Showing papers in "Microwave and Optical Technology Letters in 2004"
TL;DR: In this article, a new ultra-wideband (UWB) antenna for UWB applications is proposed, which is designed to operate from 3.2 to 12 GHz and consists of a rectangular patch with two steps, a single slot on the patch, and a partial ground plane.
Abstract: In this paper, we propose a new ultra-wideband (UWB) antenna for UWB applications. The proposed antenna is designed to operate from 3.2 to 12 GHz. It consists of a rectangular patch with two steps, a single slot on the patch, and a partial ground plane. Details of the proposed antenna design and measured results are presented and discussed. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 40: 399–401, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11392
304 citations
TL;DR: In this paper, the authors derived a new condition for isotropic dielectric-magnetic materials exhibiting negative phase velocity, and the equivalence of that condition with previously derived conditions.
Abstract: The derivation of a new condition for characterizing isotropic dielectric-magnetic materials exhibiting negative phase velocity, and the equivalence of that condition with previously derived conditions, are pre-
242 citations
TL;DR: In this paper, a square planar monopole antenna capable of providing a very wide impedance bandwidth of larger than 10 GHz is presented, which is achieved by using a new impedance-matching technique of cutting a pair of notches at the two lower corners of the square plane.
Abstract: A new square planar monopole antenna capable of providing a very wide impedance bandwidth of larger than 10 GHz is presented. The ultra-wideband property for the proposed antenna is achieved by using a new impedance-matching technique of cutting a pair of notches at the two lower corners of the square planar monopole. With suitable dimensions of the notches chosen, the impedance bandwidth of the proposed antenna can be greatly enhanced to be larger than four times that of a corresponding simple square planar monopole antenna (about 10.7 versus 2.5 GHz in this study). A constructed prototype with an ultra-wideband property covering the 2–11-GHz band for IEEE 802.16a operation is presented and discussed. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 42: 463–466, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20337
137 citations
TL;DR: In this article, a frequency-selective surface (FSS) superstrate was proposed as an alternative to an EBG type of dielectric superstrate to reduce its height and facilitate the fabrication process.
Abstract: In this paper, we introduce a novel design for a high-directivity Electromagnetic Band Gap (EBG) resonator antenna that utilizes a frequency-selective surface (FSS) superstrate. The above type of superstrate is proposed as an alternative to an EBG type of dielectric superstrate—investigated previously by the authors—to reduce its height and facilitate the fabrication process. Although FSS superstrate and the patch antenna comprise a composite resonator, we begin by investigating the FSS structure characteristics first before dealing with the combination. We vary several important parameters, such as the distance between the FSS superstrate and the ground plane of the antenna, and the dimensions of the FSS superstrate, to determine their effect on the resonant frequency and the quality factor of the unit cell of the FSS. The above study enables us to derive some guidelines for an optimum array size of the FSS superstrate that eventually leads to a maximum directivity for the FSS antenna composite, as evidenced via a comparison of the quality factors of the FSS, the unit cell, and the composite. It is demonstrated that the directivity of the antenna with an optimized array size of the FSS superstrate increases by 17.29 to 24.92 dBi for three different strip-dipole lengths, as compared to that of the patch antenna alone (maximum 6 dBi). © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 43: 462–467, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20502
134 citations
TL;DR: In this paper, the directivity and gain of several types of time-modulated linear antenna arrays are obtained, including arrays with isotropic elements, parallel short dipoles, and collinear short dipole.
Abstract: In this paper, the directivity and gain of several types of time-modulated linear antenna arrays are obtained. Three types of array elements are considered: arrays with isotropic elements, parallel short dipoles, and collinear short dipoles. Curves of directivity as functions of inter-element spacing and sidelobe levels (SLLs) are presented. A comparison between the computed and measured gains of a time-modulated printed dipole linear array shows reasonable agreement. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 42: 167–171, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20241
96 citations
TL;DR: In this paper, the overall reflection and transmission coefficients of a multilayered structure consisting of metamaterial and dielectric slabs are analyzed for anti-reflection coatings and high-reflectivity coatings.
Abstract: Expressions are given for the overall reflection and transmission coefficients of a multilayered structure consisting of metamaterial and dielectric slabs. Small-reflection approximations are discussed. Two applications are proposed: anti-reflection coatings and high-reflection coatings. For the first application, a structure consisting of two slabs of the same width and opposite permittivities is studied. If the structure is placed between two semi-infinite media of the same kind, the reflection vanish, while if these two media are different, the reflection depends only on their characteristics and on the angle of incidence. This device could be advantageously used as an antenna radome. For the second application, a structure consisting of a large number of identical pairs of slabs of high and low opposite permittivities and of the same widths, embedded in the same medium, is studied. This structure's transmittance variation with frequency shows no ripples, and has a large passband and a monotonous quasi-symmetric rise to the right and to the left of the central frequency. The distinctive feature of these devices is the weakening of the influence of the frequency, the angle of incidence or the polarization on the propagation processes. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 40: 460–465, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20005
90 citations
TL;DR: A new method is presented to extend the traditional multilevel fast multipole algorithm (MLFMA) and fast inhomogeneous plane‐wave algorithm (FIPWA) seamlessly into the low‐frequency range, using evanescent‐wave extrapolation and translation techniques to overcome the low-frequency breakdown problem.
Abstract: A new method, the low-frequency fast inhomogeneous plane-wave algorithm (LF-FIPWA) is presented to extend the traditional multilevel fast multipole algorithm (MLFMA) and fast inhomogeneous plane-wave algorithm (FIPWA) seamlessly into the low-frequency range. It uses evanescent-wave extrapolation and translation techniques to overcome the low-frequency breakdown problem. The accuracy can be well controlled over a broad frequency range. Numerical examples show the effectiveness of this new algorithm. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 40: 117–122, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11302
82 citations
TL;DR: In this paper, a 2D FDFD method was used to analyze the dispersion and attenuation characteristics of a ferrite-filled waveguide with 0M0 178.0 mT, 0H0 80.0 and 0H 0 141.2 mT.
Abstract: H 0H0 jH /2 , (10) M 0M0. (11) At first, the analysis is performed to obtain the dispersion characteristics of a ferrite-filled waveguide with 0M0 178.0 mT, 0H0 80.0, and 141.2 mT, respectively. The magnetic loss H is assumed to be zero in this calculation. The numerical results calculated by the present method (see Fig. 3), agree very well with the theoretical results and the 3D FDTD numerical results. Secondly, the present method is also employed for analyzing the attenuation characteristic of a ferrite-filled waveguide. In this calculation, the magnetic losses H are chosen as 79.6 and 796 A/m (1.0 and 10.0 Oe, respectively), 0M0 178.0 mT, and 0H0 141.2 mT. The results for these calculations, shown in Figure 4, also show good agreement with the theoretical results and the 3D FDTD numerical results. 4. CONCLUSION A 2D FDFD method to analyze the dispersion characteristic of ferrite devices has been presented and demonstrated. The calculated result of the dispersion and attenuation characteristic of a ferrite-filled waveguide agrees very well with the theoretical result obtained from analytical approach and the 3D FDTD numerical result. Although the final eigen equation employed only four transverse-field components, it was confirmed to be sufficient for the analysis of the dispersion characteristics of ferrite devices. Therefore, it was shown to be more efficient than the method using six field components. In the calculation, although the elimination of longitudinal components does not help to reduce the memoryspace requirement due to the increased number of terms in the remaining equations, the calculation time is considerably reduced, as compared to the case in which six field components are involved. Furthermore, when the frequency characteristic for a narrow range, for example, a resonator analysis made of artificial material, the FDFD method becomes more attractive, since it can effectively analyze the dispersion characteristics for a limited frequency range.
82 citations
TL;DR: In this article, a parametric study of the feeding structure is conducted using FDTD code to assess the influence of the dimension of the slope-strip feed line on the antenna performance and to find the optimal impedance bandwidth.
Abstract: A parametric study of the feeding structure is conducted using FDTD code in order to assess the influence of the dimension of the slope-strip feed line on the antenna performance and to find the optimal impedance bandwidth. In the design process, a rectangular radiating patch with dimensions 25 25 mm is chosen. The dimensions of the slope-strip feeding structure are determined by the parameters H, h, and t. The parameter t is the horizontal offset of the free end of the slope-strip feed line from the center location of the patch. Here, h (the distance between the free end of the slope-strip feed line and the radiation patch) is selected to be 0.5 mm. The simulated results demonstrate that the parameters H and t are two important variables which affect the antenna’s impedance-bandwidth characteristics. Figure 2 illustrates the normalized impedance (normalized to 50) and return loss of the antenna for various heights H of the foam substrate with t 0.0 mm and for various values of t with H 8 mm. It is seen that, for the case with H 8 mm and t 0, the optimal bandwidth performances are achieved. Using the abovementioned design dimensions, a prototype of the proposed antenna was successfully implemented and measured. Figure 3 illustrates the experimental return loss of the constructed prototype with H 8 mm, h 0.5 mm, and t 0 mm, which shows that the simulated results in general agree with the measured data. The impedance bandwidth, determined from 10-dB return loss, reaches 2.26 GHz (3.10 –5.36 GHz) or about 53.4%, referenced to the center frequency of 4.23 GHz. The simulated and experimental results show that the proposed antenna structure has a similar radiation characteristic with that of the L-strip-fed microstrip patch antenna in [5]. 3. CONCLUSION A slope-strip line-feeding technique for a microstrip antenna has been introduced. An antenna fed by the shaped microstrip has been investigated, fabricated, and tested. Experimental data show that the antenna achieves optimal impedance characteristics with a bandwidth of 53.4% for less than 10-dB return loss. This new antenna may find potential applications in broadband antennaarray designs and corresponding wireless-communication systems. ACKNOWLEDGMENT
82 citations
TL;DR: In this paper, a uniplanar and bimetal structure with split-ring resonators was proposed for a CPW-SRR-CPW system, which exhibits almost negligible insertion losses in the pass band, and sharp cutoff and a high level of rejection in the stop band, with few unit cells.
Abstract: Coplanar waveguide (CPW) transmission lines periodically coupled to split-ring resonators (SRRs) are analyzed, designed, and characterized. Due to inductive coupling between the lines and SRRs, signal propagation is inhibited in the vicinity of the resonant frequency of the rings. The result is a stop-band behavior that can be of interest for the elimination of frequency parasitics in CPW-based devices. Two different approaches are envisaged: a uniplanar structure, where CPW and rings share the same metal level; and a bimetal structure with SRRs etched on the back side of the substrate. It has been found that the latter exhibits almost negligible insertion losses in the pass band, and sharp cutoff and a high level of rejection in the stop band, with few unit cells. Since ring dimensions are small compared to the signal wavelength at resonance, the proposed SRR-CPWs are very promising for the design of miniaturized microwave circuits. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 40: 3–6, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11269
79 citations
TL;DR: In this article, the use of an asymmetrical feed probe is shown to significantly increase the impedance bandwidth of a square planar monopole antenna, and the effect of the asymmetry on radiation patterns is also shown.
Abstract: The use of an asymmetrical feed probe is shown to significantly increase the impedance bandwidth of a square planar monopole antenna. The feed probe is offset from the center of the planar element. The optimum location of the feed probe is shown to increase the impedance bandwidth by a factor of 3.4. The effect of the asymmetry on radiation patterns is also shown. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 40: 156–158, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11313
TL;DR: In this article, a new T-shaped monopole antenna with a CPW feed line is presented, and the theoretical analysis is based on the finite-difference time-domain (FDTD) method.
Abstract: A new T-shaped monopole antenna with a CPW feed line is presented. The theoretical analysis is based on the finite-difference time-domain (FDTD) method. The novel antenna is designed, fabricated, and then measured. The measured results, which agree with the numerical calculations very well, are given. The measured bandwidth of the antenna is approximately 116% for VSWR ≤ 2.0. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 43: 50–52, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20372
TL;DR: In this article, the design and experimental results of low profile microstrip dipole antenna with tapered balun shows fairly good performances in this design, with wide bandwidth and low power loss tapered microstrip line to overlap coplanar stripline transition that provided unbalanced to balanced equal power of 180° phase difference.
Abstract: In this design, the dipole antenna fed network with tapered balun is studied. The design and experimental results of low profile microstrip dipole antenna with tapered balun shows fairly good performances in this paper. The feed network with wide bandwidth and low power loss tapered microstrip line to overlap coplanar stripline (CPS) transition that provided unbalanced to balanced equal power of 180° phase difference. The achieved planar dipole antenna exhibits 19% of 10-dB bandwidth. Full wave EM analyses shows good agreement with those experimental data. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 40: 344–346, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11374
TL;DR: In this article, the defect frequencies of an electromagnetic bandgap superstrate with the objective of enhancing the directivity of a patch antenna at two frequency bands were investigated and two different defect configurations, the first is introduced by the ground plane of the antenna while the other is produced by a row of rods with dissimilar dielectric constants in the EBG structure, are examined in detail in order to achieve dual-band operation.
Abstract: In this paper, we propose a novel design technique to control the defect frequencies of an electromagnetic bandgap (EBG) superstrate with the objective of enhancing the directivity of a patch antenna at two frequencies. Two different defect configurations, the first of which is introduced by the ground plane of the antenna while the other is produced by a row of rods with dissimilar dielectric constants in the EBG structure, are examined in detail in order to achieve dual-band operation. We begin by investigating the EBG structure and varying several of its parameters to determine the locations of the bandgap and defect frequencies, as well as their controllability. Finally, the promising designs for the EBG superstrates, which provide enhanced directivities for the EBG antenna, are evaluated to validate the proposed design scheme. It is demonstrated that the directivity of the antenna with a 12 × 3 EBG superstrate increases to 18 and 18.5 dBi, respectively, at the two design frequency bands, as compared to that of the antenna alone (maximum 10 dBi) without the superstrate. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 42: 25–31, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20196
TL;DR: In this article, the authors present a simulation of a left-handed metamaterial using the finite-difference time-domain (FDTD) method in conjunction with perfectly matched layers (PMLs).
Abstract: The increasing interest in negative-index metamaterials requires a formulation capable of a full analysis of wave propagation in such materials. Since two-dimensional (2D) problems have been largely explored in the literature, the natural step is a three-dimensional (3D) formulation of a metamaterial. In this work, we present a simulation of a left-handed metamaterial using the finite-difference time-domain (FDTD) method in conjunction with perfectly matched layers (PMLs). First, we develop a PML to work with a Drude medium model. Then we apply our formulation to a 3D domain and compare our results with 2D problems. Finally, we simulate a dipole on the top of a metamaterial slab, presenting the field distribution in three different directions. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 40: 201–205, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11328
TL;DR: In this paper, a comprehensive simulation of ultra-wideband signal propagation in indoor environments is presented, based on time domain electromagnetic modeling of transmitting and receiving antennas and the analysis of wave propagation through indoor channels using the time-domain uniform theory of diffraction.
Abstract: A comprehensive simulation of ultra-wideband signal propagation in indoor environments is presented. The simulation is based on time-domain electromagnetic modeling of transmitting and receiving antennas and the analysis of wave propagation through indoor channels using the time-domain uniform theory of diffraction. The antennas are a pair of TEM horns which are modeled as arrays of vee dipoles. The analysis of these antennas is performed directly in the time domain, without the need for transforming the solutions from the frequency domain to the time domain. The frequency dependence of materials utilized in the structure on the indoor channel is accounted for in the channel simulation. The simulation results are compared with the corresponding measured results. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 42: 103–108, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20221
TL;DR: In this article, a dual-frequency shorted T-shaped monopole antenna is proposed for WLAN operation in the 2.4 and 5 GHz bands for a laptop as an internal antenna.
Abstract: A novel dual-frequency shorted T-shaped monopole antenna is proposed. The T-shaped monopole is comprised of two horizontal arms of different lengths, which generate two separate resonant modes for the desired dual-frequency operation, and one vertical arm is short-circuited to a ground plane through an inverted-L strip for good impedance matching. A prototype suited for WLAN operation in the 2.4- and 5-GHz bands for a laptop as an internal antenna is constructed and tested. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 41: 202–203, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20093
TL;DR: In this article, the characteristics of nonlinear left-handed transmission lines (NL-LH) were analyzed in terms of dispersion and nonlinearity characteristics, and its voltage-wave partial differential equation was derived.
Abstract: The characteristics of nonlinear left-handed (NL-LH) transmission lines (TLs) are discussed for the first time. A LH-TL with varactor-diode series capacitance is analyzed in terms of dispersion and nonlinearity characteristics, and its voltage-wave partial differential equation is derived. Numerical responses of the NL-LH-TL to harmonic and pulse waves illustrate the conjoint effects of frequency dispersion and nonlinearity. Potential applications are suggested. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 40: 471–473, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20007
TL;DR: In this paper, a defected microstrip structure (DMS) was proposed to reduce the size of a rectangular patch antenna by increasing its electric length, without degrading its performance.
Abstract: A defected microstrip structure (DMS) is proposed to reducing the size of a rectangular patch antenna by increasing its electric length, without degrading its performance. To illustrate this advantage, one conventional and one proposed defected patch antenna were developed and measured at 1.77 GHz. The simulated and measured results concerning the radiation patterns and bandwidth of both antennas are very closely related, but the proposed defected antenna achieves 22% of total-area reduction. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 43: 481–484, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20508
TL;DR: In this paper, the mutual coupling between two planar inverted-F antennas (PIFAs) based on a ground plane is studied numerically and experimentally, and several arrangements of collinear, orthogonal, and parallel PIFA elements with interelement spacing ranging from 0.1λ to 0.9λ are examined at the design frequency of 2.45 GHz, and in the 2.0-3.0 GHz frequency band.
Abstract: Mutual coupling between two planar inverted-F antennas (PIFAs) based on a ground plane is studied numerically and experimentally. Several arrangements of collinear, orthogonal, and parallel PIFA elements with interelement spacing ranging from 0.1λ to 0.9λ are examined at the design frequency of 2.45 GHz, and in the 2.0–3.0-GHz frequency band. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 42: 224–227, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20259
TL;DR: In this paper, the antenna includes four elements excited with equal amplitudes but with a relative phase difference of 0, −90, −180, and −270°, and an RF trap filter is located within the horizontal portion so that the antenna provides good gain coverage at all three frequency bands.
Abstract: The antenna includes four elements excited with equal amplitudes but with a relative phase difference of 0°, −90°, −180°, and −270°. Each element includes a vertical and horizontal portion. An RF trap filter is located within the horizontal portion so that the antenna provides good gain coverage at all three frequency bands of a modernized global positioning system.
TL;DR: In this paper, an etched fiber Bragg grating (FBG) embedded into a beam is used to measure the curvature of the beam and the reflection power of the grating is measured by an optical power meter.
Abstract: We present a new bend sensor which can measure the curvature using an etched fiber Bragg grating (FBG) embedded into a beam. The reflection power of the grating detected by an optical power meter varies linearly with the curvature of the beam. This sensor is in- dependent of temperature. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 43: 414 - 417, 2004; Published online in Wiley Inter- Science (www.interscience.wiley.com). DOI 10.1002/mop.20486
TL;DR: The partial dielectric-loaded TEM horn (PDTEM) structure, which maintains ultra-wideband antenna characteristics over a bandwidth ratio greater than 20:1 in order to improve the impulse-radiation characteristics for ground penetrating radar systems is described in this article.
Abstract: The partial dielectric-loaded TEM horn (PDTEM) structure, which maintains ultra-wideband antenna characteristics over a bandwidth ratio greater than 20:1 in order to improve the impulse-radiation characteristics for ground penetrating radar systems is described in this paper. It is shown that high-gain and low-input-reflection levels over the operational band are attainable for TEM horns with proper dielectric, absorber, and resistive loadings. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 41: 333–336, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20133
TL;DR: In this article, the axial-ratio bandwidth enhancement was achieved for circularly polarized (CP) microstrip patch antenna using dual and four L-shaped probe feeds by controlling the excitation phase and angular orientation of the horizontal portion of each L-probe.
Abstract: Impedance-bandwidth enhancement of microstrip antennas using an L-shaped probe feed has previously been demonstrated. In this paper, axial-ratio bandwidth enhancement is achieved for circularly polarized (CP) microstrip patch antenna using dual and four L-shaped probe feeds. By controlling the excitation phase and angular orientation of the horizontal portion of each L-probe, circular polarization can be generated with wide axial-ratio bandwidth by exciting the circular patch. In the dual L-shaped probe case, the impedance and axial-ratio bandwidth are 42% and 27.23%, respectively. On the other hand, for the four L-shaped probes case, both of these figures increase to 45%. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 42: 263–265, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20272
TL;DR: In this paper, a 1.67 cm-long test structure was found to have a minimum insertion loss of 1.74 dB at the passband center of 29 GHz, within 0.57 dB of the lowest insertion loss predicted by full-wave numerical simulations, indicative of the high precision and smooth surface morphology of the EFAB process.
Abstract: Miniature rectangular coaxial transmission line (with a 300 × 300 μm outer conductor) is simulated, fabricated, and tested up to the Ka band. It is made by the electrochemical fabrication (EFAB™) of nickel such that the center conductor is supported primarily by ≈λ/4 stubs that also establish a resonant passband. The minimum insertion loss of a 1.67-cm-long test structure is found to be 1.74 dB at the passband center of 29 GHz. This is within 0.57 dB of the lowest insertion loss predicted by full-wave numerical simulations, indicative of the high precision and smooth surface morphology of the EFAB process. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 40: 365–368, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11383
TL;DR: In this article, a folded-loop antenna with a reflector for mobile handsets at the 2.0-GHz band is analyzed, taking the effect of the human head into account.
Abstract: A folded-loop antenna with a reflector for mobile handsets at the 2.0-GHz band is analyzed, taking the effect of the human head into account. The reflector is arranged between the human head and the driver. The width and height of the reflector are chosen to be slightly smaller and larger than those of the driver, respectively. Based upon numerical investigations, this antenna is found to enhance radiation efficiency by 20% and reduce peak specific absorption rates (SARs) averaged over 1 g and 10 g of tissues by 70%–85%. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 40: 272–275, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11350
TL;DR: In this article, the behavior of a 2D model of an extended hemielliptic silicon lens of a size typical for THz applications is accurately studied for the case of a plane E-wave illumination.
Abstract: The behavior of a 2D model of an extended hemielliptic silicon lens of a size typical for THz applications is accurately studied for the case of a plane E-wave illumination. The full-wave analysis of the scattering problem is based on the Muller's boundary integral-equations (MBIE) that are uniquely solvable. A Galerkin discretization scheme with a trigonometric basis leads to a very efficient numerical algorithm. The numerical results related to the focusability of the lens versus its rear-side extension and the angle of the plane-wave incidence, as well as near-field profiles, demonstrate strong resonances. Such effects can change the principles of optimal design of lens-based receivers. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 43: 515–518, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20520
TL;DR: In this paper, a frequency-agile microstrip patch antenna is presented, where a micromachined membrane is used as the ground plane below the antenna patch, and an air gap between above the ground planes is introduced.
Abstract: A frequency-agile microstrip patch antenna is presented. A micromachined membrane is used as the ground plane below the antenna patch. Actuation of this membrane introduces an air gap between above the ground plane, and enables control of the antenna-resonant frequency from 16.8 to 17.82 GHz (approximately 6% variation). © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 43: 64–67, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20376
TL;DR: In this paper, a multilevel partitioning method (UV-MLP) is developed to solve the volume-scattering problem, which involves creating a rank table of transmitting and receiving block sizes and their separation.
Abstract: A UV multilevel partitioning method (UV-MLP) is developed to solve the volume-scattering problem. The method involves creating a rank table of transmitting and receiving block sizes and their separation. The table can be set up speedily using coarse-coarse sampling. For a specific scattering problem with given geometry, the scattering structure is partitioned into multilevel blocks. By looking up the rank in the predetermined table, the impedance matrix for a given transmitting and receiving block is expressed as a product of U and V matrices. We illustrate the method for 2D volume scattering by discrete scatterers. Multiple scattering is cast into the Foldy–Lax equations of partial waves. We show that UV decomposition can be applied directly to the impedance matrix of partial waves of higher order than the usual lowest-order Green's function. Numerical results are illustrated for randomly distributed cylinders that are one wavelength in diameter. For scattering by 1024 cylinders on a single PC processor with a 2.6-GHz CPU and 2-GB memory, only 14 CPU min are required to obtain the numerical solution. If subsectional volumetric discretization with the method of moments (MoM) is applied to this problem, the equivalent number of volumetric unknowns is 80,425. Furthermore, for 4096 cylinders that have 321,700 equivalent numbers of volumetric unknowns, it takes only 7.34 sec for one matrix-vector multiplication. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 41: 354–361, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20140
Abstract: The connection loss between single-mode fiber and photonic crystal fiber (PCF) is analyzed by using a full-vector finite-element method. PCF parameters for achieving low loss connection (for example, less than 0.5 dB) are reported. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 40: 378–380, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11387