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Antennas and Propagation Magazine, IEEE

Popular Articles (April 2015)

Includes the top 50 most frequently downloaded documents for this publication according to the most recent monthly usage statistics.
  • 1. Mobile-Phone Antenna Design

    Publication Year: 2012 , Page(s): 14 - 34
    Cited by:  Papers (18)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (12400 KB) |  | HTML iconHTML  

    This paper is a survey of internal antennas in mobile phones from 1997 to 2010. It covers almost 60 GSM and 3G handsets, ranging from the first GSM handset with an internal antenna to the current Nokia, Sony-Ericsson, Motorola, and Apple handsets. The paper discusses different types of mobile-phone antennas, feeding structures, active antennas, isolation, and antenna loading techniques. This paper examines different design techniques for mobile-phone antennas, and the limitations of antenna design due to manufacturing technologies and the effect of handset materials. Antenna performance parameters, including S parameters, radiation efficiency, SAR, and TRP/TIS are reported for the surveyed handsets. The effective antenna volume for every antenna is calculated, in order to determine the average volume/space required for each antenna type and the corresponding performance. Some of the handsets are further simulated using commercial electromagnetic simulators to illustrate the electromagnetic-field distributions. This paper summarizes the antenna design parameters as a function of handset performance, and presents a short summary of design procedure. View full abstract»

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  • 2. An Overview of the Theory and Applications of Metasurfaces: The Two-Dimensional Equivalents of Metamaterials

    Publication Year: 2012 , Page(s): 10 - 35
    Cited by:  Papers (47)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (5576 KB)  

    Metamaterials are typically engineered by arranging a set of small scatterers or apertures in a regular array throughout a region of space, thus obtaining some desirable bulk electromagnetic behavior. The desired property is often one that is not normally found naturally (negative refractive index, near-zero index, etc.). Over the past ten years, metamaterials have moved from being simply a theoretical concept to a field with developed and marketed applications. Three-dimensional metamaterials can be extended by arranging electrically small scatterers or holes into a two-dimensional pattern at a surface or interface. This surface version of a metamaterial has been given the name metasurface (the term metafilm has also been employed for certain structures). For many applications, metasurfaces can be used in place of metamaterials. Metasurfaces have the advantage of taking up less physical space than do full three-dimensional metamaterial structures; consequently, metasurfaces offer the possibility of less-lossy structures. In this overview paper, we discuss the theoretical basis by which metasurfaces should be characterized, and discuss their various applications. We will see how metasurfaces are distinguished from conventional frequency-selective surfaces. Metasurfaces have a wide range of potential applications in electromagnetics (ranging from low microwave to optical frequencies), including: (1) controllable “smart” surfaces, (2) miniaturized cavity resonators, (3) novel wave-guiding structures, (4) angular-independent surfaces, (5) absorbers, (6) biomedical devices, (7) terahertz switches, and (8) fluid-tunable frequency-agile materials, to name only a few. In this review, we will see that the development in recent years of such materials and/or surfaces is bringing us closer to realizing the exciting speculations made over one hundred years ago by the work of Lamb, Schuster, and Pocklington, and later by Mandel'shtam and Veselago. View full abstract»

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  • 3. Antenna Array Developments: A Perspective on the Past, Present and Future

    Publication Year: 2015 , Page(s): 86 - 96
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (3265 KB)  

    This paper presents a historical development of phased-array antennas as viewed by the authors. Arrays are another approach to high-gain antennas as contrasted with reflector antennas. They originated a little over 100 years ago and received little attention at first. WWII elevated their importance through use in air defense. Since then, the development of computers and solid-state devices has made arrays a very valuable tool in radio-frequency systems. Radio astronomy and defense applications will continue to push the state of the art for many years. View full abstract»

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  • 4. Compressive Sensing in Electromagnetics - A Review

    Publication Year: 2015 , Page(s): 224 - 238
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (646 KB)  

    Several problems arising in electromagnetics can be directly formulated or suitably recast for an effective solution within the compressive sensing (CS) framework. This has motivated a great interest in developing and applying CS methodologies to several conventional and innovative electromagnetic scenarios. This work is aimed at presenting, to the best of the authors' knowledge, a review of the state-of-the-art and most recent advances of CS formulations and related methods as applied to electromagnetics. Toward this end, a wide set of applicative scenarios comprising the diagnosis and synthesis of antenna arrays, the estimation of directions of arrival, and the solution of inverse scattering and radar imaging problems are reviewed. Current challenges and trends in the application of CS to the solution of traditional and new electromagnetic problems are also discussed. View full abstract»

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  • 5. Wideband Magnetoelectric Dipole Antennas With Dual Polarization and Circular Polarization

    Publication Year: 2015 , Page(s): 110 - 119
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2836 KB)  

    A new 45 degrees dual-polarized magnetoelectric dipole antenna is proposed. The antenna is excited by two -shaped probes placed at a convenient location. The measured overlapped impedance bandwidth is 48% with standing-wave ratio (SWR) 1.5 from 1.69 to 2.76 GHz. The measured gains vary from 7.6 to 9.3 dBi and from 7.6 to 9.4 dBi for port 1 and port 2, respectively. The isolation between the two ports is larger than 30 dB. The proposed antenna achieves a low cross-polarization level of less than 21 dB and a low back radiation level of less than 29 dB over the operating frequency range. With a broadband 90 phase shifter and a power divider, the proposed antenna can radiate circularly-polarized (CP) wave and exhibit a wide impedance bandwidth (SWR 2) of 90% from 1.23 to 3.23 GHz, which covers the whole 3-dB axial-ratio (AR) bandwidth of 82% from 1.28 to 3.05 GHz. In this operation frequency band, the proposed CP antenna has a broadside gain of larger than 5 dBi above 1.45 GHz. Considering the common overlapped bandwidth limited by the impedance, AR, and gain, the proposed antenna exhibits an effective bandwidth of 71%. View full abstract»

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  • 6. The Theory of Characteristic Modes Revisited: A Contribution to the Design of Antennas for Modern Applications

    Publication Year: 2007 , Page(s): 52 - 68
    Cited by:  Papers (65)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (10534 KB) |  | HTML iconHTML  

    The objective of this paper is to summarize the work that has been developed by the authors for the last several years, in order to demonstrate that the Theory of Characteristic Modes can be used to perform a systematic design of different types of antennas. Characteristic modes are real current modes that can be computed numerically for conducting bodies of arbitrary shape. Since characteristic modes form a set of orthogonal functions, they can be used to expand the total current on the surface of the body. However, this paper shows that what makes characteristic modes really attractive for antenna design is the physical insight they bring into the radiating phenomena taking place in the antenna. The resonance frequency of modes, as well as their radiating behavior, can be determined from the information provided by the eigenvalues associated with the characteristic modes. Moreover, by studying the current distribution of modes, an optimum feeding arrangement can be found in order to obtain the desired radiating behavior. View full abstract»

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  • 7. The art of UHF RFID antenna design: impedance-matching and size-reduction techniques

    Publication Year: 2008 , Page(s): 66 - 79
    Cited by:  Papers (189)  |  Patents (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (8940 KB) |  | HTML iconHTML  

    Radio-frequency identification technology, based on the reader/tag paradigm, is quickly permeating several aspects of everyday life. The electromagnetic research mainly concerns the design of tag antennas having high efficiency and small size, and suited to complex impedance matching to the embedded electronics. Starting from the available but fragmented open literature, this paper presents a homogeneous survey of relevant methodologies for the design of UHF passive tag antennas. Particular care is taken to illustrate, within a common framework, the basic concepts of the most-used design layouts. The design techniques are illustrated by means of many noncommercial examples. View full abstract»

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  • 8. Miniature implantable and wearable on-body antennas: towards the new era of wireless body-centric systems [antenna applications corner]

    Publication Year: 2014 , Page(s): 271 - 291
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (8121 KB) |  | HTML iconHTML  

    Wireless body-centric sensing systems have an important role in the fields of biomedicine, personal healthcare, safety, and security. Body-centric radio-frequency identification (RFID) technology provides a wireless and maintenance-free communication link between the human body and the surroundings through wearable and implanted antennas. This enables real-time monitoring of human vital signs everywhere. Seamlessly integrated wearable and implanted miniaturized antennas thus have the potential to revolutionize the everyday life of people, and to contribute to independent living. Low-cost and low-power system solutions will make widespread use of such technology become reality. The primary target applications for this research are body-centric sensing systems and the relatively new interdisciplinary field of wireless brain-machine interface (BMI) systems. Providing a direct wireless pathway between the brain and an external device, a wireless brain-machine interface holds an enormous potential for helping people suffering from severely disabling neurological conditions to communicate and manage their everyday life more independently. In this paper, we discuss RFID-inspired wireless brain-machine interface systems. We demonstrate that mm-size loop implanted antennas are capable of efficiently coupling to an external transmitting loop antenna through an inductive link. In addition, we focus on wearable antennas based on electrically conductive textiles and threads, and present design guidelines for their use as wearable-antenna conductive elements. Overall, our results constitute an important milestone in the development of wireless brain-machine interface systems, and a new era of wireless body-centric systems. View full abstract»

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  • 9. A Novel Hemispherical Dielectric Resonator Antenna With Complementary Split-Ring-Shaped Slots and Resonator for Wideband and Low Cross-Polar Applications

    Publication Year: 2015 , Page(s): 120 - 128
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1864 KB)  

    In this paper, a novel hemispherical dielectric resonator antenna (HDRA) with complementary split rings and slots is proposed and investigated. The complementary split-ring resonators (CSRRs) are etched from the ground plane, which are pierced though slots extending from the ground plane up to the HDRA. The dielectric material used is Rogers TMM10, which has a dielectric constant of "r ¼ 9:2. The CSRR-shaped slot on HDRA lowers down the quality factor (Q-factor) of the antenna, thus enhancing the bandwidth. Furthermore, the current distribution across the CSRR slots on the ground plane is out of phase, which results in current cancelation along the CSRR and hence reduces the cross-polar component of the radiation pattern significantly. The measured value of bandwidth of the proposed structure is 30% centered at 1.9 GHz, offering a gain of 6 dBi. The cross-polar level is more than 40 dB, which is much lower than the copolar pattern. The first two modes of the HDRA are preserved. View full abstract»

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  • 10. Near Vertical Incidence Skywave Propagation: Elevation Angles and Optimum Antenna Height for Horizontal Dipole Antennas

    Publication Year: 2015 , Page(s): 129 - 146
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (4534 KB)  

    Near Vertical Incidence Skywave (NVIS) communication uses the ionosphere as a reflector to cover a continuous area with a radius of at least 150 km around the transmitter, on frequencies typically between 3 and 10 MHz. In developing countries, in areas lacking any other telecommunication infrastructure, it is used on a daily basis for voice and data communication. It may also be used in ad-hoc emergency (disaster) communication in other regions. This paper proposes optimum heights above ground for horizontal dipole antennas for NVIS, based on simulations and empirical data. First, the relationship between elevation angle and skip distance is obtained using ionospheric ray tracing. The high elevation angles found by simulation are confirmed by elevation angle measurements using a professional radio direction finder. The measurements also show the dominance of NVIS over ground wave propagation starting at a short distance. For these elevation angles, the optimum receive and transmit antenna heights above ground are derived using antenna simulations. A distinction is made between optimum transmit signal strength and optimum received signal-to-noise ratio (SNR). These optima are verified experimentally, demonstrating a novel evaluation method that can be used in the presence of the fading typical for ionospheric propagation. For farmland soil ( 20 mS/m, "r 17) the optimum height above ground for the transmit antenna is 0.180.22. If the antenna is lowered to 0.02 a transmit signal loss of 12 dB occurs. This corresponds with the theory. The receive antenna height, however, while appearing uncritical in the simulations, showed a clear optimum at 0.16 and a 27 dB SNR deterioration when lowered to 0.02. View full abstract»

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  • 11. An overview of fractal antenna engineering research

    Publication Year: 2003 , Page(s): 38 - 57
    Cited by:  Papers (233)  |  Patents (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1365 KB) |  | HTML iconHTML  

    Recent efforts by several researchers around the world to combine fractal geometry with electromagnetic theory have led to a plethora of new and innovative antenna designs. In this report, we provide a comprehensive overview of recent developments in the rapidly growing field of fractal antenna engineering. Fractal antenna engineering research has been primarily focused in two areas: the first deals with the analysis and design of fractal antenna elements, and the second concerns the application of fractal concepts to the design of antenna arrays. Fractals have no characteristic size, and are generally composed of many copies of themselves at different scales. These unique properties of fractals have been exploited in order to develop a new class of antenna-element designs that are multi-band and/or compact in size. On the other hand, fractal arrays are a subset of thinned arrays, and have been shown to possess several highly desirable properties, including multi-band performance, low sidelobe levels, and the ability to develop rapid beamforming algorithms based on the recursive nature of fractals. Fractal elements and arrays are also ideal candidates for use in reconfigurable systems. Finally, we provide a brief summary of recent work in the related area of fractal frequency-selective surfaces. View full abstract»

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  • 12. Grating Lobe Suppression in Aperiodic Phased Array Antennas Composed of Periodic Subarrays with Large Element Spacing

    Publication Year: 2015 , Page(s): 76 - 85
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1540 KB)  

    The techniques of grating lobe (GL) suppression in planar phased array antennas composed of periodic subarrays with rectangular or triangular grids with large element spacing are considered. GL suppression is achieved using an aperiodic arrangement of subarrays. This approach provides a means to decrease GLs without a significant increase in structural complexity relative to periodic arrays; moreover, other antenna parameters do not essentially change compared with periodic arrays. Estimations of maximum GL suppression are presented. Antenna characteristics such as sidelobe level, beam efficiency, and aperture efficiency are also considered. The influences of element radiation pattern and amplitude tapering are analyzed. Examples of radiation patterns of such phased arrays are given. View full abstract»

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  • 13. Slotted Microstrip Antennas for Circular Polarization with Compact Size

    Publication Year: 2013 , Page(s): 124 - 137
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2843 KB) |  | HTML iconHTML  

    Circularly polarized diagonally symmetric slotted microstrip-patch antennas are proposed with compact size. The compact circularly polarized (CP) diagonally symmetric slotted microstrip-patch (DSSMP) antenna design rules are also summarized. Circularly polarized radiation can be achieved using any arbitrarily shaped slots in diagonal directions on the square microstrip-patch antenna. Different shapes for the slots are studied and compared, based on the fixed overall volume of the antenna for circularly polarized diagonally symmetric slotted microstrip-patch antennas. The cross-shaped-slot diagonally symmetric slotted microstrip-patch antenna is compact when compared with the circular-, square-, and circular-ring-shaped diagonally symmetric slotted microstrip-patch antennas. A measured 3 dB axial-ratio (AR) bandwidth of around 0.7% (6.0 MHz) with 2.0% (18.0 MHz) impedance bandwidth was achieved. The measured boresight gain was more than 3.3 dBic over the operating band, while the overall antenna size was 0.272λ0 × 0.272λ0 × 0.0138λ0 at 0.905 GHz. View full abstract»

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  • 14. Atmospheric Attenuation in Wireless Communication Systems at Millimeter and THz Frequencies [Wireless Corner]

    Publication Year: 2015 , Page(s): 48 - 61
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2299 KB)  

    This paper intends to give an overview about atmospheric propagation effects affecting millimeter and terahertz (THz) communication systems. The main focus is on attenuation caused by atmospheric gases and liquid water droplets, either in the form of suspended particles into clouds or rain falling hydrometeors. Theoretical aspects about each of them are presented, emphasizing on those that deserve special attention as frequency increases. Statistics of attenuation estimated from meteorological data and some experimental results, as in the case of rain attenuation, obtained in Madrid, Spain, are presented throughout the paper, thus providing further insights about the phenomena discussed. View full abstract»

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  • 15. A wideband circularly polarized stacked slotted microstrip patch antenna

    Publication Year: 2013 , Page(s): 84 - 99
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2972 KB) |  | HTML iconHTML  

    A wideband, single-feed, circularly polarized, stacked, square, slotted microstrip patch antenna is proposed for radio-frequency-identification-reader applications. The proposed antenna consists of an upper square asymmetric slotted patch, stacked over a lower square asymmetric slotted radiating patch and a microstrip stub, along with a coaxial feed. The wideband circularly polarized radiation of the antenna is achieved using a microstrip stub in the lower patch and a stacked slotted square patch. The proposed antenna is designed using a combination of low-cost FR4 substrate and foam. The measured 10 dB return-loss bandwidth of the antenna was around 21% (833 MHz to 1033 MHz), and the 3 dB axial-ratio bandwidth of the antenna was around 13.4% (835 MHz to 955 MHz). The gain was around 7.0 dBic over the 3 dB axial-ratio bandwidth. The overall antenna volume was 0.601λ0 × 0.601λ0 × 0.895λ0 (where λ0 is the free-space wavelength at 900 MHz). View full abstract»

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  • 16. Reconfigurable Antennas

    Publication Year: 2013 , Page(s): 49 - 61
    Cited by:  Papers (11)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (3057 KB) |  | HTML iconHTML  

    Reconfigurable antennas change polarization, operating frequency, or far-field pattern in order to cope with changing system parameters. This paper reviews some of the past and current technology applicable to reconfigurable antennas, with several examples of implementations. Mechanically movable parts and arrays are discussed, as well as more-recent semiconductor-component and tunable-material technologies applicable to reconfigurable antennas. View full abstract»

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  • 17. Cognitive-radio and antenna functionalities: A tutorial [Wireless Corner]

    Publication Year: 2014 , Page(s): 231 - 243
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (3577 KB) |  | HTML iconHTML  

    This paper discusses the fundamental principles of a cognitive-radio RF system. The key points required to achieve a true cognitive-radio device are outlined. The operation of a cognitive-radio system is mainly divided into two tasks. In the first task, a cognitive-radio device searches and identifies any part of the spectrum that is not occupied. The second task consists of achieving an optimal mode of communication by allocating the appropriate channels to be used. In this paper, the RF requirements required to operate a cognitive-radio device are detailed. Such a device can adopt one of two scenarios of a cognitive-radio system: the “interweave” or “underlay” mode of operation. For both scenarios, a cognitive cycle is followed. This cycle consists of the following four steps: (1) observe, (2) decide, (3) act, and (4) learn. A cognitive-radio engine is responsible for managing and integrating these four functions together into a single cognitive-radio device. In this tutorial, the realization of the four functions of a cognitive-radio cycle are detailed for both types of cognitive radio, and various RF front-end examples are presented and discussed. View full abstract»

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  • 18. Finite-difference time-domain (fdtd) matlab codes for first- and second-order em differential equations [testing ourselves]

    Publication Year: 2014 , Page(s): 221 - 239
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (5386 KB) |  | HTML iconHTML  

    A set of two-dimensional (2D) electromagnetic (EM) MATLAB codes, using both first-order coupled differential (Maxwell) equations and second-order decoupled (wave) equations, are developed for both transverse-magnetic (TM) and transverse-electric (TE) polarizations. Second-order MUR type absorbing boundary conditions are used to simulate free space. Metamaterial (MTM) modeling is also included. Performance tests in terms of computational times, memory requirements, and accuracies were done for simple EM scenarios with magnetic field, current, and voltage comparisons. The codes may be used for teaching and research purposes. View full abstract»

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  • 19. A Review of Broadband Dual Linearly Polarized Microstrip Antenna Designs with High Isolation [Education Column]

    Publication Year: 2014 , Page(s): 238 - 251
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (3904 KB) |  | HTML iconHTML  

    Dual-polarized antennas are used to achieve polarization diversity in order to increase the capacity and reliability of wireless communication links. In order to cater to increased wireless communication traffic, dual-polarized antennas are required having broad bandwidths and high isolation between two orthogonal ports. Various dual-polarized antenna designs have been explored to achieve broad bandwidth and high isolation across the entire band of interest. This paper reviews various techniques proposed in recent years for the design of dual linearly polarized antennas to achieve high isolation and broad bandwidth. A detailed analysis of these techniques in terms of their advantages and limitations is presented. View full abstract»

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  • 20. A survey of various propagation models for mobile communication

    Publication Year: 2003 , Page(s): 51 - 82
    Cited by:  Papers (192)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2342 KB) |  | HTML iconHTML  

    In order to estimate the signal parameters accurately for mobile systems, it is necessary to estimate a system's propagation characteristics through a medium. Propagation analysis provides a good initial estimate of the signal characteristics. The ability to accurately predict radio-propagation behavior for wireless personal communication systems, such as cellular mobile radio, is becoming crucial to system design. Since site measurements are costly, propagation models have been developed as a suitable, low-cost, and convenient alternative. Channel modeling is required to predict path, loss and to characterize the impulse response of the propagating channel. The path loss is associated with the design of base stations, as this tells us how much a transmitter needs to radiate to service a given region. Channel characterization, on the other hand, deals with the fidelity of the received signals, and has to do with the nature of the waveform received at a receiver. The objective here is to design a suitable receiver that will receive the transmitted signal, distorted due to the multipath and dispersion effects of the channel, and that will decode the transmitted signal. An understanding of the various propagation models can actually address both problems. This paper begins with a review of the information available on the various propagation models for both indoor and outdoor environments. The existing models can be classified into two major classes: statistical models and site-specific models. The main characteristics of the radio channel - such as path loss, fading, and time-delay spread - are discussed. Currently, a third alternative, which includes many new numerical methods, is being introduced to propagation prediction. The advantages and disadvantages of some of these methods are summarized. In addition, an impulse-response characterization for the propagation path is also presented, including models for small-scale fading, Finally, it is shown that when two-w- y communication ports can be defined for a mobile system, it is possible to use reciprocity to focus the energy along the direction of an intended user without any explicit knowledge of the electromagnetic environment in which the system is operating, or knowledge of the spatial locations of the transmitter and the receiver. View full abstract»

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  • 21. Application of the Memristor in Reconfigurable Electromagnetic Devices

    Publication Year: 2015 , Page(s): 239 - 248
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1576 KB)  

    The recently popularized memristor, short for memory resistor, is investigated in this paper for its potential as a new and attractive method for enabling reconfigurable radio-frequency (RF) devices. The charge- or flux-controlled resistance of this "fourth circuit element" allows for easy reconfigurability and maintains its configured state in the absence of controlling signals. A specialized finite-difference time-domain simulation code is developed and employed to design devices with embedded memristors. The time-domain code allows observation of the nonlinear memristor switching characteristics and real-time functionality of the reconfigurable device. Several different reconfigurable RF devices are designed here to demonstrate the versatility of the memristor and determine the behavior of systems which utilize them. View full abstract»

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  • 22. The Measurement of Complex Antenna Transfer Functions for Ultra-Wideband Antennas in a Compact Range [Measurements Corner]

    Publication Year: 2014 , Page(s): 163 - 170
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (5222 KB) |  | HTML iconHTML  

    Ultra-wideband (UWB) communications technology increasingly plays an important role in modern communications systems. The complex antenna transfer function (CATF) of a UWB antenna provides valuable information that can be used for better UWB channel and communication system designs. Currently, only the two-antenna and three-antenna measurement techniques are used to measure the transfer functions and impulse responses of UWB antennas. In this paper, a modified version of the gain-transfer method is presented to enable the characterization of UWB antennas using a compact antenna test range facility (CATR). A double-ridged guide horn (DRGH) antenna was used as a UWB transfer-standard, and the complex antenna transfer function of the transfer-standard was determined a priori using full-wave simulations. The gain-transfer method to measure the complex antenna transfer function of UWB antennas in a compact antenna test range was illustrated with two test cases. In the first test case, the measured complex antenna transfer function of an ETS-Lindgren double-ridged guide horn antenna was verified with numerical data from a FEKO model of the antenna. The second case compared the complex antenna transfer function of a UWB circular disc monopole antenna measured in a compact antenna test range to measured data using two identical antennas in a two-antenna measurement setup. View full abstract»

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  • 23. Inverse and Determinant of a Square Matrix by Order Expansion and Condensation [EM Programmer's Notebook]

    Publication Year: 2015 , Page(s): 28 - 32
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (172 KB)  

    A simple and straightforward fast iterative method is presented for computing the inverse and determinant of any square matrix by successively applying order condensation and order expansion in an iterative process. Applying the optimal iteration process, which comprises only some 20 lines of the MATLAB source code (using only simple elementary arithmetical operations), the inverse matrix can be computed within minutes from any given square matrix, even of relatively large size (such as 999), with real or complex entries, and irrespective of whether the matrix is singular or nonsingular. View full abstract»

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  • 24. Review of 20 Years of Research on Microwave and Millimeter-wave Lenses at ???Instituto de Telecomunica????es???

    Publication Year: 2015 , Page(s): 249 - 268
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2998 KB)  

    Starting from a challenge in the early 1990s to develop a highly shaped beam dielectric lens antenna for a pilot 150 Mb/s cellular mobile broadband system operating in the 60-GHz band, several new developments have been accomplished over more than 20 years at Instituto de Telecomunicações in the areas of millimeter-wave shaped dielectric lens antennas and planar metamaterial lenses. We review here a few representative examples with numerical and experimental results, covering applications in mobile broadband communications, radiometry, satellite communications, multigigabit short-range communications, and sublambda near-field target detection. View full abstract»

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  • 25. Definition and Misuse of Return Loss [Report of the Transactions Editor-in-Chief]

    Publication Year: 2009 , Page(s): 166 - 167
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (505 KB)  

    As Editor-in-Chief of the Transactions, I have noticed over the past year or so that the occasional incorrect use of the term return loss has now grown into a flood of misuse. Perhaps over 30% of all antenna papers submitted to the Transactions in the past twelve months have used return loss incorrectly. The reason for this is uncertain. To remind everyone of the correct terminology, I review the definition of return loss, briefly outline the history of the term, and give some examples of current misuse. View full abstract»

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  • 26. Radio Propagation Channel Measurements for Multi-Antenna Satellite Communication Systems: A Survey

    Publication Year: 2014 , Page(s): 102 - 122
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (4199 KB) |  | HTML iconHTML  

    For the terrestrial infrastructure, the multiple-input multiple-output (MIMO) architecture is a key technology that has brought the wireless gigabit vision closer to reality. Satellite communication systems have not been immune from this wave of innovation, and theoretical and experimental efforts have recently been devoted to the investigation of the applicability of multiple-antenna techniques to these systems. This paper intends to highlight and critically present the most important results from measurement campaigns conducted to characterize the radio channel of multi-antenna satellite systems. Emphasis is given on the viability of MIMO technology over satellite, and the potential enhancements in terms of channel capacity and link reliability that can be achieved through spatial and/or polarization diversity. The configurations under investigation range from very simple single-input multiple-output (SIMO) systems, with multiple antennas only at the terrestrial receiver, to quite complex and challenging systems, such as dual-satellite multiple-input single-output (MISO) systems, and single-satellite dual-polarized MIMO systems. The spotlight is on land mobile satellite (LMS) systems in outdoor radio propagation environments. However, satellite-to-indoor reception is also included. View full abstract»

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  • 27. Mutual coupling reduction in waveguide-slot-array antennas using electromagnetic bandgap (EBG) structures

    Publication Year: 2014 , Page(s): 68 - 79
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (6378 KB) |  | HTML iconHTML  

    The application of an electromagnetic bandgap (EBG) structure as a tool for reduction of mutual coupling in planar waveguide-slot-array antennas (WSAA) is investigated for the first time. First, surface-wave suppression was demonstrated by placing an EBG array over the ground plane of a linear 1 × 4 waveguide-slot-array antenna. Two 1 × 4 waveguide-slot-array antennas were then put next to each other, with the EBG array over the conducting plane separating them, and up to 10 dB reduction in mutual coupling was observed. Based on these achievements, a planar 2 × 4 waveguide-slot-array antenna was designed using the EBG array to reduce mutual coupling. The EBG array compensated for the undesired frequency shift due to mutual coupling through surface-wave suppression. In addition, the radiation patterns of the EBG-loaded antenna remained almost the same as for the unloaded antenna, with a 1 dB increase in antenna gain. Finally, EBG-loaded and simple 2 × 4 waveguide-slot-array antennas were fabricated, and simulation results were compared with measurements, with good agreement. As a key feature of this approach, a planar waveguide-slot-array antenna could be constructed by designing a linear antenna and then forming an array from multiples of the antenna, without the need for any new design, by imposing the EBG structure to reduce the mutual coupling between the adjacent waveguides. View full abstract»

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  • 28. CRLH metamaterial leaky-wave and resonant antennas

    Publication Year: 2008 , Page(s): 25 - 39
    Cited by:  Papers (84)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (10319 KB) |  | HTML iconHTML  

    Composite right-/left-handed (CRLH) transmission-line (TL) metamaterials, with their rich dispersion and fundamental right-/left-hand duality, represent a paradigm shift in electromagnetics engineering and, in particular, for antennas. This paper presents an overview of the most practical leaky-wave and resonant CRLH antennas, which all exhibit functionalities or/and performance superior to prior state of the art. The leaky-wave antennas provide full-space dynamic scanning capability, with fan beams, conical beams in uni-planar configurations, pencil beams without any complex feeding network, and actively shaped beams based on the concept of aperture digitization. The resonant antennas offer alternative properties and a solution to beam-squinting when no scanning is required, including multi-band (dual/tri-band) operation, zeroth-order high efficiency, high directivity, and planar electric and magnetic monopole radiators. View full abstract»

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  • 29. Genetic algorithms in engineering electromagnetics

    Publication Year: 1997 , Page(s): 7 - 21
    Cited by:  Papers (210)  |  Patents (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1860 KB)  

    This paper presents a tutorial and overview of genetic algorithms for electromagnetic optimization. Genetic-algorithm (GA) optimizers are robust, stochastic search methods modeled on the concepts of natural selection and evolution. The relationship between traditional optimization techniques and the GA is discussed. Step-by-step implementation aspects of the GA are detailed, through an example with the objective of providing useful guidelines for the potential user. Extensive use is made of sidebars and graphical presentation to facilitate understanding. The tutorial is followed by a discussion of several electromagnetic applications in which the GA has proven useful. The applications discussed include the design of lightweight, broadband microwave absorbers, the reduction of array sidelobes in thinned arrays, the design of shaped-beam antenna arrays, the extraction of natural resonance modes of radar targets from backscattered response data, and the design of broadband patch antennas. Genetic-algorithm optimization is shown to be suitable for optimizing a broad class of problems of interest to the electromagnetic community. A comprehensive list of key references, organized by application category, is also provided View full abstract»

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  • 30. Conductive Inkjet-Printed Antennas on Flexible Low-Cost Paper-Based Substrates for RFID and WSN Applications

    Publication Year: 2009 , Page(s): 13 - 23
    Cited by:  Papers (45)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2320 KB) |  | HTML iconHTML  

    In this paper, a review of the authors' work on inkjet-printed flexible antennas, fabricated on paper substrates, is given. This is presented as a system-level solution for ultra-low-cost mass production of UHF radio-frequency identification (RFID) tags and wireless sensor nodes (WSN), in an approach that could be easily extended to other microwave and wireless applications. First, we discuss the benefits of using paper as a substrate for high-frequency applications, reporting its very good electrical/dielectric performance up to at least 1 GHz. The RF characteristics of the paper-based substrate are studied by using a microstrip-ring resonator, in order to characterize the dielectric properties (dielectric constant and loss tangent). We then give details about the inkjet-printing technology, including the characterization of the conductive ink, which consists of nano-silver particles. We highlight the importance of this technology as a fast and simple fabrication technique, especially on flexible organic (e.g., LCP) or paper-based substrates. A compact inkjet-printed UHF ldquopassive RFIDrdquo antenna, using the classic T-match approach and designed to match the IC's complex impedance, is presented as a demonstration prototype for this technology. In addition, we briefly touch upon the state-of-the-art area of fully-integrated wireless sensor modules on paper. We show the first-ever two-dimensional sensor integration with an RFID tag module on paper, as well as the possibility of a three-dimensional multilayer paper-based RF/microwave structure. View full abstract»

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  • 31. The double-directional radio channel

    Publication Year: 2001 , Page(s): 51 - 63
    Cited by:  Papers (180)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1120 KB) |  | HTML iconHTML  

    We introduce the concept of the double-directional mobile radio channel. It is called this because it includes angular information at both link ends, e.g., at the base station and at the mobile station. We show that this angular information can be obtained with synchronized antenna arrays at both link ends. In wideband high-resolution measurements, we use a switched linear array at the receiver and a virtual-cross array at the transmitter. We evaluate the raw measurement data with a technique that alternately used estimation and beamforming, and that relied on ESPRIT (estimation of signal parameters via rotational invariance techniques) to obtain superresolution in both angular domains and in the delay domain. In sample microcellular scenarios (open and closed courtyard, line-of-sight and obstructed line-of-sight), up to 50 individual propagation paths are determined. The major multipath components are matched precisely to the physical environment by geometrical considerations. Up to three reflection/scattering points per propagation path are identified and localized, lending insight into the multipath spreading properties in a microcell. The extracted multipath parameters allow unambiguous scatterer identification and channel characterization, independently of a specific antenna, its configuration (single/array), and its pattern. The measurement results demonstrate a considerable amount of power being carried via multiply reflected components, thus suggesting revisiting the popular single-bounce propagation models. It turns out that the wideband double-directional evaluation is a most complete method for separating multipath components. Due to its excellent spatial resolution, the double-directional concept provides accurate estimates of the channel's multipath-richness, which is the important parameter for the capacity of multiple-input multiple-output (MIMO) channels View full abstract»

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  • 32. Efficient Analysis of Frequency-Selective Surfaces by a Simple Equivalent-Circuit Model

    Publication Year: 2012 , Page(s): 35 - 48
    Cited by:  Papers (20)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (4630 KB) |  | HTML iconHTML  

    The transmission and reflection properties of frequency-selective surfaces (FSSs) are evaluated through a simple and accurate first-order circuit approach. The approximate analysis, based on the parallel between real structure and a lumped-LC-network counterpart, is also useful for acquiring physical insights into the working principles of frequency-selective surfaces. The first part of the paper describes a technique for computing lumped parameters of the most common frequency-selective-surface elements. The L and C parameters representing a given frequency-selective-surface element are derived only one time, at normal incidence, and stored, so as to form a database. The second part of the paper deals with the derivation of simple relations allowing the generalization of the stored LC couples in the case where the frequency-selective surface is printed or embedded in arbitrarily thick dielectric slabs, when the incident angle is varied from normal incidence, or if a different periodicity with respect to the reference periodicity is adopted. The generalized lumped parameters are included in an equivalent transmission line for computing the response of generic frequency-selective-surface configurations with no additional computational effort. The results obtained through the simplified model presented here are verified by a careful comparison with MoM simulations. View full abstract»

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  • 33. DiffEq: A MATLAB-Based Discrete-Time System Simulator [Testing Ourselves]

    Publication Year: 2015 , Page(s): 42 - 47
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1145 KB)  

    A MATLAB-based discrete-time system simulator (DiffEq) is introduced. This tool investigates linear constant-coefficient difference equations, which represent linear time-invariant finite-dimensional discrete-time systems. Closed-form analytical solutions can be expressed as a superposition of homogeneous and particular solutions, and this distinction gives valuable insights into the transient and steady-state behavior of the system. The transfer function, impulse response, characteristic roots, and simulation diagram of the system are obtained for different input types and initial conditions. View full abstract»

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  • 34. The Effect of Broadband Matching in Simultaneous Information and Power Transfer

    Publication Year: 2015 , Page(s): 192 - 203
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2181 KB)  

    This paper presents the effect of broadband matching in simultaneous information and power transfer along with an implementation. The narrowband characteristic of antennas has limited the applications of simultaneous information and power transfer. The performance improvements in terms of channel capacity and power delivery under broadband matching have been demonstrated. Electromagnetic simulation and multiobjective optimization are performed to analyze the tradeoff between the channel capacity and power delivery in different matching conditions. The performance gain using the matching networks has been demonstrated and analyzed. View full abstract»

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  • 35. Fractal antennas: a novel antenna miniaturization technique, and applications

    Publication Year: 2002 , Page(s): 20 - 36
    Cited by:  Papers (185)  |  Patents (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (3675 KB) |  | HTML iconHTML  

    Fractal geometry involves a recursive generating methodology that results in contours with infinitely intricate fine structures. This geometry, which has been used to model complex objects found in nature such as clouds and coastlines, has space-filling properties that can be utilized to miniaturize antennas. These contours are able to add more electrical length in less volume. In this article, we look at miniaturizing wire and patch antennas using fractals. Fractals are profoundly intricate shapes that are easy to define. It is seen that even though the mathematical foundations call for an infinitely complex structure, the complexity that is not discernible for the particular application can be truncated. For antennas, this means that we can reap the rewards of miniaturizing an antenna using fractals without paying the price of having to manufacture an infinitely complex radiator. In fact, it is shown that the required number of generating iterations, each of which adds a layer of intricacy, is only a few. A primer on the mathematical bases of fractal geometry is also given, focusing especially on the mathematical properties that apply to the analysis of antennas. Also presented is an application of these miniaturized antennas to phased arrays. It is shown how these fractal antennas can be used in tightly packed linear arrays, resulting in phased arrays that can scan to wider angles while avoiding grating lobes View full abstract»

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  • 36. Wideband Circularly Polarized E-Shaped Patch Antenna for Wireless Applications [Wireless Corner]

    Publication Year: 2010 , Page(s): 219 - 229
    Cited by:  Papers (16)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (4744 KB)  

    A new technique to achieve a circularly polarized probe-fed single-layer microstrip-patch antenna with a wideband axial ratio is proposed. The antenna is a modified form of the conventional E-shaped patch, used to broaden the impedance bandwidth of a basic patch antenna. By letting the two parallel slots of the E patch be unequal, asymmetry is introduced. This leads to two orthogonal currents on the patch and, hence, circularly polarized fields are excited. The proposed technique exhibits the advantage of the simplicity of the E-shaped patch design, which requires only the slot lengths, widths, and position parameters to be determined. Investigations of the effect of various dimensions of the antenna have been carried out via parametric analysis. Based on these investigations, a design procedure for a circularly polarized E-shaped patch was developed. A prototype has been designed, following the suggested procedure for the IEEE 802.11big WLAN band. The performance of the fabricated antenna was measured and compared with simulation results. Various examples with different substrate thicknesses and material types are presented and compared with the recently proposed circularly polarized U-slot patch antennas. View full abstract»

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  • 37. Wireless Power Transfer for Mobile Applications, and Health Effects [Telecommunications Health and Safety]

    Publication Year: 2013 , Page(s): 250 - 253
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1661 KB) |  | HTML iconHTML  

    Recent interest and current optimism regarding battery-charging wireless power-transfer technology are driven by the ubiquity of cell phones and other mobile communication devices. In some ways, this is to make a dream come true: a truly wireless mobile or portable communication device, completely free from being tethered in any way. The concept of wireless power transfer is not new, even for charging batteries. Cellular service users and customers may be annoyed by or do not want to be bothered with having to plug the mobile device into an electrical outlet. If this is true - as appears to be the case - then time may well provide a fix to the grief. Aside from not having to plug in the mobile phone or laptop, a more probable cause for the sudden interest in battery charging through wireless power transfer may come from the potential for mobile communication devices to get their electrical power the same way they get their data. Unlike wireless communication uses, the level of transmitted electromagnetic power required for large-scale or commercial implementation of wireless power transfer could be substantial. A key feature of the system design and research effort should be consideration of biological effects and human safety. View full abstract»

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  • 38. Propagation Models for Body-Area Networks: A Survey and New Outlook

    Publication Year: 2013 , Page(s): 97 - 117
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (4276 KB) |  | HTML iconHTML  

    This article is a review of wireless body-area network (BAN) channel models, with observations about the selection of the best channel model in terms of both first- and second-order statistics. Particular insight into the dominant factors that affect propagation for body-area networks is given. Important second-order statistical measures are discussed, where coherence times and fade durations are of particular interest. The IEEE 802.15.6 standard is used as a basis for the review, with observations and insights given about body-area networks. In this context, narrowband and ultra-wideband (UWB) models are summarized for different measurement environments and carrier frequencies. On-body, in-body, and off-body propagation models are discussed where appropriate. In general, lognormal fading or gamma fading models of the body-area network channel are most applicable. A goodness-of-fit criterion that directly trades off model error and complexity is presented, which gives a new outlook for channel modeling. By this new outlook it is demonstrated that through significant simplification of individual link propagation models for body-area networks, it is possible to combine link models with only a few parameters. Common misconceptions regarding the appropriateness of applying traditional path-loss measures to these short-range networks are then exposed. Finally, the use of relays, which is an option in IEEE 802.15.6, is shown to be important for maintaining reliability in various body-area-network propagation scenarios. View full abstract»

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  • 39. Design of small-size wide-bandwidth microstrip-patch antennas

    Publication Year: 2003 , Page(s): 75 - 83
    Cited by:  Papers (64)  |  Patents (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (568 KB) |  | HTML iconHTML  

    Several designs for small-size wide-bandwidth microstrip antennas are examined through simulation and experiment. Designs are presented based on two wideband patch antennas: the U-slot patch antenna, and the L-probe-fed patch antenna. Several techniques are utilized to reduce the resonant length of these wideband microstrip-patch antennas: increasing the dielectric constant of the microwave substrate material, the addition of a shorting wall between the conducting patch and the ground plane, and the addition of a shorting pin between the conducting patch and the ground plane. Simulation and experimental results confirm that the size of the antennas can be reduced by as much as 94%, while maintaining impedance bandwidths in excess of 20%. View full abstract»

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  • 40. Design of corrugated horns: a primer

    Publication Year: 2005 , Page(s): 76 - 84
    Cited by:  Papers (27)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (820 KB) |  | HTML iconHTML  

    Typical example of horn is shown where the inside wall is manufactured in a succession of slots and "teeth". The purpose of the corrugated surface is to provide the means to support the propagation of hybrid modes within the horn. Hybrid modes are basically a combination of TE and TM modes. Some basic information for the inexperienced horn designer to get started in designing their corrugated horn is provided. The class of circularly symmetrical corrugated horns and the parameters in designing are considered. As an example a standard Ku-band operation from a typical Earth station is also considered. View full abstract»

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  • 41. Analysis and Design of Mobile Device Antenna???Speaker Integration for Optimum Over-the-Air Performance

    Publication Year: 2015 , Page(s): 97 - 109
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2416 KB)  

    In this paper, the mutual coupling between a mobile device antenna and a closely integrated miniature moving-coil speaker is investigated. The analysis focuses on the speaker radio-frequency harmonic resonance characteristics and the antenna radiation efficiency degradation due to the presence of a speaker. First, antenna structures with simplified speaker models were numerically examined to assess the impacts of speaker harmonic resonance, antenna pattern, speaker location, and coupling mechanisms on antenna radiation performance. Subsequently, highly detailed speaker models based on commercial speaker designs were characterized through simulations and hardware prototyping. The analysis results reveal that the degradation of antenna radiation efficiency is associated with the enhancement of nonradiative energy stored in a conductively or capacitively coupled resonant speaker. Based on the coupling characteristics, practical design guidelines were proposed to achieve cost-effective antenna-speaker coexistence and optimum antenna radiation efficiency even under the most stringent design constraints. View full abstract»

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  • 42. MoM antenna simulations, with Matlab: RWG basis functions

    Publication Year: 2001 , Page(s): 100 - 107
    Cited by:  Papers (21)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (460 KB)  

    The Matlab implementation of an MoM antenna simulation code is presented, primarily (but not exclusively) for educational purposes. The PDE toolbox is used to generate the mesh. Evaluating the MoM matrix entries using the Rao-Wilton-Glisson (RWG) basis functions is discussed. The delta-function generator is used to model the feed point. Built-in Matlab functions are used for post-processing. Results for several examples, including thin-strip dipoles, a monopole on a ground plane and a wide-band slot antenna, are presented View full abstract»

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  • 43. Performance of a small loop antenna in the 3-10 MHz band

    Publication Year: 2005 , Page(s): 51 - 56
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (539 KB) |  | HTML iconHTML  

    The performance of a typical small loop antenna of 1 m diameter is presented at frequencies in the range 3.6-10.1 MHz. It is argued that the antenna may reasonably describe as electrically small in this frequency range. Measurements of the antenna's bandwidth and, hence, Q factor are presented, along with direct measurements of the radiated field at various distances with a carefully measured RF input power. The radiation efficiency of the loop is derived from the measurements, and is compared with theoretical predictions of the efficiency based on classical electromagnetics. Close agreement is demonstrated between measurements and predictions. Consistency with the Chu bandwidth limit is also demonstrated for this antenna. View full abstract»

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  • 44. GPS Landing System Reference Antenna

    Publication Year: 2010 , Page(s): 104 - 113
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1431 KB) |  | HTML iconHTML  

    The GPS landing system (GLS) is a reality today, and will undoubtedly become the workhorse system in the future. GPS aircraft navigation is currently utilized for aircraft en-route, terminal, and initial-approach navigation. It is expected that in 2009, a Category I GPS landing system will start its initial phase of a worldwide deployment. The ARL-1900 antenna was designed specifically to satisfy the stringent requirements for the Category I, II, and III GPS landing system reference-receiver stations. A difficult problem for a Category I, II, and III GPS landing systems is the mitigation of ground-reflected multipath effects. The antenna must provide coverage of the upper hemisphere while suppressing ground-reflected multipath. In addition, the antenna must operate at the L1, L2, and L5 GPS frequencies, have right-hand circular polarization, and ideally have constant carrier and code (group) delay throughout the coverage region. Over a period of 15 years, BAE Systems has developed the ARL-1900 antenna, a unique antenna with near-ideal performance that satisfies the stringent requirements for a Category I, II, and III GPS landing systems. This paper reviews the requirements for a GPS landing system reference antenna, presents the design principles for the ARL-1900 antenna, describes its implementation, and presents performance data. View full abstract»

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  • 45. Design of Compact, Low-Profile, Wideband, Dual-Frequency Patch Antennas Based on Complementary Co-Directional SRRs

    Publication Year: 2014 , Page(s): 72 - 89
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (12229 KB) |  | HTML iconHTML  

    A traditional microstrip antenna is capable of exhibiting good dual-band operation via slotting a complementary codirectional split resonant ring (CCSRR) unit on the rectangular radiating patch. Thanks to the advantage of low mutual coupling between the co-directional ring-slots in such a complementary co-directional split resonant ring unit, the antenna's operating frequency band, which originates from the complementary co-directional split resonant ring's resonance, is significantly expanded with the addition of more co-directional ring-slots. Antennas comprised of zero, a single, dual, and triple complementary co-directional split resonant rings were designed, fabricated, measured, and comprehensively compared. According to our investigation, besides operating in their inherent TM100 modes, the proposed antennas have the advantages of providing a lower and much wider operating range than that in the TM100 mode. This is especially more than a 9% impedance bandwidth, even with such a low profile (only 0.0316λ0 in height). More importantly, uniformly good radiation characteristics, including excellent broadside main beams with high polarization purity, and large front-to-back ratios (FTBRs), were achieved in both frequency ranges, on the whole. View full abstract»

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  • 46. The impedance-boundary condition

    Publication Year: 1996 , Page(s): 31 - 35
    Cited by:  Papers (17)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (848 KB)  

    Part of the material presented in this article has been collected in the framework of a research activity on the history of ray optics. The aim of this project is collect some reprints of the most-significant original papers of the history of ray optics, from the seventeenth century (i.e., from the work by Rene Descartes) up to now. The purpose of the article is to show that the impedance-boundary condition (IBC)-usually referred both in western countries and in the former USSR as the Leontovich condition was also derived independently by another Russian scientist, A.N. Shchulkin. He published the IBC in 1940, in his book, Propagation of Radio Waves View full abstract»

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  • 47. Transformation Electromagnetics: An Overview of the Theory and Applications

    Publication Year: 2010 , Page(s): 24 - 46
    Cited by:  Papers (51)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (6721 KB) |  | HTML iconHTML  

    The recently introduced transformation-electromagnetics techniques provide a new methodology for designing devices that possess novel wave-material interaction properties. They are based on the form invariance of Maxwell's equations under coordinate transformations. These methods provide an extremely versatile set of design tools that employ spatial-coordinate transformations, where the compression and dilation of space in different coordinate directions are interpreted as appropriate scalings of the material parameters. The most famous transformation-optics device is the cloak of invisibility. However, a wide variety of other devices are also possible, such as field concentrators, polarization rotators, beam splitters, beam collimators, and flat lenses. In this paper, an overview of transformation-electromagnetics device design techniques is presented. The paper begins by introducing the underlying design principle behind transformation electromagnetics. Several novel transformation-based device designs are then summarized, starting with electromagnetic cloaks that have spherical shell or cylindrical annular shapes, More general cloaking designs of noncircular annular geometries are treated, and the application of cloaking to RF/microwave antenna shielding is also discussed. Following this, device designs that employ transformations that have discontinuities .on the domain boundary are presented. Unlike those used for cloaks, this type of transformation is capable of modifying the fields outside of the device. Examples of this type of transformation-electromagnetics device are presented, which include flat near-field and far-field focusing lenses, wave collimators for embedded sources (e.g., antennas), polarization splitters and rotators, and right-angle beam benders. View full abstract»

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  • 48. A Review of Implantable Patch Antennas for Biomedical Telemetry: Challenges and Solutions [Wireless Corner]

    Publication Year: 2012 , Page(s): 210 - 228
    Cited by:  Papers (22)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (3142 KB)  

    Biomedical telemetry permits the transmission (telemetering) of physiological signals at a distance. One of its latest developments is in the field of implantable medical devices (IMDs). Patch antennas currently are receiving significant scientific interest for integration into the implantable medical devices and radio-frequency (RF)-enabled biotelemetry, because of their high flexibility in design, conformability, and shape. The design of implantable patch antennas has gained considerable attention for dealing with issues related to biocompatibility, miniaturization, patient safety, improved quality of communication with exterior monitoring/control equipment, and insensitivity to detuning. Numerical and experimental investigations for implantable patch antennas are also highly intriguing. The objective of this paper is to provide an overview of these challenges, and discuss the ways in which they have been dealt with so far in the literature. View full abstract»

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  • 49. Broadband proximity-fed square-ring microstrip antennas

    Publication Year: 2014 , Page(s): 89 - 107
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (11157 KB) |  | HTML iconHTML  

    The fundamental and higher-order modes of a compact ring microstrip antenna are discussed. This provides insight into the functioning of this configuration. To increase its bandwidth and gain, various broadband proximity-fed configurations of a ring microstrip antenna in the 1000 MHz frequency band are proposed. A detailed explanation for the broadband behavior of all these configurations is presented. The proximity-fed square-ring antenna yielded a bandwidth of more than 250 MHz. A further increase in its bandwidth was realized by cutting a pair of rectangular slots on the edges of the ring patch. The pair of slots reduced the orthogonal TM02 mode's resonance frequency of the patch and, along with the fundamental TM10 mode, yielded a bandwidth of more than 350 MHz. Furthermore, the proximity-fed gap-coupled configurations of rectangular-slot-cut C-shaped patches, which were derived from the ring patch, are proposed. These yielded a bandwidth of more than 500 MHz (>43%). Both of these slot-cut compact configurations gave broadside radiation patterns with gains of more than 6 dBi over the bandwidth. To further increase the gain and bandwidth of the slot-cut ring antenna, a multi-resonator configuration with parasitic ring patches, gap-coupled along the two coordinate axes, is proposed. This configuration yielded a bandwidth of more than 400 MHz with a peak gain of 9 dBi. In this configuration, a further increase in the bandwidth was realized by cutting a pair of rectangular slots on the edges of the ring patches that were gap-coupled along one of the coordinate axes. This configuration gave a bandwidth of more than 500 MHz with a peak gain of 9 dBi. View full abstract»

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  • 50. A Dual-Polarized Planar-Array Antenna for S-Band and X-Band Airborne Applications

    Publication Year: 2009 , Page(s): 70 - 78
    Cited by:  Papers (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (4432 KB) |  | HTML iconHTML  

    A new dual-frequency dual-polarized array antenna for airborne applications is presented in this paper. Two planar arrays with thin substrates (R/T Duroid 5880 substrate, with epsivr = 2.2 and a thickness of 0.13 mm) are integrated to provide simultaneous operation at S band (3 GHz) and X band (10 GHz). Each 3 GHz antenna element is a large rectangular ring-resonator antenna, and has a 9.5 dBi gain that is about 3 dB higher than the gain of an ordinary ring antenna. The 10 GHz antenna elements are circular patches. They are combined to form the array with a gain of 18.3 dBi, using a series-fed structure to save the space of the feeding line network. The ultra-thin array can be easily placed on an aircraft's fuselage, due to its lightweight and conformal structure. It will be useful for wireless communication, radar, remote sensing, and surveillance applications. View full abstract»

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Aims & Scope

The IEEE Antennas and Propagation Magazine covers all areas relating to antenna theory, design, and practice.

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Editor-in-Chief
Mahta Moghaddam