Low order anti-aliasing filters for sparse signals in embedded applications

Major emphasis, in compressed sensing (CS) research, has been on the acquisition of sub-Nyquist number of samples of a signal that has a sparse representation on some tight frame or an orthogonal basis, and subsequent reconstruction of the original signal using a plethora of recovery algorithms. In this paper, we present compressed sensing data acquisition from a different perspective, wherein a set of signals are reconstructed at a sampling rate which is a multiple of the sampling rate of the ADCs that are used to measure the signals. We illustrate how this can facilitate usage of anti-aliasing filters with relaxed frequency specifications and, consequently, of lower order.     

Some formulas and applications of nonuniform sampling ofbandwidth-limited signals

An exact nonuniform sampling scheme is proposed based on Cauchy's residue theorem. The noise behavior is studied and the consequences for possible applications given. An inherently nonuniform sampling instrument is built and used in experiments. The results of the application of the formulas for the processing of astronomical data and the error correction of high-frequency network analyzers are given     

Analysis of perforated magnetic shields for electric power applications

The shielding performance of perforated magnetic shields for electric power applications is described. The shielding of an axisymmetric induction heating device is studied as a function of frequency, number of perforations and dimensions of the perforations. From the numerical point of view, the perforations cause the numerical model to be 3D. A numerical optimisation is carried out to find the optimal geometry with respect to the shielding factor and the volume of the shield. For the optimisation, two approaches are presented. The first approach is fast and easy-to-implement, but has limited accuracy. It uses a classical 2D axisymmetric model where the perforations are approximated by 'axisymmetric air gaps' resulting in a segmented shield. It is shown how to modify the 2D model to obtain results that are similar to the ones of a 3D model. The second approach is more accurate although quite fast, but more difficult to implement. It combines a 3D thinshell finite element model with the unmodified 2D model in a space mapping optimisation algorithm. The validation of both models is based on experimental work for an unperforated shield and for the optimised perforated shield.     

Use of modulated excitation signals in medical ultrasound. Part II: Design and performance for medical imaging applications

In the first paper, the superiority of linear FM signals was shown in terms of signal-to-noise ratio and robustness to tissue attenuation. This second paper in the series of three papers on the application of coded excitation signals in medical ultrasound presents design methods of linear FM signals and mismatched filters, in order to meet the higher demands on resolution in ultrasound imaging. It is shown that for the small time-bandwidth (TB) products available in ultrasound, the rectangular spectrum approximation is not valid, which reduces the effectiveness of weighting. Additionally, the distant range sidelobes are associated with the ripples of the spectrum amplitude and, thus, cannot be removed by weighting. Ripple reduction is achieved through amplitude or phase predistortion of the transmitted signals. Mismatched filters are designed to efficiently use the available bandwidth and at the same time to be insensitive to the transducer's impulse response. With these techniques, temporal sidelobes are kept below 60 to 100 dB, image contrast is improved by reducing the energy within the sidelobe region, and axial resolution is preserved. The method is evaluated first for resolution performance and axial sidelobes through simulations with the program Field II. A coded excitation ultrasound imaging system based on a commercial scanner and a 4 MHz probe driven by coded sequences is presented and used for the clinical evaluation of the coded excitation/compression scheme. The clinical images show a significant improvement in penetration depth and contrast, while they preserve both axial and lateral resolution. At the maximum acquisition depth of 15 cm, there is an improvement of more than 10 dB in the signal-to-noise ratio of the images. The paper also presents acquired images, using complementary Golay codes, that show the deleterious effects of attenuation on binary codes when processed with a matched filter, also confirmed by presented simulated images.     

Analysis of voltage signals from superconducting accelerator magnets

We present two techniques used in the analysis of voltage tap data collected during recent tests of superconducting magnets developed by the Superconducting Magnet Program at Lawrence Berkeley National Laboratory. The first technique was used on a quadrupole to provide information about quench origins that could not be obtained using the time-of-flight method. The second technique illustrates the use of data from transient flux imbalances occurring during magnet ramping to diagnose changes in the current-temperature margin of a superconducting cable. In both cases, the results of this analysis contributed to make improvements on subsequent magnets.     

Analysis of a three-coil contactless power transfer system for high-power applications

Recently, contactless power transfer (CPT) has become very popular in various fields of applications such as electronic appliances, medical implant devices, electrical vehicles, etc. When air gap distance between the transmitting and receiving coils of a CPT system increases, coupling coefficient between the coils decreases. In a large-air-gap CPT system, by incorporating an additional coil between the transmitting and receiving coils, coupling coefficient can be enhanced. Consequently, efficiency of a large-air-gap CPT system is improved. In this study, a three-coil system has been compared with a two-coil system using basic circuit models. Thereafter, the basic circuit models of two-coil and three-coil systems have been studied to confirm energy efficiency differences between the two systems for high-power applications. Using simplified circuit models, conditions for higher energy efficiency of a three-coil system than a two-coil system have been derived and it has been established that power transfer efficiency of a three-coil system has improved significantly in comparison with a traditional two-coil system. To confirm the theory, a two-coil and a three-coil systems with an air gap distance of 18 cm and a lateral misalignment of 3.5 cm have been verified using Ansys simulation tool for an output power of 2 kW.     

Analysis of optical absorption in silicon nanowire arrays for photovoltaic applications

This paper presents analysis of the optical absorption in silicon nanowire arrays that have potential applications in solar cells. The effects of wire diameter, length, and filling ratio on the absorptance of nanowire arrays are simulated. The study reveals that nanowire arrays with moderate filling ratio have much lower reflectance compared to thin films. In a high-frequency regime, nanowire arrays have higher absorptance than their thin film counterparts. In low-frequency regime, nanowire arrays absorb less but can be designed to approach that of the film by changing the filling ratio.     

Analysis of damped sinusoidal signals via a frequency-domaininterpolation algorithm

An algorithm for the estimation of the parameters that characterize a linear combination of damped sinusoids is presented. The procedure is based on an interpolation scheme applied to the discrete Fourier transform samples. At first, a single damped exponential signal is analyzed; then the results are extended to multiple damped sinewaves. Numerical simulations show the good accuracy obtained under various measurement conditions; both the effects of spectral interference and wideband noise are considered, proving the reliability of the proposed method in a number of engineering applications     

Software-configurable converter for sensor signals

A new approach to the organization of software for sensor signal converters is considered. A solution to the problem using an operational system and modelling within that system is proposed.     

Analysis of matching errors in comparison of microwave noise signals

Translated from Izmeritel'naya Tekhnika, No. 11, pp. 52–54, November, 1991.     

Analysis of correlation properties of random processes using short signals

The possibility of studying the correlation properties of random processes within the framework of a multifractal formalism is considered. It is shown that the calculation of Hölder exponents allows one to judge on the correspondence of an analyzed signal to a process with known statistical properties using a significantly smaller amount of experimental data as compared to that necessary for evaluating the law of correlation decay by means of calculations of the autocorrelation function.     

一种新的火炮振动加速度信号积分处理方法及其应用

本文介绍了一种简称为"分时段校零积分法"的数值积分处理方法.它可将火炮振动加速度信号经积分获得相应的速度与位移信号.文中简要分析了该方法的原理,叙述了为准确获得加速度信号所采用的相关技术措施,包括加速度计的选型、缓冲、滤波与安装,并结合实验室与靶场测试结果,讨论了它的一些有效应用前景.     

超声多普勒信号的频谱分析

超声多普勒信号具有非平稳性，利用传统的短时傅里叶变换分析该信号不能同时得到较高的时间频率精度，为克服这一缺点，本文简要介绍了多普勒信号频谱分析的几种新方法，并将它们和传统的方法进行性能的比较。     

Tactile warning signals for in-vehicle systems

The last few years have seen growing interest in the design of tactile warning signals to direct driver attention to potentially dangerous road situations (e.g. an impending crash) so that they can initiate an avoidance maneuver in a timely manner. In this review, we highlight the potential uses of such warning signals for future collision warning systems and compare them with more traditional visual and auditory warnings. Basic tactile warning signals are capable of promoting driver alertness, which has been demonstrated to be beneficial for forward collision avoidance (when compared to a no warning baseline condition). However, beyond their basic alerting function, directional tactile warning signals are now increasingly being utilized to shift the attention of the driver toward locations of interest, and thus to further facilitate their speeded responses to potential collision events. Currently, many researchers are focusing their efforts on the development of meaningful (iconic) tactile warning signals. For instance, dynamic tactile warnings (varying in their intensity and/or location) can potentially be used to convey meaningful information to drivers. Finally, we highlight the future research that will be needed in order to explore how to present multiple directional warnings using dynamic tactile cues, thus forming an integrated collision avoidance system for future in-vehicle use.     

Measuring system for investigating noise-like signals

A measuring system for investigating noise-like signals is described. The arrangement can be used in robot vision systems and to record and measure electromagnetic interference.Translated from Izmeritel'naya Tekhnika, No. 8, pp. 57–59, August, 1995.