Analysis of the zonal and rectangular slots on a conductingspherical cavity

The zonal slot cut on a conducting spherical cavity is analyzed rigorously. The slot is excited asymmetrically, which excites higher order azimuthal modes. The Green's function approach is used to formulate an integral equation for the magnetic current in the slot, which is solved using the moment method (MoM). New recurrence formulas are derived so that within their stable region the admittance integrals can be evaluated without the need for any numerical integration. In this case, the solution is very easy to implement with extremely short computation time. The effects of the latitude angle on the peak resistance and percentage bandwidth are investigated. Furthermore, the cavity resonance modes and their degeneracy are examined by plotting the expansion coefficients of the magnetic current. In addition, the problem of a rectangular slot in the nonequatorial plane is also studied. Measurements are carried out and good agreement between theory and experiment is obtained     

Transmission through dielectric-filled slots in a conductingcylindrical shell of arbitrary cross section: TE case

A simple moment solution is summarized for the problem of electromagnetic transmission through dielectric-filled slots in a conducting cylindrical shell of arbitrary cross section. The system is excited by a plane-wave polarized transverse electric (TE) to the axis of the shell. The equivalence principle is used to replace the shell and the dielectric by equivalent electric and magnetic surface currents radiating into an unbounded medium. Two different sets of coupled integral equations involving the surface currents are obtained by enforcing the boundary conditions on the tangential components of the total electric and magnetic fields. The method of moments is used to solve the integral equations. Pulses are used for both expansion and testing functions. Special attention is paid to circular and rectangular shells. Results for shell surface current, the internal field, and the aperture field are presented. For the case of air dielectric filling, the results computed using the electric field and/or the magnetic field formulation are in very good agreement with published data. In general, it is observed that the effect of filling a slot with a dielectric is not predictable from a simple theory     

球形天线罩对垂直电偶极子辐射特性的影响

给出由负折射媒质构成的球形天线罩包围的垂直电偶极子在空间辐射的电磁场解析表达式.讨论了偶极子的位置与球形天线罩材料的电磁特性对辐射场的影响.理论分析和计算结果表明:当偶极子位于球心时,辐射的电磁场和文献[8]的结果吻合很好;随着场点与球心距离的增加,偶极子的放置位置对辐射场影响变小;相对于普通介质和自由空间,负折射媒质构成的球形天线罩增强了垂直偶极子的空间辐射特性.     

Resonant length of longitudinal slots and validity of circuit representation: Theory and experiment

Pertinent theory for the design of longitudinal slot arrays is reviewed and its dependence on the dominant mode scattering off a single slot is pinpointed. The critical need to know resonant length versus slot offset is emphasized and the desirability of determining this information theoretically rather than experimentally is argued. Then method of moments solutions are used to calculate resonant length versus slot offset for given waveguide dimensions and frequency. These theoretical results are compared to new, carefully obtained experimental data. Agreement is found to be so good, it is concluded that one can dispense with the costly gathering of experimental input data when designing longitudinal slot arrays fed by standard rectangular waveguide. A critical look is taken at the validity of representing the longitudinal slot as a shunt element on an equivalent transmission line. This assumption is found to be more and more questionable as thebdimension is reduced. For quarter-height guide, an alternate design procedure is suggested as being more accurate.     

Self-pulsating semiconductor lasers: theory and experiment

We report detailed measurements of the pump-current dependency of the self-pulsating frequency of semiconductor CD lasers. A distinct kink in this dependence is found and explained using a rate-equation model. The kink denotes a transition between a region where the self-pulsations are weakly sustained relaxation oscillations and a region where Q-switching takes place. Simulations show that spontaneous emission noise plays a crucial role in the cross-over     

Nonlinear control of a series DC motor: theory and experiment

The control problem for a series DC motor is considered. Based on a nonlinear mathematical model of a series-connected DC motor, it is shown that the combination of a nonlinear transformation and state feedback (feedback linearization) reduces the nonlinear control design to a linear control design. To demonstrate its effectiveness, an experimental study of this controller is presented. These experimental results are also compared with a simulation of the closed-loop system. Finally, it is shown that a nonlinear observer (with linear error dynamics) for speed and load torque can be constructed based only on measurements of the motor current. Experimental results of this speed and load-torque estimator are also presented     

Aperture coupling to a coaxial air line: theory and experiment

Coupling through a circular aperture in the shield of a coaxial air line is studied theoretically and experimentally. Polarizability theory is used to compute the effective dipole moments that excite the coaxial line in the internal region. Measurements of shielding effectiveness were made in a reverberation chamber over wide frequency ranges. Agreement between theory and measurements is generally within ±10 dB. Recommendations for improvements in the measurements and theory are made for achieving the closer agreement that would be desirable for an artifact standard for shielding effectiveness measurements     

A fully three-dimensional simulation of a ground-penetrating radar:FDTD theory compared with experiment

A fully three-dimensional, finite-difference time-domain (FDTD) model of a ground-penetrating radar is described. The FDTD simulation completely models the transmitting and receiving antennas, the antenna feeds, the dispersive Earth, and the buried object. Results of scattering from three different buried cylindrical pipes are compared to previously measured results for a one-third size scale model of an actual radar and are shown to be in good agreement     

Scattering from an open spherical shell having a circular apertureand enclosing a concentric dielectric sphere

The generalized dual series solution is presented for the scattering of an arbitrary plane wave from an open spherical shell having a circular aperture and enclosing a concentric homogeneous dielectric sphere. This solution explicitly exhibits the correct edge behavior, and it can handle spheres that are electrically small or large without special considerations. A variety of cross-section results is presented for the normally incident case. It is shown that effects corresponding to the presence of the interior cavity dominate all of the scattering data. In particular, the cross sections exhibit new resonance features that are due to the cavity-backed nature of the aperture and depend on the characteristics of the interior sphere. The results demonstrate that interior information is contained in the exterior scattering data     

A fast diffusion-driven photodetector: theory and experiment

A high-speed photodetector has been demonstrated. Prototype silicon devices have detection bandwidths of 5 GHz and are limited by neither the saturation-velocity transit time nor the carrier lifetime. These detectors use a combination of the Dember effect and the east of generating fine photocarrier gratings, and scale to bandwidths of several hundred gigahertz     

Optimized overlay metrology marks: theory and experiment

In this paper, we provide a detailed analysis of overlay metrology mark and find the mapping between various properties of mark patterns and the expected dynamic precision and fidelity of measurements. We formulate the optimality criteria and suggest an optimal overlay mark design in the sense of minimizing the Cramer-Rao lower bound on the estimation error. Based on the developed theoretical results, a new overlay mark family is proposed-the grating marks. A thorough testing performed on the new grating marks shows a strong correlation with the underlying theory and demonstrate the superior quality of the new design over the overlay patterns used today.     

Output characterization of a frequency shifted feedback laser:theory and experiment

Frequency shifted feedback cavity (FSFC) lasers can generate continuous broadband radiation or periodic picosecond pulses. To better understand these two different regimes a passive FSFC is modeled and its output in the time and frequency domains is calculated. Calculations of the FSFC output indicate that peaks observed using a Fabry-Perot spectrum analyzer can only occur when the FSFC cavity length and intracavity frequency shift satisfy a resonance condition. Calculations also indicate that a radio frequency spectrum analysis of the intensity should show sharp peaks which are independent of the FSFC frequency shift. Additionally, pulses propagating in a FSFC are insensitive to frequency shift detunings, suggesting applications as a stable source of ultrashort laser pulses. Experimental evidence confirming these findings is reported. Results indicate that a FSFC does not support conventional laser modes     

Polysilicon emitters for bipolar transistors: a review andre-evaluation of theory and experiment

A critical review is presented of the theories proposed in the literature to explain the current gain enhancement of polysilicon emitter bipolar transistors. From these theories a simplified analytical formulation is chosen which models the blocking properties of the interface, including tunneling through the interfacial oxide, reduced grain boundary mobility at the polysilicon/silicon interface, and the potential barrier created by segregated dopant, which can all give rise to an enhanced current gain. Also modeled are the mechanisms which limit the extent of any gain enhancement, such as recombination in the single-crystal emitter, in the bulk of the polysilicon, and at the polysilicon/silicon interface. This model is then applied in an original manner to a selection of experimental data in an effort to identify the dominant current gain mechanisms in polysilicon emitter transistors as a function of a given set of fabrication conditions     

Quasi-optical planar arrays with FETs and slots

This work describes the design concept and experimental results for prototypes of two-dimensional quasi-optical power-combining arrays. Several different quasi-optical circuits were used to obtain the fundamental data for this study. How to incorporate the antenna input impedance into the active antenna circuit and how to analyze the strong coupling condition with two operating modes are addressed using large-signal analysis. Several circuit configurations are demonstrated, including a single active antenna operating at 9.3 and 24.0 GHz, a six-element linear power-combining array operating at 15.6 GHz, and four-element and sixteen-element two-dimensional power combining arrays operating at 10.4 and 7.8 GHz. Important characteristics such as antenna patterns and tuning ranges are discussed. The prospects for a two-dimensional monolithic quasi-optical power-combining array are discussed     

Mutual admittance of slots on a cone: Solution by Ray technique

An approximate asymptotic Green's function for the surface magnetic field due to a magnetic dipole on a general convex conducting surface is developed. Based largely on the classical work of V. A. Fock and the current GTD recipes, this solution is presented in a form that admits ray interpretations, and can be simply evaluated. We apply the Green's function to calculate the mutual admittance between two slots on a cone. The numerical results are in very good agreement with experiments.     

Radiation from multiple circumferential slots on a conductingcircular cylinder

Electromagnetic wave radiation from multiple circumferential slots on a conducting circular cylinder is theoretically investigated. The Fourier transform/series technique is used to represent the continuous and discrete modes of the scattered field. The mode matching is utilized to constitute a set of simultaneous equations for the discrete modal coefficients. The residue calculus is applied to transform the scattered field integral representations into fast-converging series forms, thereby facilitating the numerical computations. Numerical computations illustrate the behavior of radiation in terms of the slot geometry, the incident mode, and the operating frequency     

一种新型的开弧形槽超宽带印刷天线的设计

设计了一种新型的开弧形槽超宽带印刷天线。该天线采用对称结构的"眼睛"形状作为辐射面,在矩形面开两个对称的1/4圆弧槽和一个半圆槽作为大地面,并且引入四节微带馈线进行阻抗匹配。通过对该天线的参数仿真和优化并进行实物制作和性能测试。结果表明,此天线的频带宽度为2.3~3.9 GHz(S11<–10 d B),相对阻抗带宽达到51.6%。该天线具有良好的方向图,满足超宽带天线的性能要求。     

The power spectrum of injection lasers: The theory and experiment on a nonlinear model of lasing

A comprehensive treatment of the theory and experiment on a nonlinear model of injection lasers develops a general way to find the order underlying the complexities of the emission spectrum of lasers operated far above threshold by describing the emission in terms of a few measurable parameters of the cavity and material. The theory is largely unpublished, while the experimental work covers publications fortified with more recent studies and considerable new work. The laser is described by rate equations in which the gains and losses are approximated as prorated averages over one round trip. The gain contains an explicit nonlinearity described by a critical power at which the gain begins to saturate. The steady state solution at low level is the linear theory. At high level, the excited power in each cavity mode is an explicit function of its particular gain and loss coefficients. To express the characteristics of the radiation in terms of observables, the dependence of gain and loss coefficients on mode number are deduced by modeling. The unsaturated gain is taken as parabolic in frequency, while the loss coefficients are deduced by decomposing each cavity mode into three independent sets of waveguide modes. For a cavity with sawed side walls, this gives a scattering loss proportional to the square of the lateral mode number, which determines the shape of the lateral profile of the beam. The summation of the modal powers over all cavity modes expresses the lateral profile, the frequency spectrum, and the total power in terms of an overdrive parameter X associated with the dynamical state of the laser, which is an implicit function of the population inversion. Relating X to the spontaneous emission at short wavelength gives a set of equations, involving only observables, which determines all the parameters in the summation. The equations reveal previously unknown relations between power, spontaneous emission, beam width, spectral width, and polarization. The critical power is expressed from first principles in terms of phenomenological optical constants.The experiments examine the relation by pulsed studies at room temperature of wide lasers with sawed sides or stripe contacts. It is shown that many of the lasers have the dispersion of box modes assumed in the summation of the distribution function. At high enough power that a statistical average over the excited modes is meaningful, the general predictions are verified. The lateral profile has the correct shape to about 10 dB below the peak, its width grows as $\text{(X)}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$, and it's peak as $\text{(X)}{}^{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}$. The power dependence of the polarization ratio follows quantitatively the predicted shape, and the total power is quadratic in X. Extensive records of 21 lasers with a wide variety of internal structures are intercompared, showing that all have a similar coefficient of side wall loss, that the curvature of gain against wavelength varies widely, and that the critical power $\text{P}{}^1$ seems to be a general constant of the predicted magnitude, independent of internal structure, cavity geometry, and facet area. The same constant is also found for wide cavities with Hermite-Gaussian modes and one narrow stripe cavity. There is a discussion of geometries not yet covered, including lasers with many transverse modes and narrow stripe and cw lasers.     

Compact dual-frequency microstrip antenna with a pair of bent slots

A novel, compact, dual-frequency design for cutting a pair of bent slots in the centre of a rectangular patch is demonstrated. For fixed dual-frequency operation, the proposed design provides an antenna-size reduction as high as 32% compared to that of using a simple patch without the slots. Experimental results of the proposed design, with various sizes of the bent slots, are presented and analysed