Corner effects on the mutual impedance between edge slots

An analysis for calculating the mutual impedance between two edge slots in a linear slotted waveguide array is presented. The analysis uses a 90° wedge Green's function to account for the influence of the waveguide corners on the evaluation of the external mutual coupling. A novel asymptotic formula for the 90° wedge Green function's is derived to expedite the numerical analysis for slots with large separation. Numerical results show that the phase of mutual impedance retards linearly with slot separation and the magnitude decays as the separation is increased. However, the mutual impedance of edge slots is larger and decays more slowly than that of longitudinal slots or other slots in a large ground plane. The distinguished characteristics can be attributed to the energy guiding effect of the waveguide corners, which is discovered and verified mathematically and numerically. Also shown in the numerical calculations are the incremental conductances of the individual slots in a linear edge slot array, which are compared, and found to be in good agreement, with the available experimental data     

Efficiency of the GSM-GPRS Air Interface for Real-Time IP Traffic Flows With and Without Packet Dropping

One IP terminal can occupy a single slot or a multiple number of slots within time frames in the GSM and GPRS, respectively. A limited number of radio resources (slots) are allocated in a base station for such IP terminals. If one IP terminal can occupy only one slot discontinuously in a time frame, there is one possibility resorting to all IP terminals to preserve active mode at a time. Thus, the number of accepted call in the GSM is the same as that of the radio resource. Similarly, if one terminal can occupy a multiple number of slots discontinuously/dynamically in a time frame, the number of accepted calls is obtained by dividing the number of radio resources during that time by the maximum allowed number of slots per IP terminal. A burstiness factor is defined for the IP traffic over GSM-GPRS air interface. Traffic channel efficiency with a bursty real-time IP traffic is unacceptably low, especially with the range of acceptable call loss probabilities pertaining to a lower burstiness factor. The channel efficiency can be enhanced and the call loss probability can be suppressed significantly if a higher maximum number of calls is accepted. Allocated radio resources are less than the maximum number of packet transmissions at a time. Therefore, some packets could be dropped from the real-time transmission system. A complete analysis for the real-time IP packet transmission over the single slot GSM and dynamically variable multislot GPRS air interface without packet dropping, and with packet dropping that increases the channel efficiency is executed. Results show that the channel efficiency as well as the packet dropping probability increases with increasing call intensity, maximum number of admitted IP calls and the burstiness factor.     

Scattering of volume magnetostatic waves by periodic slot lattices

Scattering of volume magnetostatic waves excited in thin films by the lattices composed of metal ribbons and slots in a metal screen is analyzed. A boundary value problem for the Maxwell equations is formulated and solved in the static approximation. An algorithm for the numerical solution of this boundary value problem is proposed. Scattering of volume magnetostatic waves by 2D periodic lattices of slots that are infinite along one coordinate and finite along the other coordinate is studied for an arbitrary orientation of slots and an arbitrary angle of incidence of the magnetostatic wave. The energy-band structure of lattices is analyzed. The possibility of formation of magnon crystals based on the slot lattices is demonstrated.     

有限元\边界元混合算法分析波导裂缝阵列天线

研究了一种分析波导裂缝阵列天线的方法。将有限元-边界元混合算法(FE-BI)应用于波导裂缝阵列天线的计算中,建立理论分析模型,计算波导裂缝上的等效磁流,进而求解整个天线阵列的远场辐射特性。为了检验这种方法的正确性,将所得的数值计算结果与测试值进行了比较,结果表明:FE-BI法可以作为计算波导裂缝阵列天线的一种有效的方法。     

Parametric analysis of slot-loaded trapezoidal patch antennas

Slot-loaded trapezoidal patch antennas are analyzed in order to achieve a multifrequency operation. A moment method formulation based on new analytical entire domain basis functions is developed and compared to the one involving the Rao-Wilton-Glisson (1982) RWG triangular discretization. The numerical results obtained through the new efficient implemented code are compared to the measurements showing a good agreement. A parametric analysis of such antennas is also presented leading to useful design graphs showing the main antenna properties (resonance frequencies, cross-polarization levels, matching, etc.) as a function of the patch geometrical dimensions, symmetric collocation of the slots on the patch, and slot dimensions.     

Scattering of surface magnetostatic waves by periodic slot gratings

Scattering of the magnetostatic surface waves generated in thin films by the gratings formed from slots in a metal screen is theoretically analyzed. A boundary-value problem for the Maxwell equations is formulated and solved in the static approximation. An algorithm of numerical solution of the boundary-value problem is proposed. Scattering of magnetostatic surface waves by 2D periodic slot gratings that are infinite along one coordinate and finite along the other coordinate is studied for an arbitrary orientation of slots and an arbitrary angle of incidence of the magnetostatic wave. The band structure of gratings is studied. The possibility of formation of magnonic crystals based on slot gratings is demonstrated.     

On the Propagation of Leaky Waves in a Longitudinally Slotted Rectangular Waveguide

The field theory approach is used to study leaky-wave propagation in a rectangular waveguide with long nonresonant slots in the narrow walls. Radiation from the slots is confined by parallel plates which act as transmission lines guiding the energy away from the slots. The complex dispersion equations for TE waves are examined and solved using an iterative numerical technique. Propagation characteristics both in the axial and transverse directions are presented, along with the electric field distribution and power flow. Restrictions on the analysis and on the power-handling capacity imposed by slot width also are described. Measurements of the phase characteristics of the dominant mode are in good agreement with theoretical values.     

Study of various shapes of the coupling slot in CPW-fed microstripantennas

A numerical modeling based on the solution of coupled integral equations is used for the characterization of CPW-fed aperture-coupled microstrip antennas. Various shapes of excitation slots, such as open stubs, slot loops, and capacitively and inductively coupled slots, are investigated in terms of return loss and front-to-back radiated power ratio. It is shown that a centered CPW open stub gives a minimum of back radiation while allowing for easy matching. The slot-loop excitation seems to be a convenient feeding mechanism that also allows the insertion of active devices     

Propagation on a Ported Coaxial Cable Buried in Flat Earth

Consider a horizontal coaxial cable with periodic slots in the outer conductor. This ?leaky cable? is buried in the earth as one component of an intruder detection system. We develop the theory for surface-wave propagation on the cable in the presence of the planar air-earth interface. Numerical results are included for the phase velocity and attenuation constant as functions of the various parameters. Data are presented for the electric-field strength at the air-earth interface, and the electric-field distribution in the air region above the buried cable.     

Analysis of planar slot arrays using magnetic currents andmagnetomotive force

An effective approach to the analysis of planar slot arrays constructed on a metal-coated dielectric slab is suggested. In the framework of the method, radiation and scattering characteristics of such arrays are obtained from treating the problem of guided mode diffraction with a finite number of transverse slots cut in metallization. The idea of magnetic currents and magnetomotive force is used to solve the problem; in doing so, mutual relations between the slots are taken into consideration. Some numerical results in the specific case of a uniform finite-periodic array are given. Moreover, the design problem aimed at reduction of sidelobes using nonuniform quasi-periodic slot arrays is considered. Applying the proposed analysis to the designed array, one can determine the deviation of actual radiation characteristics from the desired ones, thus correcting the design procedure if necessary     

Regularization of space-time integral equations in the problem of diffraction of electromagnetic pulses by N slots

Space-time integral equations describing diffraction of ultrashort electromagnetic pulses by slots in a screen located on a media interface are solved. The solution is based on separation of the static components of the kernels of the integral equations and the subsequent application of the collocation method.     

基于哈希算法的动态TDMA时隙分配研究

动态时隙分配机制是Ad Hoc网络提高组网效率的重要方面。提出了一种基于哈希算法的动态时隙资源分配机制-HP_TDMA算法。该算法将节点的时隙需求划分为3种情况:节点不需要使用时隙、只需要使用主时隙和需要竞争额外时隙。在时隙竞争阶段采用哈希算法获得节点对时隙使用的优先级顺序表,按照优先级表配置节点对时隙的使用。经过仿真分析得出采用哈希算法的时隙分配策略能够高效地利用时隙资源,提高信道利用率。     

Mutual coupling between parallel columns of periodic slots in aground plane surrounded by dielectric slabs

Arrays of slots with arbitrary orientation in an infinite conducting plane that are infinitely periodic in one dimension and finitely periodic in another dimension are considered. The plane is bounded on each side of dielectric slabs of finite thickness and infinite extent. Single columns of slots are represented by equivalent magnetic scattering currents, which are solved for by the moment method. The mutual coupling (admittance) between slot columns in the presence of the stratified media is found by the array scanning method, which expresses the admittance as the average of the scan admittance of an artificially constructed doubly infinite array of slots over all real scan angles. The technique avoids the use of Sommerfeld integrals, but still gives rise to singularities at scan angles corresponding to the resonant excitation of surface waves. An analytical approximation removes these surface wave singularities, making numerical implementation of the method practical     

Development of the Fel’d’s concepts on the slotted waveguide devices in the works of researchers from the Karazin National University

The development of the Fel??d??s concepts on the slotted waveguide emitters in various slot systems is presented. Various narrow slots (slots with coordinate boundaries and tilted slots whose length is comparable with one half of wavelength, electrically long slots whose length is no less than one hundred wavelengths, slots in waveguides that are uniformly or partially filled with insulator, infinite slots, slots with reflecting walls, and slots that are uniformly or partially filled with insulator) are considered. The analysis of the effect of the waveguide wall thickness, the selection of the approximating function for the electric field in the slot, the correctness of the representation of the tensor Green function, and the application of the potential vector eigen-functions of the Helmholtz equation in the study of the magnetic field in the slot region are discussed.     

Coupling by slots in rectangular waveguides with arbitrary wall thickness

A method for evaluating the coupling between two rectangular waveguides, coupled by a slot of arbitrary dimensions in a wall of arbitrary thickness is described. The method is based on the solution, by numerical techniques, of a pair of coupled integral equations. Results for typical shunt and series slots are presented.     

Detailed FD-TD analysis of electromagnetic fields penetratingnarrow slots and lapped joints in thick conducting screens

The physics of electromagnetic-wave transmission through narrow slots and tapped joints in thick conducting screens is examined in detail by applying numerical models to compute both field distributions within the slots and joints, and fields transmitted to the shadow region. The primary modeling tool is the finite-difference time-domain (FD-TD) method, using a Faraday's-law contour integral approach to modify the basic FD-TD algorithm to properly model the slot physics, even when the slot gap width is much less than one space lattice cell. Finely sampled method-of-moments (MM) models are used to validate the FD-TD tool for relatively simple straight slots; FD-TD is then used to explore properties of more complicated lapped joints which are widely used for shielding purposes at junctions of metal surfaces. It is found that previously reported slot resonances occur in a more general sense for lapped joints as path-length resonances. In addition to greatly enhanced power transmission, path-length resonances can result in total fields within the joint exceeding the incident fields by more than one order of magnitude. Sample field distributions for this case are given     

An Adaptive Beaconing MAC Protocol Providing Energy-Efficient Healthcare Service

We present an Adaptive Beaconing Medium Access Control (AB-MAC) protocol based on time division multiple access (TDMA) in order to provide healthcare services. The purpose of our protocol is to gain not only energy-efficiency but also provide low delivery latency when both periodic data and event-driven data are present. In order to satisfy these requirements, we propose standby slots that are deployed during each beacon interval. The standby slots are able to identify unscheduled data with low delivery latency. An adaptive beacon is then provided that quickly reschedules the time slots. Furthermore, the AB-MAC asymmetrically assigns energy consumption to a coordinator instead of the sensor nodes when possible in order to reduce sensor node energy waste. In this paper, we analyze the IEEE 802.15.4 and the AB-MAC, and evaluate their energy consumption and delivery latency. NS-2 simulations are used to validate the numerical analysis. The evaluation results indicate that the AB-MAC is a more suitable protocol than the IEEE 802.15.4 when used in WBANs.     

网络编码双向机会协作系统无线传输方案频谱效率比较分析

文章对放大转发双向机会协作通信系统(OR-TW-AFNC)的频谱效率进行了详细地研究,运用适当的数学证明和近似分析获得了OR-TW-AFNC系统两时隙、三时隙和四时隙传输方案平均“和速率”的近似封闭解析解。数值分析结果表明,对于OR-TW-AFNC系统的三种不同传输方案,依不同的信道实现和信噪比范围,这三种系统的频谱效率是不同的;特别是在低信噪比区域,由于三时隙方案有效地利用了直径传播信号,其相应的频谱效率要高于两时隙方案。与此同时,比较分析结果也表明文章所得近似封闭解析解是正确的、可靠的。      

Scattering of H-polarized waves from conducting strips inthe presence of an electrically uniaxial half-space-a singularintegrodifferential equation approach

Electromagnetic scattering from perfectly conducting infinitely long strips in the presence of an electrically uniaxial half-space is treated analytically. A uniform H-polarized plane wave is incident from the isotropic region. As a prerequisite to this approach, the H-mode scalar Green's function of the structure is developed. Its use in connection with the reciprocity theorem leads to a singular integrodifferential equation for the current density induced on the scatterer surface. The equation is solved for strips parallel or perpendicular to the interface, located above or embedded in the anisotropic region, following a special technique based on the theory of singular integral equations that has been developed in connection with strips and slots and E- or H-polarized incident waves. Numerical results for the induced current density and for the scattered far field in a variety of cases are presented in graphical form. Whenever possible they are compared with existing results based on purely numerical procedures     

Analysis of Distributed-Lumped Strip Transmission Lines

A calculation method for obtaining characteristic impedances and phase velocities of striplines, which are regarded as consisting of distributed-lumped elements such as so-called wiggly lines, is presented with numerical results. The numerical calculations have been carried out for a) single stripline with slots at the outer edges, b) coupled stripline with rectangular wiggling, and c) coupled stripline with slots at the outer edges. Experimental work has also been accomplished to verify the present method. Results show good agreement with calculations.