Estimating the subsolar magnetopause position from soft X-ray images using a low-pass image filter

The Lunar Environment heliospheric X-ray Imager(LEXI)and Solar wind Magnetosphere Ionosphere Link Explorer(SMILE)missions will image the Earth’s dayside magneto pause and cusps in soft X-rays after their respective launches in the near future,to specify glo bal magnetic reconnection modes for varying solar wind conditions.To suppo rt the success of these scientific missions,it is critical to develop techniques that extract the magnetopause locations from the observed soft X-ray images.In this research,we introduce a new geometric equation that calculates the subsolar magnetopause position(RS)from a satellite position,the look direction of the instrument,and the angle at which the X-ray emission is maximized.Two assumptions are used in this method:(1)The look direction where soft X-ray emissions are maximized lies tangent to the magnetopause,and(2)the magnetopause surface near the subsolar point is almost spherical and thus RSis nea rly equal to the radius of the magneto pause curvature.We create synthetic soft X-ray images by using the Open Geospace General Circulation Model(OpenGGCM)global magnetohydrodynamic model,the galactic background,the instrument point spread function,and Poisson noise.We then apply the fast Fourier transform and Gaussian low-pass filte rs to the synthetic images to re move noise and obtain accurate look angles for the soft X-ray pea ks.From the filte red images,we calculate RS and its accuracy for different LEXI locations,look directions,and solar wind densities by using the OpenGGCM subsolar magnetopause location as ground truth.Our method estimates RS with an accuracy of<0.3 RE when the solar wind density exceeds>10 cm-3.The accuracy improves for greater solar wind densities and during southward interplanetary magnetic fields.The method ca ptures the magnetopause motion during southwa rd interplaneta ry magnetic field turnings.Consequently,the technique will enable quantitative analysis of the magnetopause motion and help reveal the dayside reconnection modes for dynamic solar wind conditions.This technique will suppo rt the LEXI and SMILE missions in achieving their scientific o bjectives.

A Passive Low-Pass Filter on Low-Loss Substrate

The loss mechanisms of different passive devices （on-chip inductors and capacitors） on different substrates are analyzed and compared. OPS （oxidized porous silicon） and HR （high-resistivity） substrates are used as low-loss substrates for on-chip planar LPF （low pass filter） fabrication. For the study of substrate loss, a planar coil inductor is also designed. Simulation results show that Q （the quality factor） of the inductor on both substrates is over 20. Measurements of the LPF on OPS substrate give a - 3dB bandwidth of 2.9GHz and a midband insertion loss of 0.87dB at 500MHz. The LPF on HR substrate gives a - 3dB bandwidth of 2.3GHz and a midband insertion loss of 0.42dB at 500MHz.

Design of a compact low-pass filter with wide stopband

This paper presents a novel low-pass filter （LPF） with sharp rejection, wide stopband and compact size, which are realized by the defected ground structure （DGS） and the defected microstrip structure （DMS）. The equivalent circuit model is proposed and the circuit parameters are extracted by the circuit simulation software. The parameters measured are 3 dB cutoff frequency fc of 5.2 GHz, the insertion loss less than 0.5 dB from DC to 4.0 GHz and S21 less than -20 dB within the wide stopband from 6 GHz to 16 GHz. The results of the circuit optimization agree well with those of the full wave simulation and the measured ones, which validate the effectiveness of the equivalent circuit model. The size of the proposed LPF is decreased compared with normal LPF. This LPF can be applied in rectennas to eliminate high order harmonics.

Design of low-pass filter based on a novel defected ground structure

A novel defected ground structure （DGS） for the microstrip line is proposed in this paper. The DGS lattice has more defect parameters so that it can provide better performance than the conventional dumbbell-shaped DGS. Selectivity is improved by 97.2% with a sharpness factor of 24.6%. The method is applied to the design of a low-pass filter to confirm validity of the proposed DGS.

Image Inpainting Detection Based on High-Pass Filter Attention Network

Image inpainting based on deep learning has been greatly improved.The original purpose of image inpainting was to repair some broken photos, suchas inpainting artifacts. However, it may also be used for malicious operations,such as destroying evidence. Therefore, detection and localization of imageinpainting operations are essential. Recent research shows that high-pass filteringfull convolutional network (HPFCN) is applied to image inpainting detection andachieves good results. However, those methods did not consider the spatial location and channel information of the feature map. To solve these shortcomings, weintroduce the squeezed excitation blocks (SE) and propose a high-pass filter attention full convolutional network (HPACN). In feature extraction, we apply concurrent spatial and channel attention (scSE) to enhance feature extraction and obtainmore information. Channel attention (cSE) is introduced in upsampling toenhance detection and localization. The experimental results show that the proposed method can achieve improvement on ImageNet.

Compact Metamaterial Microstrip Low-Pass Filter

Complimentary hexagonal-omega structures are used to design compact, low insertion loss (IL), low pass filter with sharp cut-off. It has been designed for improvement of roll-off performance based on both μ and ε negative property of the complimentary hex-omega structure while maintaining the filter pass-band performance. By properly designing and loading the hexagonal-omega structure in the ground of microstrip line not only improve the roll-off of the low pass filter, but also reduced the filter size. The simulated results indicate that the proposed filter achieves a flat pass band with no ripples as well as selectivity of 19.68 dB/GHz, corresponding to 5-unit cells hex-omega structures. This significantly exceeds the 5.6 dB/GHz selectivity of the conventional low pass filter design, due to sub-lambda dimensions of the hex-omega structure. A prototype filter implementing area is: 0.712λg x 0.263λg, λg being the guided wavelength at 3-dB cut-off frequency (fc). The proposed filter has a size smaller by 36.2%.

Microstrip Low-Pass Elliptic Filter Design Based on Implicit Space Mapping Optimization

It is a time-consuming and often iterative procedure to determine design parameters based on fine, accurate but expensive, models. To decrease the number of fine model evaluations, space mapping techniques may be employed. In this approach, it is assumed both fine model and coarse, fast but inaccurate, one are available. First, the coarse model is optimized to obtain design parameters satisfying design objectives. Next, auxiliary parameters are calibrated to match coarse and fine models’ responses. Then, the improved coarse model is re-optimized to obtain new design parameters. The design procedure is stopped when a satisfactory solution is reached. In this paper, an implicit space mapping method is used to design a microstrip low-pass elliptic filter. Simulation results show that only two fine model evaluations are sufficient to get satisfactory results.

Comparative Study of Low-Pass Filter and Phase-Locked Loop Type Speed Filters for Sensorless Control of AC Drives

High quality speed information is one of the key issues in machine sensorless drives,which often requires proper filtering of the estimated speed.This paper comparatively studies typical low-pass filters(LPF)and phase-locked loop(PLL)type filters with respect to ramp speed reference tracking and steady-state performances,as well as the achievement of adaptive cutoff frequency control.An improved LPF-based filter structure with no ramping and steady-state errors caused by filter parameter quantization effects is proposed,which is suitable for applying LPF for sensorless drives of AC machines,especially when fixed-point digital signal processor is selected e.g.in mass production.Furthermore,the potential of adopting PLL for speed filtering is explored.It is demonstrated that PLL type filters can well maintain the advantages offered by the improved LPF.Moreover,it is found that the PLL type filters exhibit almost linear relationship between the cutoff frequency of the PLL filter and its proportional-integral(PI)gains,which can ease the realization of speed filters with adaptive cutoff frequency for improving the speed transient performance.The proposed filters are verified experimentally.The PLL type filter with adaptive cutoff frequency can provide satisfactory performances under various operating conditions and is therefore recommended.

双同步坐标系解耦滤波器复变量建模与分析

针对解耦双同步坐标系锁相环(DDSRF-PLL)传统实变量模型阶数较高、序分量响应不易观察、滤波性能评估困难等问题,提出了一种基于复变量的DDSRF-PLL建模方法。首先,建立了其复变量模型,分析了序分量响应特性,该复变量模型表明正序基波输出模型对负序基波分量实现负无穷大的衰减,同时可得到其他频率序分量的衰减增益;然后,基于提出的复变量模型,设计了二阶低通滤波器以显著增强解耦网络的滤波性能,并进一步分析了高阶低通滤波器的可行性与必要性。研究表明采用二阶低通滤波器即可满足大部分场景下的谐波抑制要求,且具有计算量小、模型阶数低、易于数字实现的优点。实验结果验证了所提复变量模型的正确性与有效性。

Uncertainties of landslide susceptibility prediction: Influences of random errors in landslide conditioning factors and errors reduction by low pass filter method

In the existing landslide susceptibility prediction(LSP)models,the influences of random errors in landslide conditioning factors on LSP are not considered,instead the original conditioning factors are directly taken as the model inputs,which brings uncertainties to LSP results.This study aims to reveal the influence rules of the different proportional random errors in conditioning factors on the LSP un-certainties,and further explore a method which can effectively reduce the random errors in conditioning factors.The original conditioning factors are firstly used to construct original factors-based LSP models,and then different random errors of 5%,10%,15% and 20%are added to these original factors for con-structing relevant errors-based LSP models.Secondly,low-pass filter-based LSP models are constructed by eliminating the random errors using low-pass filter method.Thirdly,the Ruijin County of China with 370 landslides and 16 conditioning factors are used as study case.Three typical machine learning models,i.e.multilayer perceptron(MLP),support vector machine(SVM)and random forest(RF),are selected as LSP models.Finally,the LSP uncertainties are discussed and results show that:(1)The low-pass filter can effectively reduce the random errors in conditioning factors to decrease the LSP uncertainties.(2)With the proportions of random errors increasing from 5%to 20%,the LSP uncertainty increases continuously.(3)The original factors-based models are feasible for LSP in the absence of more accurate conditioning factors.(4)The influence degrees of two uncertainty issues,machine learning models and different proportions of random errors,on the LSP modeling are large and basically the same.(5)The Shapley values effectively explain the internal mechanism of machine learning model predicting landslide sus-ceptibility.In conclusion,greater proportion of random errors in conditioning factors results in higher LSP uncertainty,and low-pass filter can effectively reduce these random errors.

基于高频方波注入的永磁同步电机控制优化

提出一种利用高频正交方波电压注入静止坐标系的内置式永磁同步电动机无传感器控制的新方案。该方法是对传统高频旋转正弦电压注入法的改进,通过离散高频电流来建立整个信号过程。提出了一种不含低通滤波器的位置估计方法,并减小了高通滤波器引起的相移。该无传感器控制方法受到数字滤波器的不利影响会减少,可以解决当前基于静止坐标系的注入方法的常见缺点。

胎儿心率采集信号噪声滤波电路设计及仿真

胎心仪使用硅晶传感器对孕妇孕期体内胎儿心率进行无创监测,胎儿心率是一种微弱信号,信噪比低且母体干扰信号强,包含大量与胎儿心率相似的低频信号,都使胎心信号解析十分困难。本文提出了一种应用于单晶片收发模式胎心仪的多级MFB(Multiple Feedback,无限增益多路反馈电路)滤波电路,此电路对微弱的胎心音进行放大和滤波预处理,并使用软件仿真的方法合理选择滤波电路参数,经过滤波预处理的心率信号进入CPU进行自相关算法得到心率数值。最终实验结果表明:经过此多级MFB滤波电路的胎心音信号信噪比高,滤除高频干扰和大部分低频信号的同时有效保留胎儿心脏搏动波形,从而使胎心计探头在胎心30mm范围内能准确的得到胎儿心率,且扬声器播放音频无杂音。

S波段六位高精度移相器设计

采用0．25μmGaAs高电子迁移率晶体管（HEMT）7-艺设计了一款六位S波段数字移相器．移相器采用高低通和全通网络结构，运用了提高相位精度和抑制级联散射的方法．移相器在0°～360°相位范围内以5．625°步进，在2．1～2．7GHz频率范围内，最小相位均方根误差仅为1．13°．频带范围内插入损耗小于6．3dB，幅度均衡小于0．4dB，输入输出反射系数小于一10dB．

改进型感应电机电压模型磁链观测器设计

针对传统电压模型磁链观测器中引入低通滤波器后,带来幅值相位误差及滤波最佳截止频率选择问题,本文提出了一种高通滤波器和低通滤波器串联,且对电压模型中的电压项和电流项分别积分的改进型电压模型转子磁链观测器.文中分析了该改进型磁链观测器性能提高的原因,推导了高通滤波器和低通滤波器引起的幅值和相位误差补偿算法.仿真和实验验证了补偿算法的有效性,并且新的改进型转子磁链观测器在电机全速范围内具有优良的稳态和动态性能,具有较高的工程实践价值.

联合采用高通低通滤波与Hilbert-黄变换的非线性信号分析

经验模态分解方法无法分离2倍频内信号分量而可能导致模态混叠,这是应用著名的Hilbert-黄变换(Hilbert-Huang Transform,HHT)分析非线性信号时无法回避的问题,而消除模态混叠对于准确分析非线性信号具有重要意义。在此背景下,提出了一种联合采用高通低通滤波与Hilbert-黄变换的非线性信号分析方法,以解决这一问题。首先,提出了基于HHT瞬时频率的、用于判断是否发生模态混叠的指标;在此基础上为解决常规经验模态分析方法无法分解2倍频内信号的问题,采用傅里叶变换分析存在模态混叠的信号,并通过高通低通滤波将2倍频内的信号分离。之后,对经过滤波后的信号进行经验模态分解,并与之前未发生模态混叠的分量整合,得到原始信号完整的本征模态函数分量,进而计算得到各分量的瞬时频率和瞬时幅值。最后,用算例说明了所提方法的基本特征。

应用MAX264设计程控滤波器

本设计应用集成芯片MAX264设计一个程控滤波器。该滤波器主要由3个模块组成:前置放大、滤波电路、单片机显示与控制电路等。前置放大采用集成运放AD620构成;滤波器采用MAX264。然后利用单片机对MAX264编程,实现低通、高通及椭圆滤波器。通过测试达到了以下要求:输入正弦电压振幅为10mV时,总增益为40dB,通频带为100Hz～40kHz,;低通和高通滤波器,其-3dB截止频率fc在1～20kHz范围内可调,频率步进为1kHz,低通在2fc处总电压增益不大于30dB;高通在0.5fc处总电压增益不大于30dB;四阶椭圆型低通滤波器,带内起伏≤1dB,-3dB通带为50kHz,-3dB通带误差不大于5%。

基于集总元件的多级高低通移相器设计

本文分析了多级高低通滤波器型移相器的带宽特性,在移相量较小时,使用单级滤波器来实现,中等移相量要用三级,移相量大时,需要五级。在此基础上,设计加工了P波段五位移相,并给出了调试和测试结果。

频分复用有源滤波电路的EWB仿真设计

通过对高、低通二阶有源滤波电路的频率特性分析,得出滤波电路的参数设计方法,并采用EWB仿真软件在计算机上进行了仿真设计,该电路用于两路频分复用线路中,可以根据需要方便划分传输信号的频段。笔者计算分析与计算机仿真研究都说明在电路中合理选择相关元件参数情况下,可以使电路的高、低通输出特性均理想,并具有相同的截止频率。该项研究为两路频分复用电路的滤波电路参数设计提供了理论与实验的依据。

X波段4 bit MMIC数字移相器的设计与实现

基于WIN 0.25μm GaAs赝配高电子迁移率晶体管(PHEMT)工艺,设计并制备了一款X波段4 bit单片微波集成电路(MMIC)数字移相器。22.5°和45°移相单元采用开关滤波型拓扑结构,90°和180°移相单元采用高低通滤波型拓扑结构。对拓扑结构工作原理进行分析,并采用ADS2014软件完成电路的电磁仿真及优化。测试结果表明,该4 bit MMIC数字移相器获得了优良的宽带性能,且与仿真结果吻合良好。在8~13 GHz频带内,移相器的均方根(RMS)相位精度误差小于6.5°,插入损耗优于-6.8 dB,RMS插入损耗波动低于0.5 dB,输入回波损耗优于-13 dB,输出回波损耗优于-9.5 dB。该4 bit MMIC数字移相器在相对带宽为47%的X频段内性能优良,适用于有源相控阵雷达等通信系统中。

X波段六位移相器设计

采用SiGe BiCMOS工艺设计了一个X波段六位移相器。该移相器工作频率8~12GHz,移相范围为360°,步进5.625°。移相器采用高通/低通滤波器结构,通过六级移相单元以及多个单刀双掷开关级联实现。测试结果显示,芯片在1.2V的电源电压下,10GHz频率处插损约为15dB,在64种移相状态下,RMS相位误差1.6°,幅度偏差0.3dB,端口回波损耗小于-16dB。芯片不包含焊盘的尺寸约为2.65mm×0.81mm。