Showing papers in "IEEE Transactions on Antennas and Propagation in 2004"
TL;DR: A study of boundary conditions is presented indicating the invisible wall technique outperforms absorbing and reflecting wall techniques and is integrated into a representative example of optimization of a profiled corrugated horn antenna.
Abstract: The particle swarm optimization (PSO), new to the electromagnetics community, is a robust stochastic evolutionary computation technique based on the movement and intelligence of swarms. This paper introduces a conceptual overview and detailed explanation of the PSO algorithm, as well as how it can be used for electromagnetic optimizations. This paper also presents several results illustrating the swarm behavior in a PSO algorithm developed by the authors at UCLA specifically for engineering optimizations (UCLA-PSO). Also discussed is recent progress in the development of the PSO and the special considerations needed for engineering implementation including suggestions for the selection of parameter values. Additionally, a study of boundary conditions is presented indicating the invisible wall technique outperforms absorbing and reflecting wall techniques. These concepts are then integrated into a representative example of optimization of a profiled corrugated horn antenna.
2,165 citations
TL;DR: This paper reviews recent research findings concerning antennas and propagation in MIMO systems and considers issues considered include channel capacity computation, channel measurement and modeling approaches, and the impact of antenna element properties and array configuration on system performance.
Abstract: Multiple-input-multiple-output (MIMO) wireless systems use multiple antenna elements at transmit and receive to offer improved capacity over single antenna topologies in multipath channels In such systems, the antenna properties as well as the multipath channel characteristics play a key role in determining communication performance This paper reviews recent research findings concerning antennas and propagation in MIMO systems Issues considered include channel capacity computation, channel measurement and modeling approaches, and the impact of antenna element properties and array configuration on system performance Throughout the discussion, outstanding research questions in these areas are highlighted
985 citations
TL;DR: The particle swarm optimizer shares the ability of the genetic algorithm to handle arbitrary nonlinear cost functions, but with a much simpler implementation it clearly demonstrates good possibilities for widespread use in electromagnetic optimization.
Abstract: Particle swarm optimization is a recently invented high-performance optimizer that is very easy to understand and implement. It is similar in some ways to genetic algorithms or evolutionary algorithms, but requires less computational bookkeeping and generally only a few lines of code. In this paper, a particle swarm optimizer is implemented and compared to a genetic algorithm for phased array synthesis of a far-field sidelobe notch, using amplitude-only, phase-only, and complex tapering. The results show that some optimization scenarios are better suited to one method versus the other (i.e., particle swarm optimization performs better in some cases while genetic algorithms perform better in others), which implies that the two methods traverse the problem hyperspace differently. The particle swarm optimizer shares the ability of the genetic algorithm to handle arbitrary nonlinear cost functions, but with a much simpler implementation it clearly demonstrates good possibilities for widespread use in electromagnetic optimization.
877 citations
TL;DR: In this article, the authors proposed a reactive impedance surface (RIS) as a substrate for planar antennas that can miniaturize the size and significantly enhance both the bandwidth and the radiation characteristics of an antenna.
Abstract: The concept of a novel reactive impedance surface (RIS) as a substrate for planar antennas, that can miniaturize the size and significantly enhance both the bandwidth and the radiation characteristics of an antenna is introduced. Using the exact image formulation for the fields of elementary sources above impedance surfaces, it is shown that a purely reactive impedance plane with a specific surface reactance can minimize the interaction between the elementary source and its image in the RIS substrate. An RIS can be tuned anywhere between perfectly electric and magnetic conductor (PEC and PMC) surfaces offering a property to achieve the optimal bandwidth and miniaturization factor. It is demonstrated that RIS can provide performance superior to PMC when used as substrate for antennas. The RIS substrate is designed utilizing two-dimensional periodic printed metallic patches on a metal-backed high dielectric material. A simplified circuit model describing the physical phenomenon of the periodic surface is developed for simple analysis and design of the RIS substrate. Also a finite-difference time-domain (FDTD) full-wave analysis in conjunction with periodic boundary conditions and perfectly matched layer walls is applied to provide comprehensive study and analysis of complex antennas on such substrates. Examples of different planar antennas including dipole and patch antennas on RIS are considered, and their characteristics are compared with those obtained from the same antennas over PEC and PMC. The simulations compare very well with measured results obtained from a prototype /spl lambda//10 miniaturized patch antenna fabricated on an RIS substrate. This antenna shows measured relative bandwidth, gain, and radiation efficiency of BW=6.7, G=4.5 dBi, and e/sub r/=90, respectively, which constitutes the highest bandwidth, gain, and efficiency for such a small size thin planar antenna.
653 citations
TL;DR: It is shown that, in this line, left-handedness can be achieved without losses over an unlimited bandwidth, from the cutoff of the resulting high-pass filter to infinity, with excellent agreement with theory.
Abstract: A transmission line (TL) approach of left-handed (LH) materials is proposed. The transmission characteristics of an ideal LH-TL are presented, the constitutive parameters of an equivalent LH material are derived and shown to be negative, and some LH-transmission paradoxes are explained. Next, a method to design an artificial LH-TL in the form of an ideal lumped-elements ladder network is described and illustrated with simulation results. It is shown that, in this line, left-handedness can be achieved without losses over an unlimited bandwidth, from the cutoff of the resulting high-pass filter to infinity, with excellent agreement with theory. Finally, a microstrip implementation of the LH line for microwaves, using interdigital capacitors and stub inductors, is demonstrated, with moderate insertion loss and a broad bandwidth of the order of 100%.
558 citations
TL;DR: In this paper, a woodpile EBG made up of magneto-dielectric material is proposed for the design of novel EM structures with applications in the VHF-UHF bands.
Abstract: In this paper, the unique features of periodic magneto-dielectric meta-materials in electromagnetics are addressed. These materials, which are arranged in periodic configurations, are applied for the design of novel EM structures with applications in the VHF-UHF bands. The utility of these materials is demonstrated by considering two challenging problems, namely, design of miniaturized electromagnetic band-gap (EBG) structures and antennas in the VHF-UHF bands. A woodpile EBG made up of magneto-dielectric material is proposed. It is shown that the magneto-dielectric woodpile not only exhibits band-gap rejection values much higher than the ordinary dielectric woodpile, but also for the same physical dimensions it shows a rejection band at a much lower frequency. The higher rejection is a result of higher effective impedance contrasts between consecutive layers of the magneto-dielectric woodpile structure. Composite magneto-dielectrics are also shown to provide certain advantages when used as substrates for planar antennas. These substrates are used to miniaturize antennas while maintaining a relatively high bandwidth and efficiency. An artificial anisotropic meta-substrate having /spl mu//sub r/>/spl epsiv//sub r/, made up of layered magneto-dielectric and dielectric materials is designed to maximize the bandwidth of a miniaturized patch antenna. Analytical and numerical approaches, based on the anisotropic effective medium theory (AEMT) and the finite-difference time-domain (FDTD) technique, are applied to carry out the analyzes and fully characterize the performance of finite and infinite periodic magneto-dielectric meta-materials integrated into the EBG and antenna designs.
473 citations
TL;DR: The planar inverted cone antenna (PICA) as mentioned in this paper provides ultrawideband (UWB) performance with a radiation pattern similar to monopole disk antennas, but is smaller in size.
Abstract: A new antenna, the planar inverted cone antenna (PICA), provides ultrawideband (UWB) performance with a radiation pattern similar to monopole disk antennas , but is smaller in size. Extensive simulations and experiments demonstrate that the PICA antenna provides more than a 10:1 impedance bandwidth (for VSWR<2) and supports a monopole type omnidirectional pattern over 4:1 bandwidth. A second version of the PICA with two circular holes changes the current flow on the metal disk and extends the high end of the operating frequency range, improving the pattern bandwidth to 7:1.
319 citations
TL;DR: In this article, the design of source pulses and transmitting/receiving antennas in ultrawide-band radio systems was investigated in terms of pulse fidelity and system transmission efficiency.
Abstract: This paper addresses two vital design considerations in ultrawide-band radio systems. One is that radiated power density spectrum shaping must comply with certain emission limit mask for coexistence with other electronic systems. Another is that the design of source pulses and transmitting/receiving antennas should be optimal for the performance of overall systems. The design of source pulses and transmitting/receiving antennas under the two considerations is discussed. First, the characteristics of transmitting/receiving antenna systems are described by a system transfer function. Then, the design of source pulses and transmitting antennas are studied based on the considerations for emission limits. Finally, the design of transmitting and receiving antennas are investigated in terms of pulse fidelity and system transmission efficiency. In the studies, thin wire dipoles with narrow bandwidths and planar dipoles with broad bandwidths are exemplified.
318 citations
TL;DR: This communication presents a novel linearly polarized pattern reconfigurable microstrip parasitic array that uses four switches to reconfigure the radiation pattern into three variations over a shared 2:1 VSWR bandwidth, and has potential applications in mobile communication devices and large phased antenna arrays.
Abstract: This communication presents a novel linearly polarized pattern reconfigurable microstrip parasitic array. Specifically, this antenna uses four switches (currently copper strips for proof of concept) to reconfigure the radiation pattern into three variations over a shared 2:1 VSWR bandwidth, and has potential applications in mobile communication devices and large phased antenna arrays. Both measured and simulated results of a microstrip parasitic array are provided. The effects of changes in physical dimensions and directions for future work are also discussed.
305 citations
TL;DR: In this paper, a dual-polarized L-probe patch antenna is proposed to achieve high isolation between two input ports, achieving an impedance bandwidth of 23.8% and an isolation over 30 dB.
Abstract: An experimental study of a dual-polarized L-probe patch antenna is presented. The antenna is designed to operate at around 1.8 GHz. A "dual-feed" technique is introduced to achieve high isolation between two input ports. The proposed antenna has an impedance bandwidth of 23.8% (SWR/spl les/2), 15% (SWR/spl les/1.5) and an isolation over 30 dB. In array designs, techniques for improving the isolation between two adjacent elements of an antenna array are also investigated. A two-element array with more than 30 dB isolation is designed and tested.
263 citations
TL;DR: The radiation properties of several electrically small, folded spherical helix antennas are presented in this paper, where the principle design objectives are to achieve self resonance, a low quality factor (Q), and a practical radiation resistance for small values of ka.
Abstract: The radiation properties of several electrically small, folded spherical helix antennas are presented. The primary variables considered in the design of these antennas are the number of helical turns and the number of helical arms. The principle design objectives are to achieve self resonance, a low quality factor (Q), and a practical radiation resistance for small values of ka. Designs are presented for ka less than 0.5, where the antennas are self resonant, exhibiting an efficiency in excess of 95%, a Q within 1.5 times the fundamental limit, and a radiation resistance near 50 /spl Omega/. The relationship between the number of helical turns, the number of helical arms, and achieving self resonance at low frequencies is discussed.
TL;DR: A fast beamforming algorithm based on simultaneous perturbation stochastic approximation with a maximum cross correlation coefficient criterion is proposed and the simulation and experimental results validate the algorithm.
Abstract: A low-power consumption, small-size smart antenna, named electronically steerable parasitic array radiator (ESPAR), has been designed. Beamforming is achieved by tuning the load reactances at parasitic elements surrounding the active central element. A fast beamforming algorithm based on simultaneous perturbation stochastic approximation with a maximum cross correlation coefficient criterion is proposed. The simulation and experimental results validate the algorithm. In an environment where the signal-to-interference-ratio is 0 dB, the algorithm converges within 50 iterations and achieves an output signal-to-interference-plus-noise-ratio of 10 dB. With the fast beamforming ability and its low-power consumption attribute, the ESPAR antenna makes the mass deployment of smart antenna technologies practical.
TL;DR: A new hierarchical basis of arbitrary order for integral equations solved with the method of moments derived from orthogonal Legendre polynomials which are modified to impose continuity of vector quantities between neighboring elements while maintaining most of their desirable features is presented.
Abstract: This paper presents a new hierarchical basis of arbitrary order for integral equations solved with the method of moments (MoM). The basis is derived from orthogonal Legendre polynomials which are modified to impose continuity of vector quantities between neighboring elements while maintaining most of their desirable features. Expressions are presented for wire, surface, and volume elements but emphasis is given to the surface elements. In this case, the new hierarchical basis leads to a near-orthogonal expansion of the unknown surface current and implicitly an orthogonal expansion of the surface charge. In addition, all higher order terms in the expansion have two vanishing moments. In contrast to existing formulations, these properties allow the use of very high-order basis functions without introducing ill-conditioning of the resulting MoM matrix. Numerical results confirm that the condition number of the MoM matrix obtained with this new basis is much lower than existing higher order interpolatory and hierarchical basis functions. As a consequence of the excellent condition numbers, we demonstrate that even very high-order MoM systems, e.g., tenth order, can be solved efficiently with an iterative solver in relatively few iterations.
TL;DR: In this article, a new method to numerically solve time-domain integral equations pertinent to electromagnetic surface scattering phenomena is presented, using approximate prolate spheroidal wave functions and standard Rao-Wilton-Glisson basis functions to effect the temporal and spatial discretization of the integral equations, respectively.
Abstract: A new method to numerically solve time-domain integral equations pertinent to electromagnetic surface scattering phenomena is presented. The method uses approximate prolate spheroidal wave functions and standard Rao-Wilton-Glisson basis functions to effect the temporal and spatial discretization of the integral equations, respectively. Because the temporal basis functions are noncausal, an extrapolation scheme is used to construct a system of equations that can be solved by marching on in time. Numerical results show that the proposed method is stable and that its solutions converge exponentially fast with the time-bandwidth product of the approximate prolate spheroidal wave functions to results from a frequency-domain method of moments solver that uses spatial basis functions and integration rules identical to those in the time-domain solver.
TL;DR: The results from this paper reveal that for closely spaced antennas, the termination can play a noticeable role in determining the diversity gain offered by coupled antennas.
Abstract: A new analysis of mutually coupled diversity antenna systems is presented that includes the effects of coupling on the radiation pattern and received power. This analysis, based upon the network scattering parameters, makes use of the singular value decomposition to both specify the characteristics of and analyze terminated antenna networks. The approach facilitates a simplified proof of the multiport conjugate matching condition as well as development of expressions for diversity performance as a function of various impedance terminations. Application of the analysis to coupled dipole antennas characterized using full-wave electromagnetic analysis leads to a comprehensive examination of the diversity performance obtainable for such antennas under different termination conditions. The results from this paper reveal that for closely spaced antennas, the termination can play a noticeable role in determining the diversity gain offered by coupled antennas.
TL;DR: The basic concept for the RECAP antenna is verified by comparing theoretical results with measurements for configurations in which the switches are simply wires connecting the patches, and an overview of alternate switch/control strategies, some of which were tested, is given.
Abstract: A reconfigurable aperture (RECAP) antenna is described in which a planar array of electrically small, metallic patches are interconnected by switches. The antenna can be reconfigured to meet different performance goals by changing the switches that are open and closed. The switch configuration for a particular goal is determined using an optimizer, such as the genetic algorithm. First, the basic concept for the RECAP antenna is verified by comparing theoretical results with measurements for configurations in which the switches are simply wires connecting the patches. Next, details are given for a prototype antenna in which field-effect transistor based electronic switches are used with optical control. Theoretical results for the prototype antenna are then compared with measurements for cases in which electronic reconfiguration is used to change the bandwidth of operation or steer the pattern of the antenna. Finally, an overview of alternate switch/control strategies, some of which were tested, is given along with suggestions for improving the next generation of this antenna.
TL;DR: In this article, the design and operation along with verifying measurements of a harmonic radar transceiver, or tag, developed for insect tracking are presented, where a short length of wire formed the antenna while a beam lead Schottky diode across a resonant loop formed the frequency doubler circuit.
Abstract: The design and operation along with verifying measurements of a harmonic radar transceiver, or tag, developed for insect tracking are presented. A short length of wire formed the antenna while a beam lead Schottky diode across a resonant loop formed the frequency doubler circuit yielding a total tag mass of less than 3 mg. Simulators using the method-of-moments for the antenna, finite-integral time-domain for the loop, and harmonic balance for the nonlinear diode element were used to predict and optimize the transceiver performance. This performance is compared to the ideal case and to measurements performed using a pulsed magnetron source within an anechoic chamber. A method for analysis of the tag is presented and used to optimize the design by creating the largest possible return signal at the second harmonic frequency for a particular incident power density. These methods were verified through measurement of tags both in isolation and mounted on insects. For excitation at 9.41 GHz the optimum tag in isolation had an antenna length of 12 mm with a loop diameter of 1 mm which yielded a harmonic cross-section of 40 mm/sup 2/. For tags mounted on Colorado potato beetles, optimum performance was achieved with an 8 mm dipole fed 2 mm from the beetle attached end. A theory is developed that describes harmonic radar in a fashion similar to the conventional radar range equation but with harmonic cross-section replacing the conventional radar cross-section. This method provides a straightforward description of harmonic radar system performance as well as provides a means to describe harmonic radar tag performance.
TL;DR: In this paper, a procedure for designing contoured beam reflectarrays in a defined frequency band is proposed, which consists of three layers of rectangular patch arrays backed by a ground plane.
Abstract: A procedure for designing contoured beam reflectarrays in a defined frequency band is proposed. The reflectarray consists of three layers of rectangular patch arrays backed by a ground plane. The phase of the reflection coefficient for both linear polarizations is controlled at each reflective element by adjusting the patch dimensions. To overcome the frequency band limitation of reflectarrays, the patch dimensions are adjusted to match the required phase distribution and its variation with frequency. A phase-only synthesis technique based on the intersection approach has been applied to obtain the phase distribution on the reflectarray surface. An experimental demonstration is presented by means of a medium-size two-layer reflectarray that radiates two pencil beams separated by 55/spl deg/. An 80-cm three-layer reflectarray has been designed for typical South America DBS coverage at Ku-band for dual polarization. After the optimization of the patch dimensions to match the phase distribution in the 12.8-14.2 GHz band significant improvements have been achieved in the contoured patterns. As a result, the theoretical radiation patterns practically fulfill the requirements in the coverage region within a 10% bandwidth.
TL;DR: In this article, a low profile planar monopole antenna with a shorted parasitic inverted-L wire fed using a microstrip feedline for wireless communications in the wireless local-area network (WLAN) bands is studied.
Abstract: A low-profile planar monopole antenna with a shorted parasitic inverted-L wire fed using a microstrip feedline for wireless communications in the wireless local-area network (WLAN) bands is studied. The driven monopole element and shorted parasitic wire can separately control the operating frequencies of two excited resonant modes, which cover the 2.4-, 5.2-, and 5.8-GHz WLAN bands. This antenna design is not only suitable as a monopole antenna but also as a diversity antenna for 2.4-, 5.2-, and 5.8-GHz band operations. The lower mode of the proposed antenna has an impedance bandwidth (2:1 VSWR) of about 188 MHz (2313-2501 MHz), which covers the required bandwidth for 2.4 GHz WLAN band (2400-2484 MHz); on the other band, the upper mode has a bandwidth of about 2843 MHz (3930-6773 MHz) covering the HIPERLAN band (5150-5350 MHz) and 5.8-GHz WLAN band (5725-5852 MHz). For frequencies across the three operating bands, the proposed antenna shows similar monopole-like radiation patterns, and good antenna gain across the operating bands is obtained. Details of the design considerations for the proposed antenna are described, and the experimental results of the antenna performances obtained are presented and discussed.
TL;DR: This work presents propagation measurement results at 60 GHz in order to determine the characteristics of indoor radio channels between fixed terminals and describes slow fading as well as a quasi-wide-sense stationary (QWSS) behavior of the fading, but up to 50 ms of time.
Abstract: This work presents propagation measurement results at 60 GHz in order to determine the characteristics of indoor radio channels between fixed terminals. Path loss measurements are reported for line-of-sight (LoS) and non-line-of-sight (NLoS) cases, fading statistics in a physically stationary environment are extracted and a detailed investigation of the people movement effect on the temporal fading envelope is performed. Models that presented to predict path loss provide excellent fitting with errors of 1.13 and 3.84 dB for LoS and NLoS topographies, respectively. The dynamic range of fading in a quiescent environment is 8.8 dB and increased to 35 dB when a person moves between the fixed terminals with the channel becoming extremely nonstationary. Temporal variations induced by the moving people depend on the speed, the number of individuals the body sizes and the environment. Slow fading is observed as well as a quasi-wide-sense stationary (QWSS) behavior of the fading, but up to 50 ms of time.
TL;DR: A new approach of EM wave propagation through seawater is presented and the experimental results conducted in the laboratory and the real environment of seawater are presented.
Abstract: The nature of the ocean environment and its vast size has necessitated the development of sophisticated equipment and techniques for various underwater applications including diver-to-diver communications, ROV/AUV docking, communications and oil and gas explorations. To facilitate scientific exploration a wide variety of systems and vehicles have been developed to operate within the shallow continental shelf region or in deep oceans. For successful underwater electromagnetic (EM) wave operation, knowledge is required of the wave transmission properties of seawater over all distances both short and long. This information is required for such activities such as: sensor systems, imaging, position fixing, measurement of speed, obstacle detection and avoidance, guidance, communication of data/voice and remote control. This paper presents a new approach of EM wave propagation through seawater. The experimental results conducted in the laboratory and the real environment of seawater is presented.
TL;DR: In this paper, a smooth-walled spline-profile horn for specific application in the 80-120 GHz band was proposed. But the results of a theoretical and measurement study of the smooth-wall spline profile horn were presented.
Abstract: At millimeter-wave frequencies, corrugated horns can be difficult and expensive to manufacture. As an alternative we present here the results of a theoretical and measurement study of a smooth-walled spline-profile horn for specific application in the 80-120 GHz band. While about 50% longer than its corrugated counterpart, the smooth-walled horn is shown to give improved performance across the band as well as being much easier to manufacture.
TL;DR: Thin, broad-band, E-shaped microstrip patch antennas (ESPAs), operating in the 5-6 GHz frequency range, are presented, suitable for WLAN adaptor cards in the PCMCIA format, allowing users of current notebook computers to upgrade to this high-speed wireless standard at a low cost.
Abstract: Thin, broad-band, E-shaped microstrip patch antennas (ESPAs), operating in the 5-6 GHz frequency range, are presented. They are intended for high-speed (IEEE 802.11a, 54 Mb/s) wireless computer local area networks (WLAN) and other wireless communication systems. They are suitable for WLAN adaptor cards in the PCMCIA (also known as PC) format, allowing users of current notebook computers to upgrade to this high-speed wireless standard at a low cost. Importantly, our antennas are thin enough to be accommodated in a PCMCIA card of standard 5-mm thickness, without making the antenna end thicker than the card itself. Two different closely spaced antenna pairs are also presented for diversity. A new ESPA configuration with a microstrip feed is presented for easy integration with microwave transceivers. In all cases, within the two IEEE 802.11a WLAN bands (5.15-5.35 GHz and 5.725-5.825 GHz), the reflection coefficient at the antenna input is <-10 dB and in both antenna pairs, mutual coupling between the two antennas is <-20 dB.
TL;DR: An efficient marching-on-in-time (MOT) scheme is presented for solving electric, magnetic, and combined field integral equations pertinent to the analysis of transient electromagnetic scattering from perfectly conducting surfaces residing in an unbounded homogenous medium.
Abstract: An efficient marching-on-in-time (MOT) scheme is presented for solving electric, magnetic, and combined field integral equations pertinent to the analysis of transient electromagnetic scattering from perfectly conducting surfaces residing in an unbounded homogenous medium. The proposed scheme is the extension of the frequency-domain adaptive integral/pre-corrected fast-Fourier transform (FFT) method to the time domain. Fields on the scatterer that are produced by space-time sources residing on its surface are computed: 1) by locally projecting, for each time step, all sources onto a uniform auxiliary grid that encases the scatterer; 2) by computing everywhere on this grid the transient fields produced by the resulting auxiliary sources via global, multilevel/blocked, space-time FFTs; 3) by locally interpolating these fields back onto the scatterer surface. As this procedure is inaccurate when source and observer points reside close to each other; and 4) near fields are computed classically, albeit (pre-)corrected, for errors introduced through the use of global FFTs. The proposed scheme has a computational complexity and memory requirement of O(N/sub t/N/sub s/log/sup 2/N/sub s/) and O(N/sub s//sup 3/2/) when applied to quasiplanar structures, and of O(N/sub t/N/sub s//sup 3/2/log/sup 2/N/sub s/) and O(N/sub s//sup 2/) when used to analyze scattering from general surfaces. Here, N/sub s/ and N/sub t/ denote the number of spatial and temporal degrees of freedom of the surface current density. These computational cost and memory requirements are contrasted to those of classical MOT solvers, which scale as O(N/sub t/N/sub s//sup 2/) and O(N/sub s//sup 2/), respectively. A parallel implementation of the scheme on a distributed-memory computer cluster that uses the message-passing interface is described. Simulation results demonstrate the accuracy, efficiency, and the parallel performance of the implementation.
TL;DR: In this article, a simple ray-based model is used to integrate reflection/diffraction with diffuse scattering to obtain good narrow-band and wide-band results with a low number of interactions.
Abstract: Ray tracing (RT) models are now widely adopted for field prediction in urban environment. Nevertheless, conventional RT tools still suffer for excessive central processing unit (CPU) time and inaccuracy in wide-band prediction. By increasing the maximum number of successive interactions (reflections, diffractions) little improvement in wide-band results can be usually achieved while CPU time increases exponentially. In the present paper, it is shown that by integrating reflection/diffraction with diffuse scattering, good narrow-band and wide-band results can be obtained with a low number of interactions. The adopted scattering model is a simple ray-based model, which has been embedded in a three-dimensional (3-D) RT program. The impact of diffuse scattering on narrowband and wide-band parameters is analyzed in the paper and the complete model is compared with measurements in a variety of cases, showing the validity of the approach.
TL;DR: In this paper, the simulation and experimental investigations of a printed microstrip slot antenna are presented, which is a quarter wavelength monopole slot cut in the finite ground plane edge, and fed electromagnetically by a microstrip transmission line.
Abstract: This paper presents the simulation and experimental investigations of a printed microstrip slot antenna. It is a quarter wavelength monopole slot cut in the finite ground plane edge, and fed electromagnetically by a microstrip transmission line. It provides a wide impedance bandwidth adjustable by variation of its parameters, such as the relative permittivity and thickness of the substrate, width, and location of the slot in the ground plane, and feed and ground plane dimensions. The ground plane is small, 50 mm/spl times/80 mm, and is about the size of a typical PC wireless card. At the center frequency of 3.00 GHz, its width of 50 mm is about /spl lambda//2 and influences the slot impedance and bandwidth significantly. An impedance bandwidth (S/sub 11/=-10 dB) of up to about 60% is achieved by individually optimizing its parameters. The simulation results are confirmed experimentally. A dual complementary slot antenna configuration is also investigated for the polarization diversity.
TL;DR: An electromagnetic genetic algorithm (GA) optimization (EGO) application developed for the cluster supercomputing platform is described, which allows it to combine the accuracy of full-wave EM analysis with the robustness of GA optimization and the speed of a parallel computing algorithm.
Abstract: In this paper, we describe an electromagnetic genetic algorithm (GA) optimization (EGO) application developed for the cluster supercomputing platform. A representative patch antenna design example for commercial wireless applications is detailed, which illustrates the versatility and applicability of the method. We show that EGO allows us to combine the accuracy of full-wave EM analysis with the robustness of GA optimization and the speed of a parallel computing algorithm. A representative patch antenna design case study is presented. We illustrate the use of EGO to design a dual-band antenna element for wireless communication (1.9 and 2.4 GHz) applications. The resulting antenna exhibits acceptable dual-band operation (i.e., better than -10 dB return loss with 5.3 and 7% operating bandwidths at 1.9 and 2.4 GHz) while maintaining a cross-pol maximum field level at least 11 dB below the co-pol maximum.
TL;DR: In this paper, a dual-frequency coplanar waveguide (CPW)-fed monopole antenna is proposed and experimentally studied, which utilizes the advantages of the CPW line to simplify the structure of the antenna into a single metallic level, thereby making easier the integration with the microwave integrated circuits.
Abstract: A new dual-frequency design of coplanar waveguide (CPW)-fed monopole antenna is proposed and experimentally studied. The proposed antenna utilizes the advantages of the CPW line to simplify the structure of the antenna into a single metallic level, thereby making easier the integration with the microwave integrated circuits. The two operating modes of the proposed antenna are associated with various lengths of two monopoles, in which the longer monopole works for the first resonant mode and the shorter monopole works for the second mode. Moreover, by increasing the width of the longer monopole, a broadband dual-frequency operation is demonstrated. Experimental results show that the impedance bandwidth, determined from 10-dB return loss, of the two operating frequencies can both be greater than 14%. Details of the experimental results are presented and discussed.
TL;DR: In this paper, a compact 24 GHz Yagi-Uda antenna has been developed using standard design tables and simple scaling to take into account the added capacitance due to the supporting dielectric substrate.
Abstract: A compact 24-GHz Yagi-Uda antenna has been developed using standard design tables and simple scaling to take into account the added capacitance due to the supporting dielectric substrate. The antenna results in a directivity of 9.3 dB, a front-to-back ratio of 11 dB, and a bandwidth of 2.5-3%. The Yagi-Uda antenna has been implemented in an 11-beam system using a planar array and a 2-inch Teflon spherical lens. The measured patterns show a 22 dB gain beam, a cross-polarization level of -24 dB, and a crossover level of -6 dB. The design method presented in this paper is quite straightforward, and can be used to develop low-, medium-, and even high-gain endfire Yagi-Uda antennas.
TL;DR: The results show a reduction in mutual coupling between elements and provide a possible solution to the "blind spots" problem in phased array applications with printed elements.
Abstract: Uniplanar compact electromagnetic bandgap (UC-EBG) substrate has been proven to be an effective measure to reduce surface wave excitation in printed antenna geometries. This paper investigates the performance of a microstrip antenna phased array embedded in an UC-EBG substrate. The results show a reduction in mutual coupling between elements and provide a possible solution to the "blind spots" problem in phased array applications with printed elements. A novel and efficient UC-EBG array configuration is proposed. A probe fed patch antenna phased array of 7/spl times/5 elements on a high dielectric constant substrate was designed, built and tested. Simulation and measurement results show improvement in the active return loss and active pattern of the array center element. The tradeoffs used to obtain optimum performance are discussed.