A High-Speed 12-Layer Two-Dimensional Bar-Code Detection System

A new photodetection amplifier configuration with an amplification-type current-to-voltage converter is presented to realize a high-gain wideband amplifier. A high-speed 12-layer two-dimensional (2D) bar-code detection system (BCDS), consisting of the new photodetection amplifier and a raster scanner combined with a complementary light emission drive method for laser diodes, has been developed to provide both a highly effective scanning speed and multi-layer bar-code detection. The 12-layer 2D BCDS has shown 1,250 scan/s, which is two and a half times the scanning speed of a conventional bar-code detection system. Comparison with experimental results verified that Li’s scan pattern theory provides an accurate model for laser scanning beam traces obtained by the raster scanner. As theoretical evaluation of bar-code configuration in the new system, an optimum bar-code height per one-layer is given by a function of detection length.     

Impact of electron irradiation on particle track etching response in polyallyl diglycol carbonate (PADC)

In the present work, attempts have been made to investigate the modification in particle track etching response of polyallyl diglycol carbonate (PADC) due to impact of 2 MeV electrons. PADC samples pre-irradiated to 1, 10, 20, 40, 60, 80 and 100 Mrad doses of 2 MeV electrons were further exposed to 140 MeV²⁸ Si beam and dose-dependent track registration properties of PADC have been studied. Etch-rate values of the PADC irradiated to 100 Mrad dose electron was found to increase by nearly 4 times that of pristine PADC. The electron irradiation has promoted chain scissioning in PADC, thereby converting the polymer into an easily etchable polymer. Moreover, the etching response and the detection efficiency were found to improve by electron irradiation. Scanning electron microscopy of etched samples further revealed the surface damage in these irradiated PADCs.     

Dual-output modulation in time-wavelength interleaved photonic analog-to-digital converter based on actively mode-locked laser

This Letter demonstrates the application of dual-output modulation in a photonic analog-to-digital converter(PADC) with a high sampling rate and resolution. The PADC is time-wavelength interleaved and based on an actively mode-locked laser. According to theoretical analysis, the dual-output PADC system shows a better linearity for achieving a higher dynamic range. In the experiment, third-order distortion is significantly suppressed by~40 d B when the dual-output modulator is used and the effective number of bits of the PADC has reached 9.0 bits below 0.2 GHz and 6.4 bits at 6.1 GHz in our PADC with a sampling rate of 20 GS/s.     

Inter-comparison among fast neutron dosimetric services using PADC material of different composition

A trial inter-comparison has been performed among four fast neutron dosimetric services: PSI(CH), ENEA (I), DRPS (UK), LANL (US). The PADC used for the tests has been produced by Intercast Europe S.p.A. Three sets of detectors have been employed: two of PADC standard material from two different batches, and one of PADC with the addition of 0.1% dioctylphthalate. Each set consisted of 50 detectors.

For each set of detectors, 20 have been irradiated free-in-air at 1 mSv of H^*(10) with an ²⁴¹Am–Be source at ENEA-IRP, whilst the other detectors have been used as background samples. For each batch the value of the average background signal, B, the average neutron sensitivity, S, and minimum detectable dose equivalent, MDDE, have been determined. Two identical tests have been completed and separated with a time of 4 months in order to evaluate the ageing effect on the material stored in different conditions. Each dosimetric service processed the detectors according to local routine procedures. Three laboratories used an Autoscan60 reader, whilst one laboratory has an in-house reading system. Therefore, the results of the tests allowed a comparison of either the performance PADC materials, of different batches and of different compositions, or to evaluate how different etching, reading and storage conditions affect the results.     

Digi-FH-OFDM: An all-digital wideband frequency-hopped OFDM system

Frequency-hopped spread-spectrum systems (FHSS) traditionally employ a super-heterodyne receiver architecture to perform frequency hopping in the passband. Such an architecture consists of analog blocks such as the mixer and the local oscillator that contribute greatly to the overall cost and hardware complexity of the system. The recent development of direct radio-frequency (RF) data converters has led to the possibility of having an all-digital receiver architecture where an RF signal is digitized directly to baseband, without the need to translate it to an intermediate frequency. Motivated by this, we propose an all-digital wideband frequency-hopped orthogonal frequency division multiplexing system which is abbreviated as Digi-FH-OFDM in this paper. The system performs two-stage frequency hopping — one in the wideband and the other in the baseband. The system architecture and the implementation details are presented. Real-time power spectra of the hopped signals in the wideband are obtained after transmitting them over the air via the RF data converters of the reconfigurable Xilinx Ultrascale ZCU111 RFSoC board and the Qorvo RF front end card. The bit error rate performance of the system is studied against eavesdropping and jamming attacks under a slow-fading channel and pilot-based channel estimation. The proposed Digi-FH-OFDM system outperforms the existing analog and partially digital FH-OFDM systems in terms of hardware complexity, robustness to eavesdropping and jamming, and the overall latency.     

水下目标前向声散射探测的干涉声场畸变量分析与应用

前向声散射探测中的信直比SDR;能衡量目标前向散射波与直达波的相对大小,但未考虑两种波的干涉叠加。前向散射波与直达波实际上是干涉在一起的且很难分离,因而信直比在目标探测分析中难以直接应用。以信直比为基础并计入前向散射波与直达波的干涉效果,引入了新的参量——干涉声场畸变量ΔFTL——并给出了理论计算公式。与SDR;相比,ΔFTL可以直接从声场数据中得到,在一定程度上具有不依赖先验信息的优势。以该公式为基础并结合千岛湖缩比目标探测试验数据,(1)通过估算几何扩展损失系数发现试验中的声波为球面波,结果与依据实测水文参数的射线声场模型仿真结果相符;(2)定量地证实了ΔFTL与目标穿越位置的对应关系,同时也证明了ΔFTL理论计算公式的有效性;(3)建立了一种新的直达波抑制效果评估方案,并完成了对自适应直达波抑制方法的效能评估。目标透声和航行姿态扰动对试验结果的影响可以忽略。分析结果表明:ΔFTL能够有效代替SDR,为开展前向声散射探测性能分析或直达波抑制效果评估提供理论参考。      

基于中红外光谱吸收技术的一氧化碳气体检测系统

基于中红外光谱吸收技术,利用一氧化碳(CO)气体分子在4.6 μm处的基频吸收带,采用新脉冲的红外光源和双通道的热释电探测器,研制了一种CO浓度检测系统。该系统主要由脉冲调制式宽带热光源、开放式椭球聚光镜/气室、双通道探测器、主控及信号处理模块构成。通过优化开放式椭球聚光镜/气室,气体吸收光程达到40 cm, 探测器输出电信号的幅度增加约为原来的2~3倍。因此,采用椭球聚光镜后,将在一定程度上提高系统的信噪比从而改善系统的性能指标。利用配备的CO气体样品,研究了该系统对CO气体的传感特性。实验结果显示,该系统的最小检测下限为10 ppm,在该浓度点的测量误差约为14%;在20~25 000 ppm范围内的测量误差小于7.8%;对0 ppm气体样品的连续50分钟测量结果的最大偏差约为3 ppm,标准差约为0.18 ppm。同基于量子级联激光器和分布反馈激光器的CO检测系统相比,该系统具有性价比高、光路结构简单等优势,从而在煤矿、环保等场合下的CO检测方面具有较好应用前景。     

High-speed data acquisition system and receiver configurations for time-domain radiofrequency electron paramagnetic resonance spectroscopy and imaging

Design strategies, system configuration, and operation of a dual-channel data acquisition system for a radiofrequency (RF) time-domain electron paramagnetic resonance (EPR) spectrometer/imager operating at 300 MHz are described. This system wasconfigured to incorporate high-speed analog-to-digital conversion (ADC) and summation capabilities with both internal and external triggering via GPIB interface. The sampling rate of the ADC is programmable up to a maximum of 1 GS/s when operating in a dual-channel mode or 2 GS/s when the EPR data are collected in a single-channel mode. By using high-speed flash ADCs, a pipelined 8-bit adder, and a 24-bit accumulator, a repetition rate of 230 kHz is realized to sum FIDs of 4096 points. The record length is programmable up to a maximum of 8K points and a large number of FIDs (2(24)) can be summed without overflow before the data can be transferred to a host computer via GPIB interface for further processing. The data acquisition system can operate in a two-channel (quadrature) receiver mode for the conventional mixing to baseband. For detection using the single-channel mode, the resonance signals around the center frequency of 300 MHz were mixed with a synchronized local oscillator of appropriate frequency leading to an intermediate frequency (IF) which is sampled at a rate of 2 GS/s. Comparison of quadrature-mode and an IF-mode operation for EPR detection is presented by studying the FID signal intensity across a bandwidth of 10 MHz and as a function of transmit RF power. Imaging of large-sized phantoms accommodated in appropriately sized resonators indicates that IF-mode operation can be used to obtain distortion-free images in resonators of size 50 mm diameter and 50 mm length.     

Costas编码跳频信号多普勒容限及其在多声源宽带正交检测中的应用

针对Costas信号的传统宽带匹配滤波因拷贝信号生成过程复杂而带来的计算复杂度高的问题,给出了一种通过计算宽带回波与窄带近似回波的互相关度进而得到Costas信号多普勒容限的数值计算方法,并提出利用容限值对预测目标多普勒范围进行分段窄带近似处理,从而避免了大量的时域伸缩变换,简化了拷贝信号的生成复杂度,提高了宽带匹配滤波的处理效率。随后,将这种方法扩展应用到多声源多目标的回波检测中,利用Costas信号的正交性及多普勒容限值,设计了一种宽带正交匹配检测器,大大提高了多目标声探测的效率。实验仿真和分析证明了多普勒容限求取方法的正确性及其应用于宽带正交匹配检测的有效性。      

千兆无源光网络上行光信号特性研究与检测方案

由于千兆无源光网络系统中的上行光信号采用高速突发模式,故对其特性的检测是实现实时光层监测的难点.详细分析了上行光信号的传输特性、帧开销及噪声模型.并在此基础上,设计了一种检测方案,该方案通过高阻抗的前置放大器将信号引出,不影响原系统的正常工作,从而满足了实时检测的需要;通过峰值检波电路将高频突发信号降为低频进行处理,大...     

The effects of bandwidth on the detectability of narrow- and wideband signals

The effects of masker bandwidth on the detection of narrow- and wideband signals have been investigated. For both kinds of signals, plots of threshold as a function of masker bandwidth yielded by both narrow- and wideband signals are reasonably described with two intersecting lines. Threshold initially increase with masker bandwidth and then become independent of further increases. The rate of increase depends on the signal spectrum. The bandwidth at which the lines intersect varies with signal bandwidth and also mode of masker presentation (i.e., whether the masker is gated with the signal or is present continuously). Internal filtering is most accurate when the masker is present continuously. A model is proposed in which a listener's decisions about the presence of narrow-band signals are based upon estimates of stimulus energy within a critical band. These estimates are degraded by bandwidth-dependent processing errors. When the signal to be detected spans several critical bands (i.e., is wideband), the model forms a test statistic by summing the outputs of the relevant critical bands. The model permits the contribution of each band to the sum to vary with masker bandwidth because it incorporates a form of lateral suppression. Thresholds of narrow-band signals in gated maskers and wideband signals in gated and continuous maskers are predicted by the model. However, the model fails to account for the detectability of narrow-band signals in continuous maskers.     

Lidar system for visibility monitoring

In the present paper a Lidar (light detection and ranging) system is described. It allows high-speed data acquisition of Lidar signals and meteorological parameters by means of standard instrumentation. The Lidar, controlled by a computer, utilized two laser sources (Nd: Yag and ruby), a modified Ricthey-Chretien telescope and signal detection, storage and real-time monitoring equipment. The whole system was installed in a container for field experiments.     

双线阵目标左右舷分辨概率分析

基于二元假设检验理论,研究了双线列阵对目标方位左右舷分辨的正确和错误概率。根据阵列接收窄带信号的概率密度函数,定义了左右舷判决统计量,当信号快拍数足够大时,左右舷判决统计量接近正态分布,从而可得到窄带信号的左右舷分辨概率。利用子带信号左右舷分辨概率的频率加权或波束加权,得到频率或波束加权的宽带信号左右舷分辨概率。理论和数值分析表明,窄带信号的左右舷分辨概率取决于双阵间距,而宽带信号的左右舷分辨概率对阵间距的宽容性较大。     

Performance evaluation of optical beamforming-based wideband antenna array

A wideband-generalized pattern multiplication approach to evaluate the performance of an optical beamforming-based wideband antenna array is proposed and experimentally demonstrated, which enables the far-field measurement of a large wideband array with a small anechoic chamber. Because the optimum reception of a wideband microwave signal is highly related to the time-domain distortions of the beamforming system, a correlation-receiver-based radiation pattern is applied to take the fidelity of the wideband signals into account.A four-element optical beamforming system is built to verify the feasibility of the proposed method. The results achieved by the proposed method agree well with the conventional direct measurements.     

Numerical solution to the Bloch equations:paramagnetic solutions under wideband continuous radio frequency irradiation in a pulsed magnetic field

A novel nuclear magnetic resonance(NMR) experimental scheme,called wideband continuous wave NMR(WB-CW-NMR),is presented in this article.This experimental scheme has promising applications in pulsed magnetic fields,and can dramatically improve the utilization of the pulsed field.The feasibility of WB-CW-NMR scheme is verified by numerically solving modified Bloch equations.In the numerical simulation,the applied magnetic field is a pulsed magnetic field up to 80 T,and the wideband continuous radio frequency(RF) excitation is a band-limited(0.68-3.40 GHz) white noise.Furthermore,the influences of some experimental parameters,such as relaxation time,applied magnetic field strength and wideband continuous RF power,on the WB-CW-NMR signal are analyzed briefly.Finally,a multi-channel system framework for transmitting and receiving ultra wideband signals is proposed,and the basic requirements of this experimental system are discussed.Meanwhile,the amplitude of the NMR signal,the level of noise and RF interference in WB-CW-NMR experiments are estimated,and a preliminary adaptive cancellation plan is given for detecting WB-CW-NMR signal from large background interference.     

基于FPGA的超高速线阵CCD信号采集系统的设计与实现

线阵CCD已广泛应用于在线检测、图像识别等系统,目前高帧率采集系统多在200~500Hz之间。高速线阵CCD采集系统,如1K甚至10KHz以上的采集要求,设计难度大,电路实现复杂,需要专用处理器,产品成本高,提出了一种采用并行高速FPGA驱动线阵CCD,通过常规分立元件完成模拟信号处理,实现数字信号实时传输的方案。该方案不仅简化了硬件设计上的难度,在同等性能情况下,可实现每秒万帧的高速采样,大幅度降低了成本。方案选用Altera FPGA作为控制核心,实现高速信号采集的同时,在片上实现一定的图像算法,不仅加速了图像处理速度,同时降低了计算机的处理压力。最后,本电路通过USB2.0接口,完成数据的实时传输。设计具有高帧率、高灵敏度、性能稳定,便携使用等特点,同时还有一定的通用性,已应用于一些光学系统中。     

Fabrication and characterization of ultra-low noise narrow and wide band Josephson parametric amplifiers

We have fabricated two types of lumped-element Josephson parameter amplifiers (JPAs) by using a multilayer micro-fabrication process involving wet etching of Al films. The first type is a narrow band JPA which shows typical gain above 14 dB in a bandwidth around 35 MHz. The second type is a wideband JPA which is coupled to an input 50 Ω transmission line via an impedance transformer that changes the impedance from about 15 Ω on the non-linear resonator side to 50 Ω on the input transmission line side. The wideband JPA could operate in a 200 MHz range with a gain higher than 14 dB. The amplifiers were used for superconducting qubit readout. The results showed that the signal to noise ratio and hence the readout fidelity were improved significantly.     

基于宽带分裂阵列的水下远程被动多目标检测与定向

为获取更高的水下远程多目标检测和定向性能,基于工程中广泛应用的最小方差无畸变响应(MVDR)波束形成算法,设计了大间隔分裂线列阵,通过扩大阵列有效孔径改善了空间谱峰锐度。同时提出非相干宽带预处理方法,利用MVDR在多频子带下波束宽度和间隔的非一致性来抵消由于稀布阵元造成的栅瓣效应。最终实现大间隔分裂阵和宽带非相干波束形成的互补。仿真和湖上试验结果表明,与采用宽带MVDR的均匀线列阵和采用互相关法的大间隔分裂阵相比较,所提方法能显著提高对水下远程目标的检测和分辨性能。      

An objective quality assessment method for bit-reduction coding of wideband speech.

This paper proposes a new objective quality assessment method for bit-reduction coding of wideband speech taking into account the masking effect of quantizing noise. First, this paper analyzes the reliability and sensitivity of the speech quality assessment method, based on a paired-comparison test with a modulated noise reference signal, for the bit-reduction coding of high-quality wideband speech. Then, the perception of quantizing noise is studied using speech with noise synthesized similar to the quantizing noise. The detection of quantizing noise is found to be influenced by masking by the source signal. This leads to a new method of objectively estimating the quality of coding speech by multiple regression analysis. The factors for the estimation are segmental signal-to-noise ratio, spectrum envelope distance between source signal and quantizing noise, and the similarity of the noise power envelope to the source signal in the time domain. This estimation method is applied to the parameter optimization of wideband coding systems.     

Modification induced by proton irradiation in polyallyldiglycol carbonate (PADC)

Swift heavy ions interact predominantly through inelastic scattering while traversing through any polymeric medium producing excited/ionised atoms. Beyond a certain threshold, they affect the lattice structure leading to remarkable flexibility in engineering many physical and mechanical properties of the polymer. Polyallyldiglycol carbonate (PADC) is a class of polymeric detectors which finds its applications in various fields. In the present work, PADC samples were irradiated by four different fluences (≈10¹²–10¹³ cm⁻²) of 62 MeV protons from heavy ion accelerator (ISL) at HMI, Berlin. The modifications in the proton irradiated polymers as a function of fluence have been studied through different characterisation techniques such as Fourier Transform IR, UV-Vis, Electron Spin resonance, Thermogravimetric analysis, Differential Scanning Calorimetry and Track studies. The optical band-gap was found to be constant while a decrease in transmittance of PADC was observed with the increase in proton fluence. The thermal stability of PADC was found to be an inverse function of fluence. Further, these proton irradiated PADCs were exposed to fission fragments from ²⁵²Cf source and the bulk etch-rate was improved with the increase in proton fluence and was found to be increased by 90% for the PADC irradiated at the highest fluence as compared to the pristine. Thus, proton irradiation has led to degradation of the polymer by chain scission converting it into an easily etchable material.