Application of digital signal processing in nuclear spectroscopy

Digital signal processing algorithms for nuclear particle spectroscopy are described. The algorithms are presented as recursive procedures, which can easily be programmed using modern computer programming languages. The input data flow was formed by particle detector pulses, preprocessed by a charge-sensitive preamplifier and transformed into a sequence of equidistantly sampled signals by a sampling analog-to-digital converter. The pile-up elimination procedure, the influence of the number of bits of the sampling analog-to-digital converter on the energy resolution of the spectrometer, and ballistic deficit correction are also considered. The pile-up elimination method was developed for fission fragment spectroscopy in the case of high α radioactivity of fissile targets (²³⁹Pu, ²⁴¹Am) using a Frisch-grid double ionization chamber. Since the intrinsic energy resolution of a spectrometer based on a double ionization chamber is much worse than that determined by the noise level of the charge-sensitive amplifier, an ultrapure germanium detector was used to provide the highest sensitivity to the errors introduced by measuring procedures. The effect of pile-up elimination procedure on the energy resolution was experimentally investigated at different source intensities. The main characteristics of the developed algorithms are compared with those of other processing procedures published in the literature.     

Optical signal processing using nonlinear fibers

Ultra-fast optical signal processing is a promising technology for future photonic networks. This paper describes possible applications of nonlinear fibers to optical signal processing. The third-order optical nonlinearities in a fiber are discussed by analyzing the interaction of co-propagating optical waves. The properties of a nonlinear fiber are then considered in terms of optimizing the dispersion for achieving phase matching and decreasing walk-off. A highly nonlinear fiber (HNLF) is a practical candidate for an ultra-high-speed signal processor. Using HNLF, the following experiments are successfully demonstated: ultra-broadband wavelength conversion/optical phase conjugation by four-wave mixing, 160 Gb/s optical 3R-regeneration, and optical switching up to 640 Gb/s using a parametric amplified fiber switch. Steps for further improvements are also discussed.     

Development of FPGA-based digital signal processing system for radiation spectroscopy

We have developed an FPGA-based digital signal processing system that performs both online digital signal filtering and pulse-shape analysis for both particle and gamma-ray spectroscopy. Such functionalities were made possible by a state-of-the-art programmable logic device and system architectures employed. The system performance as measured, for example, in the system dead time and accuracy for pulse-height and rise-time determination, was evaluated with standard alpha- and gamma-ray sources using a CsI(Tl) scintillation detector. It is resulted that the present system has shown its potential application to various radiation-related fields such as particle identification, radiography, and radiation imaging.     

信号处理改善波长调制光谱灵敏度的实验研究

基于可调谐半导体激光吸收光谱，提出了一种新的信号处理方法用于提高吸收光谱测量的灵敏度. 研究结果表明：采用信号处理（DSP）可以使波长调制光谱的信噪比提高一个数量级,且测量CO₂分子的时候发现一条新谱线. 这些信号处理包括多次平均、数字低通滤波以及最小二乘法拟合. 由于该方法不需要增加设备的复杂性，所以比其他噪声抑制技术更容易在实验中实施、有更实际的应用价值. 关键词： 波长调制 信号处理 半导体激光器 吸收光谱     

High-frequency signal processing using magnetic layered structures

We present a review of theoretical and experimental results for tunable microwave band-stop filters, band-pass filters, phase shifters, and a signal to noise enhancer, all based on a microstrip geometry and using a variety of magnetic thin films and layered structures. These devices are compatible in size and growth process with on-chip high-frequency electronics. For devices based on metallic ferromagnetic films of Fe and Permalloy, the operational frequency ranges from 5 to 35 GHz for external fields below 5 kOe. For the band-stop filters, we observed power attenuation up to ∼100 dB/cm, and an insertion loss on the order of ∼2-3 dB, for both Permalloy and Fe-based structures. We also explore the use of thin films of hexagonal ferrites, antiferromagnets, and liquid crystals, and show that useful devices can be constructed with films less than one 1 μm in thickness.     

Realization optical signal processing components using SOA

This paper simulated simultaneously AND and NOT logic gate with frequency converter by using semiconductor optical amplifier. These logic gates and frequency converter are obtained with SOA effects like XGM and FWM of signals. Simulative realization of these logic gates and frequency converter will lead revolution in optical signal processing for high speed operation.     

一种基于离散频谱校正的SPIDER信号处理改进方法

介绍了光谱相位相干电场重构法（SPIDER）信号处理的原理,提出一种基于离散频谱校正的SPIDER信号处理改进方法,该方法可克服采样速率不足带来的信号处理误差。试验发现：在无噪声情况下,当取的校正点数足够多,基本可以达到无偏校正;而在有噪声的情况下,应适当选取校正的点数,来增强抗噪性能。该方法能在信噪比较差的情况下,得到时间延迟τ。经过仿真计算,在光谱仪最小分辨率和测量范围的限制情况下,该方法能够突破该限制在时谱上造成栅栏效应,大大提高SPIDER中时延参数的测量精度。该方法实现简单,精度高,抗噪性能好,无需改动设备就能提高系统精度,可广泛应用于SPIDER技术中。     

High-speed optical signal processing using semiconductor optical amplifiers

The authors report on all-optical switching devices based on semiconductor optical amplifiers (SOA) in applications for optical time division multiplexing (OTDM) transmission technology. The report includes a discussion on the basic properties of an SOA, on the nonlinear processes of cross-phase modulation and four-wave mixing in the SOA used for all-optical switching, and on the application of the SOA as demultiplexer, add-drop multiplexer, clock recovery and wavelength converter. The devices considered here operate at data rates in excess of \Gb80, where electrical signal processing is not available today.     

采用无耳壳头相关传输函数的虚拟声信号处理

本文提出采用无耳壳、封闭耳道的头相关传输函数（HRTF）进行虚拟声信号处理的方法。理论分析表明，在包含功率均衡的扬声器虚拟声信号处理中，采用无耳壳、封闭耳道的头相关传输函数可有效地减少信号处理函数的谷点，从而减少声重发的音色改变。心理声学的实验结果表明，新处理方法的声像定位与传统的带耳壳、耳道的HRTF处理无显著区别，但音色较后者有所改善。因而新的方法更适合实际的虚拟声信号处理应用。     

Improved ultrasonic detection using the analytic signal magnitude

An alternative to rectification is proposed for detection of an ultrasonic signal for medical or non-destructive evaluation applications. With this technique the envelope of the ultrasonic waveform is obtained by calculation of the magnitude of the complex analytic signal. An implementation, particularly suited for digital data processing, is presented which utilizes a fast Fourier transform for computation of the quadrature component of the received signal using the Hilbert transform. An ordinary transducer, pulser, and receiver are used together with a digital data acquisition system. The results of this processing are compared with conventional rectification, both with and without smoothing. The superior resolvability of two closely spaced interfaces on the A-mode presentation is clearly evident. Similar improvement in B-mode quality will result when an image is required.     

Improved signal processing in pulsed and cw spin-flip Raman laser spectrometers

Double beam optical techniques which allow direct spectroscopic measurements using both pulsed and cw tunable spin-flip Raman lasers have been developed. The systems provide a high resolution spectrometer (spectral linewidths 0.03 cm^-1 pulsed and 0.003 cm^-1 cw) in the range 5.3–6μm. Line frequency measurements are accurate to 0.01 cm^-1 and intensity measurements to a few percent. Results of molecular spectroscopy provide a comparison of the relative performance of each system.     

虚拟时间反转水声信号检测

针对目标辐射声信号特性未知的情况,在不增加额外水声换能器的条件下,研究提高水听器阵列对水声信号检测性能的方法。首先,按照经典二元检测问题处理方法分析了常规能量检测方法的性能,在此基础上,根据虚拟时间反转处理原理,对处理后的信号构建检测统计量,推导得到了虚拟时间反转检测方法的理论门限和检测性能的表达式,并通过与常规能量检测的对比分析了虚拟时间反转检测的处理增益。使用计算机仿真实验从声源频率、接收阵列阵元数、目标距离与深度等方面分析了两种方法的检测性能。结果表明,所提出的算法相对于常规能量检测算法在性能上有显著优势,且接收阵元数是对算法性能影响最为明显的因素。     

Silicon-carbide-based extreme environment temperature sensor using wavelength-tuned signal processing

A wavelength-tuned signal-processing approach is proposed for enabling direct unambiguous temperature measurement in a free-space targeted single-crystal silicon carbide (SiC) temperature sensor. The approach simultaneously exploits the 6H SiC fundamental Sellmeier equation-based wavelength-sensitive refractive index change in combination with the classic temperature-dependent refractive index change and the material thermal-expansion path-length change to encode SiC chip temperature with wavelength. Presently, the technique is useful for fast coarse temperature measurement as demonstrated from room temperature to 1000 degrees C using a 10-peak count wavelength-tuned measurement with a 0.31 nm total wavelength change. This coarse technique can be combined with the previously presented two-wavelength signal-processing temperature measurement approach to simultaneously deliver a wide temperature range and a high-resolution temperature sensor. Applications for the sensor range from power plants to materials processing facilities.     

Spectrum analyser for area charts using electro-optical signal processing

A new method for performing the Fourier analysis of an area chart using an electro-optical technique with an ultrasonic light modulator is treated theoretically and examined experimentally. The quadratic characteristic of photodetection is investigated and its disadvantage is effectively removed by adopting a both-side-band modulation. Experimental results for simple area charts verify the usefulness of this method. Analyses for a sinusoidal area chart indicate that the bias inherent in the optical signal yields low frequency spectra and that the spectral width due to truncation of the signal by the finite aperture reduces the frequency resolution. It is shown, however, that the wavelength of this chart is accurately measurable.     

High sensitivity phonon spectroscopy of Bose-Einstein condensates using matter-wave interference

We study low-momentum excitations of a Bose-Einstein condensate using a novel matter-wave interference technique. In time-of-flight expansion images we observe strong matter-wave fringe patterns. The fringe visibility is a sensitive spectroscopic probe of in-trap phonons and is explained by use of a Bogoliubov excitation projection method applied to the rescaled order parameter of the expanding condensate. Gross-Pitaevskii simulations agree with the experimental data and confirm the validity of the theoretical interpretation. We show that the high sensitivity of this detection scheme gives access to the quantized quasiparticle regime.     

铝合金中铬元素的时间分辨激光诱导击穿光谱高灵敏检测

为了消除在激光诱导击穿光谱(LIBS)信号检测时等离子体中强的轫致电子辐射对光电倍增管和前置信号放大器造成的不良影响,提高信号检测灵敏度,设计了一种基于CR110的门控端窗光电倍增管并用于LIBS中的微弱信号检测。该门控光电倍增管与前置信号放大器组合运用既可以成功抑制激光等离子体中强的轫致电子辐射的背景干扰,又可以进一步放大微弱的原子辐射信号,提高光谱分析的灵敏度。用LIBS分析铝合金标样中的微量铬元素,采用该门控光电倍增管时其检出限可以达到5.55 ppm,与采用普通光电倍增管的相比改善了近6倍,显示出该门控光电倍增管在时间分辨信号检测领域良好的应用效果。     

Improved signal processing to detect cancer by ultrasonic molecular imaging of targeted nanoparticles

In several investigations of molecular imaging of angiogenic neovasculature using a targeted contrast agent, Renyi entropy [I(f)(r)] and a limiting form of Renyi entropy (I(f,∞)) exhibited significantly more sensitivity to subtle changes in scattering architecture than energy-based methods. Many of these studies required the fitting of a cubic spline to backscattered waveforms prior to calculation of entropy [either I(f)(r) or I(f,∞)]. In this study, it is shown that the robustness of I(f,∞) may be improved by using a smoothing spline. Results are presented showing the impact of different smoothing parameters. In addition, if smoothing is preceded by low-pass filtering of the waveforms, further improvements may be obtained.     

铝合金中铬元素的时间分辨激光诱导击穿光谱高灵敏检测

为了消除在激光诱导击穿光谱(LIBS)信号检测时等离子体中强的轫致电子辐射对光电倍增管和前置信号放大器造成的不良影响,提高信号检测灵敏度,设计了一种基于CR110的门控端窗光电倍增管并用于LIBS中的微弱信号检测。该门控光电倍增管与前置信号放大器组合运用既可以成功抑制激光等离子体中强的轫致电子辐射的背景干扰,又可以进一步放大微弱的原子辐射信号,提高光谱分析的灵敏度。用LIBS分析铝合金标样中的微量铬元素,采用该门控光电倍增管时其检出限可以达到5.55 ppm,与采用普通光电倍增管的相比改善了近6倍,显示出该门控光电倍增管在时间分辨信号检测领域良好的应用效果。     

Target parameter estimation for OTFS radar using sparse signal processing

In this paper, we consider a monostatic radar receiver for a joint communication and radar (JCR) system that transmits orthogonal time frequency space (OTFS) frames for target detection and parameter estimation. The circular prolate pulse shape (CPPS) is employed over the OTFS signal as it has lower out-of-band (OoB) power radiation in comparison with the rectangular pulse shaped (RPS) OTFS. The PAPR of CPPS OTFS signal shows lowest value for larger frame duration and hence the signal can be considered to be a good candidate for JCR system. In the Delay-Doppler (DD) domain, the radar channel is sparse and therefore, we model the target detection problem as a sparse recovery problem to generate target profiles with higher peak-to-sidelobe ratio (PSLR). The target detection is carried out in the DD domain, the time–frequency (TF) domain, and in the time domain (TD). Sparse signal recovery algorithms like the orthogonal matching pursuit (OMP) algorithm, the subspace pursuit (SP) algorithm, and the sparse Bayesian learning (SBL) based algorithm are used in target parameter estimation. The performance of these algorithms are compared in terms of their computational complexity, the root mean squared error (RMSE) in the estimates of range and velocity and PSLR value in the target profiles. Simulation results validate that the proposed CPPS OTFS based radar system could detect the targets accurately in all the three domains and produce target profiles with almost zero side lobes.