IEEE Antennas and Wireless Propagation Letters

Published by Institute of Electrical and Electronics Engineers
Print ISSN: 1536-1225
Publications
This letter presents a monolithically integrated on-chip antenna fabricated in 0.18 μm standard CMOS technology. As the antenna is used for power scavenging in a passive chip, it is designed to be matched with the rectifier circuit. The letter describes the important design considerations and the antenna characterization through measurements.
 
Fitted and scaled empirical shadow fading distribution.
This letter introduces analytical expressions for the modeling of path loss and shadow fading in residential indoor-to-outdoor scenarios. The formulas have been calibrated using channel power measurements at the radio frequencies of common cellular systems and are thus suitable for channel modeling in femtocell networks. The expressions presented here can be used as a simple propagation model in system-level simulators (SLS), as well as for comparison to other models. Furthermore, its compact formulation simplifies its use for theoretical studies of two-tier networks, while its empirical nature strengthens its validity.
 
In this letter, the TM<sub>020</sub> mode of a rectangular patch antenna is modified by partially loading a mu-negative (MNG) or double-negative (DNG) metamaterial block. With proper constitutive parameters and filling ratio, the electric fields at two radiating edges of the patch can be out of phase, and a broadside radiation pattern is achieved. A novel dual-band rectangular patch antenna loaded with a pair of conventional double-positive (DPS) and MNG metamaterial blocks is proposed as an application example of the modified TM<sub>020</sub> mode. Good impedance matching and similar patterns with broadside radiation are achieved simultaneously at both operating frequencies with a single-layer single-patch fed by a single coaxial line. Simulation shows that the modified TM<sub>020</sub> mode gives an efficient radiator with sufficient gain and very low level of cross polarization. Partial loading of a DNG metamaterial block is also discussed for some special dual-band applications.
 
A new global positioning system (GPS) antenna is proposed to cover the three GPS bands (L1, L2, and L5, namely 1575, 1227, and 1176 MHz) with the L5 band to be added after 2006. The developed antenna size is only $1.5^primeprimetimes 1.5^primeprime$ in aperture corresponding to $lambda/7timeslambda/7$ $(lambda=hboxfree hboxspace hboxwavelength)$ and $lambda/13 hboxthick$. Quadrature feeding is employed to ensure right-hand circular polarized (RHCP) radiation. The final miniature antenna exhibits a gain greater than 2 dBi, and to our knowledge this is the smallest such size for circular polarized (CP) operation covering all three bands. Detailed parametric simulations leading to the best design along with measurements for the constructed antenna are presented.
 
The impact of moving vegetation on propagating radio waves under the influence of wind had been investigated. It was found that the fast-fading component of the vegetation-shadowed signal, originating from a line-of-sight (LOS) transmitter, resembles a Rician distribution. From the measured data, a new empirical model at 1.8 GHz of the Rician k-factor has been proposed. The model characterizes the dynamic impact of the wind influence for radio waves propagating through vegetation. The proposed model was then assessed against a different set of measured data and was found to be in close agreement.
 
This letter presents a compact dual-frequency hybrid resonator antenna suitable for wireless communication applications at 1.9 and 2.45 GHz. The proposed antenna utilizes a combination of a disk dielectric resonator (DR) and a microstrip fed rectangular slot, and a circular metal sheet partially covers the top of the DR. The measured results validate the proposed design.
 
This letter describes results of a measurement campaign carried out to determine the statistics of building penetration loss for satellite systems at frequencies 10.8 and 11.1 GHz. The results obtained can be useful for either creating empirical models for several types of building materials or comparing them with existing ones at close frequencies
 
A novel design for a fully on-chip antenna operating at 140 GHz that can be fabricated with standard CMOS technology is proposed. In addition to the traditional microstrip feeding, the slot antenna is backed with an extremely thin cavity formed by two CMOS inner metal layers and vias in between. The proposed cavity prevents radiation from going inside the lossy silicon substrate and enhances the radiation of the slot antenna. It is also shown that the antenna radiation is not affected significantly by other metallic parts on the chip. Good agreement is achieved between results from a frequency-domain solver, HFSS, and a time-domain solver, CST. The simulated gain is around -2 dBi, and the radiation efficiency is around 18%, despite ohmic losses enhanced by the extreme flatness. The input 10-dB bandwidth is around 5 GHz. The total area of this antenna is 1.2 × 0.6 mm<sup>2</sup> (0.56 λ<sub>0</sub> × 0.28 λ<sub>0</sub> at 140 GHz).
 
A 16-element single-layer rectangular radial line helical array antenna is proposed and investigated. In the single-layer radial line feed system, two new probes are used to satisfy the coupling requirement. The sequential rotation technique is introduced to improve the axial ratio of the antenna. An antenna prototype is designed, simulated, and measured. The results indicate its advantages of high aperture efficiency, low input VSWR, and favorable axial ratio. The field distributions of this antenna are analyzed through simulation, which prove its advantage of high power-handling capacity. This array is also used to form an 8 × 8 array antenna, which demonstrates its ability to be used as a subarray.
 
Configuration of a compact broadband planar antenna (H = 7.2 mm, W = 18 mm, W = 15.6 mm, w = 0.6 mm, w = 1.8 mm, w = 0.75 mm, t = 0.254 mm, and L = 15 mm).
Simulated results for return loss of the planar antenna with different heights (H = 6.0, 7.2, and 8.4 mm) (L = 60 mm).  
Effect of the length (L ) of ground plane on the return loss of the compact broadband planar antenna (H = 7.2 mm).  
Radiation patterns of the compact broadband planar antenna: (a) at 1.6 GHz, (b) at 2.0 GHz, (c) at 2.5 GHz.  
Measured return loss of the compact broadband planar antenna compared to simulation results. (Inset are four photographs of the antenna prototype, which show the front view and the back view of the planar antenna, respectively.)  
A compact broadband planar antenna is developed for global positioning system (GPS), DCS-1800, IMT-2000, and WLAN handsets. The planar antenna consists of an S-strip and a T-strip which are separately printed on the two sides of a thin substrate (no via process is involved in the fabrication). The antenna size is only 18 mm$,times,$7.2 mm $,times,$0.254 mm which is more compact than previously published antenna configurations. The bandwidth of the planar antenna is enhanced by the mutual coupling between the S-strip and the T-strip. It has been demonstrated by simulation and experiment that the compact planar antenna can achieve a bandwidth of more than 50% for return loss $< {-}$10 dB with an almost unchanged radiation pattern.
 
Capacitive sensors have been designed for use as user proximity sensors in mobile-phone antennas. Sensor-induced losses were measured in 900- and 1800-MHz capacitive coupling element antennas and a 1900-MHz planar inverted-F antenna (PIFA) and compared to the RF losses caused by an impedance-matching sensor. The lengths of the capacitance sensors varied from 1 to 43 mm, which induced antenna losses from 0.05 to 1.35 dB at 1 GHz. A pair of pad sensors induced 0.1-0.25-dB losses at 0.8-1.85 GHz. The loss of capacitive sensors in sizes below 5 mm<sup>2</sup> was comparable to that of antenna-matching sensors. Total RF insertion losses due to the compared proximity sensors and loss compensation systems were 0.4 and 0.55 dB, respectively, across the 900- and 1900-MHz frequency bands.
 
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.
 
We present here the results of measurements of rain-induced attenuation in the vertically polarized signal propagating at 19.4 GHz over a 2.29-km line-of-sight (LOS) link during some rain events, which occurred in the monsoon season of the year 2001 at Amritsar, India. The total attenuation over the link path measured experimentally has been compared with that obtained using Marshal-Palmer (MP) drop size distribution and Medhurst's theoretical values and International Radio Consultative Committee (CCIR) model. Our measured results are in excellent agreement with the MP prediction.
 
A compact dual-band planar antenna developed for DCS-1900/PCS/PHS, WCDMA/IMT-2000, and WLAN applications is presented. The proposed antenna consists of a flared monopole with an additional sleeve for dual-band applications. The overall size of the antenna is 40 mm times 25 mm times 1.6 mm including the Finite Ground CPW feeding mechanism. The antenna operates in two frequency bands from 1.83 to 2.34 GHz and 3.23 to 5.76 GHz covering DCS-1900/PCS/PHS, WCDMA/IMT-2000, and WLAN bands. Simulation results along with measurements of the prototyped antenna are presented and discussed.
 
A new linearly polarized eleven feed for operation between 1 and 10 GHz is presented. This frequency band is higher than the realized before, and the input reflection coefficient is better than ${-}8$ dB over the frequency range, which also is an improvement over previous models. The log-periodic dipole petals have been designed by using a simple one-by-one parameter optimization scheme with a simulation tool based on moment method. The final analysis has been improved by applying an finite-difference time-domain (FDTD)-based solver for the central part of the feed and then a circuit network program to combine the results of the center part with the result of the dipole panels. The antenna has been manufactured by printed circuit board (PCB) technology on a metalized Kevlar sheet in order to obtain better tolerances and smaller dimensions than in previous models. Measurements show agreement with the analysis.
 
A stability and numerical dispersion analysis for the one-dimensional alternating-direction implicit finite-difference time-domain method in lossy media is presented. To conduct a general study, the conduction term is approximated by a weighted average in time. The stability analysis is based on the von Neumann method and the numerical dispersion relation is derived in a closed-form. The analytical results are validated by numerical simulations, showing that errors for both the attenuation and phase constants can be very high if the weighted-average coefficients are not properly selected.
 
To accurately determine radio coverage, it is necessary to have an omnidirectional antenna pattern. Our measurement results show that this is not the case for an antenna mounted on a vehicle. We present two improved antenna solutions with an additional ground plane in the form of a disk and a corrugated cone. The peak-to-peak variation in the horizontal plane is then reduced from 5 to 2.5 dB and 1.7 dB, respectively. Although our results are limited to a medium-size vehicle and frequencies around 2 GHz, we believe that they are of interest for all measurements where high accuracy is desired.
 
Propagation characteristics in the 2.3-GHz band were studied in a dense urban environment. Experiments at this frequency using WiMAX transmissions were conducted in dense urban western India. Coverage predictions using various models and their comparison with measured data were carried out. Path-loss exponents, mean errors, and standard deviations of all the prediction methods were deduced, and suitable models for the path-loss prediction identified.
 
A novel compact wideband planar diversity antenna for mobile terminals is proposed. It has a -10 dB impedance bandwidth from 1.904-2.504 GHz including UMTS (1.920-2.170 GHz) and 2.4 GHz WLAN (2.400-2.484 GHz) bands. The mutual coupling of the diversity antenna is below -15 dB in the whole band (about -20 dB in most of the band). The diversity performance is also evaluated by calculating the correlation coefficient and the diversity gain. The user's hand effects on both the bandwidth and the mutual coupling have been analyzed by simulation with a simple hand model and measurement.
 
A novel reconfigurable slot antenna with three switchable frequencies is presented. The uniqueness of this design is that it allows various groups of its frequency resonances to be selected electronically using three switches. Therefore, seven different states are achieved, and so three, two, or one resonances are possible at the same time. By using three sickle-shaped slots in the ground plane and three pairs of p-i-n diodes that are soldered between three metal strips inside the slots and the ground plane, the antenna can support 2.4-GHz Bluetooth and/or 3.5-GHz WiMAX and/or 5.8-GHz WLAN systems. The advantage of this design is that it overcomes the problem of conventional reconfigurable antennas of serving one frequency band at a time. The antenna design, simulation, and measurement results are presented. The antenna shows similar radiation patterns with low cross-polarization levels at all its operating frequencies. The simulated and measured results are in good agreement.
 
In this letter, we proposed a novel chip-type ceramic dielectric antenna using the advanced meander line technique for 2.4/5.8-GHz dual ISM-band applications. The proposed antenna is composed of small ceramic dielectric (8 mm × 4 mm × 1.5 mm, alumina) and substrate (thickness of 1.52 mm, TMM-4). In order to minimize the antenna's available area on the substrate and to reduce the coupling effect with the ground plane, the antenna is located at the corner of substrate. The measured bandwidth and maximum radiation gain are 2.35-2.57 GHz(VSWR < 2, 2.07 [email protected] /* */ GHz) and 5.29-6.01 GHz(1.17 [email protected] /* */ GHz), respectively. From these results, it is demonstrated that our proposed antenna can be applicable to the dual-ISM band applications.
 
This letter presents a new printed slot loop antenna with a pair of tunable strips for wireless communication systems in 2.4-GHz (2.40-2.48 GHz) and 5-GHz (5.15-5.95 GHz) bands. If a pair of the strips is inset at the center of the slot loop antenna, then the resulting impedance bandwidth for the two main operating bands can reach about 100 MHz for the 2.4-GHz band, and 1550 MHz for the 5-GHz band, thus covering the required operations of a wireless local area network (WLAN). Experimental results confirm in detail several properties of the proposed antenna design, such as the impedance bandwidth, radiation pattern and measured gain.
 
A compact wideband modified planar inverted F antenna (PIFA) with two shorting strips for 2.4/5.2-GHz wireless local area network (WLAN) operations is presented. As a starting point, two-branch strip lines derived from the dipole antenna structure are used to achieve the desired resonant frequency. One of them is connected to two shorting strips with the different length and width, and those strips generate additional resonant modes. A wideband characteristic can be optimized by tuning the parts of two shorted patches and size of each strip line segment. The proposed antenna has a low profile and can easily be fed by a 50-Omega coaxial cable. In addition to covering 2.4- and 5.2-GHz band, a wide impedance bandwidth from 2.94 to 5.82 GHz (|S11|<-10 dB, about 69% centered at 4.14 GHz) is obtained. The measured maximum radiation gains at the frequencies of 2.44, 4.14, and 5.2 GHz are about 1.6, 3.8, and 2.5 dBi, respectively. The proposed antenna is suitable for the multiband operations, covering 2.4/5.2-GHz WLAN operation
 
A small 2.4-GHz/ultrawideband (UWB) antenna suitable for integration with the printed circuit board (PCB) of a wireless universal serial bus (WUSB) dongle is presented. The antenna mainly comprises a folded radiator with bended stubs mounted on the top of a small metal box that plays the role of a ground plane. Inside the metal box, the PCB is integrated, and the potential interactive interference between the PCB and the antenna itself can be prevented. Details of this antenna are described. The overall size of this design is 7 ?? 13 ?? 42.6 mm<sup>3</sup>, approximately equal to that of a normal USB flash disk. Experimental results of the constructed prototype show that the impedance bandwidth of the proposed antenna is about 8.76 GHz, from 2.24 to more than 11 GHz, covering the whole operating band of WLAN and UWB with good radiation characteristics. Moreover, the influence of the laptop as well as the wood or metal desk on the performance of the antenna is also studied.
 
In this study, we present a simple recipe for a skin mimicking material intended for in vitro testing of implantable antennas operating at Industrial, Scientific, and Medical (ISM) (2.4 GHz2.48 GHz) band. The material is composed of de-ionized water, Triton X-100, and Diethylene Glycol Butyl Ether (DGBE). The relative dielectric constant and conductivity of the proposed material are within 0.5% and 3.4% of the properties of the reference human skin from the literature in the entire ISM band. In order to test the transmission characteristics of the material, in vitro measurements of a dual-band antenna are performed.
 
Time-based localization by terrestrial cellular mobile radio as a complement to global navigation satellite systems has gained significant attention. However, under non-line-of-sight (NLoS) conditions, the performance of positioning receivers is degraded by an additional bias. This NLoS bias is defined as the additional propagation distance between the first detectable path and the geometric line of sight. In this letter, we address the NLoS bias as obtained by a channel measurement campaign at different carrier frequencies in an outdoor-to-indoor scenario. It turns out that the obtained NLoS bias is mainly uncorrelated between different base-station links. Furthermore, the NLoS bias is found to be strongly dependent on the geometry of the scenario. In so-called ”mild” scenarios, we found out that the NLoS bias is small and almost frequency-independent. In scenarios we call ”severe,” the NLoS bias is large and frequency-dependent. Additionally, we present the joint probability distributions of the NLoS bias, the normalized power of the first detectable path, and its angle of arrival for carrier frequencies of 2.45 and 5.2 GHz. Moreover, the decorrelation distance of the NLoS bias for a moving receiver is evaluated.
 
The fading of an on-body transmission channel at 2.45 GHz is investigated. For the first time a large amount of data has been gathered in practical environments, for realistic activities, and has been subject to statistical analysis. It is clear that significant variations of the path gain and fading can occur due to the movements of body. Extensive statistical analysis has shown that fading in on-body channels is a non stationary process. This letter presents results of a number of significant statistical parameters, including level crossing rate and average fade duration.
 
CAD imagery of the 2.45-GHz electrically small slot antenna with a metal thickness of 2000 A (top), equivalent lumped circuit model (bottom).
Probe station based on-wafer measurements. (a) S of the 2000 A AUT. (b) S of the 5000 A AUT. (c) Copolarized radiation patterns of the 2000 A AUT. (d) Copolarized radiation patterns of the 5000 A AUT.  
A 2.45-GHz electrically small slot antenna (lambda<sub>0</sub>/35timeslambda<sub>0</sub>/35, 3.5times3.5 mm<sup>2</sup>) is disclosed. Miniaturization is achieved through symmetric inductive loading of an electrically small slot section. It is fabricated on a low-loss fused silica wafer through a back-etch of a 5000-Aring golden metal film, which is 31.5% of the skin depth at 2.45 GHz. The measured bandwidth is 106 MHz and the measured gain is -15 dBi. The theoretical Wheeler-Chu-McLean limit for the gain of a lambda<sub>0</sub>/35timeslambda<sub>0</sub>/35 electrically small antenna with a similar Q factor is -9.6 dBi.
 
A 2.45-GHz rectifying antenna (rectenna) using a compact dual circularly polarized (DCP) patch antenna with an RF-dc power conversion part is presented. The DCP antenna is coupled to a microstrip line by an aperture in the ground plane and includes a bandpass filter for harmonic rejections. It exhibits a measured bandwidth of 2100 MHz (10 dB return loss) and a 705-MHz CP bandwidth (3 dB axial ratio). The maximum efficiency and dc voltage are respectively equal to 63% and 2.82 V over a resistive load of 1600 Ω for a power density of 0.525 mW/cm<sup>2</sup>.
 
Variation of channel parameters with respect to distance between the MS and BS in the LOS street canyon. (a) 2.45 and (b) 5.25 GHz.
The correlation between channel parameters root mean square delay spread (DS), shadow fading, number of clusters, and Rician factors (K-factors or K) is investigated based on wide-band channel measurements. The channel measurements were performed at 2.45 and 5.25 GHz in long line-of-sight (LOS) and non-LOS (NLOS) street canyons. The relation of the channel parameters to distance is illustrated. Very high correlation between channel parameters was found in the LOS street canyon, while much lower correlation was found in the NLOS street canyon. The linear relationship between the DS and the other channel parameters is derived in the LOS case, thus allowing the use of one channel parameter (e.g., the DS) to predict the others.
 
As wearable electronic devices become increasingly popular, there is a growing interest in the design of body area networks (BAN). The propagation characteristics of such channels are of interest to assist in proper design of BAN systems. It has been shown that body movement is a primary factor in channel fading and hence channel modelling must include the effect of movement. In this letter, results are presented for a walking phantom created using animation software. Simulations of a walking avatar for three different channels at a frequency of 2.45 GHz are shown and compared to measurements made on a human body in an anechoic chamber. It is shown that such a phantom can give good prediction of mean and standard deviation of the propagation channel of a walking subject.
 
The development of electrically small antennas plays an important role in the rapidly growing mobile communication market. This work presents a novel design technique for a triple-band small internal antenna which covers the GSM/DCS/IMT-2000 bands. The proposed antenna consists of double shorting posts, feed post, and dual-crossed C-slot patch radiators. A high-frequency structure simulator simulation is employed for optimizing the design parameters, and the simulation results agree with the measured data. The IE3D simulation is also used to obtain the current distribution at the resonant frequencies. The maximum gains at the frequencies 950 and 1860 MHz are measured to be about 1.58 and 1.3 dBi, respectively. These positive antenna gains and triple-bands of the proposed antenna are very attractive features for GSM/DCS/IMT-2000 bands handset applications.
 
A triple-band stubby antenna, fed by a coaxial probe, and a tuning technique are proposed for operating at PCS, IMT-2000, and Bluetooth bands. The proposed antenna, shielded by the antenna cover, consists of two radiating elements. The impedance matching and bandwidth for the proposed antenna are mainly affected by the length of the ground patch at the bottom of a small substrate. By properly choosing the size of the ground patch, the resonant frequencies can be easily adjusted, and a wide impedance bandwidth of 59.7% (|S/sub 11/| < -10 dB), which covers the Korean PCS (1750-1870 MHz), IMT-2000 (1920-2170 MHz), and Bluetooth (2402-2483.5 MHz) can be achieved. An omnidirectional radiation pattern is obtained, and a peak antenna gain of about 3 dBi or more is measured. The electrical characteristics of the proposed antenna make it attractive for use in mobile handset applications.
 
An internal triple-band antenna fed by a microstrip line is proposed for operation in the PCS, IMT-2000, and Bluetooth bands. By using two branches of meander line, the desired resonant frequencies can be achieved. A broadband characteristic for each band is optimized by tuning the parts of the radiating patch and the size of each strip line segment. The proposed antenna and substrate are small enough to be built in a practical mobile handset. Details of the proposed technique and experimental results are presented and discussed.
 
A novel 24-GHz mixed low-temperature co-fired ceramic (LTCC) tape based system-on-package (SoP) is presented, which incorporates a fractal antenna array with an integrated grooved Fresnel lens. The four-element fractal array employs a relatively low dielectric constant substrate (CT707, ε<sub>r</sub> = 6.4), whereas the lens has been realized on a high-dielectric-constant superstrate (CT765, ε<sub>r</sub> = 68.7 ). The two (substrate and superstrate) are integrated through four corner posts to realize the required air gap (focal distance). The fractal array alone provides a measured gain of 8.9 dBi. Simulations predict that integration of this array with the lens increases the gain by 6 dB. Measurements reveal that the design is susceptible to LTCC fabrication tolerances. In addition to high gain, the SoP provides a bandwidth of 8%. The high performance and compact size (24 × 24 × 4.8 mm<sup>3</sup> ) of the design makes it highly suitable for emerging wireless applications such as automotive radar front end.
 
Simulation and measurement results are presented for two designs of high-gain linearly polarized microstrip patch antennas, operating at 24 GHz on two high-permittivity substrates: Taconic CER-10 and high-resistivity silicon. One of these designs is new. In both designs, a multilayer construction is used and the patch is coupled to a coplanar waveguide (CPW) feed through a slot. The problem of surface waves is avoided by introducing an air gap between the slot and the patch with the help of micromachining or spacer layer; in one of the designs, the superstrate effect is also employed. For the new design, the measured gain value in the forward direction exceeds 6 dBi.
 
Attenuation difference between horizontal and vertical polarization.
Phase difference between horizontal and vertical polarization.
This letter presents the results of a study on rain attenuation of an outdoor radio propagation channel at 26 GHz, which is widely used for local multipoint distribution service deployment. The difference in attenuation between vertical and horizontal polarization is compared for wide-band signals using a line-of-sight radio link with alternate polarizations by transmitting signals with horizontal and vertical polarizations. It is shown that attenuation difference due to depolarization becomes much more significant when the rainfall exceeds 70 mm/h.
 
The 28-GHz Tx-Rx terrestrial system diagram and specifications.
Comparison of rain attenuation complementary cumulative distribution functions (ccdfs) obtained from measurement, SST simulation, and ITU-R P.530-12 model.
Comparison of rain attenuation ccdfs obtained from measurement, the SST simulation using the ITU-R power-law model, and computer generation according to the ARIMA model: (a) (0, 1, 1), (b) (3, 0, 0), (c) (4, 1, 0), and (d) (5, 1, 0).
Comparison of cdfs of attenuation slope obtained from measurement and computer generation according to the ARIMA model: (a) (0, 1, 1), (b) (3, 0, 0), (c) (4, 1, 0), and (d) (5, 1, 0).
This letter reports the result of modeling of the tropical rain attenuation at 28 GHz adopting the auto-regressive integrated moving average (ARIMA) model. The result obtained is useful for the evaluation of transmission system design in radio communications at millimeter-wave frequencies in tropical areas. In this research, radio power measurement on a 56.4-m link at 28 GHz was carried out in Surabaya, Indonesia, with a data acquisition system that recorded a sample once every second. Approximation of the data by ARIMA(p,d,q) models for every rain event was carried out in order to obtain a valid time series model. In the validation, comparisons were made of the distributions of attenuation from the models against those from direct measurement of attenuation and from estimation based on the synthetic storm method. Comparisons were also made of the attenuation slope distributions against that from the measurement. Each of rain attenuation time series obtained from events in February 2009 was found to be well approached by the ARIMA model with various sets of parameters (p,d,q). The best model was found to be ARIMA (0, 1, 1) , as indicated by the Akaike Information Criteria (AIC) and Schwarz Bayesian Criteria (SBC) test results. A procedure for generating rain events based on the model is presented.
 
This work presents shape reconstruction results using TE experimental scattering data of a perfect electric conducting (PEC) cylinder. The level set method combined with the method of moments is used for the reconstruction. The experimental data are collected using two ultrawideband strip-fed dielectric resonator antennas rotating around the target. The removal of the drift noise is achieved through spatial low-pass filtering, which is a key element to improve the reconstruction.
 
Relative phase and attenuation errors as a function of the propagation angle . Results obtained for f = 10 GHz and N = N = 20.  
Relative phase and attenuation errors as a function of the frequency for several values of the propagation angle . Results obtained for N = 40 and N = 20.  
Relative phase and attenuation errors as a function of the frequency for several values of the stability factor s. Results obtained for N = 40 and = 0 .
Relative phase and attenuation errors as a function of the stability factor for several values of the spatial resolution N . Results obtained for f = 1 MHz and = 0 .  
The alternating-direction implicit finite-difference time-domain (ADI-FDTD) method is extended for modeling the propagation of transverse-electric waves in high-order, frequency-dependent media. Ohm's law is considered as the constitutive relation with the complex conductivity assumed to be a high-order rational function of the frequency. Contrary to previously reported approaches, the integration of the constitutive relation over a full time-step is not split into several substeps, which improves the computational efficiency of the resulting algorithm. In addition, the numerical dispersion relation is derived in a closed form. To illustrate the validity and accuracy of the formulation, we consider a muscle model that consists of a static conductivity and three Debye poles.
 
We present a method to incorporate the effect of the three-dimensional (3D) antenna radiation patterns into a two-dimensional (2D) multiple-inputmultiple-output (MIMO) channel model. The proposed method is a low-complexity technique that increases the accuracy of existing 2D spatial channel model (SCM) proposed by 3GPP for performance analysis of long-term evolution (LTE) MIMO. Using a realistic 3D antenna field pattern and the 2D 3GPP SCM, the 3D-to-2D transform algorithm (3D-2D-TF) gives a 5% outage capacity within 0.5 b/s/Hz when compared to a higher complexity averaging approach using 18-cut planes (18-CP) of the 3D radiation pattern. This is achieved with 6% of the run-time complexity. By not including the elevation information, the original SCM 2D model gives an outage capacity prediction error of up to 2.4 b/s/Hz as compared to the 18-CP averaging approach. The 3D-2D-TF is therefore a promising low-complexity candidate that increases the accuracy of 2D channel models for MIMO 4G performance evaluations.
 
This letter shows a fast technique to compute the physical optics (PO) integral of a rational Bzier curve. The algorithm is based on the path deformation technique. Good numerical results in terms of CPU time and accuracy are obtained.
 
The design and performance of a novel 4-arm equiangular slot spiral antenna operating in the 2nd mode are discussed in this letter. A straightforward feeding method consisting of a single vertical coaxial probe and no underlying mode forming network is proposed. Along with inherent simplicity, this feed enables design flexibility with respect to the slot-to-metal ratio, growth rate, and other spiral parameters. Numerical tools including an in-house finite element-boundary integral (FE-BI) code and Ansoft HFSS are used in designing the antenna. Good performance over an octave bandwidth is achieved, with axial ratio and WoW less than 3 dB, nominal gain of 3 dBic, and VSWR less than 1.6. Performance is verified with measurements. A method for increasing the bandwidth up to 3 : 1, which is the theoretical value determined by the excitation of the first higher order mode, is demonstrated computationally.
 
In this letter, the design of a miniaturized monopolar prefractal antenna for the 3.4-3.6 GHz WiMax band is presented. The geometrical configuration of the monopolar antenna, printed on a planar dielectric substrate, has been synthesized by means of a particle swarm optimizer in order to minimize the linear dimensions of the device and to obtain voltage standing wave ratio (VSWR) values within specifications. The results of numerical simulations are shown and compared, in terms of VSWR, with the experimental measurements
 
Measured total radiated power relative to the reference horn for three different amounts of quartz in the capacitive gap of the CLL element.  
Final design of the rounded-corner, 3D magnetic EZ antenna.  
The fabricated 3D magnetic EZ antenna with its small ground plane. As constructed, the extruded CLL element has all rounded corners.  
Comparison of the measured relative total radiated power of the 3D magnetic EZ antenna, the bare loop antenna, and two external matching network augmented semiloop antennas.  
Comparison of the predicted and measured (new NIST reverberation chamber) relative total radiated power of the EZ antenna with the small ground plane and with the large ground plane, the bare semiloop antenna, and the stubtuner matched semiloop antenna.
Several variations of a 300-MHz version of the electrically small coax-fed three-dimensional (3D) magnetic EZ antenna were designed and tested. The final version of this low-profile antenna had an electrical size that was ka ~ 0.437 at 300.96 MHz. Nearly complete matching to the 50-Omega source and high overall efficiency (nearly 100%) were achieved. The measured fractional bandwidth was approximately 1.66%. The numerically predicted and the measured results were in good agreement. Comparisons to similar-sized loop antennas that were matched to the source with both custom-made and commercially available, general purpose external matching networks confirm the performance enhancements achieved with this metamaterial-inspired, near-field resonant parasitic antenna.
 
A micromachined 300-GHz slotted waveguide antenna is demonstrated using a simple fabrication technique based on metal-coated SU-8 thick resist. The antenna is designed to be built from a four-layer structure of equal layer thickness. It is fully characterized, and the measured radiation patterns show excellent agreement with the simulation. An H-plane matched right-angle bend is integrated in the antenna in order to achieve reliable and accurate connection with standard waveguide flange. The micromachined antenna is directional and low-profile and may find applications in low-cost sensors and radars.
 
A compact 100-GHz corrugated platelet antenna array has been developed based on a corrugated feed design for the background emission anisotropy scanning telescope (BEAST) optics. The antennas in the array result in a gain of 20 dB, and a bandwidth across the full range of W-band 75-110 GHz. The side lobes are down by about -25 dB, a requirement comparable to feed horns used for observation of the cosmic microwave background. The design and fabrication presented in this letter is straightforward and inexpensive. A feature is that because the plates are not permanently bonded, the horn can be disassembled and modified to change its properties such as addition of flare plates or modified rib structures.
 
In this letter, we present a reconfigurable reflectarray cell operating at 12 GHz and fabricated in a monolithic MEMS process. A 5-bit digital control allows reconfiguration of the reflection phase over the full 360deg range, while alleviating the impact of MEMS and bias voltage tolerances on the device performances. The designed reflectarray cell exhibits low frequency phase error (large bandwidth) and excellent measured reflection loss (-0.3 dB) with regard to state-of-the-art. Close agreement between measurements and full-wave simulations is observed.
 
(a) A cross section of the relative permittivity of the original target. (b) The reconstruction of the relative permittivity with the 3D algorithm and (c) with the 2D version. (d) A cross-sectional slice of the original conductivity and (e) a corresponding reconstruction with the 3D algorithm and (f) the 2D algorithm.  
(a) Normalized objective functional values for the 3D/2D reconstructions versus iteration number. (b) Normalized relative squared error for the 3D/2D reconstructions of the permittivity/conductivity.  
This letter describes an efficient three-dimensional (3D) image reconstruction algorithm for microwave tomography. Using the thin-wire approximation with resistive voltage sources (RVS), a realistic FDTD model is created for the transmitting and receiving antennas. To verify the algorithm, image reconstruction is made from experimental data using a cylindrical test object made of sunflower oil. In the results, successful image reconstruction has been shown, indicating that the FDTD model is applicable. For comparison, a reconstruction with a two-dimensional (2D) version of the algorithm was made. A significant increase in accuracy of the reconstructed object was seen for the 3D version.
 
Top-cited authors
Manos Tentzeris
  • Georgia Institute of Technology
Tayeb A. Denidni
  • Institut National de la Recherche Scientifique
G.V. Eleftheriades
  • University of Toronto
Y.-Z. Yin
  • Xidian University
Bing-Zhong Wang
  • University of Electronic Science and Technology of China