Moving target localization for multistatic passive radar using delay, Doppler and Doppler rate measurements

Time delay and Doppler shift between the echo signal and the reference signal are two most commonly used measurements in target localization for the passive radar. Doppler rate, which can be obtained from the extended cross ambiguity function, offers an opportunity to further enhance the localization accuracy. This paper considers using the measurement Doppler rate in addition to measurements of time delay and Doppler shift to locate a moving target. A closed-form solution is developed to accurately and efficiently estimate the target position and velocity.The proposed solution establishes a pseudolinear set of equations by introducing some additional variables, imposes weighted least squares formulation to yield a rough estimate, and utilizes the function relation among the target location parameters and additional variables to improve the estimation accuracy. Theoretical covariance and Cramer-Rao lower bound(CRLB) are derived and compared, analytically indicating that the proposed solution attains the CRLB. Numerical simulations corroborate this analysis and demonstrate that the proposed solution outperforms existing methods.

Joint TDOA, FDOA and differential Doppler rate estimation： Method and its performance analysis

Considering the estimation accuracy reduction of Frequency Difference of Arrival （FDOA） caused by relative Doppler companding, a joint Time Difference of Arrival （TDOA）, FDOA and differential Doppler rate estimation method is proposed and its Cramer-Rao low bound is derived in this paper. Firstly, second-order ambiguity function is utilized to reduce the dimensionality and estimate initial TDOA and differential Doppler rate. Secondly, the TDOA estimation is updated and FDOA is obtained using cross ambiguity function, in which relative Doppler com- panding is compensated by the existing differential Doppler rate. Thirdly, differential Doppler rate estimation is updated using cross estimator. Theoretical analysis on estimation variance and Cramer-Rao low bound shows that the final estimation of TDOA, FDOA and differential Doppler rate performs well at both low and high signal-noise ratio, although the initial estimation accuracy of TDOA and differential Doppler rate is relatively poor under low signal-noise ratio conditions. Simulation results finally verify the theoretical analysis and show that the proposed method can overcome relative Doppler companding problem and performs well for all TDOA, FDOA and differential Doppler rate estimation.

A Fourier Series Proof That the Axial like the Transverse Optical Doppler Shift Impacts Time and Information Rates

In writings on relativity time, the various relations are only changed by the transverse shift. This paper proves that the axial Doppler shift does that as well and gives some impacts of that on common differential relations in physics. When a modulated signal lasting a time = T is subjected to an optical Doppler shift K (either axial or transverse or both), where K is shifted frequency/original frequency, the Doppler shifted signal will last T/K. This because all shifted harmonics of its Fourier series (with a fundamental period of T) will last 1/K times the period of the original harmonic. The reader can graph any Fourier series and then graph its shifted series. The reader will see the shifted period is T/K. The Fourier series of the original repeats when time is greater than T and the shifted one when time is greater than T/K, which means the original series only represents the signal from time = 0 to T and the shifted series represents the shifted signal from time = 0 to T/K. Hence, the shifted one has all of the information in T/K as the original has in T. Therefore everything in the series including information is T/K long in the shifted series. Therefore, both the axial and the transverse Doppler shift change time periods in a vacuum, independent of material involved. That has not been obvious for over 100 years the axial shift changes time from the definition of frequency = 1/time.

A Doppler Location Method Based on Virtual Path Difference

This paper presents a Doppler passive location method for moving targets with fixed single station using the Doppler frequency shift and time difference information.First,based on the relationship between frequency shift and path difference,the virtual path difference is calculated from the measured value of Doppler frequency shift by means of mean value correction.Then,under the assumption that the target is moving at a constant speed along a straight line,two coaxial virtual double base arrays are constructed by using the moving track of the moving target based on the method of fixed period time difference.On this basis,the moving distance of the moving target can be calculated by using the ratio relationship between the frequency difference and the radial distance between the two adjacent detection points in the middle of the array,and the linear solution of the two double base path difference positioning equations.At this point,the relative coordinate position of the moving target can be obtained by directly using the linear solution of the double base path difference positioning equation again.

基于FPGA的宽带ADCP流速校准系统

声学多普勒流速剖面仪(ADCP)可采用声学应答并发射模拟回波的方式开展流速校准,但其校准精度和校准流速下限受系统时钟精度影响,目前基于该方式的ADCP流速校准系统难以针对1 m/s以下小流速进行校准。提供了一种低成本、水池环境可实施的宽带ADCP流速校准系统方案,即基于FPGA设计一套宽带ADCP流速校准系统,采集ADCP发射声波信号并进行处理,再向ADCP发射携带水体流速信息的模拟回波信号,通过模拟流速值与实际输出值的比较,实现ADCP的流速校准。校准系统通过直接数字频率合成和锁相频率合成(DDS+PLL)的技术合成高精度时钟信号,时钟信号驱动信号采集与回放产生高精度模拟回波信号。最后,在小型消声水池内针对中心频率为300 kHz的宽带ADCP开展(0.2~1)m/s小流速校准实验,结果表明,该校准系统的测量不确定度达到(0.5%模拟流速值+0.005)m/s,验证了校准系统的可靠性。

位置欺骗对软件接收机信号跟踪参数的影响分析

针对位置欺骗如何影响接收机的问题,使用TEXBAT(Texas Spoofing Test Battery)提供的2组无欺骗干扰场景数据集和2组不同场景的GPS位置欺骗数据集,建立了GPS位置欺骗模型,分析了欺骗场景下两种相位对齐模式对欺骗攻击的影响;利用GNSS-SDR软件接收机对TEXBAT的原始高保真数字采样数据进行数据处理,分别得到软件接收机受欺骗与未受欺骗时的接收机载噪比、载波多普勒、码速率等随时间的变化情况;分析了两个位置欺骗场景对软件接收机跟踪阶段输出值的影响。实验结果表明,载噪比有大于3(dB·Hz)的波动,码速率方差会发生阶段性的增加和减少;多普勒频率的变化取决于欺骗场景的选取,不同场景的位置欺骗从不同角度有效影响了接收机定位结果。

移动物联网通信中的UFMC调制波形优化设计

移动物联网(Internet of Things, IoT)通信是6G的关键技术之一,面对多变的地面基站环境,无人机(Unmanned Aerial Vehicle, UAV)辅助通信被认为是物联网通信的重要组成部分,已受到广泛关注。通用滤波器多载波(Universal Filtered Multi-carrier, UFMC)作为一种新型非正交多载波调制技术,继承了正交频分复用(Orthogonal Frequency Division Multiplexing, OFDM)的优势,主要应用在短数据包突发通信场景中,被认为适用于下一代无线物联网通信。但是,在无人机的高速移动环境下,通信信号会遭受显著的多普勒频移影响,产生严重的载波间干扰(Inter Carrier Interference, ICI),导致UFMC系统性能的显著下降。为了缓解ICI问题,本文首先理论分析、推导了存在多普勒频移时UFMC系统的信干噪比(Signal to Interference plus Noise Ratio, SINR)。根据SINR分析,可见将UFMC波形滤波器通带波动优化调控的足够小以及加快过渡带衰减有利于提升系统抗ICI能力。因此,本文提出了基于波形滤波器优化设计的干扰抑制方法,构建了符合UFMC通信需求的波形滤波器最优化设计数学模型,该模型可以有效地调控波形滤波器的通带波动,通过遍历搜索可求解得到使系统误符号率(Symbol Error Rate, SER)相对最优的波形滤波器。在考虑多普勒频移的系统仿真中,SER对比结果表明:与采用传统波形滤波器的UFMC系统相比,本文根据约束最小最大(Constraint Minimax, CMM)准则遍历搜索设计的波形滤波器可以有效地抑制系统ICI从而改善SER。这为未来移动物联网通信系统的波形设计提供了参考。

经阴道彩色多普勒超声应用于子宫切口妊娠诊断的效果分析

目的 评估经阴道彩色多普勒超声(TVCDS)应用在子宫切口妊娠(CSP)诊断中的效果及对检出率的影响。方法 纳入2019年3月至2023年3月的52例疑似CSP患者,均接受经腹部彩色多普勒超声(TACDS)、TVCDS检查,参照手术结果,评价2种超声技术的诊断效能、不同分型检出率。结果 52例疑似CSP患者最终确诊42例,其中TVCDS准确度(83%)、灵敏度(88%)高于TACDS(63%和62%)(P<0.05),二者特异度差异无统计学意义(P>0.05);手术结果显示42例CSP患者中混合包块型14例、单纯妊娠囊型25例、宫腔型3例,其中TVCDS混合包块型检出率(93%)、单纯妊娠囊型检出率(92%)、总检出率(88%)均高于TACDS(57%、64%与62%),(P<0.05),二者宫腔型检出率差异无统计学意义(P>0.05)。结论 TVCDS可以提高CSP诊断准确度、灵敏度,提高CSP分型检出率,值得推广。

大规模低轨星座多普勒定位算法

基于典型的Starlink星座构型,对大规模低轨星座多普勒定位算法展开研究。实验结果表明,理想条件下低轨星座多普勒单点定位精度可以在3~6 m。为保证米级的定位精度,低轨卫星的位置精度和速度精度应为米级每秒或厘米级每秒。C频段信号受到的电离层误差若不做改正,将导致定位精度变差2 m左右。对流层误差将使得定位结果变差几十米。此外,使用轨道高度为550 km的低轨卫星的多普勒频移定位时,接收机的初值误差应小于300 km,否则部分历元将不能收敛到正确的接收机位置。

彩色多普勒血流成像联合胎心监护无负荷试验在孕晚期高危产妇胎儿宫内窘迫诊断中的效能

目的:探讨彩色多普勒血流成像(CDFI)联合胎心监护无负荷试验(NST)在孕晚期高危产妇胎儿宫内窘迫诊断中的效能。方法:回顾性分析2020年8月至2022年8月该院收治的108名孕晚期高危产妇的临床资料,入院后均行CDFI、NST检查,以产后结果为“金标准”,统计CDFI、NST单项及联合检查诊断孕晚期高危产妇发生胎儿宫内窘迫的结果,比较CDFI、NST单项及联合检查诊断孕晚期高危产妇发生胎儿宫内窘迫的效能。结果:产后结果显示,108名孕晚期高危产妇中,39名发生产前胎儿宫内窘迫;CDFI检查结果显示,25名发生产前胎儿宫内窘迫;NST检查结果显示,24名发生产前胎儿宫内窘迫;CDFI联合NST检查结果显示,38名发生产前胎儿宫内窘迫;CDFI、NST检查诊断孕晚期高危产妇发生胎儿宫内窘迫的灵敏度、特异度、准确度、漏诊率、误诊率、阳性预测值、阴性预测值比较,差异均无统计学意义(P>0.05);CDFI联合NST检查诊断孕晚期高危产妇发生胎儿宫内窘迫的灵敏度、准确度均高于二者单项检查,漏诊率低于二者单项检查,差异有统计学意义(P<0.05)。结论:CDFI联合NST检查诊断孕晚期高危产妇发生胎儿宫内窘迫的效能高于二者单项检查。

ADCP水池校准方法研究

提出一种在实验室消声水池环境下对声学多普勒流速剖面仪(ADCP)进行校准的方法。通过发射仿真回波信号,利用频率和延时时间实现量值溯源,进而实现对流速和深度的校准。研制了一套ADCP水池校准系统,以2波束614.4 kHz ADCP为校准对象,设计不同的流速分布实现对水层流速校准,探究底跟踪信号非限幅下的校准,设计多波束和单波束对比实验。对底跟踪速度进行不确定度评定,结果表明,在0~2.5 m/s速度下,不确定度最大为2.30 mm/s,验证了该校准方法的可行性。

彩色多普勒超声在盆腔附件囊性占位早期筛查诊断中的价值分析

目的:分析彩色多普勒超声对盆腔附件囊性占位的诊断价值。方法:选取2021年2月至2024年2月70例盆腔附件囊性占位患者,入选患者分别进行经腹彩色多普勒超声检查与经阴道彩色多普勒超声检查,以病理学检查为金标准,评价不同超声检查方法的诊断价值。结果:70例患者病理组织学诊断良性病变60例,其中子宫内膜异位囊肿20例、囊腺瘤30例、输卵管积液10例;恶性病变10例,均为囊腺癌;经阴道彩色多普勒超声的敏感性、阳性预测值均高于经腹彩色多普勒超声,差异有意义(P<0.05)。结论:经阴道彩色多普勒超声检查的诊断价值高,可推广使用。

Endometrial Injury and Sub Endometrial Doppler Study to Predict Uterine Receptivity in Women with Unexplained Infertility: A Randomized Controlled Trial

Objectives: The aim of this work was to compare the effectiveness and safety of endometrial scratching at different times of the menstrual cycle on cumulative pregnancy rate and also to assess and clarify its relationship and effect on sub-endometrial vasculature blood flow by Doppler ultrasound, in cases of unexplained infertility attempting to conceive spontaneously (without ovulation induction). Study Design: A prospective randomized clinical control study. Patients and Methods: A total of 252 eligible participants were included in the study and randomly allocated using block randomization into three groups: Group A (n = 84): endometrial scratching was performed during the pre-ovulatory days and Group B (n = 84): endometrial scratching has been done at day 7 of the cycle. Group C (control group): includes 84 cases without endometrial scratching. The Doppler ultrasound will be done. The pulsatility index (PI) and resistance index (RI) of endometrial and sub endometrial arteries were calculated. All women were followed up to 3 months. Results: Cumulative pregnancy rate is 21.42% and 28.57% in the study groups A and B respectively which is higher than group C (control group) (4.76%) but with statistically insignificant P-value = 0.254. There is statistically significant difference in RI & PI between the studied groups and the control group on day 13 (P value < 0.001). There is statistically significant difference in PI between day 13 and day 6 for the same group in both groups (A&B) (P value < 0.003), while there is no statistically significant difference in Group C (P value = 0.156). Conclusion: Endometrial scratching is a cost-effective and easy technique which may improve clinical pregnancy rates and endometrial blood flow in women with unexplained infertility.

彩色多普勒超声对糖尿病下肢动脉粥样硬化的诊断研究

目的研究采用彩色多普勒超声诊断在糖尿病下肢动脉粥样硬化中的作用。方法选取2022年4月—2023年4月临沂市人民医院收治的136例疑似糖尿病下肢动脉粥样硬化患者为研究对象,均进行彩色多普勒超声诊断,血管造影诊断作为金标准,计算彩色多普勒超声诊断诊断效能以及不同疾病类型的诊断符合率。结果彩色多普勒超声诊断的灵敏度98.00%、特异度98.84%、准确度98.53%、阳性预测值98.00%、阴性预测值98.84%,kappa=0.968。彩色多普勒超声诊断出不光滑无斑块4例、不光滑有斑块43例、管腔内膜光滑1例,诊断符合率分别为80%、97.73%、100%。结论彩色多普勒超声对糖尿病患者下肢动脉粥样硬化的诊断有一定的指导意义,并能明确其病变部位。

心脏彩超对慢性心衰的心脏结构与血液流速及波动速度状态的鉴别诊断

目的分析心脏彩超对慢性心力衰竭患者心脏结构、血流速度及波动速度状况的鉴别诊断效果。方法将本院2022年1月-2023年6月治疗的90例慢性心衰患者(视为观察组)临床诊疗资料进行回顾性分析,按照左室射血分数分为正常组(n=23例)、下降组(n=67例);选取同期来院体检者视为对照组(n=90例),均实施心脏彩超检查,分析其临床鉴别诊断效能。结果与对照组相比,观察组LVEF较低,但是LVEDD、LAD较高,组间差异有统计学意义(P<0.05)。正常组LVEF表达水平低于下降组,但LVEDD、LAD表达水平均高于对照组,组间差异有统计学意义(P<0.05)。Ⅲ级、Ⅳ级患者LVEF表达水平低于Ⅰ级、Ⅱ级,组间差异有统计学意义(P<0.05)。结论心脏彩超检查可以清楚直观地体现慢性心衰患者心脏组织、血流速度与波动速度,能为临床医师鉴别区分疾病、制定个性化诊疗方式提供一定参考依据。

彩色多普勒超声联合钼靶X线对不同分期乳腺癌检出率比较

目的探讨彩色多普勒超声联合钼靶X线对不同分期乳腺癌的检出率。方法选取鹤壁市人民医院普外科2010年4月至2022年6月收治的90例疑似乳腺癌患者。患者均接受彩超及钼靶X线检查。分析彩色多普勒超声、钼靶X线及两者联合诊断结果与病理学结果的一致性,分析,分析彩色多普勒超声、钼靶X线及两者联合诊断的敏感度、特异度、阳性预测值、阴性预测值、准确度。结果以病理学结果为金标准,Kappa一致性检验发现,彩色多普勒超声、钼靶X线、联合诊断与病理学结果高度一致,差异有统计学意义(Kappa值=0.823、0.733、0.929,P<0.05)。两者联合诊断的敏感性、特异度、阳性预测值、阴性预测值、准确度分别为97.40%、92.31%、98.68%、85.71%、92.86%;彩色多普勒超声单独检测早期乳腺癌的敏感性、特异度、阳性预测值、阴性预测值、准确度分别为88.31%、53.85%、90.54%、62.50、88.89%。钼靶X线单独检测早期乳腺癌的敏感性、特异度、阳性预测值、阴性预测值、准确度分别为84.42%、46.15%、91.67%、55.56%、87.78%。两者联合诊断早期乳腺癌的敏感性、特异度、阳性预测值、阴性预测值、准确度97.40%、92.31%、98.68%、92.86%、96.67%均高于彩色多普勒超声、钼靶X线单独检测。结论彩色多普勒超声与钼靶X线对不同分期乳腺癌诊断各有优势,且联合诊断的临床价值更高。

肺部彩色多普勒超声在小儿肺炎临床治疗中的应用价值

目的 探讨肺部彩色多普勒超声在评估小儿肺炎临床治疗中的应用价值。方法 选取2021年6月至2022年6月在该院就诊的以肺炎为诊断入院的80例患儿为研究对象,根据患儿住院期间的影像学检查分为超声组(44例)和X线组(36例),2组同时给予布地奈德混悬液雾化吸入治疗;以临床最终诊断为“金标准”,对比2组患儿的诊断结果、临床疗效、临床症状消失时间、住院时间及不良反应发生情况。结果 超声组患儿肺炎检出率[72.72%(32/44)]与X线组[55.56%(20/36)]比较,差异无统计学意义(P>0.05)。超声组诊断准确性(90.91%)、灵敏度(93.75%)明显高于X线组(61.11%、60.00%),差异有统计学意义(P<0.01);而超声组特异度(83.33%)与X线组(66.67%)比较,差异无统计学意义(P>0.05)。超声组总有效率(81.81%)优于X线组(61.11%),差异有统计学意义(P<0.05)。超声组患儿咳嗽消失时间[(4.69±0.79)d]、肺部啰音消失时间[(4.28±0.69)d]、发热消失时间[(1.78±0.95)d]与X线组[(5.63±1.07)、(4.93±0.73)、(2.83±1.20)d]比较,差异均有统计学意义(P<0.01)。2组患儿住院时间比较,差异无统计学意义[(7.02±1.19)d vs.(7.61±1.60)d,P>0.05]。2组不良反应发生率比较,差异无统计学意义(P>0.05)。结论 肺部彩色多普勒超声对小儿肺炎的诊断价值较X线检查更高,且对于小儿来说更具安全性及可反复操作性,能够更好地监测患儿的病情发展情况,为临床疾病的确诊、治疗等提供依据。

高动态环境下数据链信号载波频率估计算法

针对高动态环境下Link16数据链信号载波同步问题,设计了一种基于相邻符号相位差与两步式频率估计相结合的多普勒频率估计算法。该算法引入一种导频插入式数据结构,然后在此基础上对接收信号进行取辐角处理,再借助相邻符号位的相位差去除一阶频率偏移量,最后对观测序列求和得到变化率估计值。一阶多普勒频偏估计采用快速傅里叶变换与自相关结合方式来完成。理论分析和仿真结果表明,所提算法在频偏估计算法的基础上消除了多普勒变化率的影响,能实现多普勒变化率的有效估计。与其他算法相比,所提算法进一步增强了数据链系统传输的可靠性与动态环境适应能力,并且在估计精度方面具有优越的性能。

彩超引导下自体动静脉内瘘初期或疑难内瘘穿刺的应用

目的探讨彩超在自体动静脉内瘘(autologous arteriovenous fistula,AVF)初期或疑难内瘘穿刺的应用。方法选取大冶市人民医院血液透析室AVF首次使用患者及疑难内瘘穿刺患者,共60例,电脑随机分为2组,每组各30例,一组为彩超引导下穿刺组,另一组为常规盲穿组,对比观察2组一次穿刺成功率、穿刺部位血肿形成、动脉瘤、感染、血栓形成的情况。结果彩超引导组一次穿刺成功率明显高于盲穿组,穿刺部位血肿形成、动脉瘤、感染、血栓形成均明显低于常规盲穿组,差异具有统计学意义(P<0.05)。结论采用彩超引导下AVF穿刺,操作简单,安全可靠,可明显提高AVF初期或疑难内瘘一次穿刺成功率,并减少血肿形成、动脉瘤、感染、血栓形成等并发症的发生。

经阴道彩色多普勒联合β-人绒毛膜促性腺激素对早期宫外孕的诊断价值分析

目的探讨经阴道彩色多普勒(TVCDS)联合β-人绒毛膜促性腺激素(β-HCG)对早期宫外孕的诊断价值。方法选取2018年5月至2021年5月于本院就诊的86例疑似早期宫外孕患者作为研究对象,所有疑似患者均接受TVCDS与血清β-HCG检查,最终经手术或保守治疗确诊与排除。比较不同诊断方式诊断结果、宫外孕与正常妊娠孕妇β-HCG水平,分析TVCDS联合β-HCG诊断宫外孕的效能。结果86例疑似患者中,确诊宫外孕患者53例,宫外孕确诊率为61.63%。宫外孕与正常妊娠孕妇初检β-HCG水平比较差异无统计学意义;48 h后复检,两者β-HCG水平均高于初检时,且宫外孕患者β-HCG水平低于正常妊娠孕妇,差异有统计学意义(P<0.05)。TVCDS联合β-HCG诊断早期宫外孕的灵敏度、符合率、AUC值均高于β-HCG与TVCDS单一诊断,漏诊率低于β-HCG与TVCDS单一诊断,且TVCDS灵敏度、AUC值均高于β-HCG,漏诊率低于β-HCG,差异均有统计学意义(P<0.05);TVCDS与β-HCG符合率比较差异无统计学意义;β-HCG、TVCDS及TVCDS联合β-HCG特异度、误诊率比较差异无统计学意义。结论TVCDS联合β-HCG诊断早期宫外孕的灵敏度、符合率均较高,可降低早期宫外孕的漏诊、误诊风险。