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2010-07-03
PIER
Vol. 105, 445-461, 2010
download: 299
Electromagnetic Optimal Design and Preparation of Broadband Ceramic Radome Material with Graded Porous Structure
Fei Chen Qiang Shen Lianmeng Zhang
Silicon nitride (Si3N4) ceramic is a promising ultra-high speed (> 5 mach) broadband (1-18 GHz) radome material because of its excellent high-temperature resistance, good mechanical and dielectric properties. Si3N4 ceramics with A-sandwich wall structure are successfully applied to passive self-direction high transmission efficiency broadband radome (1-18 GHz). In the present study, a novel graded porous wall structure for broadband radome is promoted. The feasibility of using this structure is carried out by a computer aided design for the wall structure based on the microwave equivalent network method. By optimizing the layer number (n), structural coefficient (p), thickness (d) and dielectric constant (ε) of each layer, the power transmission efficiency at 1-18 GHz of graded porous Si3N4 ceramic radome is calculated. Si3N4 ceramics with graded porous structure are then prepared according to the design. The prepared sample exhibits a good graded porous structure with the porosity range from ~ 2% to 63%. The tested power transmission efficiency at 1-18 GHz for the obtained sample matches well with the calculation results, indicating that the graded porous structure is feasible for the broadband radome application.
ELECTROMAGNETIC OPTIMAL DESIGN AND PREPARATION OF BROADBAND CERAMIC RADOME MATERIAL WITH GRADED POROUS STRUCTURE
2010-07-03
PIER
Vol. 105, 425-444, 2010
download: 129
A Tri-Band Bandpass Filter Realized Using Tri-Mode T-Shape Branches
Yun Liu Wen-Bin Dou Yong-Jiu Zhao
In this paper, we present a tri-band filter design using tri-mode T-shaped branches connected by λ/4 transmission lines. By analyzing the input admittance of a T-shape branch with commensurate electrical lengths, three resonant modes with two transmission zeros between are found and design formulas are derived. The filter can be regarded as a combination of three bandpass filters with only one set of coupling elements. To realize different bandwidths for each, the admittance slope of each resonating mode is set as required. A genetic algorithm is used in solving related equations to obtain the impedance of each line in a T-shape branch, followed by a final optimization. A three-pole tri-band filter having passbands of 0.6-0.9, 1.35-1.65 and 2.1-2.4 GHz, is designed, fabricated and measured with low passband insertion losses of < 0.7 dB and high rejection of > 60 dB between the passband regions. As a generalization, necessary to achieve a tri-band filter with arbitrary passbands, a non-commensurate version of the T-shape branch is introduced. An example filter design is given with the passbands asymmetrically located at 0.7-1, 1.65-1.95, and 2.2-2.3 GHz. This technique is able to achieve good design flexibility with respect to bandwidth ratios. This is validated by studying the maximum impedance variations of a T-shape branch when the bandwidth ratios vary.
A TRI-BAND BANDPASS FILTER REALIZED USING TRI-MODE T-SHAPE BRANCHES
2010-06-29
PIER
Vol. 105, 403-424, 2010
download: 136
Performance and Robustness of a Multistatic Mist Beamforming Algorithm for Breast Cancer Detection
Martin O'Halloran Martin Glavin Edward Jones
Ultra-Wideband (UWB) radar is one of the most promising emerging technologies for the early detection of breast cancer, and the development of robust beamforming algorithms for imaging has been the subject of a significant amount of research. Extending the monostatic Microwave Imaging via Space Time (MIST) beamformer originally developed by Bond et al., the authors proposed the Multistatic MIST beamforming algorithm that uses the spatial diversity of the receiving antennas to acquire more energy reflected from dielectric scatterers which propagate outwards via different routes, while compensating for multistatic path-dependent attenuation and phase effects. In this paper, the performance and robustness of the Multistatic MIST beamformer is examined across a range of potential clinical scenarios. The multistatic beamformer is directly compared with the traditional monostatic beamformer and the effects of the additional multistatic channels is investigated. Furthermore, the robustness of the beamformer with respect to tumor size and location, variations in dielectric properties, and significantly, different fibroglandular tissue distributions within the breast based on recently published data, is examined.
PERFORMANCE AND ROBUSTNESS OF A MULTISTATIC MIST BEAMFORMING ALGORITHM FOR BREAST CANCER DETECTION
2010-06-29
PIER
Vol. 105, 383-402, 2010
download: 134
Effect of Steering Error Vector and Angular Power Distributions on Beamforming and Transmit Diversity Systems in Correlated Fading Channel
A. Waheed Umrani Yongliang Guan Fahim A. Umrani
A comparative analysis of transmit diversity and beamforming for linear and circular antenna arrays in a wireless communications system is presented. The objective is to examine the effect of random perturbations, angular power distributions on transmit diversity and beamforming system. The perturbations are modeled as additive random errors, following complex Gaussian multivariate distribution, to the antenna array steering vectors. Using outage probability, probability of error, and dynamic range of transmitter power as performance measures, we have shown significant effects of array perturbations on the two systems under spatially correlated Rayleigh fading channel. We also examine the effect of angular power distributions (uniform, truncated Gaussian, and truncated Laplacian), which corresponds to different propagation scenario, on the performance of the two systems. Results show that the central angle-of-arrival can have significant impact on system performance. And the transmit diversity system with truncated Laplacian distribution performs better as compared to other power distributions, and linear array is a preferable configuration for transmit diversity system. We conclude that array perturbations must not be neglected in the design of transmit diversity and beamforming systems.
EFFECT OF STEERING ERROR VECTOR AND ANGULAR POWER DISTRIBUTIONS ON BEAMFORMING AND TRANSMIT DIVERSITY SYSTEMS IN CORRELATED FADING CHANNEL
2010-06-28
PIER
Vol. 105, 365-381, 2010
download: 173
Transient Responses of Some Antennas Under the Impact of an Intentionally Incident High-Power Electromagnetic Pulse
Zheng Jiang Wen-Yan Yin Qi-Feng Liu Shuai Zhang
ƒAn improved finite difference time domain (FDTD) method is employed for fast capturing transient responses of reconfigurable and multiple-input-multiple-output (MIMO) antennas under the impact of an intentional high-power electromagnetic pulse (EMP) but with different waveforms, respectively, where lumped element and sub-cellular thin-wire algorithms and coaxial feed model are integrated together for handling such three-dimensional antennas used for wireless communication. Parametric studies are carried out to show effects of high-power EMP waveforms, its polarization state and incident direction on the transient coupled voltages on the coaxial feed line and across the diodes, with sufficient information obtained for understanding the interaction between the EMP and the antennas.
TRANSIENT RESPONSES OF SOME ANTENNAS UNDER THE IMPACT OF AN INTENTIONALLY INCIDENT HIGH-POWER ELECTROMAGNETIC PULSE
2010-06-26
PIER
Vol. 105, 347-364, 2010
download: 129
Improving Subwavelength Resolution of Multilayered Structures Containing Negative-Permittivity Layers by Flatting the Transmission Curves
Yi Jin
Multilayered structures consisting of alternating negative-permittivity and dielectric layers are explored to obtain high-resolution imaging of subwavelength objects. The peaks with the smallest |ky| (ky is the transverse wave vector) on the transmission curves, which come from the guided modes of the multilayered structures, can not be completely damped by material loss. This makes the amplitudes of the evanescent waves around these peaks inappropriate after transmitted through the imaging structures, and the imaging quality is not good. To solve such a problem, the permittivity of the dielectric layers is appropriately chosen to make these sharp peaks merge with their neighboring peaks, whose corresponding guiding modes in the multilayered structure are cutoff. Wide flat upheavals are then generated on the transmission curves so that evanescent waves in a large range are transmitted through the structures with appropriate amplitudes. In addition, it is found that the sharp peaks with the smallest |ky| can be eliminated by adding appropriate coating layers and wide flat upheavals can also be obtained.
IMPROVING SUBWAVELENGTH RESOLUTION OF MULTILAYERED STRUCTURES CONTAINING NEGATIVE-PERMITTIVITY LAYERS BY FLATTING THE TRANSMISSION CURVES
2010-06-20
PIER
Vol. 105, 333-346, 2010
download: 156
Generalized Equivalent Conductor Method for a Chaff Cloud with an Arbitrary Orien- Tation Distribution
Dong-Wook Seo Ji-Hee Yoo Kyoung Il Kwon Noh-Hoon Myung
A recently presented equivalent conductor (EC) method enables fast computation for the radar cross section (RCS) of a chaff cloud. Despite its good performance, the EC method is restrictively applicable due to the complex orientation distribution of chaff and the incident angle. In this paper, a generalized equivalent conductor (GEC) method is presented for estimating the RCS of an actual chaff cloud. The proposed method can be applied to any orientation distribution of the chaff cloud by using a weight function and a weighted average, as well as to any incident angle by employing a method of moment (MoM). Numerical results are presented for three scenarios and validated with results of the MoM.
GENERALIZED EQUIVALENT CONDUCTOR METHOD FOR A CHAFF CLOUD WITH AN ARBITRARY ORIEN- TATION DISTRIBUTION
2010-06-19
PIER
Vol. 105, 313-332, 2010
download: 805
Investigations of Foliage Effect on Modern Wireless Communication Systems: a Review
Yu Song Meng Yee Hui Lee
In this paper, a large number of studies of the effect of the foliage on single or lines of trees on modern wireless communication systems are reviewed. The paper is focused on the experimental works mainly done for commercial applications such as cellular communication and high speed point-to-point fixed link at the microwave and millimeter wave frequencies. For this review study, the development of the foliage loss prediction methods and the factors influencing the tree-induced shadowing effect are highlighted. In view of current research work in this area, some possible future works are proposed to improve the performance of modern wireless communication systems with the effect of foliage.
INVESTIGATIONS OF FOLIAGE EFFECT ON MODERN WIRELESS COMMUNICATION SYSTEMS: A REVIEW
2010-06-16
PIER
Vol. 105, 295-311, 2010
download: 114
Investigation of Classifiers for Early-Stage Breast Cancer Based on Radar Target Signatures
Raquel Cruz Conceicao Martin O'Halloran Edward Jones Martin Glavin
Ultra Wideband (UWB) radar has been extensively investigated as a means of detecting early-stage breast cancer. The basis for this imaging modality is the dielectric contrast between normal and cancerous breast tissue at microwave frequencies. However, based on the dielectric similarities between a malignant and a benign tumour within the breast, differentiating between these types of tissues in microwave images may be problematic. Therefore, it is important to investigate alternative methods to analyse and classify dielectric scatterers within the breast, taking into account other tumour characteristics such as shape and surface texture of tumours. Benign tumours tend to have smooth surfaces and oval shapes whereas malignant tumours tend to have rough and complex surfaces with spicules or microlobules. Consequently, one classification approach is to classify scatterers based on their Radar Target Signature (RTS), which carries important information about scatterer size and shape. In this paper, Gaussian Random Spheres (GRS) are used to model the shape and size of benign and malignant tumours. Principal Components Analysis (PCA) is used to extract information from the RTS of the tumours, while eight different combinations of tumour classifiers are analysed in terms of performance and are compared in terms of two possible approaches: Linear Discriminant Analysis (LDA) and Quadratic Discriminant Analysis (QDA).
INVESTIGATION OF CLASSIFIERS FOR EARLY-STAGE BREAST CANCER BASED ON RADAR TARGET SIGNATURES
2010-06-12
PIER
Vol. 105, 273-294, 2010
download: 347
Compact Patch Antenna Design for Outdoor RF Energy Harvesting in Wireless Sensor Networks
Zhi Wei Sim Roger Shuttleworth Martin J. Alexander Bruce D. Grieve
In this paper, two compact patch antenna designs for a new application --- outdoor RF energy harvesting in powering a wireless soil sensor network --- are presented. The first design is a low-profile folded shorted patch antenna (FSPA), with a small ground plane and wide impedance bandwidth. The second design is a novel FSPA structure with four pairs of slot embedded into its ground plane. Performance of both antennas was first simulated using CST Microwave Studio. Antenna prototypes were then fabricated and tested in the anechoic chamber and in their actual operating environment --- an outdoor field. It was found that the FSPA with slotted ground plane achieved a comparable impedance bandwidth to the first design, with an overall size reduction of 29%. Simulations were also carried out to investigate the effects of different design parameters on the performance of the proposed slotted ground plane FSPA.
COMPACT PATCH ANTENNA DESIGN FOR OUTDOOR RF ENERGY HARVESTING IN WIRELESS SENSOR NETWORKS
2010-06-12
PIER
Vol. 105, 253-272, 2010
download: 152
Bandwidth Enhancement of an Analog Feedback Amplifier by Employing a Negative Group Delay Circuit
Heungjae Choi Yongchae Jeong Chul Dong Kim James Stevenson Kenney
We will demonstrate an alternative topology to greatly increase the operating bandwidth of an analog RF feedback power amplifier. A limited operating bandwidth due to the group delay mismatch of a feedback loop discouraged the use of an RF feedback technique in spite of its powerful linearization performance and great tolerance capability. By introducing a negative group delay circuit (NGDC) in the feedback loop, group delay match condition could be satisfied. With the fabricated 2-stage distributed element negative group delay circuit with a 30MHz of bandwidth and a -9 ns of group delay for a wideband code division multiple access (WCDMA) downlink band, the proposed feedback amplifier with the proposed topology experimentally achieved an adjacent channel leakage ratio of -53.2 dBc with a cancellation bandwidth of over 50 MHz.
BANDWIDTH ENHANCEMENT OF AN ANALOG FEEDBACK AMPLIFIER BY EMPLOYING A NEGATIVE GROUP DELAY CIRCUIT
2010-06-12
PIER
Vol. 105, 231-251, 2010
download: 175
Pareto Optimal Yagi-Uda Antenna Design Using Multi-Objective Differential Evolution
Sotirios K. Goudos Katherine Siakavara Elias Vafiadis John Sahalos
Antenna design problems often require the optimization of several conflicting objectives such as gain maximization, sidelobe level (SLL) reduction and input impedance matching. Multi-objective Evolutionary Algorithms (MOEAs) are suitable optimization techniques for solving such problems. An efficient algorithm is Generalized Differential Evolution (GDE3), which is a multi-objective extension of Differential Evolution (DE). The GDE3 algorithm can be applied to global optimization of any engineering problem with an arbitrary number of objective and constraint functions. Another popular MOEA is Nondominated Sorting Genetic Algorithm-II (NSGA-II). Both GDE3 and NSGA-II are applied to Yagi-Uda antenna design under specified constraints. The numerical solver used for antenna parameters calculations is SuperNEC, an object-oriented version of the numerical electromagnetic code (NEC-2). Three different Yagi-Uda antenna designs are considered and optimized. Pareto fronts are produced for both algorithms. The results indicate the advantages of this approach and the applicability of this design method.
PARETO OPTIMAL YAGI-UDA ANTENNA DESIGN USING MULTI-OBJECTIVE DIFFERENTIAL EVOLUTION
2010-06-11
PIER
Vol. 105, 213-229, 2010
download: 115
Modal Analysis of Multilayer Conical Dielectric Waveguides for Azimuthal Invariant Modes
Amir Saman Amin Mohammad Mirhosseini Mahmoud Shahabadi
By using field expansion in terms of the Legendre polynomials and Schelkunoff functions, Maxwell's equations in the spherical coordinate system are cast into a matrix form which lends itself to the analysis of a multilayer conical waveguide. The matrix formulation is then used to obtain an eigen-value problem whose eigen-values are the allowable wave-numbers for propagation in the radial direction. To verify the proposed numerical approach, it is used to evaluate the resonance frequency of a partially filled spherical resonator. The computed resonance frequencies are then compared with those obtained using commercial software based on the finite-element method. The computation time is enormously reduced using the semianalytical method of this work. Although results are shown for lossless isotropic dielectrics, the method is also applicable to conical waveguides made of lossy dielectrics even with negative permittivity.
MODAL ANALYSIS OF MULTILAYER CONICAL DIELECTRIC WAVEGUIDES FOR AZIMUTHAL INVARIANT MODES
2010-06-11
PIER
Vol. 105, 193-212, 2010
download: 478
Optical Properties of Photonic Crystal Fibers with a Fiber Core of Arrays of Subwavelength Circular Air Holes: Birefringence and Dispersion
Daru Chen Ming-Leung Vincent Tse Hwa-Yaw Tam
We propose a kind of novel photonic crystal fibers (PCFs) based on a fiber core with arrays of subwavelength circular air holes, achieving the flexible control of the birefringence or the dispersion property of the PCFs. A highly birefringent (HB) PCF is achieved by employing arrays of subwavelength circular air hole pairs in the fiber core, which are arranged as a conventional hexagonal lattice structure with a subwavelength lattice constant. The HB-PCF is with uniform and ultrahigh birefringence (up to the order of 0.01) in a wavelength region from 1.25 μm to 1.75 μm or even a larger region, which, to the best of our knowledge, is the best birefringence property of the PCFs. A dispersion-flattened (DF) PCF with near-zero dispersion is achieved by employing arrays of subwavelength circular air holes in the fiber core arranged as a conventional hexagonal lattice structure with a subwavelength lattice constant, which contributes negative waveguide dispersion to the PCF. The proposed design of the DF-PCF provides an alternate approach for the dispersion control of the PCF. Besides the high birefringence and the flattened near-zero dispersion, the proposed PCFs with a fiber core of arrays of subwavelength circular air holes have the potential to achieve a large mode area single mode PCF.
OPTICAL PROPERTIES OF PHOTONIC CRYSTAL FIBERS WITH A FIBER CORE OF ARRAYS OF SUBWAVELENGTH CIRCULAR AIR HOLES: BIREFRINGENCE AND DISPERSION
2010-06-11
PIER
Vol. 105, 171-191, 2010
download: 238
Derivation of Klein-Gordon Equation from Maxwell's Equations and Study of Relativistic Time-Domain Waveguide Modes
Oleg Tretyakov Ozlem Akgun
A initial-boundary value problem for the system of Maxwell's equations with time derivative is formulated and solved rigorously for transient modes in a hollow waveguide. It is supposed that the latter has perfectly conducting surface. Cross section, S, is bounded by a closed singly-connected contour of arbitrary but smooth enough shape. Hence, the TE and TM modes are under study. Every modal field is a product of a vector function of transverse coordinates and a scalar amplitude dependent on time, t, and axial coordinate, z. It has been established that the study comes down to, eventually, solving two autonomous problems. i) A modal basis problem. Final result of this step is de…nition of complete (in Hilbert space, L2) set of functions dependent on transverse coordinates which originates a basis. ii) A modal amplitude problem. The amplitudes are generated by the solutions to Klein-Gordon equation (KGE), derived from Maxwell's equations directly, with t and z as independent variables. The solutions to KGE are invariant under relativistic Lorentz transforms and subjected to the causality principle. Special attention is paid to various ways that lead to analytical solutions to KGE. As an example, one case (among eleven others) is considered in detail. The modal amplitudes are found out explicitly and expressed via products of Airy functions with arguments dependent on t and z.
DERIVATION OF KLEIN-GORDON EQUATION FROM MAXWELL'S EQUATIONS AND STUDY OF RELATIVISTIC TIME-DOMAIN WAVEGUIDE MODES
2010-06-09
PIER
Vol. 105, 157-170, 2010
download: 264
Application of Ica Technique to PCA Based Radar Target Recognition
Chih-Wei Huang Kun-Chou Lee
In this paper, the ICA (independent component analysis) technique is applied to PCA (principal component analysis) based radar target recognition. The goal is to identify the similarity between the unknown and known targets. The RCS (radar cross section) signals are collected and then processed to serve as the features for target recognition. Initially, the RCS data from targets are collected by angular-diversity technique, i.e., are observed in directions of different elevation and azimuth angles. These RCS data are first processed by the PCA technique to reduce noise, and then further processed by the ICA technique for reliable discrimination. Finally, the identification of targets will be performed by comparing features in the ICA space. The noise effects are also taken into consideration in this study. Simulation results show that the recognition scheme with ICA processing has better ability to discriminate features and to tolerate noises than those without ICA processing. The ICA technique is inherently an approach of high-order statistics and can extract much important information about radar target recognition. This property will make the proposed recognition scheme accurate and reliable. This study will be helpful to many applications of radar target recognition.
APPLICATION OF ICA TECHNIQUE TO PCA BASED RADAR TARGET RECOGNITION
2010-06-09
PIER
Vol. 105, 141-155, 2010
download: 121
An Adaptive Cavity Setup for Accurate Measurements of Complex Dielectric Permittivity
Giuseppe Addamo Giuseppe Virone Davide Vaccaneo Riccardo Tascone Oscar A. Peverini Renato Orta
In order to enhance the accuracy of the complex permittivity data employed in Ground Penetrating Radar (GPR) techniques, an adaptive cavity setup is presented. The use of moveable walls permits to relax the mechanical constraints on the sample dimensions so that it can be employed also in complicate measurement condition as, for example, in the case of wet samples. Moreover, exploiting the cavity resonance phenomenon, low loss materials, such as some type of marbles, can be accurately evaluated. The numerical characterization, the parametric analyses and the L-band measurement results show the validity and the reliability of this configuration.
AN ADAPTIVE CAVITY SETUP FOR ACCURATE MEASUREMENTS OF COMPLEX DIELECTRIC PERMITTIVITY
2010-06-07
PIER
Vol. 105, 119-139, 2010
download: 120
Bistatic Scattering from Two-Dimensional Dielectric Ocean Rough Surface with a PEC Object Partially Embedded by Using the g -Smcg Method
Wei-Jie Ji Chuang-Ming Tong
An efficient approach called general sparse matrix canonical grid (G-SMCG) method is proposed to analyze the electromagnetic scattering from 2-D dielectric rough surface with a conducting object partially buried. In this paper, the scattering of 3-D arbitrarily shaped object is computed by using the traditional method of moments (MoM)with RWG basis function, and the scattering of rough surface is analyzed by using the SMCG method. The coupling interactions between an object and rough surface are calculated by iterative method. Combing the ocean rough surface with Pierson Moskowitz (PM) spectrum, the bistatic scattering coefficients of typical objects buried in the ocean surface have been computed by using the proposed method. Then the accuracy and efficiency of this method are discussed. Finally, the bistatic scattering coefficients of a ship located on ocean surface are calculated, and the influence of sea state and wind direction on the scattering coefficients is indicated.
BISTATIC SCATTERING FROM TWO-DIMENSIONAL DIELECTRIC   OCEAN ROUGH SURFACE WITH A PEC OBJECT PARTIALLY EMBEDDED BY USING THE G-SMCG METHOD
2010-06-07
PIER
Vol. 105, 103-118, 2010
download: 221
Microwave Scattering and Absorption by a Multilayered Lossy Metamaterial --- Glass Cylinder
Juozas Bucinskas Liudmila Nickelson Viktoras Shugurovas
Here we present the rigorous electrodynamical solution of diffraction problem about the microwave scattering by a multilayered cylinder. The number and thickness of layers is not limited. We offer the solution when the central core of multilayered cylinder can be made of different isotropic materials as a metamaterial, a ceramic matter or a semiconductor as well as of a perfect metal. The isotropic coated layers can be of strongly lossy materials. The signs of the complex permittivity and the complex permeability can be negative or positive in different combinations. Here we present dependencies of the scattered power of the incident perpendicularly and parallel polarized microwaves by the metamaterial-glass cylinder on signs of metamaterial permittivity as well as permeability. Here are also presented the glass layer absorbed power and the metamaterial core absorbed power dependent on the hypothetic metamaterial permittivity and permeability signs at the wide range frequencies 1-120 GHz. The metamaterial core of cylinder has a radius equal to 0.0018 m and the thickness of the coated acrylic-glass layer is 0.0002 m. We have found some conditions when the scattered-power has minimal values and the absorbed power by the coated acrylic glass layer is constant in a very wide frequency range. We have discovered that the glass layer absorbed power decreases with increasing of the frequency at the range 1-120 GHz for both microwave polarizations.
MICROWAVE SCATTERING AND ABSORPTION BY A MULTILAYERED LOSSY METAMATERIAL --- GLASS CYLINDER
2010-06-04
PIER
Vol. 105, 93-102, 2010
download: 332
Design of Dual-Band Bandpass Filters Using a Dual Feeding Structure and Embedded Uniform Impedance Resonators
Ru-Yuan Yang Hon Kuan Cheng-Yuan Hung Chang-Sin Ye
In this paper, a simple method and structure to design a dual-band bandpass filter (BPF) by using a dual feeding structure and embedded uniform impedance resonator (UIR) is presented. In this structure, two passbands can be designed individually and several transmission zeros can be created to improve the band selectivity and stopband performance. The first passband is determined by the dual feeding structure and the second passband is determined by the UIR. Moreover, by using the inter coupling in the UIR, the performance of the second passband can be easily tuned without degrading the first passband. In order to verify the design concept, two filter examples, including 0.9/1.575 GHz for multi-services communication and 2.4/5.7 GHz for wireless local area network (WLAN), are designed in this study. Experimental results of the fabricated samples show a good agreement with the simulated results.
DESIGN OF DUAL-BAND BANDPASS FILTERS USING A DUAL FEEDING STRUCTURE AND EMBEDDED UNIFORM IMPEDANCE RESONATORS