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Antennas and Propagation, IEEE Transactions on

Issue 3 • Date March 2012

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Displaying Results 1 - 25 of 64
  • Table of contents

    Page(s): C1 - 1205
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  • IEEE Transactions on Antennas and Propagation publication information

    Page(s): C2
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  • Low Profile, Miniaturized, Inductively Coupled Capacitively Loaded Monopole Antenna

    Page(s): 1206 - 1213
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    A novel high-gain low-profile miniaturized antenna with omnidirectional vertically polarized radiation, similar to a short dipole is presented. The proposed design focus is on increasing the gain and improving the polarization purity of the radiated field in the horizontal plane. The gain and polarization improvement are achieved by isolating the feed structure from a miniaturized resonant radiating structure composed of an in-plane capacitor and a structurally embedded transformer. The antenna topology is developed, based on circuit model and through full-wave simulations the equivalence is established. The equivalent circuit model assists in the initial design, and then minor modifications are required to achieve the desired frequency of operation. The initial topology of the proposed antenna, the so-called Inductively Coupled Capacitively Loaded Monopole Antenna (ICCLMA), consists of two metal layers, a feeding pin and a shorting pin. The performance of the proposed antenna is compared to that of an ordinary inverted F antenna and a more recent low profile vertically polarized antenna (LMMMA) . It is shown that the gain of ICCLMA is 9 dB and 4 dB higher than that of the conventional inverted-F antenna and the LMMMA, respectively. To simplify the fabrication process a modified single-layer ICCLMA topology is presented and optimized. Finally, a design procedure to further reduce the lateral dimension of ICCLMA is presented. A procedure for accurate measurement of antennas with small ground planes is also presented. View full abstract»

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  • A Novel Low-Profile Compact Directional Ultra-Wideband Antenna: The Self-Grounded Bow-Tie Antenna

    Page(s): 1214 - 1220
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    Low-profile directional ultra-wideband (UWB) antennas are strongly demanded in many UWB applications. However, few such UWB antennas have been reported. To meet the demands, an original novel low-profile directional UWB antenna-the self-grounded Bow-Tie is developed and presented here. This new UWB antenna has a compact and simple geometry, and ultra-wideband performance, such as presented here over a frequency range of 2-15 GHz with about -10 dB reflection coefficient, stable radiation patterns, and good time-domain impulse response. Measurements of a prototype of the antenna have verified the design and the simulation. It can be foreseen that this new antenna will find many applications in the different areas in UWB technology. View full abstract»

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  • Circularly Polarized Crossed Dipole Antenna With Phase Delay Lines for RFID Handheld Reader

    Page(s): 1221 - 1227
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    To produce circularly polarized (CP) radiation, a small, double-sided, crossed dipole antenna with two metal strips loaded for phase delay is proposed. The proposed antenna uses two orthogonal, unequal length dipoles, connected in parallel to a coaxial probe feed. It requires no matching network. The required power and phase relationships are obtained by proper choice of dipole lengths and the metal strips attached to them. The antenna also operates at its half wavelength orthogonal modes, for the UHF band. The phase delay metal strip generates the two resonant modes for CP radiation. Simulated and measured results indicate that the crossed dipole structure can produce CP radiation. An impedance bandwidth (VSWR ≤ 2) of about 11.8% and a 3-dB axial-ratio (AR) bandwidth of about 3.3% around the center frequency of 925 MHz were measured. View full abstract»

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  • VHF Adaptive Antenna Using a Rear Defogger

    Page(s): 1228 - 1236
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    An array antenna for the VHF band, which has several ports on a defogger, is proposed. In addition, the concept of a reactively steered adaptive array is introduced to form an adaptive beam pattern. The resistivity of a heating wire does not degrade the receiving performance significantly. The cost of the adaptive array consisting of a single receiver is low, and this array does not impact the industrial design. Its performance is evaluated by numerical simulation and experiments over a bandwidth of FM radio. View full abstract»

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  • A New Fabry-Perot Resonator Antenna Fed by an L-Probe

    Page(s): 1237 - 1244
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    A new Fabry-Perot resonator (FPR) antenna fed by an L-probe is proposed for mobile applications that require relatively low antenna gains. The proposed antenna consists of two parallel metal plates that are perpendicular to the ground plane. Its resonance frequency can be controlled by changing the separation between the parallel plates, as similar to that of the FPR. A probe resonance near the FPR mode is utilized to widen the impedance bandwidth. To reduce the cross polarization, a groove is introduced to each parallel plate. Ansoft HFSS was used to simulate the antenna, and a prototype operating in K-band was fabricated to verify the simulation. Reasonable agreement between the measured and simulated results is observed. The prototype has a 10-dB impedance bandwidth of 5% and the maximum gain of 11.1 dBi. The proposed antenna is simple and, more importantly, not too tiny to fabricate even at millimeter-wave frequencies. View full abstract»

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  • Smooth-Walled Light-Weight Ka-Band Shaped Horn Antennas in Metallized Foam

    Page(s): 1245 - 1251
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    Several smooth-walled axis-symmetrical dielectric-loaded horn antennas with large flare angles have been designed and characterized in Ka-band. They have been optimized using an in-house CAD tool based on the BoR-FDTD technique and genetic algorithms. Two antenna configurations have been compared: in the first case, only the metallic profile of the horn is shaped and the radiating aperture remains flat, whereas in the second one, the shapes of the horn profile and the aperture are simultaneously optimized. The impact of both techniques in terms of antenna size and performance is discussed. An original fabrication process (metallized foam) has been developed to produce monolithic prototypes. Two prototypes with optimized shapes have been fabricated, and their main characteristics (radiation characteristics, bandwidth, compactness, weight) are compared to those of a standard conical horn used as a reference (same flare angle, same diameter, but without shaped profile). Our results show that the proposed design and fabrication procedures enable us to produce reduced-size horns with high radiation efficiency; the total loss, including the transition loss, is lower than 1 dB in average around 29.5 GHz. View full abstract»

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  • Semi-Analytical Modeling of Coaxial Feeds

    Page(s): 1252 - 1260
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    A highly accurate semi-analytical model is given for the widely used practical topology of a coaxial feed exciting an arbitrary grounded planar structure. The probe connecting the inner conductor of the coaxial topology to the planar structure may cross an arbitrary number of layers. The core of the model is the comparison of the actual configuration with a parallel plate system, which can be studied quasi-analytically. It is shown that most of the modal fields found in the parallel plate system can be transferred to the actual configuration without modification. This allows to build a highly accurate model, without having to compromise calculation times. It is shown that in practical single and double layered cases, the model reduces to adding a capacitor in parallel. It is thus extremely easy to incorporate in existing modeling tools. View full abstract»

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  • A Simplified Feed Model for Investigating the Cross Polarization Reduction in Circular- and Elliptical-Rim Offset Reflector Antennas

    Page(s): 1261 - 1268
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    An analytic model for the primary feed of offset reflector antennas is presented that facilitates a more general investigation of the cross polarization reduction in both asymmetric and inter-cardinal planes. It includes both first and second order azimuthal modes, primarily the TE11 and TE21 type modes, and allows selection of symmetric and asymmetrical patterns, with different field tapers in the principal planes. Using this model first the influence of the second order TE21 mode on the cross polarization of an offset reflector with a circular rim is investigated. Then, the problem for an offset reflector with an elliptic rim is also studied. It is shown that minimizing the cross polarization in the asymmetric plane does not necessarily reduce it globally, as in the inter-cardinal plane it remains high. The procedure for reduction of the cross polarization globally and its effects on the sidelobe levels of the reflector antenna are also investigated. With the proposed feed model, the aperture efficiency of the reflector antenna is improved compared with a standard Gaussian feed with the same edge taper. Based on this study, a dual-mode circular waveguide horn is also proposed and designed. Its performance on an offset reflector antenna is studied and shown that the cross polarization levels are reduced quite satisfactorily within a respectable frequency band. View full abstract»

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  • Performance Improvements of Center-Fed Reflector Antennas Using Low Scattering Struts

    Page(s): 1269 - 1280
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    Conventional metallic struts used to support the feed in center-fed reflector antennas can significantly degrade the sidelobe, directivity and cross-polarization performances of the antenna. A promising approach to improve center-fed antenna performance is to use low scattering struts made of a metallic core covered with hard electromagnetic surfaces. In this paper, the performance improvements achievable by replacing conventional metallic struts by low scattering struts are studied for two space-based center-fed reflector antenna applications: a Ku-Band satellite communication antenna and the Sentinel-3 satellite C-Band/Ku-Band radar altimeter antenna. Measurements performed on these antennas show significant performance improvements (sidelobe levels, peak directivity, cross-polarization levels) when using the designed low scattering struts compared to using the conventional state of the art metallic struts. Two different configurations of low scattering struts using hard electromagnetic surfaces have been studied: a One Layer design using a single layer of dielectric material and a novel Two Layer design using two layers of dielectric. The performance improvements obtained with both designs are presented and discussed. Detailed comparisons between measurements and predictions are also presented. View full abstract»

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  • Stored Energy and Quality Factor of Spherical Wave Functions–in Relation to Spherical Antennas With Material Cores

    Page(s): 1281 - 1290
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    We present closed-form expressions for central properties of spherical wave functions of arbitrary order in relation to arbitrarily sized spherical antennas with lossless solid material cores. These properties are the electric or magnetic spherical surface current distribution radiating a spherical wave, the excitation coefficients for the internal and external spherical waves, the radiated power, the internal and external stored electric and magnetic energies, the difference of total electric and total magnetic energy, the cavity and radiating resonance conditions, and the quality factor. We investigate the variation of the internal/external and electric/magnetic stored energies with the electrical size of the antenna to study their relative significance for the quality factor. View full abstract»

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  • Exact Gaussian-Beam Theory for Outgoing and Standing Spherical Waves: Application to Transmitting and Receiving Antennas

    Page(s): 1291 - 1302
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    Outgoing spherical vector-wave functions are expressed in terms of Gaussian beams (also called complex source-point beams) radiating in all directions. By use of a vector-wave expansion, the electromagnetic field of an arbitrary source of finite extent is thus expressed in terms of Gaussian beams with weights determined directly from the spherical expansion coefficients of the source. These outgoing-wave formulas allow the field of any transmitting antenna to be expressed in terms of Gaussian beams. Elementary Gaussian-beam receivers are introduced as the electromagnetic field at complex points in space. The outputs of elementary Gaussian-beam receivers pointing in all directions determine the spherical expansion coefficients in a standing-wave expansion. These standing-wave formulas allow the output of any receiving antenna to be expressed in terms of the outputs of elementary Gaussian-beam receivers. Combining the formulas for outgoing and standing waves produces a new antenna-antenna transmission formula based solely on Gaussian beams. The theory is exact and validated through numerical examples. View full abstract»

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  • A Wideband Reconfigurable Transmitarray Element

    Page(s): 1303 - 1311
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    Transmitarrays have been shown to be viable architectures for achieving high-directivity reconfigurable apertures. Two reconfigurable transmitarray elements, using single and stacked patches, based on proximity-coupled feeding and two balanced reconfigurable bridged-T phase shifters are presented. Both designs achieve over 400 of phase range and achieve average insertion losses of 3.6 dB. Compared to existing proposed transmitarray elements, the stacked-patch element has a much smaller physical profile, with a lens thickness of only 0.17 λ in free-space, while achieving a large bandwidth of 500 MHz at 5 GHz (10%). Other considerations such as the mutual coupling and beam squint of an array using the stacked-patch element are also discussed. View full abstract»

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  • Dielectric Rod Antenna Array With Substrate Integrated Waveguide Planar Feed Network for Wideband Applications

    Page(s): 1312 - 1319
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    Dielectric rod antenna (DRA) elements have numerous advantages over conventional waveguide and horn antenna elements. They have low insertion loss, broadband input match, high mutual decoupling efficiency, and low-cost manufacturing. Additionally, the radiation pattern of the dielectric rod antenna is almost frequency-independent. However, its feeding is generally a challenge. This paper demonstrates a novel ultrawideband (UWB) eight-element DRA fed by a wideband substrate integrated waveguide (SIW) structure. The eight-way feed net work has less than 1.1 dB insertion loss and only ±0.9 dB and ±4° amplitude and phase imbalance, respectively. The developed low-cost and compact dual-layer DRA design covers over 40% bandwidth at X-band. It has a good input match, almost constant radiation pattern with a gain of 14.5 ± 2 dB over the frequency band, low dispersion, low squint performance, and almost flat group delay, which are essential requirements for many UWB ap plications. The developed array antenna is compact and occupies only 10 × 9 cm2. View full abstract»

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  • Prototype Design of a Modular Ultrawideband Wavelength-Scaled Array of Flared Notches

    Page(s): 1320 - 1328
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    A prototype modular ultrawideband wavelength- scaled array of flared notches has been designed, built, measured and validated with full-wave modeling tools. Wavelength-scaled arrays operate over ultrawide bandwidths with significantly-reduced element counts, maintaining a relatively-constant beam size by utilizing phased-array radiators of different size. The prototype phased array presented here is designed to operate over an 8:1 bandwidth (1-8 GHz), demonstrating a 12-degree beam capacity at 2 GHz, 4 GHz, and 8 GHz. The architecture achieves a reduction in element count by a factor of 6.4-only 160 elements per polarization as compared to a conventional 1024-element phased array of the same aperture size-at the cost of reduced beamwidth capacity in the higher frequency range. Performance metrics (active VSWR and radiation characteristics) of the wavelength-scaled array are measured and validated against full-wave simulations. The technology is presented as a viable alternative to more expensive conventional ultrawideband arrays with dense uniform element layouts. View full abstract»

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  • 60-GHz LTCC Integrated Circularly Polarized Helical Antenna Array

    Page(s): 1329 - 1335
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    A 60-GHz wideband circularly polarized (CP) helical antenna array of 4 × 4 elements is designed and fabricated using low temperature cofired ceramic (LTCC) technology. The flexible via hole distribution is fully utilized to achieve a helical antenna array to obtain good circular polarization performance. Meanwhile, grounded coplanar waveguide (GCPW) to stripline is utilized for probe station measurement. Unlike traditional helical antennas, the proposed helical antenna array is convenient for integrated applications. The fabricated antenna array has dimension of 12 × 10 × 2 mm3. The simulated and measured impedance, axial ratio (AR) and radiation pattern are studied and compared. The proposed antenna array shows a wide measured impedance bandwidth from 52.5 to 65.5 GHz for | S11| <; -10dB, wideband measured AR bandwidth from 54 to 66 GHz for AR <;3 dB, respectively. View full abstract»

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  • Dual-Band Horn Array Design Using a Helical Exciter for Mobile Satellite Communication Terminals

    Page(s): 1336 - 1342
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (519 KB) |  | HTML iconHTML  

    A horn array antenna is proposed for dual-band and dual-polarization operation. The array is optimally designed to be used as a feeder in mobile satellite terminals with a hybrid antenna (HA) structure, but it can be also used independently as a phased array. The array has an oval-shaped rim to maximize the efficiency of the HA, and is composed of 20 horn elements in a hexagonal structure. The element has a horn radiator with a conical helix, which is placed inside the horn and excited by two ports for TX and RX at both ends. Therefore, the antenna can be simultaneously operational in the Ka-band TX and K-band RX frequency bands, using a compact structure providing left-hand circular polarization (LHCP) for TX and right-hand circular polarization (RHCP) for RX. The fabricated array is connected with active channel modules having 20 channels each for TX and RX, and it was experimented on within a beam scanning range of -5° to +5° in the azimuth and elevation directions using phase control of the ac tive channel module. The antenna has a minimum gain of 21.7 dBi over the TX band and 19.7 dBi over the RX band over the desired scan region. The maximum pointing error is about 0.32° and the pointing loss is approximately 1.3 dB. In addition to meeting the above RF requirements, the antenna is designed to meet environmental specifications such as wind loads as required for mobile terminals. View full abstract»

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  • Rotman Lens-Based Retrodirective Array

    Page(s): 1343 - 1351
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    A new type of broadband retrodirective array, which has been constructed using a microstrip Rotman lens, is presented. Automatic tracking of targets is obtained by exploiting the conjugate phase response of the beamforming network which is exhibited when the input ports are terminated with either open or short circuits. In addition, the true time-delay property of the Rotman lens gives broadband operation of the self-tracking array when used in conjunction with Vivaldi antennas. The simulated and measured bistatic and monostatic radar cross-section (RCS) patterns of a structure consisting of 13 beamports and 12 array ports are presented at frequencies in the range 8-12 GHz. Significantly enhanced RCS within the scan coverage ±40° is demonstrated by comparing the retrodirective behavior of a 12-element Vivaldi array terminated with and without the Rotman lens. View full abstract»

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  • Efficient Gain Optimization Techniques for Azimuth Beam/Null Steering of Inverted-F Multiport Parasitic Array Radiator (MuPAR) Antenna

    Page(s): 1352 - 1361
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    The multiport parasitic array radiator (MuPAR) antenna is a compact low-profile beam-steering antenna, which is composed of two excited inverted-F elements and two parasitic elements with variable reactors. Although the MuPAR antenna seems to have a good potentiality to achieve full azimuthal beam/null steering performance, the detailed controllability of the beam and null has not been clarified yet. This is because the two different types of variables, which are excitation coefficients and reactance values, make the gain optimization problem complex and difficult. Thus, in this paper, we have first developed a generalized model of the inverted-F MuPAR antenna. For the accurate modeling, structural features of inverted-F antennas are taken into account, and also the closed-form gain definition for the MuPAR antenna is derived. The formulation enables us to efficiently obtain both excitation coefficients and reactance values with optimization techniques. Applying the model to both a gradient-based optimization and a particle swarm optimization successfully, the beam/null forming performances of the four-element MuPAR antenna is made clear. Through experiments including numerical calculations and measurements at 2.45 GHz, the validity of our model and precise formulation is confirmed. View full abstract»

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  • On-Board Calibration Methods for Mechanical Distortions of Satellite Phased Array Antennas

    Page(s): 1362 - 1372
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    In satellite phased-array antennas, mechanical distortions, which may be due to vibrations caused when launching the satellite into the orbit or thermal variations in the orbit, result in significant degradation of electrical performance. In this paper, two on-board calibration methods are proposed for such mechanical distortions: One compensates for the element phase differences resulting from mechanical distortions, and the other is used to set the best-fit phase distribution obtained from the measured phases. The latter method is effective even at a low signal-to-noise ratio (SNR). The proposed methods have been validated by experiments, through which the theoretically predicted calibration accuracy of the methods has been successfully reproduced. View full abstract»

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  • Subarray Design Diagnostics for the Suppression of Undesirable Grating Lobes

    Page(s): 1373 - 1380
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    This paper investigates various subarray pattern distortions that can cause the appearance of grating lobes with the aim to provide an insightful and valuable first-order diagnostic tool for antenna array designers. In typical subarray configurations, the emergence of undesirable grating lobes is a possibility due to distortions in the subarray array factor which can be caused by feeding errors, mutual coupling between elements and/or feed lines, or other discrepancies. This paper will focus on systematic errors that can arise in subarray designs that feature common element excitation schemes. Distortions will be categorized by amplitude and phase errors separately, demonstrating their distinct manifestations in each excitation scheme. Recognition of these manifestations can lead to better subarray designs and save significant time in the development of large array antennas. The concepts introduced here will be supported by analytical array factor calculations for 1 × N linear subarrays, full-wave simulations of a 1 × 4 subarray and 1 × 16 array, and representative measurements of two 1 × 16 arrays at Ku-band. View full abstract»

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  • Near-Field Analysis of Electromagnetic Interactions in Antenna Arrays Through Equivalent Dipole Models

    Page(s): 1381 - 1389
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    This paper presents an analysis of the near fields of antenna arrays using an alternative approach taking into account field variations due to mutual coupling. The method does not require solving Maxwell's equations under the customary boundary condition, but is based instead on searching for equivalent dipole models that are capable of reproducing the same radiated fields of the actual array (ideally obtained through accurate measurement.) We treat mutual coupling between array elements as essentially a multiple scattering effect and propose a method to calculate the near field of arbitrary linear arrays with significant electromagnetic coupling. It is found that a single (analytical) dipole model obtained under certain circumstances, which are detailed in the paper, can be used to predict correctly the near field radiated by arbitrary-size antenna arrays. The paper ends by developing an application of the equivalent dipole method by expanding the near fields into a sum of propagating and nonpropagating parts. It is shown that the 3-D spatial Fourier transform required in this expansion can be eliminated when the dipole model is used in computing the near field in the domain of the validity of the model. View full abstract»

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  • A Novel Multilevel Matrix Compression Method for Analysis of Electromagnetic Scattering From PEC Targets

    Page(s): 1390 - 1399
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    We present a new multilevel matrix compression method (MLMCM) and its application to the analysis of scattering problems from three-dimensional (3-D) arbitrary-shaped conductors. The compression is achieved without generating the full subblocks of the matrix by the rank-based method. Unlike the conventional rank-based method, incoming compression matrix and outgoing compression matrix are defined when coupling with a cluster of its far interaction groups. Only a small translation matrix is redefined for every two coupling groups. The merits of the proposed method are: 1) it is kernel function-independent and can be applied to arbitrary complex media; 2) it is more efficient than conventional rank-based methods. This paper shows numerical results to demonstrate the validity of the proposed method. View full abstract»

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  • Vector Green's function for S-parameter measurements of the electromagnetic volume integral equation

    Page(s): 1400 - 1413
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    We present a variation of the electric-field volume integral equation (VIE) for inhomogeneous media that is tailored for microwave S-parameter measurements. The kernel of the standard VIE is a dyadic Green's function that can relate fields in the object domain to observed scattered fields outside the object domain. Here, we derive a kernel we call a vector Green's function that gives, instead of observed fields, observed S-parameter measurements that would be obtained in a bistatic antenna setup. This formulation directly links the object properties to microwave measurements in a way that is useful to many microwave applications. This derivation uses an antenna model based on the source-scattering matrix formulation. We show how this vector Green's function can be obtained from simulation and validate this model with several experiments. View full abstract»

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IEEE Transactions on Antennas and Propagation includes theoretical and experimental advances in antennas.

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Editor-in-Chief                                                 Kwok W. Leung