Crosstalk-based capacitance measurements: theory and applications

Geometry scaling increases the relative effect of coupling capacitances on performance, power, and noise so that they need to be carefully taken into account during process development, characterization, and monitoring. In the last decade, charge-based capacitance measurements (CBCMs) have been widely used to estimate on-chip wiring and coupling capacitances because of their accuracy and simplicity. We provide a thorough theoretical and experimental study of CBCMs applied to the selective extraction of cross-coupling capacitances. We take a historical perspective starting from the original CBCM approach proposed by Chen in 1996, and we present a new technique for crosstalk-based capacitance measurements (CTCMs). CTCMs improve the accuracy and usability of CBCMs while reducing the complexity of the test structures. We present the theory of CTCM, we provide experimental results demonstrating its improved accuracy, and we discuss its application to a wide range of process monitoring and testing tasks. Experimental results are used throughout the paper to support the discussion.     

Multiresolution moment filters: theory and applications

We introduce local weighted geometric moments that are computed from an image within a sliding window at multiple scales. When the window function satisfies a two-scale relation, we prove that lower order moments can be computed efficiently at dyadic scales by using a multiresolution wavelet-like algorithm. We show that B-splines are well-suited window functions because, in addition to being refinable, they are positive, symmetric, separable, and very nearly isotropic (Gaussian shape). We present three applications of these multiscale local moments. The first is a feature-extraction method for detecting and characterizing elongated structures in images. The second is a noise-reduction method which can be viewed as a multiscale extension of Savitzky-Golay filtering. The third is a multiscale optical-flow algorithm that uses a local affine model for the motion field, extending the Lucas-Kanade optical-flow method. The results obtained in all cases are promising.     

Grayscale level connectivity: theory and applications

A novel notion of connectivity for grayscale images is introduced, defined by means of a binary connectivity assigned at image-level sets. In this framework, a grayscale image is connected if all level sets below a prespecified threshold are connected. The proposed notion is referred to as grayscale level connectivity and includes, as special cases, other well-known notions of grayscale connectivity, such as fuzzy grayscale connectivity and grayscale blobs. In contrast to those approaches, the present framework does not require all image-level sets to be connected. Moreover, a connected grayscale object may contain more than one regional maximum. Grayscale level connectivity is studied in the rigorous framework of connectivity classes. The use of grayscale level connectivity in image analysis applications, such as object extraction, image segmentation, object-based filtering, and hierarchical image representation, is discussed and illustrated.     

Two-dimensional subband transforms: theory and applications

The one-dimensional subband FFT (SB-FFT) and one-dimensional SB-DCT were extended to the two-dimensional (2-D) case to obtain the 2-D SB-FFT and the 2-D SB-DCT. The two-dimensional subband transforms are based on subband decomposition of the input sequence in both dimensions. They use knowledge about the input signal to obtain an approximation to their transform by discarding the computations in bands that have little energy in both dimensions. Computational savings can be obtained from calculating only the remaining subbands. In many applications the computational speed is so important that some error in the calculated transform can be accepted. In image processing, due to the nature of most natural scenes, most of the energy content of the corresponding digitised images is concentrated predominantly in the low-low spatial frequency domain. The concentration of the energy in a localised region of the transform domain makes the approximate subband transform computation quite suitable for the calculation of the 2-D image spectra. The complexity and accuracy of both 2-D transforms are studied in detail in the paper. The approximation errors in both transforms are derived for a general case, in which any band out of M bands is to be computed. Both transforms are modified to be fully adaptive to select the band of interest to be computed. Image transform application examples are included. Savings in computational complexity of image transforms are shown. The efficiency of subband transforms of different images is indicated by computing the signal-to-noise ratio in the reconstructed images.     

Combined coding and modulation: theory and applications

The theoretical aspects of the encoding process are investigated, resulting in a precise definition of linear codes together with theorems that clarify how they can be obtained. A particular subset of linear codes, called superlinear codes, for which the performance analysis is highly simplified is identified. The most relevant performance measures for the analysis of this class of codes are discussed. The minimum Euclidean distance and the event and bit error probabilities are found analytically using the uniform error property (when applicable) or variations on it. This yields accurate upper and lower bounds to the error rate at the price of reasonable computational complexity. The theory is then applied to the search for `good' codes and to their performance evaluation. The cases of 16- and 32-PSK codes, which are good candidates for use in digital satellite transmission, are considered. Several new results in terms of error event and bit error probabilities are presented, showing considerable gains in terms of SNR with respect to the uncoded case     

Discrete frequency warped wavelets: theory and applications

We extend the definition of dyadic wavelets to include frequency warped wavelets. The new wavelets are generated and the transform computed in discrete-time by alternating the Laguerre transform with perfect reconstruction filterbanks. This scheme provides the unique implementation of orthogonal or biorthogonal warped wavelets by means of rational transfer functions. We show that the discrete-time warped wavelets lead to well-defined continuous-time wavelet bases, satisfying a warped form of the two-scale equation. The shape of the wavelets is not invariant by translation. Rather, the “wavelet translates” are obtained from one another by allpass filtering. We show that the phase of the delay element is asymptotically a fractal. A feature of the warped wavelet transform is that the cut-off frequencies of the wavelets may be arbitrarily assigned while preserving a dyadic structure. The new transform provides an arbitrary tiling of the time-frequency plane, which can be designed by selecting as little as a single parameter. This feature is particularly desirable in cochlear and perceptual models of speech and music, where accurate bandwidth selection is an issue. As our examples show, by defining pitch-synchronous wavelets based on warped wavelets, the analysis of transients and denoising of inharmonic pseudo-periodic signals is greatly enhanced     

亚波长薄膜堆栈超构材料：理论及应用

亚波长薄膜堆栈超构材料,作为超构材料领域一个特殊的组成部分,因其具有亚波长厚度、无需复杂光刻加工以及可低成本大面积制备等诸多优点,吸引了人们越来越多的关注。本文聚焦回顾近些年亚波长薄膜堆栈超构材料相关研究进展,首先简要回顾了多层薄膜堆栈体系的基础理论研究方法,侧重介绍了亚波长薄膜堆栈超构材料的新理论新设计;接着,着重介绍了基于亚波长薄膜堆栈超构材料的若干典型应用,具体包括结构色调控、光致发光增强、窄带红外光源、红外伪装以及其他一些有趣应用;最后,探讨并展望了亚波长薄膜堆栈超构材料领域未来的发展方向以及其可能遇到的问题挑战。     

Complete-to-overcomplete discrete wavelet transforms: theory and applications

A new transform is proposed that derives the overcomplete discrete wavelet transform (ODWT) subbands from the critically sampled DWT subbands (complete representation). This complete-to-overcomplete DWT (CODWT) has certain advantages in comparison to the conventional approach that performs the inverse DWT to reconstruct the input signal, followed by the a/spl grave/-trous or the lowband shift algorithm. Specifically, the computation of the input signal is not required. As a result, the minimum number of downsampling operations is performed and the use of upsampling is avoided. The proposed CODWT computes the ODWT subbands by using a set of prediction-filter matrices and filtering-and-downsampling operators applied to the DWT. This formulation demonstrates a clear separation between the single-rate and multirate components of the transform. This can be especially significant when the CODWT is used in resource-constrained environments, such as resolution-scalable image and video codecs. To illustrate the applicability of the proposed transform in these emerging applications, a new scheme for the transform-calculation is proposed, and existing coding techniques that benefit from its usage are surveyed. The analysis of the proposed CODWT in terms of arithmetic complexity and delay reveals significant gains as compared with the conventional approach.     

Wavelet footprints: theory, algorithms, and applications

Wavelet-based algorithms have been successful in different signal processing tasks. The wavelet transform is a powerful tool because it manages to represent both transient and stationary behaviors of a signal with few transform coefficients. Discontinuities often carry relevant signal information, and therefore, they represent a critical part to analyze. We study the dependency across scales of the wavelet coefficients generated by discontinuities. We start by showing that any piecewise smooth signal can be expressed as a sum of a piecewise polynomial signal and a uniformly smooth residual (Theorem 1). We then introduce the notion of footprints, which are scale space vectors that model discontinuities in piecewise polynomial signals exactly. We show that footprints form an overcomplete dictionary and develop efficient and robust algorithms to find the exact representation of a piecewise polynomial function in terms of footprints. This also leads to efficient approximation of piecewise smooth functions. Finally, we focus on applications and show that algorithms based on footprints outperform standard wavelet methods in different applications such as denoising, compression, and (nonblind) deconvolution. In the case of compression, we also prove that at high rates, footprint-based algorithms attain optimal performance (Theorem 3).     

2-D symmetry: theory and filter design applications

In this comprehensive review article, we present the theory of symmetry in two-dimensional (2-D) filter functions and in 2-D Fourier transforms. It is shown that when a filter frequency response possesses symmetry, the realization problem becomes relatively simple. Further, when the frequency response has no symmetry, there is a technique to decompose that frequency response into components each of which has the desired symmetry. This again reduces the complexity of two-dimensional filter design. A number of filter design examples are illustrated.     

The theory of top-loaded antennas: Integral equations for the currents

The general problem involving the distribution of current and the driving-point impedance of a top-loaded antenna is formulated. Consideration is given to an idealized structure having one or more cylindrical top-loading elements. For the practically important case involving conductors of small radius, the axial currents are obtained as the solution to a pair of coupled integral equations. Approximate solutions obtained by numerical methods for the invertedL-,T-, and four-element top-loaded antennas are compared with measured driving-point impedances. Satisfactory agreement indicates the possibility of utilizing the theory in the analysis of practical configurations involving many top-loading elements.     

Specular null polarization theory: applications to radarmeteorology

Specular null polarization theory (SNPT) has been recently introduced for the case of coherent scattering where a 2×2 scattering matrix is sufficient to describe the scattering process. In this paper, SNPT is extended to the case of incoherent scattering. Optimum polarization states are derived and the results are discussed in relation to the classic radar optimum polarizations. In traditional radar polarimetry, modeling of the radar receive/transmit network is included in the radar voltage equation and consequently this affects the optimum polarizations and polarization responses of scatterers. SNPT eliminates this effect and therefore allows for a more direct analysis of scatterers. Modeling of ensembles of precipitation particles is used to illustrate the results of the analysis     

无透镜片上显微成像技术:理论、发展与应用

同时实现大视场、高分辨率成像是光学显微技术发展至今不断追求的永恒目标。传统光学显微镜由于其光学设计原理限制,空间带宽积一般总是限制在百万像素量级,从而无法同时兼顾高分辨率与大视场。另一方面,复杂的光学系统也使显微镜变得日趋昂贵、笨重、复杂且难以维护,极大地限制了其推广和应用。无透镜片上显微成像技术是近年来发展出的一种新概念计算成像技术:其不利用成像透镜聚焦,而直接将所观测的样本紧贴于成像器件光敏面上方记录图像,并结合相应的图像恢复算法实现清晰物像的反演与重构。由于具有视野大、分辨率高、无需标记、成本低、便携性好和可实现三维（3D）成像等优点,无透镜片上显微镜有望拓展传统显微成像技术的疆界,成为一种新型的快捷、便携的就地检验（POCT）工具。文中从无透镜成像基本原理、实验系统、重构方法及其典型应用进行了综述。最后,讨论了无透镜显微成像现存的一些关键问题以及今后可能的发展方向。     

电子出射波重构的基本原理和应用

随着场发射枪透射电子显微镜的普及，电镜的信息分辨极限和点分辨率成为表征电镜分辨本领的两个重要指标。由于电镜衬度传递函数的振荡特性，用场发射透射电镜拍摄的高分辨像在其点分辨率和信息分辨极限之间的信息很难解释。电子出射波重构就是通过拍摄系列欠焦高分辨像，计算获得电子离开样品表面的出射波函数，将电镜的分辨本领由点分辨率延伸到其信息分辨极限，井消除球差、欠焦、像散等影响，有望在中等电压电镜上获得近埃、乃至亚埃级可直接解释的高分辨像，实现C、N、O等轻元素单原子列探测，为今后定量电子显微学研究奠定基础。     

Small-signal theory of unipolar injection currents in solids

Small-signal behavior of unipolar currents injected in semiconductors or insulators is theoretically studied. The one-dimensional problem of plane-parallel electrodes is considered. Analysis neglects diffusion but takes into account carrier mobility field dependence, ionized impurities, and trapping. Arbitrary boundary conditions are assumed. The present theory describes the small-signal response by a set of four complex quantities recalling the Llewellyn-Peterson coefficients for vacuum tubes. The present paper represents a generalization of previous results obtained by Yoshimura in the following respects: new physical phenomena (hot carrier effects and trapping) are taken into account, and new applications of the derived coefficients are suggested. This paper also contains a brief comment on physical situations and devices that can be studied by the present theory, paying particular attention to high-frequency negative-resistance devices.