The orthogonal method for the geometry synthesis of a linearantenna array

The orthogonal method for geometry synthesis of a linear antenna array is presented. We start from an initial array, and we perturb the element positions by using an iterative procedure and applying the orthogonal method. Applications for arrays with uniform excitation give patterns with the desired sidelobe level     

On the performance of orthogonal space-time block coding with quantized feedback

Orthogonal space-time block coding (OSTBC) is a recent technique that provides maximal diversity gains on a space-time channel at a very modest computational cost. Recently, several authors have suggested to improve the performance of an OSTBC system by using a feedback of channel state information from the receiver to the transmitter. In this letter, we study the performance of an OSTBC system with quantized low-rate feedback. We establish conditions under which the system achieves full diversity and we also analyze the performance of a method that employs a feedback consisting of only one information bit.     

Generalized array pattern synthesis by the method of alternating orthogonal projections

A geometric formulation of the "null-steering" array antenna pattern synthesis problems for arbitrary array geometries is proposed. The formulation allows the use of some simple intuitive techniques for the construction of the array weights. In particular it is shown that the optimum weight vector can be obtained in an appropriately selected "weight vector subspace" via a recursive projection algorithm starting from its known projection on the vector lying in the constrained "look direction." The algorithm is computationally very simple and can be used for on-line solution of synthesis problems for complex array geometries.     

On a direct method of analysis and synthesis of the SPRT

The behavior of the sequential probability ratio test (SPRT) can be described using four performance measures, i.e., the probabilities of both types of erroralpha_{0}, alpha_{1}, and the average test lengths (or sample sizes)E_{0}, E_{1}for the given decision problem. Whereas Bayes optimality of the SPRT is well-known from the work of Wald and Wolfowitz, there is no method to evaluate the performance measures except for Wald's approximations. We present a method to evaluate the performance measures given the thresholds of the SPRT.     

On the autocorrelation function of quantized signal plus noise

We derive, in this paper, an exact formula for the autocorrelation function of a quantized sum of a deterministic signal and Gaussian noise. This result shows that if the voltage between quantizing levels is small compared to the rms noise voltage, the quantized autocorrelation function differs from the unquantized autocorrelation function by an error term of simple form. An example is included to illustrate the analysis.     

On the excitation of a circular loop antenna by travelling-and standing-wave current distributions

Presented here is an exact formulation of the electric and magnetic (EM) fields radiated by a circular loop antenna, assuming both travelling- and standing-wave current distributions. By using a differential current element positioned in an azimuthal direction as the starting point, the paper systematically develops the EM fields radiated by the circular loop via a vector potential theory. This approach leads to a general integral representation for the radiation characteristics of the loop antenna where we completely evaluate the resulting expressions, when the excitations of the loop assume travelling- and standing-wave distribution forms. In addition, this paper briefly examines a method to generate approximately such current distributions by coupling the loop to a two- or four-wire transmission line. Furthermore, the paper discusses a graphical representation of the current distribution plotted as a function of frequency or loop size. From the field expressions determined, we derive generalized closed-form results for some important design parameters for the loop antenna. These parameters include the radial component of the Poynting vector, the total power radiated by the loop, the directivity, the radiation resistance, and the effective area and height of the antenna. When we specialize to the important case of uniform current excitation, the exact values of the parameters deduced from the general expressions, are summarized and exhibited in a comprehensive table. This table facilitates the computations of these important physical parameters. Further analysis involving small argument and asymptotic approximations in the residts for the travelling-wave current excitation leads to closed-form expressions in terms of tabulated functions. Numerical results presented, include the fields radiated by the loop when the standing-wave current excitation admits a Fourier series representation. The present approach via potential theory reveals that the fields can be calculated in any arbitrary direction : this is consistent with a previous observation of Knudsen (1951, 1953) who employed a different approach.     

Voiced speech excitation synthesis using a sinusoidal model

A modification to the `shape-invariant' sinusoidal speech model is proposed, whereby the phases of the component sinewaves used for the excitation are made to add coherently at each glottal closure. Applied to pitch and time-scale modification, higher quality synthetic speech is produced when large changes are required     

OPTIMIZATION OF THE MAGNETIC DEFLECTION SYSTEM BY THE METHOD OF ORTHOGONAL DESIGN

By using the expressions of the field parameters and with the aid of the Orthogonal DesignMethod,we optimized the design of the saddle delection yoke with a ferromagnetic shield.The results ob-tained agree with the practical model.It is pointed out that the end ear and the distribution of the fieldparameter B_0(z)have important effects on the deflection aberrations.An example is given,in which the elec-tron optical properties of the deflection coils having cosine distribution and finite length and that of the de-flection coils having distributed winding are compared.     

A flexible optimization method for the pattern synthesis ofequispaced linear arrays with equiphase excitation

A synthesis method is proposed for linear arrays having equiphase excitation currents. In addition to allowing for the exact specification of the beamwidth and for the specification of individual sidelobe levels by index or as a function of bearing (e.g., angularly extended nulls), multiple deep narrow nulls can be specified at arbitrary bearing angles. The method is suitable for the design of broadside or endfire arrays with sum or difference patterns and can also be used for the design of superdirective arrays with good radiation efficiencies and sensitivity properties. For computational efficiency, the method uses a new constrained multivariable Remez-type L_∞ approximation technique     

Synthesis and optimization for arrays of nonparallel wire antennas by the orthogonal method

The orthogonal method is presented for synthesis and optimization problems of arrays of straight nonparallel thin-wire antennas. First, by the moment method, the far-zone field and the performance indices of the away are represented by expressions useful for applying the orthogonal method. By a procedure similar to the Gram-Schmidt method, the far-zone field and the indices of the array are modified. The new expressions, by a suitable procedure, give helpful formulas for synthesis and optimization. Several examples for possible uses are included.     

Computation of optical resonator modes by the method of resonance excitation

A novel computational method is used to calculate the modes of an optical resonator. The method is a computer simulation of the physical experiment of exciting a resonator externally and adjusting its length to resonate the various modes; the output at each resonance is purified by means of mode filters consisting of suitably adjusted resonators in tandem. The method is powerful and useful, and is applicable to resonators of arbitrary configuration. Calculated results for a Fabry-Perot resonator with a Fresnel number of ten are presented.     

Explicit geometry dependence of MOS transistor parameters by the pseudoboundary method

The pseudoboundary method is an engineering technique to extend the use of a single parameter set over the entire geometric design space for VLSI circuits. The technique eliminates adverse effects, such as negative output conductance, by clamping the evaluation of geometric dependence terms at the systematically determined boundaries of a primary region. The use of this technique is essential for accurate simulation of analog and digital circuits as well as prediction of circuit performance using next-generation submicron VLSI fabrication technologies. Results demonstrating the effectiveness of the technique using the widely accepted Berkeley short-channel IGFET model (BSIM) are presented, with data from transistors of different geometries ranging from 0.5 to 70 m.     

A method for the constructive synthesis of an antenna array of crossed orthogonal electric dipoles located near a perfectly conducting sphere

A method for the constructive synthesis of an antenna array of crossed orthogonal dipoles located over a perfectly conducting sphere is proposed. The method is based on a modification of the genetic algorithm for solving the problem of constructive synthesis of the antenna array. In implementation of this method, specific features of a known electrodynamic model are used with the radial coordinate of the radiator taken into account.     

Numerical solutions for orthogonal wavelet filters by Newton method

The wavelet transform has recently generated much interest in applied mathematics, signal processing and image coding. Mallat (1989) used the concept of the function space as a bridge to link the wavelet transform and multiresolution analysis. Daubechies (1990) added regularity conditions to find 2N, 2N10, tap coefficients for orthogonal wavelet filters. Owing to the difficulty of finding their closed solutions for large N a numerical method called the Newton method is proposed. We constructed the orthogonal wavelet filter with 2N-tap coefficients by N linear equations and N nonlinear equations. The 2N-tap, 2N10, coefficients we found are very consistent with those of Daubechies. Also, the method can be used to find the orthogonal wavelet filter with N-tap coefficients for N>10.     

Estimation of the mean of a quantized signal

The accuracy with which the mean of an analog signal can be estimated from the mean after quantization by an analog/digital converter is examined. The mean of the quantized signal is a good measure of the mean of the input, down to lower values of input noise than is commonly supposed.     

On convergence of information contained in quantized observations

By the well-known information processing theorem, quantizations of observations reduce values of convex information functionals such as the information divergence, Fisher information, or Shannon information. This paper deals with the convergence of the reduced values of these functionals to their original unreduced values for various sequences P/sub n/ of partitions of the observation space. There is extensive literature dealing with this convergence when the partitions are nested in the sense P/sub n/ /spl sub/ P/sub n+1/ for all n. A systematic study for nonnested partitions P/sub n/, often considered in the literature, seems to be missing. This paper tries to partially fill this gap. It proves the convergence for the most common types of partitions. The results are formulated for generalized information divergences (Csiszar (1963, 1967, 1973) divergences), generalized Fisher information, and generalized Shannon information. Their applicability is illustrated on the Barron (1992) estimators of probability distributions.     

On the geometry of isotropic arrays

We consider array geometries whose direction-of-arrival (DOA) estimation performance is isotropic. An isotropic array is one whose Cramer-Rao bound (CRB) on the DOA of a single source is uniform for all angles. For both planar arrays and volume arrays we derive necessary and sufficient conditions on array element locations so that the array is isotropic. We also present several designs of isotropic planar and volume arrays. The results apply to both narrowband and wideband scenarios. We analyze the special case where a planar array is used to estimate the DOA of three-dimensional (3-D) source. Finally, we compare isotropic array performance to the best possible array performance.     

On the excitation of VLF waves

The ratio between the excitation factors of vertically and horizontally polarized sources is equal to the squared ratio between the characteristic impedance of free space and the ground level coupling impedance of TE and TM field components. This relation provides an analytical check of numerically calculated excitation factors. Also, the need of directly calculating the two excitation factors of an anisotropic environment may be obviated if the excitation factor of an isotropic environment is used for estimating the dominant field components of a given quasi-TM or quasi-TE mode.     

正交条纹级次分区域预编码校正Gamma非线性方法

数字投影仪的非线性响应是近年来研究的热点问题,因为数字投影仪虽然能避免物理光栅投影的各种缺陷,但其自身的非线性直接影响了输出信息,是相位误差的主要来源,进而影响了测量精度。针对数字条纹投影三维测量中存在的Gamma非线性和不同区域Gamma值并不一致的问题,提出一种通过正交条纹级次分区域预编码校正Gamma非线性方法,通过正交条纹划分区域,对每个区域使用多项式拟合计算预编码值校正该区域条纹图像。使用该方法校正后相位误差减少了82.24%,适用于任意投影仪与相机之间的位置关系,只需要精细化计算一套分区域预编码系数并由此生成编码条纹图,即可满足该系统此后的测量需求,该方法灵活性强、精确度高。     

On orthogonal designs and space-time codes

Orthogonal-design-based space-time (ODST) codes of size (n/spl times/n) offer maximum diversity gain advantage and a simple yet optimal decoding algorithm under an arbitrary signal alphabet or constellation A. However, these designs only exist for n=2, 4, 8 when A is real and for n=2 when A is complex. In this letter, we address the question of the existence of ODST codes of other sizes when A is restricted to be a proper subset of either real or complex numbers. We refer to these as restricted-alphabet ODST (RA-ODST) codes. We show that real RA-ODST codes of size greater than 8 that also guarantee maximum diversity advantage do not exist. Without the diversity requirement, RA-ODST codes exist only when A={a,-a}, 0