Showing papers in "Piers Online in 2007"
TL;DR: In this article, the authors compared computed propagation charac- teristics of picosecond pulses on coplanar waveguides with experiments, and extracted transmission-line parameters, including resistance, inductance, conductance, and capacitance, from S-parameters up to subterahertz frequencies.
Abstract: Building on our previous work that compared computed propagation charac- teristics of picosecond pulses on coplanar waveguides (CPW's) with experiments, we extract transmission-line parameters, including resistance, inductance, conductance, and capacitance, from S-parameters up to subterahertz frequencies. The distributed-element circuit model is an- alyzed for applications in CPW-based circuit design. DOI: 10.2529/PIERS060912144405
38 citations
TL;DR: In this article, a review of various modeling strategies (classical, semiclassical and quantum mechanical based) for normal metals and discusses their limitations with frequency at room temperature is presented.
Abstract: Commercial electromagnetic modeling software employs overly-simplifled models for the terahertz simulation of metal structures. For the flrst time, this paper gives a unique review of various modeling strategies (classical, semiclassical and quantum mechanical based) for normal metals and discusses their limitations with frequency at room temperature. High frequency CAD software packages employ overly-simplifled models for the electromagnetic simulation of metal structures; using either classical skin-efiect or classical relaxation-efiect models. At room temperatures, these models are accurate beyond the upper edges of the microwave and sub-millimeter-wave parts of the frequency spectrum, respectively. However, semiclassical models are needed to extend modeling well into the terahertz region or at signiflcantly lower temperatures. Here, issues relating to the specular or difiuse nature of electron re∞ections at the air-metal interface become apparent at very low temperatures. Within the near-infrared, visible and ultra-violet parts of the frequency spectrum, Commer- cial CAD software packages again may employ overly-simplifled empirically-fltted relaxation-efiect models, which only work over relatively narrow spectral bandwidths. However, to be accurate, an analytical model must be adopted that employs a quantum mechanical treatment, as this takes into account both energy dispersion and electron wavefunctions. The author has investigated modeling strategies for normal metals. In one study, experimental measurements that suggested the possibility of anomalous room-temperature conduction losses were examined between DC and 12.5THz (1). It was found that the classical relaxation-efiect model was still valid up to these frequencies. In another study, an elaborate semiclassical model to describe anomalous excess conduction losses at room temperature was found to be completely erroneous (2). In order to create accurate analytical models, it is important to develop semiclassical modeling strategies (3) or develop quantum mechanical treatments. To this end, and for the flrst time, this paper will review various approaches to the modeling of normal metals at room temperature. More importantly, their limitations will be discussed in detail. It will be shown that a number of well-know approaches have severe limitations to general applications. 2. CLASSICAL TREATMENT Drude's model of intraband transitions describes an ideal system of free electrons having a spherical Fermi surface. The classical relaxation-efiect model takes into account electron-phonon collisions, represented by the following expression for surface impedance, ZSR, in terms of Drude's model for intrinsic bulk conductivity, aeR:
34 citations
TL;DR: In this article, a one-dimensional magnetic plasmon propagating in a linear chain of single split ring resonators is proposed, where the subwavelength size resonators interact mainly through exchange of conduction current.
Abstract: A one-dimensional magnetic plasmon propagating in a linear chain of single split ring resonators is proposed. The subwavelength size resonators interact mainly through exchange of conduction current, resulting in stronger coupling as compared to the corresponding magneto-inductive interaction. Finite-difference time-domain simulations in conjunction with a developed analytical theory show that efficient energy transfer with signal attenuation of less then 0.57 dB/microm and group velocity higher than 1/4c can be achieved. The proposed novel mechanism of energy transport in the nanoscale has potential applications in subwavelength transmission lines for a wide range of integrated optical devices.
32 citations
TL;DR: The study indicates that during laboratory exposure to 884MHz wireless signals, components of sleep, believed to be important for recovery from daily wear and tear, are adversely afiected.
Abstract: In the current study we assessed possible efiects of prolonged (3 hours) exposure to 884MHz GSM wireless communication signals on self-reported symptoms, cognitive function, and electroencephalographically (EEG) recorded sleep. The study group consisted of 36 women and 35 men. Twenty-two women and sixteen men reported symptoms they speciflcally related to mobile phone use (SG). The rest of the participants reported no mobile phone-related symptoms (NG). Potential participants volunteering for the study were evaluated by physicians, including some biochemical assessments, to rule out medical conditions that could interfere with study variables of interest. Once selected, participants spent three difierent sessions in the laboratory. The ha- bituation session was followed by two subsequent sessions. In these subsequent sessions, subjects were either exposed to sham exposure (sham) or 884MHz GSM wireless communication signals for 3 hours (an average of 1.4W/kg including periods of DTX and Non-DTX. Exposure directed to the left hemisphere). Data was collected before, during and following the exposure/sham ses- sions. Data collected included self-reported symptoms, including headache, cognitive function, mood, and electroencephalographic recordings. During actual exposure, as compared to sham exposure, sleep initiated one hour after exposure was afiected. There was a prolonged latency to reach the flrst cycle of deep sleep (stage 3). The amount of stage 4 sleep was also decreased in exposed subjects. NG subjects reported more headaches during exposures vs. sham exposure. Neither group (SG and NG) was able to detect the true exposure status more frequently than by chance alone. The study indicates that during laboratory exposure to 884MHz wireless signals, components of sleep, believed to be important for recovery from daily wear and tear, are adversely afiected. Moreover, participants that otherwise have no self-reported symptoms related to mobile phone use, appear to have more headaches during actual radiofrequency exposure as compared to sham exposure. However, subjects were not able to detect the true exposure status more often than would have been expected by statistical chance alone. Additional self-reported flndings, biochemical, performance and electrophysiological data are currently being analyzed. Possible health implications from the flndings will also be further explored.
32 citations
TL;DR: In this article, a CPW-fed slot antenna for wideband application was designed and simulated at frequency 2.4GHz and simulated with various width of slot antenna in both sides for input impedances matching and simulated by IE3D software package of Zeland.
Abstract: In this paper, a CPW-fed slot antenna for wideband application was designed and simulated. In order to examine the performances of this antenna, a prototype was designed at frequency 2.4GHz and simulated with various width of slot antenna in both sides for input impedances matching and simulated by IE3D software package of Zeland. The simulation result of bandwidth is 1.65GHz (2.1{3.75 GHz) which covers the standard frequency of IEEE 802.11 b/g (2.4{2.4835GHz) and Wimax (2.3{3.6GHz). With these performances, the proposed antenna can be used in wideband applications. DOI: 10.2529/PIERS061009084055
31 citations
TL;DR: The present work suggests an alternative approach for the prediction of path loss based on a NN-methodology which uses detailed description of the entire coverage area and uses the detailed environment proflle instead of the mean values of its structural parameters.
Abstract: This paper presents an alternative procedure for the prediction of propagation path loss in urban environments. It is based on Neural Network (NN) algorithms and uses the detailed environment proflle instead of the mean values of its structural parameters. The general performance of the NN shows its efiectiveness to yield results with satisfactory accuracy in short time. The received results are compared to the respective ones yielded by the Ray-Tracing model and exhibit satisfactory accuracy either for uniform or for non-uniform distribution of the manmade structured environment. 1. INTRODUCTION The prediction of electromagnetic wave propagation is of great importance in the design and plan- ning of a cellular-network both for mobile and flxed wireless-access systems. A prediction, based on theoretical models, is really valuable since it ofiers the capability of determining optimum base locations, in order to obtain suitable data rates, to estimate their coverage and evaluate the quality of the wireless network without the need of expensive and time consuming measurements. The theoretical models used for the estimation of the path-loss in various urban or suburban areas, even within buildings, are grouped in two categories (1): the empirical or statistical models (e.g., the COST-231-Walflsch-Ikegami model, the Hata model, etc.) and the site-speciflc or de- terministic ones (e.g., the Ray Tracing technique, the Image Method, the FDTD or the Moment Method, etc.). The models of the former category are easier to implement and require less compu- tational efiort but are less sensitive to the environment's physical and geometrical structure. Those of the latter category have a certain physical basis and are more accurate but at the cost of more computations and at the necessity of more detailed information about the coverage area. In the present work, a prediction model based on Neural Network (NN)-architectures is pro- posed. Published works have introduced the NN-methodologies as e-cient techniques for indoor and outdoor estimation of path-loss propagation. They have given solutions, using measured or theoretically produced data and feeding the input of the NN by the values of some of the geometry parameters of the environment, e.g., the mean height and mean dimensions of the buildings and the mean width of the roads (2{6). In the work at hand a Multiple Layer Perceptron (MLP) neural network was composed, and the collections of data, by which it was trained, include the detailed environment proflle. These data were produced using the Ray Tracing technique. Although the calculation for the training collections were made for simple and uniform distribution of the man- made structures, the appropriate grid modeling of the built-up area as well as the way by which the input data were presented to the NN made it e-cient to give, in the generalization phase, results for arbitrary environments, if their proflle is provided. 2. FORMULATION The propagation of radio waves in built-up areas is strongly in∞uenced by the nature of the en- vironment, in particular by the size and the density of the buildings. Urban areas are dominated by tall building blocks with high density and non uniform distribution. Empirical prediction mod- els use mean values for the parameters of the manmade terrain (meanly the mean values of the roads' widths or of the buildings' height). Many proposed NN models use also these parameters as information for the NN. The present work suggests an alternative approach for the prediction of path loss based on a NN-methodology which uses detailed description of the entire coverage area. The used Neural Network was composed via a Multiple Layer Perceptron (MLP) architecture. The input layer consists of a large number of nodes that accept analytical information for the structure of the built-up environment as well as for the coordinates of the position at which the path-loss is going to be estimated. A single node output layer gives the value of this path loss.
28 citations
TL;DR: The advantage of the new algorithm is that it takes pseudo-polar grid instead of Cartesian grid to perform the inverse Fourier transform, and it involves only 1-D interpolation, which leading to a more fast and accurate performance.
Abstract: In this study we analyzed the potential use of Pseudo-Polar FFT algorithm for image reconstruction of synthetic aperture radiometer, and developed an effective method to improve the image reconstruction accuracy and computational efficiency simultaneously. The advantage of the new algorithm is that it takes pseudo-polar grid instead of Cartesian grid to perform the inverse Fourier transform, and it involves only 1-D interpolation, which leading to a more fast.and accurate performance. As a critical stage, the interpolation algorithms that perform the changing from polar grid to pseudo-polar grid are present. At last, the superiority of the new algorithm is validated by numerical simulation. It is believed that the new approach may have wide-spread application in science and practice for synthetic aperture radiometer system.
27 citations
TL;DR: In this paper, the authors proposed a broadband composite right/left-handed (CRLH) transmission line by using complementary split rings resonators (CSRRs), which can be tailored in order to collapse the typical frequency gap present between the left and right-handed transmission bands.
Abstract: It was recently shown (1) that it is possible to achieve broadband composite right/left handed (CRLH) transmission lines by using complementary split rings resonators (CSRRs). Making use of balanced CRLH/CSRR-based metamaterial transmission lines, high pass fllters are designed. Good performance and small dimensions are achieved. The results open the door to new design possibilities in microwave circuitry by using this type of CRLH metamaterial transmission lines. DOI: 10.2529/PIERS060802072849 In microwave engineering, two main approaches exist to obtain left-handed transmission lines. One of them is the dual transmission line approach (2{4), which is based on loading transmission lines with series capacitances and shunt inductances. The other one is the resonant-type approach (5,6), which combines resonant sub-wavelength particles, such as split rings resonators (SRRs) or their dual counterparts (CSRRs), with shunt inductances or series capacitances etched on a host transmission line. Traditionally, it was supposed that the use of structures based on the resonant- type model was limited to narrow band applications. However, as occurs in the dual transmission line model, resonant-based left handed structures exhibit also a right-handed transmission band at higher frequencies due line parasitics (7). This allows us to obtain a composite right/left handed (CRLH) behaviour. The line can be tailored in order to collapse the typical frequency gap present between the left handed and right handed transmission bands. Namely, it is possible to make coin- cident the upper and the lower limits of the left and the right-handed bands, respectively (balance case), with the result of a continuous transition between both transmission bands. Although up to now it was not exploited, the balance case is also achievable by means of the resonant approach, what makes possible to obtain broad-band responses by using CRLH resonant-type transmission lines. The basic cell of the structure is represented in Fig. 1(a). It consists on a CSRR etched on the ground plane of a microstrip line, and located underneath a capacitive gap etched on the top layer (conductor strip). The CSRR provides the negative value of the dielectric permittivity in the vicinity of its resonance frequency, whereas the negative value of the magnetic permeability needed to obtain the left-handed behaviour is related to the efiect of the series capacitance due to the gap. This structure is modelled by the equivalent T-circuit model shown in Fig. 1(b) (8). The CSRR is modelled by the resonant tank LC-CC, which is electrically coupled to the line through the capacitance C. The capacitance Cg models the series gap, and L accounts for the line inductance. The right handed transmission band is due to line parasitics (L and C), but also to the CSRR (which behaves capacitively at high frequencies). The analysis of the equivalent circuit model reveals the behaviour of the structure. The phase shift per cell, `, (dispersion relation) and Bloch impedance, ZB, are given by:
26 citations
TL;DR: In this article, a subsurface holographic radar using a multi-frequency signal has been developed for inspecting dielectric construction materials on the U.S. Space Shuttle.
Abstract: A subsurface holographic radar using a multi-frequency signal has been developed for inspecting dielectric construction materials. The characteristic feature of this device is the ability to obtain one-sided radar soundings/images with a high sensitivity and high resolution (2cm) in the frequency band of 3.6{4.0GHz. One promising application of the device is non- destructive evaluation of the heat protection system and other materials on the U.S. Space Shuttle, and proposed crewed exploration vehicle (CEV). The advantages of this continuous- wave holographic radar over traditional impulse subsurface radars are discussed and illustrated by experimental results. The disastrous loss of the space shuttle Columbia, as well as even more recent dangerous incidents that were thankfully resolved, have aroused interest in possible new methods and devices for non- destructive testing and evaluation of the Space Shuttle Thermal Protection System, the external fuel tank insulating foam, and other materials and structures on the shuttle (see Figure 1), proposed CEV, and other space vehicles. Voids in or under the external tank insulating foam are considered potential sites for \cryopumping" where water seeps in and then evaporates explosively at altitude, pulling the foam from the tank (Figure 2). One of the possible means for non-destructive testing (NDT) and evaluation of structural ma- terials is subsurface radar. This method is based on the propensity of electromagnetic waves to be re∞ected at permittivity contrasts. Up to now, the use of radar for NDT has been hindered by
23 citations
TL;DR: In this paper, the photonic band gap (PBG) crystals have been used as a perfectly re-ecting substrate for many millimeter wave applications, and the fln line directional coupler with PBG substrate was analyzed using the TTL | Transverse Transmission Line | method.
Abstract: The photonic band gap (PBG) crystals have been used as a perfectly re∞ecting substrate for many millimeter wave applications. In his work the fln line directional coupler with PBG substrate was analyzed using the TTL | Transverse Transmission Line | method. Comparing with the other full wave methods the TTL is e-cient, making possible a signiflcant algebraic simpliflcation of the equations involved in the process. In order to analyze the structure the coupling were determined. Numerical results obtained for this flnline coupler are presented.
21 citations
TL;DR: In this article, the narrow slot loop antenna and linear slot antenna fed by microstrip line are designed for dual frequency at 2.44 GHz and 5.25 GHz on the standard of IEEE 802.11b/g (2.4{2.4835 GHz), IEEE 802j/a (5.15{5.35 GHz).
Abstract: | The narrow slot loop antenna and linear slot antenna fed by microstrip line are designed for dual frequency at 2.44 GHz and 5.25 GHz on the standard of IEEE 802.11b/g (2.4{2.4835 GHz), IEEE 802.11j/a (5.15{5.35 GHz), and IEEE 802.16d (5.7{5.9 GHz).
TL;DR: Two types of approximate maximum likelihood (ML) detection based on minimum mean squared error (MMSE), MMSE-CML (conditional ML) detection andMMSE- CLML (Conditional local ML) Detection, for MIMO communication system are derived.
Abstract: We derive two types of approximate maximum likelihood (ML) detection based on minimum mean squared error (MMSE), MMSE-CML (conditional ML) detection and MMSE- CLML (conditional local ML) detection, for MIMO communication system. A simple reliability judge rule to judge the estimate of the transmit symbols is also given. For the proposed MMSE- CML detection, received signals are flrst sent into MMSE detector to do linear equalization, then the estimate of transmit signals is judged in reliability judge module; If the estimate is judged to be reliable, we take the estimate as the flnal result; if not, the received signals are then sent into conditional ML (CML) detector to get the flnal result; Unlike conventional ML detector, the CML detector performs a tree search till the estimate satisfles the reliability judge rule or an entire tree search has been done. For the proposed MMSE-CLML detection, we use CLML search instead of CML search in MMSE-CML, which searches in the neighborhood of the output provided by the MMSE detector. Simulation results show that the MMSE-CML detector achieves near the same performance as optimal CML detector at reduced complexity, and MMSE-CLML detector achieves suboptimal performance at remarkably reduced complexity. DOI: 10.2529/PIERS070205100143
TL;DR: In this article, an e-shaped slot antenna for wireless communications is presented, which is designed for dual frequency band 2.4{2.52GHz and 4.32GHz.
Abstract: This paper present an e-shaped slot antenna for wireless communications. The antenna is designed for dual frequency band 2.4{2.52GHz and 4.82{6.32GHz, which support WLAN communications coverage IEEE 802.11b/g (2.4{2.4835GHz), IEEE 802.11j (4.90{5.091), IEEE 802.11a (5.15{5.35GHz), and IEEE 802.16d (5.7{5.9GHz). The bandwidth at low reso- nant frequency and high resonant frequency are about 0.12GHz and 1.5GHz, respectively. The simulation results of e-shaped slot antenna are analyzed by using Method of Moment (MoM) from IE3D Software. DOI: 10.2529/PIERS061007105447
TL;DR: In this article, a rectangular slot antenna which comprises of two conductor strips located in a slot cut in the ground plane was investigated for dual frequency IEEE 802.11b/g (2.4{2.4835GHz), IEEE802.11a (5.15{5.35GHz) and 802.16d(5.7{ 5.9GHz) for low frequency and is 5.05{8.18GHz for high frequency.
Abstract: Rectangular Slot antenna fed by microstrip line is designed for standard of IEEE 802.11b/g (2.4{2.4835GHz), IEEE 802.11a (5.15{5.35GHz), and IEEE 802.16d (5.7{5.9GHz). A rectangular slot antenna which comprises of two conductor strips located in a slot cut in the ground plane was investigated for dual frequency. This antenna was analyzed by using IE3D commercial software from Zeland (1). In this case, the frequency range at return loss i10dB is 2.26{2.61GHz for low frequency and is 5.05{8.18GHz for high frequency. DOI: 10.2529/PIERS061007105855
TL;DR: In this paper, a coherent model for simulating interaction of electromagnetic waves with forests has been developed, which allows the retrieval of interferometric and fully polarimetric data, and is used to simulate the impact of border efiects in the monostatic case with high resolution.
Abstract: A coherent model for simulating interaction of electromagnetic waves with forests has been developed. It allows the retrieval of interferometric and fully polarimetric data. Forests considered, including flnite size ones, are generated from a description following ground truth. This model is used here to simulate the impact of border efiects in the monostatic case with high resolution. DOI: 10.2529/PIERS061006120418 Radar remote sensing of forests turns out to be of great importance for environmental issues and military ones. To predict and analyze the performances, direct discrete models has been proposed (see (1{5) for example) to account for the wave interaction addressing SAR conflgurations. Most of these models assume that over∞own areas are horizontally statistically homogeneous and of inflnite extent. However, borders are often present in SAR images. Logically, their role is enhanced when the imaged landscape is composed of parcels of relatively small extent, and also when the SAR resolution is important. In these cases, simulation of SAR data require correct account of the presence of these boundaries. In the flrst part of the paper it is described how the electromagnetic model takes into account these efiects. Section 3 illustrates and analyses the results obtained in C-band, stating from previous simulations matched to ERS data (7).
TL;DR: In this article, a novel quadrature voltage controlled oscillator (QVCO) using current-reused tech-nique and back-gate coupling is presented, which can be used for low-power applications.
Abstract: A novel quadrature voltage controlled oscillator (QVCO) using current-reused tech- nique and back-gate coupling is presented. The QVCO realized with LC-tank is demonstrated in a 0.18um RF CMOS 1P6M process. Using the current-reused technique e-ciently reduces the power dissipation. However, by stacking switching transistors in series like a cascade, the architecture cannot perform well in phase noise. Through an improved circuit schematic with back-gate coupling, the phase noise of the circuit can be lowered. As a result of reducing four transistors in the circuit, the total power dissipation can be cut down even more. The simulation shows the phase noise is around i107dBc/Hz at 1MHz ofiset and the output frequency tuning range of the fabricated QVCO is 600kHz ranging from 5.15 to 5.75GHz for 802.11a. The circuit draws only 1.5mA from a 1.8-V supply. Compared with the recent works, the proposed topologies show a better phase noise performance and can be adopted for low-power applications.
TL;DR: In this article, a coplanar waveguide (CPW) bandpass filter using Composite Right/Left-handed (CRLH) Zeroth-order Resonators has been studied.
Abstract: Design and performance of a coplanar waveguide (CPW) bandpass filter (BPF) using Composite Right/Left-handed (CRLH) Zeroth-order Resonators have been studied. The Bloch analysis is applied based on the S parameters to derive the characteristics of the eigenmodes (Bloch modes), from which the right/left-handed frequency band and the zeroth-order resonant frequency are clearly determined. Then, the susceptance slope parameter of the resonator is extracted and the admittance (J-) inverters are introduced to synthesize a capacitively coupled CPW BPF. The measured results show that the size of the filter is greatly reduced (more than 60%) when compared to a conventional structure. DOI: 10.2529/PIERS060906061911
TL;DR: In this article, the relationship between C-band backscatter measurement on the physical structure of rice flelds and its growth stages was investigated based on a ground-based scatterometer experiment conducted on rice Flelds at Sungai Burung site in Malaysia for the year 2005 growing season.
Abstract: This paper investigates the relationship between C-Band backscatter measurement on the physical structure of rice flelds and its growth stages. The study is based on a ground- based scatterometer experiment conducted on rice flelds at Sungai Burung site in Malaysia for the year 2005 growing season. Seven C-band scatterometer acquisitions at full polarization, namely Horizontal-Horizontal, Horizontal Vertical, Vertical-Horizontal, Vertical-Vertical polar- ization with incidence angle from 0 - to 60 - , were measured. At the same time, ground truth data for an entire rice growing season were obtained at 12-day intervals from September to December 2005. The dates were chosen so as to coincide with RADARSAT-1 image acquisitions. The paper describes the experiment and investigates the radar sensitivity to the physical structures of rice at difierent polarization and incident angles for difierent rice growth stages. Based on the result, a close agreement of backscattering coe-cient between the scatterometer and RADARSAT-1 was obtained. DOI: 10.2529/PIERS060904212430
TL;DR: In this paper, a new Direction of Arrival (DoA) estimation method based on Neural Networks (NNs) is presented, which is especially designed for a Switched-Beam System (SBS).
Abstract: A new Direction of Arrival (DoA) estimation method based on Neural Networks (NNs) is presented. The proposed NN-DoA procedure is especially designed for a Switched-Beam System (SBS), whose basic component is an 8 £ 8 Butler Matrix (BM). The technique is simple and appropriate for real time applications. Simulations of DoA estimation tests show accurate results even for a big set of simultaneously incident signals.
TL;DR: In this article, a photonic crystal flber with triangle-lattice array in a silica matrix has been simulated by fast multipole method, and it is demonstrated that lower conflnement loss and higher birefringence can be realized in the condition of fewer rings of air holes.
Abstract: In this paper the mode property of a photonic crystal flber with triangle-lattice array in a silica matrix has been simulated by fast multipole method. The PCFs studied in this paper have a silica core, obtained by introducing a defect, that is by removing three holes in the center of the flber transverse section. The model flelds, efiective index and conflnement loss about the fundamental mode in the flbre are analysed and compared. It is demonstrated that lower conflnement loss and higher birefringence can be realized in the condition of fewer rings of air holes. At the wavelength of 1.55"m the conflnement loss is 7:3£10 i6 dB/m and the birefringence is 1:65£10 i3 in this flber. The simulation results show that birefringence of this triangle-lattice PCF is dominated by inner-ring air holes in the flbre efiectively. The simulation results in this paper have important meaning for instructing the fabrication of birefringent photonic crystal flber. 1. INTRODUCTION In recent year, great interest has been focused on the study of photonic crystal flber (PCF). By using the structure adjustability of the PCF, zero dispersive wavelength moving towards short- wave spectroscopy, chromatic dispersion compensating, dispersion truncating, high nonlinearity and birefringence can be realized (1{15). The mode birefringence of PCF mainly comes from the geometer structure of flber and the usual method to cause birefringence is employing double-core or multi-core structure, changing the flber core or the shape of the air holes and altering the distri- bution of the air holes. High birefringence PCF can be used in optical flber sensor, interferometer and polarizer, etc. In addition, by designing the high birefringence and intensive nonlineality PCF required, we can make a flber not only high birefringence, but also intensive nonlineality. We can also make the large mode property polarization maintaining PCF (15). This can make the prop- erty of PCF integrate, so it can be used in the Raman magniflcation, ex-continous spectum of the polarization, four-wave frequency mixing and the crossing phase modulation. The development of the birefringence PCF will promote the study and appliance of the new photoelectric device. In the progress of making the PCF flber, we flnd that maintaining the ideal structure of the flber and the number of air holes layers of the PCF cladding is a contradiction (2,4,17). Generally speaking, the more layers the PCF cladding have, the smaller the conflnement loss will be, but at the same time increasing the layers will make the distortion of the air holes a big problem when the flbers are produced. On the fundament of the traditional triangular arrayed air holes, this article proposes a birefringence structure PCF which has C2v symmetry. And by using the fast multipole method, its modal property is numerically simulated. It is found that in this PCF, there will be several conductive modes, and its fundamental mode has very low conflnement loss and high birefringence. 2. BASIC THEORY The ordinary solution about multipole theory at the complex boundary electrostatic fleld has been deduced and developed by Zheng Qinhong. Nie Zaiping (22) analyzed the three dimensional vector scattering of complicated object by using the fast multipole method. These examples show that the multipole method is an efiective way to analyze electromagnetic fleld theory. Using the multipole method to simulate the dispersion and the loss property of microstructured flber is originally proposed by T. P. White and B. T. Kuhlmey (23{25) in Sydney University. Zhao Mingzhu (26) also simulated the PCF by using multipole method. This method is adopted when the air holes of microstructured flber is cylindrical. By using this method, we can get real part and imaginary part of the efiective refractive index of the flber and the mode propagation constant. And then by using the real part, we can analyze the dispersion, or using the imaginary part to analyze the conflnement loss of limited cladding air holes. We can also use this method to get its propagation constant corresponding to the input wavelength (or frequency). Accordingly, we can consider the material dispersion in the progress of simulation by using the Sellmeier formula. In this paper, the theory of T. P. White (23,24) is used for reference
TL;DR: In this article, the bend structure of leaky-wave antennas based on curve tapered design has been investigated and a new tapered microstrip LWA was designed running a simple procedure which use an FDTD code, and using a physical grounding structure along the length of the antenna, which allows to use only half of the structure.
Abstract: The bend structure of leaky-wave antennas based on curve tapered design has been proposed and investigated. The new leaky-wave antenna (LWA) was designed running a simple procedure which use an FDTD code, and using a physical grounding structure along the length of the antenna, which allows to use only half of the structure, the adoption of a simple feeding, and the reduction of sidelobes. The good performance of this new tapered microstrip LWA are mainly wider band, higher gain, and higher e-ciency whit reference to conventional uniform microstrip LWAs. Bending the curve tapered LWA, the major performance noticed of this antenna were the wider beam of radiation pattern and a further reduction of back lobes. Moreover since the tapering of linear LWA involves the variation of both phase and leakage constant, all the emitted rays are focused in a corresponding angular interval, allowing to obtain from the ray optical model a closed formula to predict the main beam angle of linear and curve taper LWA. Finally from theoretical analysis it should be appreciated that, as the relative dielectric constant of the substrate approaches 1, the leaky wave antenna bandwidth becomes much wider, improving its performance.
TL;DR: In this article, the authors proposed a S-shaped microstrip patch antenna fed by dual offset electromagnetically coupled to generate wideband operation in the 5-6 GHz frequency range.
Abstract: Novel Design of S-shaped microstrip patch antenna fed by dual offset electromagnetically coupled to generate wideband operation in the 5–6 GHz frequency range is presented. It is demonstrated that by adding two slots opposite to each other to a rectangular patch and using dual offset electromagnetically coupled, wideband operation can be satisfactorily achieved. In advance, the two slots in the rectangular patch can reduce the area of the patch to 19.62%. Importantly, this antenna design is thin and small to be accommodated in a PCMCIA card of standard 5 mm thickness. DOI: 10.2529/PIERS060801042546
TL;DR: In this article, the authors investigated the crosstalk between a single-ended line and a differential pair, and between differential pairs are investigated in the case of multiconductor line, using the mode decomposition technique.
Abstract: The crosstalk between a single-ended line and a differential pair, and between differential pairs are investigated in this paper. First, the telegrapher’s equations for multiconductor line are applied. Then the telegrapher’s equations are solved by using the mode decomposition technique. Finally the mixed-mode S-parameters are derived to investigate the crosstalk and mode conversion.
TL;DR: In this article, the exact formulas for the induced electric surface current and the equivalent electric surface currents on the open cylindrical surface due to an arbitrary narrow-band beam have been shown in their closed-form expressions within the context of the cylinrical harmonics, which gives information about the validity of the Physical Optics (PO) approximation.
Abstract: The exact formulas for the induced electric surface current (in the scattering phe- nomenon) and the equivalent electric surface current (in the difiraction phenomenon) on the open cylindrical surface due to an arbitrary narrow-band beam have been shown in their closed-form expressions within the context of the cylindrical harmonics, which gives information about the validity of the Physical Optics (PO) approximation. Both the Electric Field Integral Equation (EFIE) and the Magnetic Field Integral Equation (MFIE) are used to flnd the induced (equiva- lent) electric surface currents in the context of the cylindrical harmonics. The numerical example of the scattering and difiraction of the Hermite Gaussian beam from the open cylindrical surface is shown. The result is useful for the evaluation of the validity of the PO approximation in the cylinder-like surface.
TL;DR: In this paper, an improved solution of the nonlinear and ill-posed inverse problem of electrocardiography is presented, where the heart activity is modeled by three di®erent equivalent cardiac sources: 1 moving dipole, 2 and 5 fixed location rotating dipoles.
Abstract: An improved solution of the non-linear and ill-posed inverse problem of electro-cardiography is presented. The hearts activity is modeled by three di®erent equivalent cardiac sources: 1 moving dipole, 2 and 5 fixed location rotating dipoles. For this purpose a three dimensional volume conductor model of the human body is constructed based on a classical anatomic atlas. This is excited by each one of the cardiac sources. For the inverse problem a Least Squares (LS) optimization scheme is employed, aiming at the matching of the potential distribution calculated on the torso surface to the corresponding distribution measured with the aid of multiple electrodes. The efficiency of the method stems from the employment of arbitrary shaped hexahedral elements within the volume conductor model for the minimization of the required computational resources, while the model realistically reflects the body internal structure. Finally, the algorithm is successfully tested using measured data available online. (Less)
TL;DR: In this article, an accurate equivalent circuit model for the microstrip line with a complementary split ring resonator (CSRR) and the parameter extraction method was presented, and a high-pass filter with steep rejection was designed based on the model.
Abstract: An accurate equivalent circuit model for the microstrip line with a complementary split ring resonator (CSRR), and the parameter extraction method, are presented. A highpass filter with steep rejection is designed based on the model. The measurement results confirm the efficient analysis and design procedure and the validity of the highpass filter configuration.
TL;DR: A novel wireless epidural pressure sensor unit which can be implanted in a burr hole drilled in the skull is proposed, which operates at an ISM band of 2.4GHz and radiates a microwave signal as a function of pressure.
Abstract: Intracranial pressure (ICP) monitoring has a signiflcant role in the diagnosis and prognosis of various brain diseases. The most prevalent technique of monitoring ICP is using catheter based systems, which involve risks including infection, brain damage and patient dis- comfort. A novel wireless epidural pressure sensor unit which can be implanted in a burr hole drilled in the skull is proposed. The unit operates at an ISM band of 2.4GHz and radiates a microwave signal as a function of pressure. In-vitro and in-vivo tests were performed to study the e-ciency of this measurement technique. This paper presents the design issues and experimental results of the prototype devices developed so far.