Electrodynamic characteristics of a strip antenna in a magnetoplasma

The problem of the distribution of a current in an antenna that is an infinitesimally thin, perfectly conducting narrow strip is considered. The antenna is embedded in an anisotropic plasma medium, oriented perpendicularly to an external magnetic field, and excited by an external electromotive force. The problem is reduced to a system of singular integral equations. On the basis of these equations, expressions for the distribution of the current and the antenna impedance are derived and analyzed.     

Application of a switched-capacitor circuit to converting a two-wire to a four-wire hybrid function

A new switched-capacitor circuit using an integral feedback capacitor is proposed. A capacitor in a CR integrator which uses an operational amplifier is regarded as an information transmission element. By switching this capacitor from the input side to the output side periodically, a sampled-data transmission circuit is produced which has better frequency response than that of an ordinary integrator. The technique is shown applied to a solid-state two-wire to four-wire hybrid function in telephone communication.     

Electromagnetic propagation along a wire in a tunnel-approximate analysis

The propagation of electromagnetic waves along an axial wire in an underground tunnel is analyzed from a perturbation theory point of view. The formulation is compared with that of J. R. Wait in which he solves an exact mode equation approximately, and a modified tunnel wall admittance is thus identified. Attenuation computed on the basis of the approximate formulation is compared with exact results of Wait and Hill.     

Analysis of magnetic stimulation of a concentric axon in a nervebundle

The authors present an analysis of magnetic stimulation of an axon located at the center of a nerve bundle. A three-dimensional axisymmetric volume conductor model is used to determine the transmembrane potential response along an axon due to induced electric fields produced by a toroidal coil. The authors evaluate four such models of an axon located in: (1) an isotropic nerve bundle with no perineurium, (2) an anisotropic nerve bundle without a perineurium, (3) an isotropic nerve bundle surrounded by a perineurium, and (4) an anisotropic nerve bundle surrounded by a perineurium. The transmembrane polarization computed along an axon for the above four models is compared to that for an axon located in an infinite homogenous medium. These calculations indicate that a nerve bundle with no sheath has little effect on the transmembrane potential. However, the presence of a perineurium around the nerve bundle and anisotropy in the bundle significantly affects the shape of the transmembrane response. Therefore, during magnetic stimulation, nerve bundle anisotropy and the presence of perineurium must be taken into account for calculation of stimulus intensities for threshold excitation     

Floorplanning using a tree representation: a summary

We present an ordered tree (O-tree) structure to represent nonslicing floorplans. The O-tree uses only n (2+[lg n]) bits for a floorplan of n rectangular blocks. We define an admissible placement as a compacted placement in both x and y directions. For each admissible placement, we can find an O-tree representation. We show that the number of possible O-tree combinations is O(n!2/sup 2n-2//n/sup 1.5/). This is very concise compared to a sequence pair representation that has O((n!)/sup 2/) combinations. The approximate ratio of sequence pair and O-tree combinations is O(n/sup 2/(n/4e)/sup n/). The complexity of an O-tree is even smaller than a binary tree structure for a slicing floorplan that has O(n!2/sup 5n-3//n/sup 1.5/) combinations. Given an O-tree, it takes only linear time to construct the placement and its constraint graph. We have developed a deterministic floorplanning algorithm utilizing the structure of O-tree. Empirical results on MCNC (www.mcnc.org) benchmarks show promising performance with average 16% improvement in wire length and 1% less dead space over the previous central processing unit (CPU) intensive cluster refinement method.     

Radiation from a generalized antenna in a stratified medium

Exact calculations are made of the electromagnetic field radiated by an arbitrary current distribution in an arbitrary stratified lossy medium. The medium thus characterized can include both a stratified earth and a many layer stratified ionosphere. The results of the investigation, which include the input resistance and the efficiency of the antenna, are useful for designing antennas in the ELF, VLF and LF bands. (The theory is applied to the case of an ELF-ring antenna.)     

某型伪码测距雷达的数字AGC设计

论述了某航天器伪码测距雷达接收机外部AGC的设计原理和具体实现,并重点讨论了如何根据射频前端的输出来设计全数字AGC,来扩展接收机的动态范围.该文的讨论对于DS-SS（扩展频谱数字）接收机和伪码测距雷达接收机的数字AGC设计有参考意义.     

Electromagnetic scattering model for a tree trunk above a tiltedground plane

An efficient and realistic electromagnetic scattering model for a tree trunk above a ground plane is presented. The trunk is modeled as a finite-length stratified dielectric cylinder with a corrugated bark layer. The ground is considered to be a smooth homogeneous dielectric with an arbitrary slope. The bistatic scattering response of the cylinder is obtained by invoking two approximations. In the microwave region, the height of the tree trunks are usually much larger than the wavelength. Therefore the interior fields in a finite length cylinder representing a tree trunk can be approximated with those of an infinite cylinder with the same physical and electrical radial characteristics. Also an approximate image theory is used to account for the presence of the dielectric ground plane which simply introduces an image excitation wave and an image scattered field. An asymptotic solution based on the physical optics approximation is derived which provides a fast algorithm with excellent accuracy when the radii of the tree trunks are large compared to the wavelength. The effect of a bark layer is also taken into account by simply replacing the bark layer with an anisotropic layer. It is shown that the corrugated layer acts as an impedance transformer which may significantly decrease the backscattering radar cross section depending on the corrugation parameters. It is also shown that for a tilted ground plane a significant cross-polarized backscattered signal is generated while the co-polarized backscattered signal is reduced     

Optimization of a synchronous reluctance machine for a sensorless drive with a wide field-weakening range

For more than one century, electrical machines have been utilized for electrical drives. Nowadays, in most applications the electrical machine is fed by an inverter. Three types of machines are available for such purposes: the asynchronous induction machine, the permanent magnet excited synchronous machine and the synchronous reluctance machine. Reluctance machines represent an alternative to the other types when utilized in high-performance drives with a wide speed range. Due to the rotor saliency, these machines have an inherent suitability for a position-sensorless control. The parameters of a 5 kW machine with a maximum speed of 8000 rpm are evaluated by means of nonlinear finite element analyses. With regard to an application in a high-performance drive with a wide field-weakening range and a position-sensorless control scheme, the characteristics are calculated for the conventional reluctance machine as well as the reluctance machine with additional permanent magnets in the rotor. The comparison of the characteristics of the conventional reluctance machine and the permanent magnet assisted reluctance machine clearly shows the improved performance in terms of electromagnetic torque and power factor due to the interior permanent magnets. Thereby, the suitability for the application in position-sensorless drives due to the high effective saliency is preserved.     

Integration of a modulated barrier photodiode with a doped-channelquasi-MISFET

An integration scheme for a front-end photoreceiver is demonstrated, wherein an identical GaAs-InGaAs-AlGaAs heterostructure is used for realizing a modulated barrier photodiode (MBP) and a doped-channel quasi-MISFET. The detectors exhibit optical gains of 200. The FETs have an extrinsic transconductance of 250 mS/mm, with f_f=12 GHz and f_max=21 GHz     

Radiation from a small monopole in a uniaxially anisotropic plasma

The radiation field of a small monopole over a ground plane covered with a uniaxially anisotropic plasma with an arbitrary inclination of the optical axis is studied. A steepest descent evaluation of the field integrals has been performed under the elliptic condition, and some calculated power patterns have been studied in comparison with those for a small dipole in an unbounded uniaxially anisotropic plasma. For an arbitrary inclination of the optic axis, considerable differences between the power patterns of the two configurations have been observed. Lateral waves and concentrated field regions are found to occur from mode coupling at the surface of the ground plane.     

Susceptibility analysis of wiring in a complex system combining a3-D solver and a transmission-line network simulation

This paper deals with the application of electromagnetic field-to-transmission-line coupling models for large cable systems analysis. It emphasizes the use of Agrawal's (1980) model applied here in a numerical simulation of an electromagnetic susceptibility problem up to 500 MHz. Based on the concepts of EM topology, the proposed methodology consists in calculating the incident fields with a three-dimensional (3-D) computer code and the coupling on cables with a multiconductor transmission-line network computer code. In order to validate the efficiency of this methodology in an industrial context, an experiment has been performed on a prototype wiring installed in a Renault Laguna car, stressed by an EM plane wave. Numerous validation configurations have been carried out. First, the prototype cable network under study has been tested on a ground plane to validate the coupling model but also, to validate the cable-network topology itself. Second, EM fields have been measured onto the structure and inside the structure. Then, they have been compared to 3-D calculations, performed with an FDTD code. Third, comparisons between measurements and calculations of bulk currents and voltages on 50 Ω loads on the wiring have been achieved     

Characteristics of a multimode laser diode in a dual-interferometerconfiguration

The results of an experimental investigation of an interferometric sensor scheme using a Michelson interferometer in conjunction with a Fabry-Perot reference cavity, illuminated by light from a multimode compact disk (CD)-type laser diode, are reported. The results are compared with the results of calculations using a simple theoretical model and good agreement is seen. Potential applications to interferometric-based sensors are discussed     

Design of a Thin Film Infrared Barcode on a Flexible Substrate

We report the design, fabrication and characterization of an infrared barcode. This barcode is composed of a bilayer of titanium and amorphous silicon on a flexible Kapton substrate. Information encoded in the barcode shows high contrast when viewed with an infrared imaging system in the 8 to 12 μm spectral region. The barcode information is concealed under visible viewing conditions, i.e., the barcode appears as an untreated, uniform metal sheet to a detector of visible radiation (400 to 700nm).     

Polarisation insensitive wavelength conversion using a lightinjected DFB-LD with a loop configuration

A configuration is proposed for polarisation insensitive wavelength conversion using an oscillating LD. By employing a loop with a polarisation beamsplitter, an optical signal is always injected into an LD in the TE mode irrespective of its polarisation state. An experiment using an MQW DFB-LD demonstrates the operation for a 4.5 Gbit/s signal     

Radiation from a rectangular waveguide with a lossy flange

The radiation from a rectangular waveguide with a lossy flange coating is studied both analytically and experimentally. An analytic method using Fourier analysis and an impedance boundary condition is proposed. The experiment was performed using a flange covered with a rubber ferrite sheet at an X-band frequency. The numerical and measured results agree well and show that the lossy flange improves the E-plane radiation pattern and the crosspolar radiation. A boresight gain drop of about 2 db is predicted theoretically and measured experimentally     

Generation of a single-lobe radiation pattern from a phased-array laser using a near-contact variable phase-shift zone plate

A very simple and practical technique to generate a stable, narrow-angle single-lobe far-field radiation pattern from an ordinary twin-lobe phase-locked laser diode array is demonstrated. A variable phase-shift zone plate mounted close to the laser output facet is used to readjust the phase distribution of the array into an all-in-phase distribution producing the desired single narrow-lobe far-field pattern.     

Radiation pattern of a vertical linear antenna over a conducting strip

The theoretical and experimental radiation patterns of an extended vertical line antenna placed over an infinite conducting strip are presented. The results show the nature of dependence of the level of back radiation upon the strip width and antenna height.     

Wavelength switching of a fiber laser with a Sagnac loop reflector

A multiwavelength fiber laser is constructed with an elliptical core erbium-doped fiber serving as an anisotropic gain medium. A broadband fiber reflector and a Sagnac loop reflector form a Fabry-Perot resonant cavity. Three lasing wavelengths are obtained which are stable over an hour at room temperatures. With one of them as reference wavelength, we can switch the other two by a polarization controller. The lasing wavelengths are also tunable. The effects of the anisotropic gain behavior of the erbium-doped fiber are also explored.