Showing papers in "IEEE Antennas and Wireless Propagation Letters in 2003"
TL;DR: In this article, a compact one-dimensional phase shifter is proposed using alternating sections of negative refractive index (NRI) metamaterials and printed transmission lines (TL).
Abstract: A compact one-dimensional phase shifter is proposed using alternating sections of negative refractive index (NRI) metamaterials and printed transmission lines (TL). The NRI metamaterial sections consist of lumped element capacitors and inductors, arranged in a dual TL (high-pass) configuration. By adjusting the NRI-medium lumped element values, the phase shift can be tailored to a given specification. Periodic analysis is applied to the structure and design equations are presented for the determination of the lumped element parameters for any arbitrary phase shift. To validate the design, various phase shifters are simulated and tested in coplanar waveguide (CPW) technology. It is demonstrated that small variations in the NRI-medium lumped element values can produce positive, negative or 0/spl deg/ phase shifts while maintaining the same short overall length. Thus, the new phase shifter offers some significant advantages over conventional delay lines: it is more compact in size, it exhibits a linear phase response around the design frequency, it can incur a phase lead or lag which is independent of the length of the structure and it exhibits shorter group delays.
400Â citations
TL;DR: New meander line antennas with improved gain are proposed as low-profile self-resonant tags for application in passive radio frequency identification.
Abstract: New meander line antennas with improved gain are proposed as low-profile self-resonant tags for application in passive radio frequency identification. Antenna shape and size is optimized by genetic algorithm, taking conductor losses into account. Examples are presented for application at 869 MHz with antennas of different materials and sizes.
279Â citations
TL;DR: Computed and measured data show that, by utilizing this technique, the height of PIFAs can effectively be reduced by more than 50%, thereby reducing the overall phone thickness.
Abstract: The ground plane of a mobile phone plays an important role on the performance of a planar inverted-F antenna (PIFA). In addition to exploring novel antennas, the effective utilization of the mobile phone ground plane and its associated volume is crucial to a successful design. We propose a uniquely modified ground plane configuration to design ultra-thin PIFAs. Both singleand dual-band design examples are provided. Computed and measured data for 900 and 1900 MHz band cases show that, by utilizing this technique, the height of PIFAs can effectively be reduced by more than 50%, thereby reducing the overall phone thickness.
218Â citations
TL;DR: In this paper, the numerical analysis and experimental characterization of an ultrawideband (UWB) antenna designed for radiating short microwave pulses is presented, which consists of a pyramidal horn, a ridge, and a curved launching plane terminated with resistors.
Abstract: We report the numerical analysis and experimental characterization of an ultrawideband (UWB) antenna designed for radiating short microwave pulses. The antenna consists of a pyramidal horn, a ridge, and a curved launching plane terminated with resistors. The pyramidal horn is connected to the outer conductor of the coaxial feed and serves as the ground plane. The curved launching plane is connected to the central conductor of the coaxial feed. Detailed three-dimensional finite-difference time-domain (FDTD) simulations have been conducted to assist with the characterization of the antenna. FDTD results are compared with experimental data and are shown to be in good agreement. We demonstrate that the antenna exhibits a very low voltage standing wave ratio (/spl les/1.5) over a wide frequency range from 1 to 11 GHz and a very high fidelity (/spl ges/0.92). The spatial distribution of radiated energy is characterized both in the time domain, using transient field observations at various angles, as well as in the frequency domain, using single-frequency far-field radiation patterns. We conclude that this antenna offers high-fidelity transmission and reception of ultrashort microwave pulses with minimal distortion.
177Â citations
TL;DR: In this article, the differential evolution algorithm is employed both to shape the beam requirements and to suppress the sideband patterns, and the results show that the time-modulated linear array can be successfully used to synthesize power patterns and the excitation dynamic-range ratio can be reduced significantly as compared to those of conventional arrays.
Abstract: The time modulation technique is utilized for the synthesis of power patterns in linear arrays. The differential evolution algorithm is employed both to shape the beam requirements and to suppress the sideband patterns. Numerical results show that the time-modulated linear array can be successfully used to synthesize power patterns and the excitation dynamic-range ratio can be reduced significantly as compared to those of conventional arrays.
159Â citations
TL;DR: In this paper, the radiation efficiency, effective diversity gain, and apparent diversity gain of two parallel dipoles and how they depend on dipole spacing were calculated. But the results for 50 /spl Omega/ termination were verified by measurements of effective diversity in a reverberation chamber.
Abstract: Two parallel dipoles are often used as a reference case for measuring diversity gain. The present paper shows how to calculate the radiation efficiency, effective diversity gain, and apparent diversity gain of two parallel dipoles and how they depend on dipole spacing. We treat several cases for different terminations of the neighboring dipole; open-circuited, short-circuited, and 50 /spl Omega/ termination. The results for 50 /spl Omega/ termination are verified by measurements of effective diversity gain in a reverberation chamber.
142Â citations
TL;DR: In this article, a microstrip patch antenna using a defected ground structure (DGS) to suppress higher order harmonics is presented, where an H-shaped defect on the ground plane with only one or more unit lattices has been utilized and yielded bandstop characteristics.
Abstract: A microstrip patch antenna using a defected ground structure (DGS) to suppress higher order harmonics is presented. An H-shaped defect on the ground plane with only one or more unit lattices has been utilized and yielded bandstop characteristics. Compared with a conventional microstrip patch antenna without the DGS unit cell, the radiated power of the DGS patch antenna at harmonic frequencies has been drastically decreased.
139Â citations
TL;DR: In this paper, a dual-frequency circularly polarized shorted ring-slot rectenna (rectifying antenna) for wireless power transmission at 245 and 58 GHz was proposed, which is composed of two nested microstrip-fed shorted annular ring slot antennas and two rectifier circuits.
Abstract: A novel dual-frequency circularly polarized shorted ring-slot rectenna (rectifying antenna) for wireless power transmission at 245 and 58 GHz is proposed The rectenna is composed of two nested microstrip-fed shorted annular ring-slot antennas and two rectifier circuits Output DC voltage of over 2 V at the lower frequency band and over 1 V at the higher frequency band is achieved at a transmission distance of 2 m
133Â citations
TL;DR: A low profile egg-crate array with wideband printed flared dipole ("bunny-ear") elements was developed for dual-pol applications as discussed by the authors, and a small test array of 9/spl times/9 elements was built and tested in a 1-5 GHz experiment.
Abstract: A low profile egg-crate array with wide-band printed flared dipole ("bunny-ear") elements was developed for dual-pol applications A small test array of 9/spl times/9 elements was built and tested in a 1-5 GHz experiment Gain and scan element patterns in E-, H-, and diagonal cuts were measured Excellent results including low cross-pol were observed
129Â citations
TL;DR: In this paper, a new Luneburg lens manufacturing process was proposed to avoid the air gap caused by the inaccuracies in the curved shell manufacturing process, which degraded the performance of the lens.
Abstract: The Luneburg lens (LL) represents a very attractive candidate for many applications such as multibeam antennas, multifrequency scanning, and spatial scanning, due to its focusing properties. Indeed, it is a dielectric sphere on which each surface point is a frequency-independent perfect focusing point. This is produced by its index governing law n, which follows the radial distribution n/sup 2/=2-r/sup 2/, where r is the normalized radial position. Practically, an LL is manufactured as a finite number of concentric homogeneous dielectric shells - this is called a discrete LL. The inaccuracies in the curved shell manufacturing process produce intershell air gaps, which degrade the performance of the lens. Furthermore, this requires different materials whose relative dielectric constant covers the range 1-2. The paper proposes a new LL manufacturing process to avoid these drawbacks. The paper describe the theoretical background and the performance of the obtained lens.
93Â citations
TL;DR: In this paper, a systematic study of the performance of reflectarrays with different element shapes is presented, where the reflection properties of the printed elements versus their geometrical dimensions are calculated by using the method of moments (MoM)/boundary integral-resonant mode expansion (BI-RME) method, which permits the analysis of arbitrarily shaped elements.
Abstract: A systematic study of the performance of reflectarrays with different element shapes is presented. The reflection properties of the printed elements versus their geometrical dimensions are calculated by using the method of moments (MoM)/boundary integral-resonant mode expansion (BI-RME) method, which permits the analysis of arbitrarily shaped elements. In order to compare the element performance, four parameters are defined as "figures of merit": the range of the reflection phase; the sensitivity to fabrication tolerances; the bandwidth; the cross-polarization level. Both classical (e.g., rectangles and rectangles with tuning stubs) and novel element shapes (e.g., ridge, dogbone) are considered in the case of single-layer structures; the novel proposed shapes exhibit a good tradeoff of all the figures of merit. Double-layer structures are also analyzed, which prove their superior performance at the cost of an increased fabrication complexity.
TL;DR: In this paper, a small broadband monopole antenna is proposed, which consists of a circular disk-loaded monopole and a probe with a circular spiral strip line monopole, and the antenna occupies a cylindrical volume with a radius of /spl rho/ /spl cong/ 0.04/spl lambda/sub o/ (5.5 mm) and a height of h /spl cg/
Abstract: The paper presents a small broadband monopole antenna. The proposed structure consists of a circular disk-loaded monopole and a probe with a circular spiral strip line monopole. Broad bandwidth can be achieved through electromagnetic coupling between these two monopoles that generate two resonances closely spaced in frequency. The antenna occupies a cylindrical volume with a radius of /spl rho/ /spl cong/ 0.04/spl lambda//sub o/ (5.5 mm) and a height of h /spl cong/ 0.08/spl lambda//sub o/ (11 mm) and has 430 MHz of impedance bandwidth for VSWR<2 with a center frequency at 2.185 GHz, which is fractional bandwidth of approximately 19.7%. The gain of the antenna is more than 1.7 dBi within the entire bandwidth with good omnidirectional radiation characteristics.
TL;DR: A new built-in quad-band handset antenna for covering GSM900, DCS1800, PCS1900, and UMTS2000 bands is presented and the simulation is based on the finite-difference time-domain (FDTD) method.
Abstract: A new built-in quad-band handset antenna for covering GSM900, DCS1800, PCS1900, and UMTS2000 bands is presented. Details of the antenna are discussed along with measured and simulated results. The simulation is based on the finite-difference time-domain (FDTD) method.
TL;DR: In this article, a broadband microstrip-fed slot antenna with double rejection zero was proposed and developed by constructing simultaneously a wide-slot radiator and a quarter-wavelength microstrip line resonator.
Abstract: A novel broadband microstrip-fed slot antenna with double rejection zeros is proposed and developed by constructing simultaneously a wide-slot radiator and a quarter-wavelength microstrip line resonator. A comprehensive explanation of its operating principle is given by using an equivalent two-pole filtering network, in which the radiation resistance is perceived as the output impedance. Extensive numerical results are then obtained using a commercial electromagnetic simulator to demonstrate its attractive broadband feature. Finally, a few antenna samples are designed, fabricated, and measured to verify the predicted performance. Experimental results exhibit that the bandwidth of this proposed antenna configuration is significantly increased, by up to 32.0%, as compared to 9.0% for its traditional counterpart.
TL;DR: In this article, a compact internal quad-band handset antenna for covering the GSM900, DCS1800, PCS1900, and ISM2450 bands is presented.
Abstract: A novel compact internal quad-band handset antenna for covering the GSM900, DCS1800, PCS1900, and ISM2450 bands is presented. The proposed antenna consists of folded patches sharing a common shorting strip and occupies a total volume of 36/spl times/16/spl times/9 mm/sup 3/. Details of the antenna are discussed along with measured and simulation results. The simulation is based on the finite-difference time-domain method.
TL;DR: In this article, the role of different iteration orders for Hilbert antennas, approximately matched to the 50 /spl Omega/ line, on the bandwidth and cross-polarization level of such antennas was investigated numerically.
Abstract: We have applied a moment-method-based simulation code to perform a detailed parametric study of the bandwidth, cross-polarization level, and the feed location characteristics of the matched Hilbert antenna. It is shown that a properly chosen off-center near-the-end feed point may provide an approximate 50 /spl Omega/ real input impedance at the fundamental resonant frequency. The role of different iteration orders for Hilbert antennas, approximately matched to the 50 /spl Omega/ line, on the bandwidth and cross-polarization level of such antennas is investigated numerically. As was shown by K.J. Vinoy et al., the radiation patterns resemble those of a linear dipole and, for a fixed-area-matched Hilbert antenna, the resonant frequency can be lowered by increasing the iteration order n. However, for such matched antennas, the bandwidth for VSWR<2 is decreased and the cross-polarization level may be different for the higher iteration-order antennas.
TL;DR: In this paper, the authors proposed an antenna with cross-shaped or square-shaped lattices for harmonic suppression, which not only exhibited well-behaved bandstop characteristics, but also enhanced the bandwidth of the proposed antennas.
Abstract: Photonic bandgap (PBG) structures with cross-shaped or square-shaped lattices have been incorporated into the antenna feed network for harmonic suppression. Experimental results show that PBG structures not only exhibit well-behaved bandstop characteristics, but also enhance the bandwidth of the proposed antennas. For the proposed antenna with square-shaped lattices, the 10 dB return loss bandwidth could reach 1541 MHz (1525-3066 MHz), which is about 70% with respect to the center frequency of 2200 MHz; for the antenna with cross-shaped lattices, the bandwidth could reach 1320 MHz (1560-2880 MHz), which is about 60% with respect to the center frequency of 2200 MHz.
TL;DR: In this paper, a double element microstrip antenna array with a newly developed electromagnetic band gap (EBG) structure was investigated, showing that the S21 transmission coefficient between the elements is reduced by around 4 dB.
Abstract: A double element microstrip antenna array inserted with a newly developed electromagnetic band gap (EBG) structure has been investigated, showing that the S21 transmission coefficient between the elements is reduced by around 4 dB. As a result, sidelobe levels are reduced by 1.8 to 2.1 dB and an increase of 1 dB in the gain has been achieved, without much change in other characteristics. Using the EBG structure has proved to be a convenient way to upgrade the performance of an antenna array.
TL;DR: In this article, a folded inner small patch was proposed to improve the performance of a conventional quarter-wave patch antenna and two different geometries (U-slot and L-slit) were investigated experimentally.
Abstract: A novel technique that improves the performance of a conventional quarter-wave patch antenna is proposed. Two different geometries (U-slot and L-slit) are investigated experimentally. With the inclusion of a folded inner small patch, we achieve impedance bandwidths of 53% and 45% for the U-slot and L-slit, respectively, for a voltage standing wave ratio less than 2. Radiation patterns are stable across the whole operating frequency bands.
TL;DR: In this paper, a single series feed cross-aperture coupled microstrip antenna with the effect of hybrid feeding is proposed and demonstrated, and the characteristics according to the variation of parameters are shown.
Abstract: A single series feed cross-aperture coupled microstrip antenna with the effect of hybrid feeding is proposed and demonstrated. To understand this antenna better, the characteristics according to the variation of parameters are shown. This proposed antenna has the following advantages of the effect of hybrid feeding: improved axial ratio bandwidth (4.6%); high gain (8 dBi); flat 3 dB gain bandwidth (above 16.7%). In measured radiation patterns, we have 3 dB beamwidth of /spl plusmn/30/spl deg/ and good F/B (front to back ratio) of 20 dB.
TL;DR: In this article, the effectiveness of antenna geometry in terms of lowering or establishing a specific resonant frequency is considered as a function of the current vector alignment in closely coupled sections of wire.
Abstract: The effectiveness of antenna geometry in terms of lowering or establishing a specific resonant frequency is considered as a function of the current vector alignment in closely coupled sections of wire. The results and discussion presented expand on a previous work (Best, S.R. and Morrow, J.D., ibid., vol.1, p.112-15, 2002) where it was shown that the current vector alignment in fractal and other small space-filling antennas is significant in establishing the antenna's resonant frequency for a fixed total wire length. A variety of antenna geometries are considered to illustrate the significance and manner in which current vector alignment establishes a small antenna's resonant frequency.
TL;DR: In this article, the resonant properties of several small planar space-filling fractal antennas are considered over a range of self-resonant frequencies, including radiation resistance, efficiency, and quality factor.
Abstract: The resonant properties of several small planar space-filling fractal antennas are considered over a range of self-resonant frequencies. These space-filling antennas have differing geometries and total wire length, but occupy the same planar area. The resonant properties considered include radiation resistance, efficiency, and quality factor. It is demonstrated that the resonant properties of these antennas are essentially the same, independent of significant differences in antenna geometry and total wire length.
TL;DR: In this paper, an efficient near-field-far-field transformation technique with spherical spiral scanning is proposed, which uses a minimum number of data points and a nonredundant sampling representation of the electromagnetic field on the spiral and a fast, accurate and stable interpolation algorithm are developed to this end.
Abstract: An efficient near-field-far-field transformation technique with spherical spiral scanning, which uses a minimum number of data, is proposed. A nonredundant sampling representation of the electromagnetic field on the spiral and a fast, accurate and stable interpolation algorithm are developed to this end. By choosing the elevation step of the spiral coincident with the sample spacing needed to interpolate the field on a meridian, it is possible to reconstruct the field at any point on the spherical surface. This allows the evaluation of the data required by a spherical near-field-far-field transformation. Numerical examples assessing the effectiveness of the proposed technique are reported.
TL;DR: This derivation is based on a new "geometrical model" of omnidirectional scatterers as spatially distributed uniformly on a two-dimensional hollow-disc centered upon the mobile, which degenerates to the well-known uniform-ring or uniform-disc densities.
Abstract: The paper rigorously derives explicit closed-form expressions for the joint/marginal probability density functions of the uplink/downlink multipaths' time-of-arrival (TOA) and azimuth angle-of-arrival (AOA) in a wireless-communication fading channel. This derivation is based on a new "geometrical model" of omnidirectional scatterers as spatially distributed uniformly on a two-dimensional hollow-disc (i.e., a thick ring) centered upon the mobile. By varying the hollow-disc's thickness, this spatial density degenerates to the well-known uniform-ring or uniform-disc densities.
TL;DR: In this paper, a microstrip antenna formed by two stacked patches is proposed for dual-frequency and broadband performance, and different E-plane and H-plane arrangements are studied to achieve an isolation between bands better than 30 dB.
Abstract: A microstrip antenna formed by two stacked patches is proposed for dual-frequency and broad-band performance. Different E-plane and H-plane arrangements are studied to achieve an isolation between bands better than 30 dB. A prototype operating at the 1.8 GHz and 3.5 GHz bands has been simulated and tested.
TL;DR: In this paper, the numerical dispersion relation of ADI-FDTD has been analyzed and verified with numerical experiments, with good agreement, and it is shown that ADI FDTD has some fundamental limits.
Abstract: The numerical dispersion relations in the literature are inconsistent for the alternate-direction-implicit finite-difference time-domain (ADI-FDTD) method. By analysis of the amplification factors, the numerical dispersion relation is rederived and verified with numerical experiments, with good agreement. The inconsistency of the numerical dispersion relation is resolved. It is shown that ADI-FDTD has some fundamental limits. For a given time step size, there is a velocity error even for zero spatial mesh. For a given spatial mesh size, the mesh does not support a numerical wave at certain time step sizes. As the Nyquist sampling limit is approached, the velocity of the wave approaches zero. At about twice the Nyquist limit, the wave does not propagate. Hence, the Nyquist criterion should be respected in choosing the time step size.
TL;DR: In this paper, a flat lens made of a realizable negative-refractive-index (NRI) metamaterial is used to focus electromagnetic waves from one homogeneous and isotropic dielectric to another.
Abstract: We report simulations demonstrating subwavelength focusing of electromagnetic waves, from one homogeneous and isotropic dielectric to another, through a flat lens made of a realizable negative-refractive-index (NRI) metamaterial. The NRI metamaterial consists of a two-dimensional inductor/capacitor (L/C) loaded transmission line (TL) network in a dual (high-pass) configuration. The microwave-circuit simulation results presented show that the voltage at the focal plane is identical to that at the source plane. The results confirm that, in addition to focusing propagating waves, evanescent waves are also restored at the focal plane by the proposed loaded TL lens, thus enhancing the resolution of the image. In addition, the nature of the voltage distribution (vertical electric field) in this "perfect-focusing" setup is clarified.
TL;DR: In this paper, the performance of space-filling curves used as small antennas is evaluated in terms of quality factor and radiation efficiency, and the influence of their topology is also considered.
Abstract: The performance of space-filling curves used as small antennas is evaluated in terms of quality factor and radiation efficiency. The influence of their topology is also considered. Although the potential use of these curves is for antenna miniaturization, their behavior is not exceptional when compared with other intuitively generated antennas.
TL;DR: An L1 Global Positioning System (GPS) antenna with improved multipath-rejection capability is presented and the antenna is realized with a shorted annular elliptical patch (SAEP).
Abstract: An L1 Global Positioning System (GPS) antenna with improved multipath-rejection capability is presented. The antenna is realized with a shorted annular elliptical patch (SAEP). Some of the characteristics of SAEP are presented briefly and a detailed account of the design is given. Measured results are presented and discussed.
TL;DR: In this article, the authors present the results of signal strength measurements at 1800 MHz in four office buildings in The Hague, illuminated by an outdoor base station with an antenna above the rooftop.
Abstract: The paper presents the results of signal strength measurements at 1800 MHz in four office buildings in The Hague, illuminated by an outdoor base station with an antenna above the rooftop. The objectives of these experiments are to study the behavior of the received signal strength at different floors of a building and to determine the main characteristics concerning cell coverage, namely, signal attenuation and variation within these buildings. It is shown that large fluctuations occur between average signal levels in line-of-sight (LOS) and non-LOS areas of multifloor buildings.