave. ©1999 John Wiley & Sons, Inc. Microwave Opt Technol Lett 21: 244–246, 1999.
51 citations
TL;DR: In this article, a new method is derived for computing the wave propagation constant γ of a uniform transmission line based on the properties of a similar and unitary matrix, and allows us to minimize the errors due to connection repeatability.
Abstract: A new method is derived for computing the wave propagation constant γ of a uniform transmission line. The new method is based on the properties of a similar and unitary matrix, and allows us to minimize the errors due to connection repeatability. These matrices are obtained from the wave cascade matrices (computed from scattering parameter measurements) of two different length lines of identical but unknown characteristic impedance. The usefulness of the new method is demonstrated by assessing the dispersion of the dielectric constant eeff and the attenuation constant α of an ultra-low-loss transmission line in the frequency range of 0.040–65 GHz. ©1999 John Wiley & Sons, Inc. Microwave Opt Technol Lett 22: 268–271, 1999.
TL;DR: In this paper, the performance of a Ku-band gold/Ba05Sr05TiO3/LaAlO3 (Au/BSTO/LAO) coupled microstip line phase shifter fabricated with a 370 nm thick BSTO film was reported.
Abstract: We report on the performance of a Ku-band gold/Ba05Sr05TiO3/LaAlO3 (Au/BSTO/LAO) coupled microstip line phase shifter fabricated with a 370 nm thick BSTO film Two hundred degrees of contiguous relative insertion phase shift (ΔϕS21), with insertion losses of 46 dB, were measured at room temperature, 143 GHz, and maximum dc voltage of 400 V These results represent significant progress toward viable compact, low-loss, thin-film ferroelectric-based phase shifters at room temperature ©1999 John Wiley & Sons, Inc Microwave Opt Technol Lett 20: 53–56, 1999
TL;DR: In this paper, a new effectie finite-difference time-domain FDTD algorithm was proposed for modeling arbitrarily shaped dielectric surfaces. But the FDTD analysis of TE scattering by rotated two-dimensional 2D cylinders proides excellent numerical results.
Abstract: This paper introduces a new effectie finite-difference () time-domain FDTD algorithm for modeling arbitrarily shaped dielectric surfaces. The new algorithm is based on an effectie medium theory that makes the dielectric tensor effectie. The proposed FDTD analysis of TE () scattering by rotated two-dimensional 2-D dielectric cylinders proides excellent numerical results. Q 1999 John Wiley & Sons, Inc. Microwave Opt Technol Lett 23: 245)249, 1999.
TL;DR: In this article, the Sierpinski gasket fractal antenna and the tree-like fractal antennas have been investigated and the matched frequencies possess a log-periodic behavior.
Abstract: Experimental results show a multiband behavior for the Sierpinski gasket fractal antenna and the tree-like fractal antenna. Such behavior has been explained by the fractal structures of the antennas. We show that the matched frequencies possess a log-periodic behavior. ©1999 John Wiley & Sons, Inc. Microwave Opt Technol Lett 23: 242–245, 1999.
TL;DR: In this article, the effects of the use of wideband radiators and subarrays are assessed by means of two representative examples, and it is shown that the potential advantage presented by using wideband slot radiators is limited, while employing subarraying in the design of planar arrays is the most effective way of improving the bandwidth.
Abstract: Resonant arrays of waveguide slots suffer from severe bandwidth limitations, which are caused by the frequency dependence of the slot properties, and by the shift in the positions of the standing-wave peaks relative to the slot positions. In this paper, the effects of the use of wideband radiators and subarrays are assessed by means of two representative examples. Results indicate that the potential advantage presented by the utilization of wideband slot radiators is limited, while employing subarraying in the design of planar arrays is the most effective way of improving the bandwidth. ©1999 John Wiley & Sons, Inc. Microwave Opt Technol Lett 22: 35–39, 1999.
TL;DR: In this article, a new design of a circularly polarized printed square-slot antenna with a rectangular conducting patch is described, where the rectangular patch is placed along one of the center lines of the square slot.
Abstract: A new design of a circularly polarized printed square-slot antenna loaded with a rectangular conducting patch is described. The rectangular patch is placed along one of the center lines of the square slot. With the selection of proper dimensions of the rectangular patch, two orthogonal resonant modes with a 90° phase difference for circular polarization (CP) can be excited by using a microstrip feed line oriented along the diagonals of the square slot. The proposed slot antenna has been implemented and experimentally studied. An impedance bandwidth of 39% (determined from 10 dB return loss) and a 3 dB CP bandwidth of 12% (defined by a 3 dB axial ratio) for the proposed antenna have been obtained. The gain variation for the frequencies within the CP bandwidth is also observed to be less than 1.3 dB. Details of the antenna design and experimental results are presented and discussed. ©1999 John Wiley & Sons, Inc. Microwave Opt Technol Lett 23: 363–365, 1999.
TL;DR: In this article, a new design of a slot-loaded equilateral-triangular microstrip antenna for dual-frequency operation is presented, where a pair of narrow slots centered in the triangular patch and oriented parallel to the patch's center line can be achieved.
Abstract: A new design of a slot-loaded equilateral-triangular microstrip antenna for dual-frequency operation is presented. Results show that, by loading a pair of narrow slots centered in the triangular patch and oriented parallel to the patch's center line, a single-feed dual-frequency operation can be achieved. The two operating frequencies are associated with the perturbed TM10- and TM20-modes of the triangular microstrip antenna, and the two frequencies are of the same polarization planes and similar broadside radiation characteristics. Also, by controlling the length of the slots and the spacing between the two slots, the frequency ratio of the two frequencies is tunable within a range of about 1.35–1.5. ©1999 John Wiley & Sons, Inc. Microwave Opt Technol Lett 23: 82–84, 1999.
TL;DR: A new design method for microwave nonhomogeneous media filters is proposed that leads to closed-form design formulas by which physical properties of the filters can be carried out in a very fast way.
Abstract: In this paper, a new design method for microwave nonhomogeneous media filters is proposed. The application of this method leads to closed-form design formulas by which physical properties of the filters can be carried out in a very fast way. The proposed formulas can be successfully used because they are less time consuming than others known in the open technical literature. Some examples of analysis and synthesis are presented. ©1999 John Wiley & Sons, Inc. Microwave Opt Technol Lett 22: 218–221, 1999.
TL;DR: In this article, the effect of the air gap between a cylindrical dielectric resonator antenna and a microstrip line on the resonant frequency, directivity, unloaded Q-factor, and impedance bandwidth are studied.
Abstract: The effect of the air gap between a cylindrical dielectric resonator antenna and a microstrip line on the resonant frequency, directivity, unloaded Q-factor, and impedance bandwidth are studied. The antenna structure is numerically simulated with a software package based on the finite-element method. Appropriate correction factors are obtained, enabling an antenna engineer to incorporate the air-gap effect into the design of a microstrip-coupled cylindrical dielectric resonator antenna. The correction factors provide good agreement with the measured results in resonant frequency, unloaded Q-factor, and impedance bandwidth, but less accurate prediction in directivity for the specified range of parameters. ©1999 John Wiley & Sons, Inc. Microwave Opt Technol Lett 20: 36–40, 1999.
TL;DR: In this article, the perfectly matched layer (PML) concept is interpreted as a change in the metric of space, and the authors use the language of differential forms applied to the electromagnetic fields and explore the metric inariance of Maxwell's equations.
Abstract: The perfectly matched layer PML concept is interpreted as a change in the metric of space. By using the language of differential forms applied to the electromagnetic fields and exploring the metric inariance of Maxwell's equations, thearious prealent PML formula- () tions Maxwellian and non-Maxwellian are unified. The analysis also reeals that other PML formulations are also possible, embodying the preious PML formulations as special cases. Q 1999 John Wiley & Sons, Inc. Microwave Opt Technol Lett 20: 124)126, 1999.
TL;DR: In this article, a dual-frequency design of a single-layer, single-feed circular microstrip antenna with an open-ring slot is demonstrated, and the frequency ratio between the two frequencies within a range of about 1.23-1.32 has also been obtained.
Abstract: A novel dual-frequency design of a single-layer, single-feed circular microstrip antenna with an open-ring slot s demonstrated. The open-ring slot is embedded close to the boundary of the circular patch, and has a small spacing between the two open ends of the slot. By selecting suitable widths of the open-ring slot, a dual-frequency operation with its two operating frequencies having similar broadside radiation patterns, the same polarization planes, and small antenna-gain differences can be obtained. The frequency ratio between the two frequencies within a range of about 1.23–1.32 has also been obtained. Details of the antenna design and experimental results for the dual-frequency performances are presented. ©1999 John Wiley & Sons, Inc. Microwave Opt Technol Lett 22: 157–160, 1999.
TL;DR: In this article, the authors theoretically investigate waveguide bends in three-dimensional dielectric photonic bandgap (PBG) materials, and they found that 100% transmission efficiency can be achieved through the 90° bend.
Abstract: We theoretically investigate waveguide bends in three-dimensional dielectric photonic bandgap (PBG) materials. The PBG materials used in this study consist of layers of alumina rods. An L-shaped waveguide is created by removing part of the rod in one layer and part of the rod in the next layer. The removed rods are perpendicular to each other. Using finite-difference time-domain (FDTD) simulations, we found that 100% transmission efficiency can be achieved through the 90° bend. ©1999 John Wiley & Sons, Inc. Microwave Opt Technol Lett 23: 56–59, 1999.
TL;DR: By using tapering techniques in recently proposed two-dimensional (2-D) photonic bandgap (PBG) structures for microstrip lines, a great improvement in the sidelobe level of the frequency response is achieved as discussed by the authors.
Abstract: By using tapering techniques in recently proposed two-dimensional (2-D) photonic bandgap (PBG) structures for microstrip lines, a great improvement in the sidelobe level of the frequency response is achieved. Simulations have been performed by using HPTM Momentum and, in accordance with the measurements, give promising potential for these structures. ©1999 John Wiley & Sons, Inc. Microwave Opt Technol Lett 22: 207–211, 1999
TL;DR: In this paper, a compact circular polarization (CP) design of a single-feed equilateral-triangular microstrip antenna with a Y-shaped slot is presented, which can have an antenna size reduction up to about 19% for operating at a given frequency for circular polarization.
Abstract: A novel compact circular polarization (CP) design of a single-feed equilateral-triangular microstrip antenna with a Y-shaped slot is presented. The Y-shaped slot is cut in the patch with its upper two arms facing either the triangle tip or the bottom side of the triangular patch. Results show that, with a proper size of the Y-shaped slot, the present proposed design can have an antenna size reduction up to about 19% for operating at a given frequency for circular polarization, as compared to the regular-size circularly polarized triangular microstrip antenna. The proposed antenna design is described and studied. ©1999 John Wiley & Sons, Inc. Microwave Opt Technol Lett 20: 31–34, 1999.