Signal processing for microcalorimeters

Most of the power in the signals from microcalorimeters occurs at relatively low frequencies. At these frequencies, typical amplifiers will have significant amounts of 1/f noise. Our laboratory systems can also suffer from pickup at several harmonics of the AC power line, and from microphonic pickup at frequencies that vary with the configuration of the apparatus. We have developed some optimal signal processing techniques in order to construct the best possible estimates of our pulse heights in the presence of these non-ideal effects. In addition to a discussion of our laboratory systems, we present our plans for providing this kind of signal processing in flight experiments.     

Signal processing: Opportunities for superconductive circuits

Prime motivators in the evolution of increasingly sophisticated communication and detection systems are the needs for handling ever wider signal bandwidths and higher data processing speeds. These same needs drive the development of electronic device technology. Until recently the superconductive community has been tightly focused on digital devices for high speed computers. The purpose of this paper is to describe opportunities and challenges which exist for both analog and digital devices in a less familiar area, that of wideband signal processing. The function and purpose of analog signal-processing components, including matched filters, correlators and Fourier transformers, will be described and examples of superconductive implementations given. A canonic signal-processing system is then configured using these components in combination with analog/digital converters and digital output circuits to highlight the important issues of dynamic range, accuracy and equivalent computation rate. Superconductive circuits hold promise for processing signals of 10-GHz bandwidth. Signal processing systems, however, can be properly designed and implemented only through a synergistic combination of the talents of device physicists, circuit designers, algorithm architects and system engineers. An immediate challenge to the applied superconductivity community is to begin sharing ideas with these other researchers.     

Signal processing techniques for CCD image sensors

Charge coupled device (CCD) image sensors are currently used in many image processing applications such as facsimile and bar code reading. Because the photodetectors in the device have finite areas, the output signal from the CCD image sensor is only an approximation to the sampled value of the image. In this paper we discuss the reconstruction of bar codes from the imperfect CCD signal by digital signal processing techniques. Schemes for encoding digital data in the form of bar codes are also discussed.     

Signal processing for multitrack digital data storage

Using a multitrack format in both optical and magnetic data storage applications yields important improvements in system performance, including higher data density and higher data transfer rates. However, the full advantage in data density can be achieved only through the use of joint equalization and joint detection. This paper addresses the complexity of implementing these functions and proposes a transform domain equalization architecture and a reduced-complexity detection method based on a breadth first search of a one-dimensional time-varying representation of a two-dimensional target response. With this method, the complexity of joint equalization and joint detection is not unreasonably greater than that of existing single-track systems and should be feasible for implementation with emerging integrated circuit technologies.     

三维前视声呐信号处理方法

三维前视声像声呐是安装在小型水下载体上的重要声学探测设备。提出了基于波达方向估计技术的三维前视声呐信号处理方法,接收阵水平方向采用波束形成技术,垂直方向采用波达方向估计技术。在波束内采用分裂孔径相位法提高水平方向分辨率,形成声呐阵前方的三维声像。仿真结果和水池实验结果表明:在接收阵面面积相同的条件下,能够获得优于常规技术的分辨率,可以实现点目标和连续目标的探测,适合于在水下载体上安装使用。     

Signal processing for in-line inspection of gas transmission pipelines

Gas transmission pipelines in the United States are primarily inspected using the magnetic flux leakage (MFL) nondestructive evaluation (NDE) technique. However, accurate analysis of the NDE signals in terms of the underlying defects requires a thorough knowledge of various operational parameters such as B-H characteristics of the pipe wall, the velocity of the scanning tool, etc. In certain situations, information about such operational parameters is either absent or hard to obtain. Appropriate signal processing techniques can be applied to the raw MFL signals to ensure that defect characterization is possible in spite of local variations in the test situation. This paper presents two such signal processing methods—one, to compensate the MFL signal for variations in pipe-material grade, and the other to remove the effects of signal distortion that occur due to the velocity of the scanning device.     

Signal processing support for the evaluation of blood toxicoxidation activity

The problem addressed in this paper is related to numerical correction of spectrometric data aimed at enhancing the quality of interpretation of the spectrum of mixed substances. A digital signal processing method is proposed to eliminate an interfering absorption spectrum and evaluate the blood toxic oxidation activity. The effectiveness of the proposed method is demonstrated using synthetic data and real-world data acquired in biophysical laboratory     

机械设备摩擦噪声的信号测试与处理

作为当代三大主要污染源之一,噪声污染已成为一个世界性的问题并且引起了世人的关注。随着工业技术的发展,由物体摩擦产生的噪声污染也越来越严重。对摩擦噪声进行测量、研究和控制,从环境保护事业出发,是十分需要的;同时通过对摩擦噪声的信号分析,还可以深入了解摩擦机理,有助于改善摩擦条件和进行工况监测。     

Signal processing techniques for landmine detection using impulseground penetrating radar

Landmines are affecting the lives and livelihoods of millions of people around the world. A number of detection techniques, developed for use with impulse ground penetrating radar, are described, with emphasis on a Kalman filter based approach. Comparison of results from real data show that the Kalman filter algorithm provides the best detection performance, although its computational burden is also the highest     

涡街流量计信号处理方法研究与系统设计

为提高涡街流量计的测量性能,提出一套双通道涡街流量计信号处理方法,通过测量通道与监测通道的配合,提升低流速的测量性能,运用脉动信号功率最大频率点周期估计算法,进一步提升测量的精度和抗震动性能,并设计基于MSP430的涡街信号处理系统。实验结果表明:该信号处理方法能有效提升涡街流量计的测量性能。     

Signal processing techniques for filtering acoustic emission data in prestressed concrete

The current state of infrastructure in the United States and worldwide has raised the need for reliable structural health monitoring techniques. Piezoelectric sensing, such as acoustic emission, has recently gained attention due to its high sensitivity and associated capability for early detection of damage. The high sensitivity of this method, however, results in the collection of data not directly related to damage growth. Current filtering procedures focus primarily on parametric analysis of the collected signals. This study focuses on developing more robust filtering techniques for acoustic emission data collected from a prestressed concrete specimen. Simulated data was generated to enable proper identification of the source of the collected signals. Filtering criteria were developed through characterization of the energy content using a wavelet transform. The developed filters were capable of separating the induced target signals from other signals with reasonable accuracy, and the results were verified through source location. The developed filters were validated using acoustic emission data collected during a load test.     

基于LabJack的信号采集与处理系统设计

为了克服传统机械设备振动信号采集与处理设备造价昂贵、通用性差、可扩展能力弱以及对操作人员知识水平要求较高的缺点,设计了基于LabJack U12数据采集卡以及LabVIEW虚拟仪器软件平台的振动信号采集与数据处理系统.该系统以数据采集卡和电荷放大器为硬件平台,完成振动信号采集工作.软件系统中集成的众多子VI可对信号进行时频域多角度、多层次的分析处理,满足工业现场和实验室常用信号处理的要求,同时系统还具有信号的实时显示、多格式保存以及复现等功能.该系统结构简单、使用方便、可扩展性及可移植性强的特点使得其完全可以满足工业测试和教学科研的要求,具有广阔的应用前景.     

Signal processing strategies with the TDEMI measurement system

A low-cost electromagnetic compatibility precompliance test-set is essential to reduce the development costs of any electrical device. In this paper we discuss the advantages of broadband time-domain preliminary compliance measurement techniques applied to all types of electromagnetic interferences. The digital signal processing of electromagnetic interference measurements allows emulating in real-time the various modes of conventional analogous equipment, e.g., peak, average, root mean square, and quasi-peak detector mode. Since time-domain techniques allow processing the whole amplitude spectrum in parallel, the measurement time may be reduced by at least one order of magnitude. Compliance measurement results for conducted and radiated emissions obtained with the time-domain electromagnetic interference (TDEMI) system are shown. The TDEMI system has a real-time bandwidth of 1.5 GHz. Measurement techniques for nonstationary signals and single events are discussed.     

Signal processing of ultrasound modulated by gas flow

Ultrasonic measurement of gas flow velocity using cross-correlation functions motivated an intensive investigation of complex modulated signals. The ultrasound signal is modulated in amplitude and also in phase by various physical effects. This paper describes signal demodulation by undersampling and subsequent separation of amplitude and phase modulated parts by the Hilbert-transform. Cross-correlation functions applied to the phase-modulated signal component produce well-defined measurements of flow velocity.     

Supercavitating pumps for cryogenic liquids

Pumps for cryogenic liquids have a number of special mechanical and insulation problems because of the low temperatures. In addition there can be hydrodynamic problems due to trying to pump the liquid near its boiling point c causing cavitation. The problems of cavitation in pumping are discussed and the limitation and effects that this imposes on the pumps. The supercavitating pump enables many of these problems to be overcome and allows the pump to be operated at inlet pressures of one third of that of conventional pumps, which has clear advantages in the cryogenic field. The characteristics are given of some prototype supercavitating pumps that have been running for over two years.     

柴油机缸盖噪声信号处理方法及故障诊断研究

柴油机的缸盖噪声信号含有很多能诊断柴油机故障的有用信息,如燃爆、气门开启和关闭信息.但是提取的缸盖噪声信号中也含有柴油机工作时产生的排气噪声和机体其它部位辐射噪声等干扰信号,且干扰信号与有用信号的频率成分在20kHz以下的频带内重叠在一起.因此如何能有效的提取有用信号十分关键.通过实验选取气门室罩距气门较近一侧的侧表面1CM外作为测点.分析了小波分解、FIR滤波、小波降噪和FIR分频带阈值处理降噪四种方法的优缺点后,发现小波降噪既能保留有用信息,又能有效将不需要的噪声信号去除,在提取缸盖噪声中的有用信息时具有明显的优势.将缸盖噪声信号降噪后发现,各种气门间隙和失火故障均可通过缸盖噪声判断出.