In this communication, a new compact UWB monopole antenna with dual band rejection is presented. The antenna is designed using FR4 substrate with dielectric constant 4.4, loss tangent 0.02 and a height of 1.59 mm. Initially the UWB antenna is designed to obtain a 153% fractional bandwidth from 2.4 GHz-21.7 GHz. The ground plane beneath the patch is etched out and a rectangular slot is introduced to obtain a broadband matching over the operating frequency range. Later the antenna is modified to get a frequency notch in the IEEE802.11a and HIPERLAN/2 WLAN operating band (5.15 GHz-5.825 GHz) to avoid potential interference. A U shaped slot is optimally introduced in the patch to get the desired performance. Finally an L shaped slot is cut from the radiating patch to filter the frequency band 3.3 GHz-3.6 GHz, which is WiMAX service band. The antenna parameters are optimized and the effects of parametric variation on antennas performance are studied and the summary is presented. The antenna is fabricated and measured results are presented. The measured results are in well agreement with the simulated results.
The subject of this article is to optimize the design of synchronous reluctance machines with massive rotor and multi-flux barrier rotor. The optimization procedure, which aims to improve simultaneously the machines' torque and the power factor, uses the cyclic coordinate method coupled with the magnetostatic finite-element (FE) field solutions. The optimization results regarding these two types of machines, which provide the optimized rotor geometrical dimensions and the influence of the current angle, are discussed.
Electromagnetic radiation by dipole antenna loaded with general bi-isotropic objects is investigated using time-domain integral equations. By introducing pairs of equivalent electric and magnetic sources, electromagnetic fields inside a homogeneous bi-isotropic region can be represented by these sources over its boundary. A series of coupled surface integral equations are obtained after imposing boundary conditions. These equations are solved numerically by the Galerkin's method that involves separate spatial and temporal testing procedures. The scaled Laguerre functions are used as the temporal basis and testing functions. The use of the Laguerre functions completely removes the time variable from computation, and the results are stable even at late times. Numerical results are presented and compared with analytical results, and similarities and differences are observed.
This research proposes a new blind tracking algorithm for smart antenna arrays by switching the main beam iteratively using the cost calculated from the received and predicted symbol. This algorithm will be called Cost Steering Algorithm Using Demodulation-Remodulation Technique COSTAUS/DRT. It is completely independent of the Least Mean Squares (LMS) or any derived version from it, and it does not need to investigate the cyclostationary properties of the incoming signal. A complete derivation and analytical model with simulation using Simulink is given in this research. The algorithm was tested under three different target motions which are a triangular motion (linear), sinusoidal motion (circular) and saw tooth motion which is an adverse case when the linear motion changes its path suddenly. The transmitter uses 16-level PSK signal with no Forward Error Correction code (FEC) in order to test the algorithm under the worst situation. The algorithm is tested under different noise power levels. The antenna array is a linear array with 16-elements.
Many algorithms exploiting the signal cyclostationarity have been shown to be effective in performing antenna array beamforming. However, these algorithms can not provide a unique weight vector for simultaneously extracting multiple signals of interest (SOIs) with distinct cycle frequencies (DCFs). They also suffer from severe performance degradation in the presence of a cycle frequency error (CFE). To simultaneously accommodate multiple SOIs with DCFs and alleviate the effects of cycle leakage due to finite data samples, we propose a cyclic sample matrix inversion (C-SMI) beamformer. To make the C-SMI beamformer robust against CFE, we present a novel objective function which is optimized by using a steepest-descent based algorithm to find the appropriate estimates of the true DCFs. The simulation results show the effectiveness of the robust C-SMI beamformer.
The beamspace domain of parasitic antenna arrays is explored in this paper, providing the aerial degrees of freedom available for use in Multiple Input-Multiple Output (MIMO) systems. The beamspace representation allows for the design of an alternative MIMO architecture based on single radio-frequency (RF) chains, and facilitates the inclusion of MIMO transceivers in devices with strict size limitations. A three dimensional orthogonal expansion is performed on the beamspace domain providing the basis patterns used for mapping of the transmitted symbols and for sampling at the receiver. The expansion is based on the Gram-Schmidt orthonormalization procedure and can be generalized for any parasitic antenna array. The multiplexing capability of ESPAR antennas is presented as a means for supporting future performance demanding communication systems. Performance evaluation results are illustrated in detail.
Rain cell size is an input requirement for rain-induced attenuation studies. It is useful in estimating the extent of a given radio link path that will traverse the rain medium in a given rain event. The ``Synthetic Storm'' approach, which requires 1-minute integration time data, is used to derive the proposed rain cell sizes for various climatic zones within South Africa. The conversion of the readily available 1-hour integration time rain rate data to the desired 1-minute rain rate is carried out first for some locations and then validated by the existing measurement data and proposed global conversion factors. By the use of rain-induced attenuation prediction equation for terrestrial links that requires rain cell size as input, contour plots of specific attenuation for two high bandwidth frequencies used in terrestrial link implementations is presented. Site diversity separation distance map is proposed as well from the link budget analysis for each location to achieve an all time link availability of 99.99% of time.
The literature describing scattering matrices for semi-analytical methods almost exclusively contains inefficient formulations and formulations that deviate from long-standing convention in terms of how the scattering parameters are defined. This paper presents a novel and highly improved formulation of scattering matrices that is consistent with convention, more efficient to implement, and more versatile than what has been otherwise presented in the literature. Semi-analytical methods represent a device as a stack of layers that are uniform in the longitudinal direction. Scattering matrices are calculated for each layer and are combined into a single overall scattering matrix that describes propagation through the entire device. Free space gaps with zero thickness are inserted between the layers and the scattering matrices are made to relate fields which exist outside of the layers, but directly on their boundaries. This framework produces symmetric scattering matrices so only two parameters need to be calculated and stored instead of four. It also enables the scattering matrices to be arbitrarily interchanged and reused to describe longitudinally periodic devices more efficiently. Numerical results are presented that show speed and efficiency can be increased by more than an order of magnitude using the improved formulation.
The main goal of this paper is to present a design procedure for a flexible compact universal UHF RFID tag antenna suitable for worldwide UHF RFID applications. Systematic design procedure is introduced through the derivation of dipole input impedance general relation using induced EMF method considering wire radius effect. T-matched chart is used to match the tag input impedance with the chip input impedance and finally develop a flow chart to summarize the design procedure. The proposed antenna compactness trend is achieved through applying meandering and Franklin shape to conventional printed dipole antenna. Flexibility trend is achieved through using liquid crystal polymer LCP material as antenna substrate. The proposed antenna covers the frequency band 865 MHz to 1078 MHz and occupies an area of 1306.6 mm2. The computed radar cross section RCS and conjugate match factor CMF insure that the proposed antenna structure is easily detectable and achieves acceptable matching level. Power reflection coefficient PRC is computed, measured and good agreement is obtained. Other antenna parameters such as radiation efficiency, gain and radiation pattern are also calculated. The proposed antenna is cheap, flexible and suitable for UHF RFID universal application.
A key structure in so-called metamaterial mediums is the elementary split-ring resonator. We consider in this paper the low-frequency electromagnetic scattering by a split-ring particle modelled as a perfectly conducting wire ring, furnished with a narrow gap, and derive analytical solutions for the electric and magnetic dipole moments for different kinds of incidence and polarisation in the quasi-static approximation. Through a vectorial homogenisation process, the expressions discovered for the dipole moments and the related polarisability dyadics are linked with the macroscopic constitutive equations for the medium. We further show that the condition for resonance of a medium consisting of simple split-rings cannot be achieved by means of the given quasi-static terms without violating the underlying assumptions of homogenisation. Nevertheless, the results are applicable for sparse medium of rings, and we derive numerical guidelines for the applicability with some examples of the effect of the considered split-ring medium on electromagnetic wave propagation.
The random wire bundle is an important factor resulting in the randomness of the interferences. This paper studies the effect of random wire positions due to the bundle rotation on the coupling with external fields and presents an efficient method to estimate the averages and standard deviations of the voltages and powers induced on the loads. Three configurations of a four-wire bundle under external fields are investigated by using the Baum-Liu-Tesche equation in the frequency domain and together with the inverse Fourier transform in the time domain, and the results show that the induced voltages and powers change as sine functions when the bundle rotates. The proposed method can estimate the averages and standard deviations of the induced voltages and powers quickly, just by three times repeated analysis, and the results agree well with those obtained statistically.
In this paper, we will study the influence of nonlinear waves (breaking waves) on the EM signature of a sea surface in bistatic case (forward propagation). Indeed, we will start the temporal numerical analysis of the scattering coefficient σHH of breaking waves in bi-static configurations. Then, we will show the first experimental validation of the numerical results using well calibrated measurements of precise breaking wave profiles. These experimental measurements have been carried out in X-band in our anechoic chamber(E³I²-EA3876-ENSTA BRETAGNE). In this work, we will consider the sea surface as a perfect conductor.
We have calculated the photonic bands of a dispersive and lossy periodic array of left-handed metamaterial layers in air. Depending on the behavior of the fields inside the metamaterial component, two categories of modes for oblique propagation are identified: the oscillatory and the tunneling modes. In order to characterize these two types of solutions, we calculate the complex photonic bands; a criterion of penetration-limit is introduced to quantify the absorption effects. Our results show that oscillatory TE and TM waves can be excited by light incident from air at low frequencies (within the metamaterial regime). In the region of high frequencies only TE tunneling modes are available. To complement the description of the absorption effects, we present transmission spectra and field profiles for TE waves in finite layered systems the two types of modes here studied.
This study reports on tunable planar metamaterial design that is capable to achieve dual-band negative index of refraction responses operating in microwave regime. Its distinctive characteristic is the usage of tuning open stub-loaded stepped-impedance resonators. Parameters retrieval algorithm, and full-wave simulation of prism-shaped structure were carried out to validate the negative refraction characteristics of metamaterial structure. The results predict its prospect as a very promising alternative to the conventional ones, which is compatibly applicable on various potential microwave devices especially when dual-band function is required. In addition to that, its design flexibility offers a various frequency bands at any possible choice, which is alterable together with any design parameters changes.
This paper derives some optimum transmit and receive antenna coefficients in wireless multipath channels based on the spherical vector wave multimode expansion of the multiple-input multiple-output (MIMO) channel matrix. The derived antenna coefficients satisfy the following specific optimization criteria: (i) maximum MIMO mean effective link gain (link MEG) based on the multimode channel realizations or (ii) maximum MIMO link MEG based on the multimode correlation matrix or (iii) correlation minimization by diagonalization of the MIMO full-correlation matrix. It is shown that the proposed approach leads to matrix equations belonging to the nearest Kronecker product (NKP) problem family, which in general have no trivial solution. However, we show that exact solutions are provided to the posed NKP problems under the assumption of the Kronecker model for the MIMO full-correlation matrix. The results are illustrated by numerical examples. The proposed approach is a complement to existing antenna pattern analysis methods.
In this paper, we propose a reference range correlation-based (RRcR) ranging technique suitable for low-power on-body wireless body sensor networks (WBSNs) via ultra wideband (UWB) radios. The proposed technique is based on the presence of reference nodes, and is assumed to have line-of-sight (LOS) links. We show that the performance of the proposed technique outperforms matched-filtering-based time-of-arrival (MF-TOA) estimators with no a priori and with perfect channel knowledge. We further show that increasing the number of reference node up to twenty provides significant enhancement in the performance traded for higher overall power consumption. Then, we study the effect of timing-misalignment on the Ziv-Zakai lower bound (ZZLB), and provide numerical results. The presented results are based on simulations in the IEEE 802.15.6a on-body-to-on-body channel (CM3) in the UWB band as well as actual measurements.
Design, simulation, and implementation of low profile microstrip spiral inductors for high power Industrial, Scientific and Medical (ISM) applications at the high frequency (HF-3-30 MHz) range are given for the first time. An accurate analytical model and algorithm have been developed to determine the simplified lumped element equivalent model parameters for spiral inductor and its physical dimensions. Five different spiral inductors are then simulated with a planar electromagnetic simulator using the physical dimensions obtained for the desired inductance values with the analytical method. The implementation method and substrate selection for spiral inductors at the HF range are given in detail for high power applications. The spiral inductors are then constructed on 100 mil Alumina substrate and measured with network analyzer. It is found that analytical, simulation and measurement results are in close agreement and the analytical method and algorithm that have been developed can be used to accurately determine the physical dimensions, and the resonant frequency of the spiral inductor for the desired inductance value.
This paper introduces a novel design of Butler matrix in substrate integrated waveguide (SIW) technology with wide frequency band characteristics. Butler matrices are particularly useful in advanced antenna design and characteristics such as wideband operation, power handling, manufacturing, integration, cost, etc. are typical issues to be addressed in many applications. The proposed planar 4×4 Butler matrix provides an interesting solution to most of these issues. Wideband operation is achieved thanks to improved cross-couplers. These components are also characterized by higher power handling when compared to $E$-plane couplers. The use of SIW technology enables to reduce insertion losses compared to other printed technologies, while maintaining most advantages of such technologies such as high integration, manufacturing simplicity, low weight, etc. The proposed design is fully described, from the elementary building blocks to the full assembly performances. The design is optimized for operation in Ku-band with a center frequency at 12.5 GHz. A prototype of the 4×4 Butler matrix is manufactured, and good performances are confirmed over 24% relative frequency bandwidth. Potential use of this sub-system in multibeam antenna design is also discussed.
Whole-body averaged specific absorption rate (WBA-SAR) is used as a metric for human protection from whole-body exposures. The frequency at which the WBA-SAR becomes maximal is called ``resonance frequency''. The present study proposes a scheme to estimate WBA-SAR at the resonance frequency based on an analogy between a human and a quarter-wavelength monopole antenna. Specifically, WBA-SAR can be estimated with the human body resistance once ankle current was obtained. Thus, it is essential to investigate the effective resistance for anatomically-based human models. Then, the effective resistances for different humans grounded on the perfect conductor are calculated to clarify the variability. The main factors for the variability were attributed to the body shape and model anatomy. In particular, WBA-SARs in human models grounded are found to be estimated from their BMI and respective measured ankle current in realistic environment, including a scenario of multiple wave exposure.
Microwave radar and microwave-induced thermoacoustic technique exploit the contrast in the permittivity and conductivity between malignant and healthy tissue. They have emerged as promising techniques for detecting breast cancers. This paper compares the imaging capability of these techniques in the presence of homogeneous and heterogeneous breast tissue. Relying on the data from the finite-difference time-domain simulations, the study shows that both techniques are capable of imaging homogeneous objects. In the presence of electromagnetic dispersion and heterogeneity, radar signals suffer from strong dispersion and multiple scattering, which decorrelate the signals with the scatterers. The microwave-induced thermoacoustic technique takes the advantage of breast being acoustically homogeneous and is capable of generating high-quality images.