Minimum-redundancy linear arrays for cyclostationarity-based sourcelocation

The problem of designing minimum-redundancy linear arrays (MRLAs) and appropriate augmentation techniques to be utilized with cyclostationarity-exploiting (cyclic) methods for source location is addressed. The MRLA geometries proposed in the literature for the conventional case, which apply equally well when the signals of interest exhibit cyclostationarity are not appropriate when they exhibit conjugate cyclostationarity. In this case, the problem of finding optimal MRLAs is restated as the problem of number theory that is commonly referred to as the postage stamp problem. Results of computer simulations show that in densely crowded environments, the use of cyclic methods with MRLA geometries and appropriate matrix augmentation techniques can offer a significant performance improvement on cyclic methods that do not resort to matrix augmentation techniques     

Phase weighting for linear antenna arrays

A novel method for introducing an amplitude taper onto a linear array is described, using equal amplitude elements with randomised phase reversals to create an effective taper.     

Optimal windowing for wideband linear arrays

The problem of constructing a wideband beam pattern that is concentrated in both angle and frequency is discussed. This paper is a direct extension of the work of Slepian and co-workers on time- and frequency-limited functions. It is shown that the singular vectors and singular functions of the mapping relating the set of weights of a linear wideband array to its far-field directivity pattern have both concentration properties and double orthogonality properties and so they can be thought of as the wideband equivalents of the discrete prolate spheroidal sequences and wave functions. These singular functions are used to obtain approximations to a frequency-invariant beam pattern.     

Electric field distributions of waveguide arrays for local tumor hyperthermia

Total electric field distributions in muscle and fat tissues, due to colinear rectangular waveguide arrays at 2.45 GHz and 915 MHz were calculated. The effect of phase difference between incident phases on the field pattern is shown. Phase adjustment is capable of furnishing control of either field-size or focused-field performance of the multi-element, direct-contact applicator. The tissue-applicator junction is analyzed by means of the Generalized Scattering Matrix (GSM) of the generalized 2-port discontinuity, assuming that the lossy homogeneous tissue is immersed in a large waveguide. This method provides an exact calculation of multimodal fields, as well as reflection and coupling coefficients in the apertures.     

Beamspace Root-MUSIC for minimum redundancy linear arrays

Beamspace Root-MUSIC, a computationally efficient beamspace implementation of Root-MUSIC developed recently for use in conjunction with a uniformly spaced linear array (ULA), is discussed. Computationally efficient methods for using beamspace Root-MUSIC in conjunction with a minimum redundancy linear array (MRLA) for both the narrowband and wideband cases are developed. The MRLA is attractive in that it offers enhanced detection performance and enhanced resolution capability relative to a ULA having the same number of elements     

Optimization of linear arrays for broadband signals

The effect of broadband signals on the far-zone field of long arrays is investigated in terms of the energy radiation pattern. A generalized directive gain is introduced which depends on the signal spectrum. With maximum directivity as a criterion it is shown that the problem of optimizing a long isotropic array with respect to a given signal can be associated with a classical eigenvalue problem. The concept of array-bandwidth is introduced. Computed curves for directivity and directive gain are given in terms of this parameter and signal bandwidth. It is shown that while little improvement in directivity is achieved by optimizing the distribution coefficients of an array, a substantial reduction in sidelobe level is obtained when the signal bandwidth is comparable to the array bandwidth.     

Theoretical and experimental SAR distributions for interstitialdipole antenna arrays used in hyperthermia

Theoretical predictions and experimental measurements of power deposition in muscle tissue phantoms are compared for various arrays of microwave dipole antennas used for hyperthermia cancer therapy. The antennas are linear coaxial dipoles which are inserted into small nylon catheters implanted in the tumor volume. The specific absorption rate (SAR) patterns for a 2-cm square array of four 915-MHz antennas are presented for both resonant and nonresonant dipoles. Arrays of dipoles with lengths much shorter than the resonant half-wavelength have a far more reactive input impedance and a much smaller absolute SAR magnitude in the array center than is seen for arrays of resonant dipoles, and the maximum SAR shifts from the array center to the antenna surfaces. The absolute length of the volume heated by the small-diameter antennas with the longer half-wavelength was longer than that of the larger-diameter antennas. SAR distributions for 4-cm square arrays of eight and nine antennas fed with equal amplitude and phase are also compared. It is shown that much of the array volume has a power deposition less than 25% of the maximum SAR and that the distribution is nonuniform for both the eight- and nine-antenna configurations     

Logical circuits for use in iterative arrays

Two logical circuits are proposed, and some examples of iterative arrays formed using them are discussed.     

Constrained beam scanning for linear arrays of antennas

A method to scan the radiation pattern of a linear array, simultaneously reducing the pattern amplitude in constant directions, is described. The scanning process is obtained by phase control of the array excitations and, if necessary, by amplitude perturbations not exceeding a small threshold.     

基于伪数据域的最小冗余线阵测向算法

利用时间信息可以有效的压制干扰和噪声,可以大大的提高角度估计性能和空间分辨率.与传统只利用空间信息的最小冗余测向算法不同,由于所提方法联合时间和空间信息而获得了更多有效阵元数以及扩展了有效阵列孔径,因此,大大的提高了估计性能.提出方法充分利用了信号的时间信息去构造伪数据矩阵,利用奇异分解或计算简单的无需特征分解的线性变换方法获得波达方向.仿真试验充分说明了所提方法不论在精度估计还是分辨能力都表现出优越的性能.     

Propagation in linear arrays of parallel wires

Consider an array of parallel perfectly-conducting wires extending between and normal to two infinite parallel perfectly-conducting planes. One wire acts as a resonator, having natural frequencies at which it is an integral number of half-wavelengths long. One might at first think that n wires would have n times as many natural frequencies. It turns out, however, that the modes characteristic of the system of many wires are plane electromagnetic waves with the field normal to the wires. All the modes of the array have frequencies for which the wires are an integral number of half-wavelengths long. In circuit terms, the wires, which act as resonators, are uncoupled. The electric and magnetic couplings are equal and opposite.     

一维线阵唯相位低副瓣技术分析

实现了基于最速下降方法(SDM)的唯相位低副瓣技术,提出了SDM方法的步长公式,对不同阵元分析了唯相位技术的低副瓣性能和能量效率水平,总结了最高副瓣电平同阵元数目的关系,分析了幅相加权对于最高副瓣电平和能量效率水平的影响。     

Mutual coupling and element efficiency for infinite linear arrays

A formulation is presented of the interrelationship among mutual coupling element efficiency, active impedance, and element radiation patterns for infinite linear (uniformly spaced) arrays. Numerical results are obtained for element efficiency and mutual coupling when the array elements are elementary dipoles. A new lower upper bonnd is obtained on element efficiency. This upper bound is expressed directly in terms of the element patterns in the open-circuit array environment.     

An optimization program for linear arrays of parallel wires

This is a composite program suitable for handling certain analysis and optimization problems involving linear arrays of parallel thin-wire antennas     

Improved coherent DOA estimation algorithm for uniform linear arrays

An improved algorithm on coherent direction-of-arrival (DOA) estimation is presented in this article, with the objective to overcome the unsatisfactory performances of estimation of signal parameter via rotational invariance techniques (ESPRIT)-like algorithms (Han and Zhang, IEEE Antennas and Wireless Propagation Letters 2005;4:443–446). On the basis of trilinear model by reconstructing a series of Toeplitz matrix from the co-variance matrix of array output, our proposed algorithm is to resolve the DOAs of coherent signals, which not only has much better DOA estimation performance than algorithms of ESPRIT-like and multi-invariance ESPRIT but also identifies more DOAs than ESPRIT-like algorithm. Simulation results demonstrate its validity.     

The root-trajectory method--A tool for analyzing linear adaptive arrays

A root-trajectory method is described that seeks to obviate the need for an extensive set of antenna patterns to describe the behavior of an adaptive array during its adaptation process. This aim is achieved by use of Schelkunoff's idea of describing a linear array in terms of an array polynomial. The roots of this polynomial have a direct interpretation in obtaining the array gain, and the trajectories of these roots during the adaptation process give a simple visualization of the dynamic behavior of the adaptive array.     

Spatial averaging of time-frequency distributions for signalrecovery in uniform linear arrays

This paper presents a new approach based on spatial time-frequency averaging for separating signals received by a uniform linear antenna array. In this approach, spatial averaging of the time-frequency distributions (TFDs) of the sensor data is performed at multiple time-frequency points. This averaging restores the diagonal structure of the source TFD matrix necessary for source separation. With spatial averaging, cross-terms move from their off-diagonal positions in the source TFD matrix to become part of the matrix diagonal entries. It is shown that the proposed approach yields improved performance over the case when no spatial averaging is performed. Further, we demonstrate that in the context of source separation, the spatially averaged Wigner-Ville distribution outperforms the combined spatial-time-frequency averaged distributions, such as the one obtained by using the Choi-Williams (1989) distribution. Simulation examples involving the separation of two sources with close AM and FM modulations are presented     

A configurable ROM circuit for use in gate arrays

A double word-line memory ROM (DWM-ROM) for use in gate arrays is described. It allows for an automatic layout by reducing the input pin count in the word lines by using two-step addressing. The advantage of this method has been verified by implementing a 16-bit microprocessor using an 8 K-gate array, based on a gate-isolated cell configuration, employing 1.5-/spl mu/m double-metal CMOS technology. The 16-bit /spl times/ 64-word ROM in the processor saves 30% of the transistor area due to the DWM-ROM.