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Antennas and Propagation, IEEE Transactions on

Issue 8 • Date Aug. 2010

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Displaying Results 1 - 25 of 46
  • Table of contents

    Page(s): C1 - 2489
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  • IEEE Transactions on Antennas and Propagation publication information

    Page(s): C2
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  • Modeling, Design and Experimentation of Wearable RFID Sensor Tag

    Page(s): 2490 - 2498
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2394 KB) |  | HTML iconHTML  

    Design of effective wearable tags for UHF RFID applications involving persons is still an open challenge due to the strong interaction of the antenna with the human body which is responsible of impedance detuning and efficiency degradation. A new tag geometry combining folded conductors and tuning slots is here discussed through numerical analysis and extensive experimentation also including the integration of a passive motion detector. The achieved designs, having size comparable with a credit card, may be applied to any part of the body. The measured performance indicates a possible application of these body-worn tags for the continuous tracking of human movements in a conventional room. View full abstract»

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  • Low Cost Planar Waveguide Technology-Based Dielectric Resonator Antenna (DRA) for Millimeter-Wave Applications: Analysis, Design, and Fabrication

    Page(s): 2499 - 2507
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    A compact, low cost and high radiation efficiency antenna structure, planar waveguide, substrate integrated waveguide (SIW), dielectric resonator antennas (DRA) is presented in this paper. Since SIW is a high Q- waveguide and DRA is a low loss radiator, then SIW-DRA forms an excellent antenna system with high radiation efficiency at millimeter-waveband, where the conductor loss dominates. The impact of different antenna parameters on the antenna performance is studied. Experimental data for SIW-DRA, based on two different slot orientations, at millimeter-wave band are introduced and compared to the simulated HFSS results to validate our proposed antenna model. A good agreement is obtained. The measured gain for SIW-DRA single element showed a broadside gain of 5.51 dB,-19 dB maximum cross polarized radiation level, and overall calculated (simulated using HFSS) radiation efficiency of greater than 95%. View full abstract»

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  • Integrated Leaky-Wave Antenna–Duplexer/Diplexer Using CRLH Uniform Ferrite-Loaded Open Waveguide

    Page(s): 2508 - 2514
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    A novel integrated leaky-wave antenna-duplexer/diplexer, based on the CRLH uniform ferrite-loaded open radiating waveguide is introduced, demonstrated and characterized both numerically and experimentally. The duplexing operation, characterized by equal Tx and Rx frequencies, is performed directly within the antenna thanks to the non-reciprocity of the ferrite, thereby suppressing the need for a circulator external to the antenna. The diplexing function, where the Tx and Rx frequencies are different, is achieved by inclining the plane of the antenna structure with respect to the normal of the radiation direction. The duplexer may be seen as the particular case of the diplexer with an inclination angle of zero. Virtually unlimited Tx → Rx isolation is provided by the leaky-wave nature of the device, which avoids typical problems of demodulation and detection/ranging errors and possible destruction of the receiver. Another advantage of this duplexer/diplexer is the possibility to tune the operation frequency by the applied magnetic bias field, whereas such tuning is prevented both by the antenna and by the circulator in conventional designs. The fabricated prototype exhibits a gain of 2.3 dBi with isolation of more than 15 dB at all ports. The diplexing frequency range reaches 400 MHz. View full abstract»

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  • An Original Antenna for Transient High Power UWB Arrays: The Shark Antenna

    Page(s): 2515 - 2522
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    A novel ultrawideband (UWB) antenna, called the Shark antenna, and designed especially for transient applications is proposed in this paper. A Shark antenna array is also conceived in order to obtain a high power UWB pulse radiation source through the frequency band [800 MHz-8 GHz]. For this application, the elementary antenna must be compact, non-dispersive, and the array must have a high transient front to back ratio. The geometry of the Shark antenna and its radiation characteristics are detailed. Moreover, an approach which evaluates the transient front to back ratio of a square array is presented. View full abstract»

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  • Resonant Effects and Near-Field Enhancement in Perturbed Arrays of Metal Dipoles

    Page(s): 2523 - 2530
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    The equivalent self impedance of a perturbed array of metal dipoles is derived and the resonant effects upon plane wave illumination are studied. It is revealed that as a result of the perturbation, the scattering within a frequency range is dominated by the excitation of the odd mode. This corresponds to significant deviation compared to the unperturbed case. It is demonstrated that within this frequency range, very strong near- fields are excited in the vicinity of the array. Following a careful calculation of the near-fields using the periodic method of moments, the near-fields for a number of perturbed array designs are calculated and an increase in the near-field strength of more than 70 times compared with the incidence is demonstrated. The results are corroborated with HFSS. View full abstract»

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  • Design and Implementation of Embedded Printed Antenna Arrays in Small UAV Wing Structures

    Page(s): 2531 - 2538
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1046 KB) |  | HTML iconHTML  

    Unmanned aerial vehicles (UAV) are extensively being used in exploration, surveillance and military applications. Such vehicles often collect data via special sensors and send the data back to the central station via wireless links. Embedded in wing structure printed antennas will eliminate the drag due to friction, and allow for extended load capability due to their extra light weight. In this work we present the design and implementation of a 4-element linear antenna array embedded in a small UAV wing structure. The antenna array operates in the 2.4 GHz ISM band. Simulations and measurements that characterize the performance of the antenna array are presented. Field measurements show the impact of utilizing beam-forming in enhancing the communication link throughput. View full abstract»

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  • Flat-Top Footprint Pattern Synthesis Through the Design of Arbitrary Planar-Shaped Apertures

    Page(s): 2539 - 2552
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    The problem of generating a flat-top main beam with an arbitrary footprint for array elements placed in an arbitrary planar aperture is considered in this paper. Some simplifying properties of the Bessel functions, encourages the general framework of the paper to encompass patterns produced by circular aperture and eventually generalize it to arbitrary aperture geometries. In this regard two synthesis methods are presented. The first method is based on the use of the Rayleigh quotient to obtain constant phase array patterns, hence, a class of generally linear phase patterns can be considered. The second approach is based on power pattern synthesis where there is no restriction on the phase of the pattern, hence, it provides us with greater flexibility. The nonlinear problem is appropriately modeled and formulated for amenable performance. These two new methods can exhibit a significant reduction in the number of unknown parameters, and high flexibility in shaping the desired main beam by arbitrary lattice geometry. View full abstract»

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  • Synthesis of Unequally Spaced Antenna Arrays by Using Differential Evolution

    Page(s): 2553 - 2561
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    Synthesis of unequally spaced linear antenna arrays is considered in this paper. A recently developed new differential evolution algorithm is applied to solve the problem. Both position-only and position-phase synthesis have been studied. Effect of angle resolution has also been investigated. Synthesis results show that our algorithm is able to obtain better synthesis result reliably and efficiently. View full abstract»

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  • Multi-Frequency Synthetic Thinned Array Antenna for the Hurricane Imaging Radiometer

    Page(s): 2562 - 2570
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1790 KB) |  | HTML iconHTML  

    A C-band four-frequency resonant stacked-patch array antenna is developed for synthetic thinned aperture radiometer measurements of hurricane force wind speeds. This antenna is being integrated into an aircraft instrument referred to as the Hurricane Imaging Radiometer (HIRAD). Details of the antenna design are presented along with antenna performance tests and laboratory measurements using a full-scale prototype array with a subset model of the HIRAD instrument. View full abstract»

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  • Electronically Reconfigurable Transmitarray at Ku Band for Microwave Applications

    Page(s): 2571 - 2579
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    An electronically reconfigurable transmitarray device at 12 GHz is presented in this work. This paper highlights the functioning of this kind of device and thoroughly examines the proposed reconfigurable transmitarray. The architecture is discussed along with the design and selection of all the constituting elements and the prototypes for all of them. In order to add reconfigurability to the transmitarray structure, 360° reflective phase shifters were designed, prototyped and validated for direct application. Eventually, a demonstrative prototype for an active transmitarray with phase shifters was assembled, and radiation pattern measurements were taken in an anechoic chamber to demonstrate the capabilities of this structure. View full abstract»

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  • Optimal Wideband Beamforming for Uniform Linear Arrays Based on Frequency-Domain MISO System Identification

    Page(s): 2580 - 2587
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    Frequency-invariant (FI) beamforming for wideband antenna arrays inevitably involves array aperture loss at the higher-end frequencies of the bandwidth. In order to minimize aperture loss and to fully utilize the array aperture at different operation frequencies, an optimal wideband beamformer for uniform linear array (ULA) is designed based on Dolph-Chebyshev's theory of beamforming. Different from the existing FI beamformers for wideband arrays, our wideband beamformer produces frequency-dependent patterns which have the narrowest mainlobe width for any given equiripple sidelobe level over a wide frequency bandwidth. These frequency-dependent patterns are obtained through using the system identification method to determine the transfer function of the beamforming network. A matrix formulation is developed to calculate the frequency-dependent optimal Riblet-Chebyshev weights for element spacings smaller than half wavelength. The transfer function of the beamforming network, which is treated as an equivalent multi-input and single-output (MISO) system, is then obtained by the method of system identification with the optimal frequency-dependent Riblet-Chebyshev weights as the input data. Numerical results are provided to verify the effectiveness and validity of the proposed method. View full abstract»

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  • Design and Performance of Frequency Selective Surface With Integrated Photodiodes for Photonic Calibration of Phased Array Antennas

    Page(s): 2588 - 2593
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    The design, fabrication, and integration of a frequency selective surface (FSS) with integrated photodiodes to allow for photonic calibration of phased array antennas is presented. The design includes embedding electrically short dipole antennas in each unit cell of the FSS, with a zero-biased photodiode placed across the gap of the diode. Fibers from an optical distribution network are passed through the honeycomb core of the frequency selective surface and pigtailed to the photodiodes. The RF performance of the frequency selective surface with integrated optics is investigated via simulations and measurements, and the results show that the structure maintains RF-transparency. View full abstract»

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  • A Through-Dielectric Radar Imaging System

    Page(s): 2594 - 2603
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1420 KB) |  | HTML iconHTML  

    Through-lossy-slab radar imaging will be shown at stand-off ranges using a low-power, ultrawideband (UWB), frequency modulated continuous wave (FMCW) radar system. FMCW is desirable for through-slab applications because of the signal gain resulting from pulse compression of long transmit pulses (1.926-4.069 GHz chirp in 10 ms). The difficulty in utilizing FMCW radar for this application is that the air-slab boundary dominates the scattered return from the target scene and limits the upper bound of the receiver dynamic range, reducing sensitivity for targets behind the slab. A method of range-gating out the air-slab boundary by significant band-limiting of the IF stages facilitates imaging of low radar cross section (RCS) targets behind the slab. This sensor is combined with a 1D linear rail and utilized as a rail synthetic aperture radar (SAR) imaging system. A 2D model of a slab and cylinder shows that image blurring due to the slab is negligible when the SAR is located at a stand-off range of 6 m or greater, and thus, the two-way attenuation due to wave propagation through the slab is the greatest challenge at stand-off ranges when the air-slab boundary is range-gated out of the scattered return. Measurements agree with the model, and also show that this radar is capable of imaging target scenes of cylinders and rods 15.24 cm in height and 0.95 cm in diameter behind a 10 cm thick lossy dielectric slab. Further, this system is capable of imaging free-space target scenes with transmit power as low as 5 pW, providing capability for RCS measurement. View full abstract»

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  • Breast Lesion Classification Using Ultrawideband Early Time Breast Lesion Response

    Page(s): 2604 - 2613
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1637 KB) |  | HTML iconHTML  

    Breast lesion characterization for discriminating between localized malignant and benign lesions is important as the current breast screening techniques do not have the required specificity to be clinically acceptable. A method using ultrawideband (UWB) microwave imaging system for such classification is proposed in this paper. The early time portion of the backscatter breast response is processed for lesion discrimination. This method provides a high resolution since the early time lesion response has the largest signal strength. A correlator is used at the receiver to extract the early response and to quantify the degree of ruggedness of a lesion through several key parameters associated with the correlation operation. Subsequently, a large scale simulation study using a two-dimensional (2D) numerical breast model with an antenna array is used for the development of a lesion classification technique. It is shown that the lesion classification method is capable of discriminating between lesions with different morphologies. View full abstract»

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  • Artificial Magnetic Materials Using Fractal Hilbert Curves

    Page(s): 2614 - 2622
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (879 KB) |  | HTML iconHTML  

    Novel configurations based on Fractal Hilbert curves are proposed for realizing artificial magnetic materials. It is shown that the proposed configuration gives significant rise to miniaturization of artificial unit cells which in turn results in higher homogeneity in the material, and reduction in the profile of the artificial substrate. Analytical formulas are proposed for design and optimization of the presented structures, and are verified through full wave numerical characterization. The electromagnetic properties of the proposed structures are studied in detail and compared to square spiral from the point of view of size reduction, maximum value of the resultant permeability, magnetic loss, and frequency dispersion. To validate the analytical model and the numerical simulation results, an artificial substrate containing second-order Fractal Hilbert curve is fabricated and experimentally characterized using a microstrip-based characterization method. View full abstract»

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  • Theory and Practice of the FFT/Matrix Inversion Technique for Probe-Corrected Spherical Near-Field Antenna Measurements With High-Order Probes

    Page(s): 2623 - 2631
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    A complete antenna pattern characterization procedure for spherical near-field antenna measurements employing a high-order probe and a full probe correction is described. The procedure allows an (almost) arbitrary antenna to be used as a probe. Different measurement steps of the procedure and the associated data processing are described in detail, and comparison to the existing procedure employing a first-order probe is made. The procedure is validated through measurements. View full abstract»

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  • Resilience to Probe-Positioning Errors in Planar Phaseless Near-Field Measurements

    Page(s): 2632 - 2640
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1237 KB) |  | HTML iconHTML  

    The phaseless techniques have been discussed in the antenna measurements community and the theories behind these techniques are well explained in literature. The issue of the noise and the presence of measurement errors are not investigated in details to provide strong impetus to the importance of phaseless measurements. In this paper the near-fields of a number of different types of antennas with high, medium and low side lobes are simulated to create some realistic cases. The probe positioning error effects are investigated by implementing random errors in the position of the simulated probe samples along different axes. A novel method is also adopted to incorporate the probe-height positioning error in an actual near-field measurement of an array antenna. It is also illustrated how the positioning errors can distort the phase distributions. Through detailed characterizations of the constructed far-field patterns, robustness of the Iterative Fourier technique even at the presence of very high probe positioning errors is demonstrated. It is shown how the utilization of a phaseless technique can significantly reduce the effects of probe positioning errors. The results are compared with the results extracted from the commonly used amplitude and phase near-field measurement techniques and the clear improvements are illustrated. View full abstract»

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  • FDTD Discrete Planewave (FDTD-DPW) Formulation for a Perfectly Matched Source in TFSF Simulations

    Page(s): 2641 - 2648
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    A technique is proposed for the generation of planewaves in the total-field scattered-field (TFSF) formulation of the FDTD method. The method is developed using the 1D properties of a planewave and optimized projection of the 3D finite difference operators to the 1D domain. The result is an efficient and accurate planewave source that can be propagated on six 1D grids concurrent with the main simulation, and that is perfectly matched to the main 2D/3D FDTD domain for any source function. Numerical simulations show that the technique is valid for any angle of propagation, and for any gridcell aspect ratio, with non-physical reflections in the scattered field domain on the order of machine precision (-300 dB). View full abstract»

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  • FDTD Analysis of Periodic Structures With Arbitrary Skewed Grid

    Page(s): 2649 - 2657
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1086 KB) |  | HTML iconHTML  

    An efficient finite-difference time-domain (FDTD) algorithm with a simple periodic boundary condition (PBC) is developed to analyze general periodic structures with arbitrary skewed grids. The algorithm is easy to implement and efficient in both memory usage and computation time. The stability criterion of the algorithm is angle independent and therefore it is suitable for implementing incidence with angle close to grazing as well as normal incidence. The validity of this algorithm is verified through several numerical examples such as dipole and Jerusalem cross frequency selective surfaces (FSS) with various skew angles. View full abstract»

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  • Cartesian Shift Thin Wire Formalism in the FDTD Method With Multiwire Junctions

    Page(s): 2658 - 2665
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    The Holland and Simpson thin wire formalism is a versatile technique to deal with wires in the FDTD method. This paper develops an approach to correctly perform a junction between several wires at any Yee's cell location. The application context is the wires parallel to Cartesian axes with any translation in the Yee's Cell. The sensitivity of the thin wire current to Cartesian shift is also minimized in our enhanced formalism. The method is presented in a general framework with non-uniform FDTD spatial steps. Beside, the wire segment length can be different of the FDTD spatial steps and also the wire position does not need to coincide with any edge or node of the Yee's cell. View full abstract»

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  • Efficient Current-Based Hybrid Analysis of Wire Antennas Mounted on a Large Realistic Aircraft

    Page(s): 2666 - 2672
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    An efficient hybrid analysis which hybridizes surface-wire integral equations (SWIE) with physical optics (PO) approximation is presented for wire antennas attached to an electrically large aircraft platform. In the analysis, the whole surface of the platform and antennas is divided into three regions, namely, the method of moments (MoM) region, the PO region and a region referred to as the joint PO-MoM (POM) region in this paper. The MoM region, generally, the smallest one among the three regions, includes wires, wire-surface junctions and a small part of the platform surface surrounding the junctions. A large part of the remaining platform surface forms the PO region with the rest being the POM region which is situated between the MoM and PO regions. The POM region is treated as a MoM region on the one hand so that the total MoM region is sufficiently large to well characterize the platform-attached antennas, whereas it is also regarded as a PO region on the other hand so that its interaction with the PO region needs not to be precisely considered so as to drastically reduce computational requirements. View full abstract»

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  • Enhancement of Efficiency of Integral Equation Solutions of Antennas by Incorporation of Network Principles – Part II

    Page(s): 2673 - 2679
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    A method is presented for enhancing the efficiency of integral equation solutions for antennas. In this paper, a folded coaxial guide junction, proposed to be part of a below the feed inductive load, is analyzed. Scattering parameters for the folded coaxial guide junction are developed to replace the coupling of the field accounted for by a coupled integral equation at the aperture joining two coaxial guides. Numerical results are shown to agree well with measurements of cascaded folded coaxial guide junctions. View full abstract»

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  • A Calderón Multiplicative Preconditioner for Coupled Surface-Volume Electric Field Integral Equations

    Page(s): 2680 - 2690
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    A well-conditioned coupled set of surface (S) and volume (V) electric field integral equations (S-EFIE and V-EFIE) for analyzing wave interactions with densely discretized composite structures is presented. Whereas the V-EFIE operator is well-posed even when applied to densely discretized volumes, a classically formulated S-EFIE operator is ill-posed when applied to densely discretized surfaces. This renders the discretized coupled S-EFIE and V-EFIE system ill-conditioned, and its iterative solution inefficient or even impossible. The proposed scheme regularizes the coupled set of S-EFIE and V-EFIE using a Calderón multiplicative preconditioner (CMP)-based technique. The resulting scheme enables the efficient analysis of electromagnetic interactions with composite structures containing fine/subwavelength geometric features. Numerical examples demonstrate the efficiency of the proposed scheme. 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