A band-pass frequency selective surface with polarization rotation

A band-pass frequency selective surface(FSS) with polarization rotation property is proposed. The proposed polarization rotating FSS(PR-FSS) is a two-dimensional periodic structure, its unit cell is an antenna-filter-antenna(AFA) module,and the polarization directions of the upper and lower antennas in each AFA module are orthogonal to each other, so the PR-FSS can achieve frequency selection and 90 degrees polarization rotation at the same time. The numerical simulation demonstrate that the anticipated frequency selection and polarization rotation are realized by the PR-FSS in the frequency band from 8.84 GHz to 10.30 GHz with a relative bandwidth of 15.26%, and the maximum insertion loss in the pass band is only 0.17 d B. Finally, one effective experiment validation is carried out, a reasonable agreement is observed between the experimental and simulated results except for a slight deviation caused by fabrication error and measurement tolerance.

Electrically triggered dual-band tunable terahertz metamaterial band-pass filter based on Si_3N_4–VO_2–Si_3N_4 sandwich

We experimentally demonstrate an electrically triggered terahertz(THz) dual-band tunable band-pass filter based on Si_3 N_4–VO_2–Si_3 N_4 sandwich-structured hybrid metamaterials. The insulator–metal phase transition of VO_2 film is induced by the Joule thermal effect of the top metal layer. The finite-integration-time-domain(FITD) method and finite element method(FEM) are used for numerical simulations. The sample is fabricated using a surface micromachining process,and characterized by a THz time-domain-spectrometer(TDS). When the bias current is 0.225 A, the intensity modulation depths at two central frequencies of 0.56 THz and 0.91 THz are about 81.7% and 81.3%, respectively. This novel design can achieve dynamically electric–thermo–optic modulation in the THz region, and has potential applications in the fields of THz communications, imaging, sensing, and astronomy exploration.

Solar-blind ultraviolet band-pass filter based on metal–dielectric multilayer structures

Solar-blind ultraviolet （UV） band-pass filter has significant value in many scientific, commercial, and military appli- cations, in which the detection of weak UV signal against a strong background of solar radiation is required. In this work, a solar-blind filter is designed based on the concept of ＂transparent metal＂. The filter consisting of Al/SiO2 multilayers could exhibit a high transmission in the solar-blind wavelength region and a wide stopband extending from near-ultraviolet to infrared wavelength range. The central wavelength, bandwidth, Q factor, and rejection ratio of the passband are numerically studied as a function of individual layer thickness and multilayer period.

PHASE CORRECTION AND BAND-PASS FILTERS IN CT IMAGING

This paper reports the use of the fast Fourier transform (FFT) in the direct Fourier transform method (DFM) in Computerized Tomography (CT) reconstruction. Phase corrections are needed in the CT reconstruction. In order to eliminate the image distortion from the basic DFM, Padding and band-pass filters are used in the improved DFM. Finally, some reconstructions from simulated projections and several experimental results are given.

Tunable graphene-based mid-infrared band-pass planar filter and its application

We have designed and proposed the edge modes supported by graphene ribbons and the planar band-pass filter consist- ing of graphene ribbons coupled to a graphene ring resonator by using the finite-difference time-domain numerical method. Simulation results show that the edge modes improve the electromagnetic coupling between devices. This structure works as a novel, tunable mid-infrared band-pass filter. Our studies will benefit the fabrication of planar, ultra-compact nano-scale devices in the mid-infrared region. A power splitter consisting of two output ribbons that is useful in photonic integrated devices and circuits is also designed and simulated. These devices are useful for designing ultra-compact planar devices in photonic integrated circuits.

DUAL MODE WIDEBAND BAND-PASS FILTER WITH NOTCHED BAND FOR COMMUNICATION SYSTEM

This paper presents a planar microstrip wideband dual mode Band-Pass Filter(BPF) from 2 GHz to 3.4 GHz with a notched band at 2.62 GHz.The dual mode band-pass filter consists of a ring resonator with two quarter-wavelength open-circuited stubs at =90o and =0o,respectively.A square perturbation stub has been put at the corner of the ring resonator to increase the narrow stopbands and improve the performance of selectivity.By using a parallel-coupled feed line,a narrow notched band is introduced at the required frequency and its Fractional BandWidth(FBW) is about 5%.The proposed filter has a narrow notched band and a wide pass-band with a sharp cutoff frequency characteristic,the attenuation rate for the sharp cutoff frequency responses is 297.17 dB/GHz(cal-culated from 1.959 GHz with-34.43 dB to 2.065 GHz with-2.93 dB) and 228.10 dB/GHz(calculated from 3.395 GHz with-2.873 dB to 3.507 GHz with-28.42 dB).This filter has the advantages of good insertion loss in both operating bands and two rejections of greater than 16 dB in the range of 1.59 GHz to 1.99 GHz and 3.49 GHz to 3.98 GHz.Having been presented in this article,the measurement results agree well with the simulation results,which validates our idea.

Electromagnetic Band Gap Loaded Square Waveguide Band-Pass Filter for Dual-Polarized Application

An Electromagnetic Band Gap (EBG) loaded square waveguide Band-Pass Filter (BPF) is proposed in this paper. It’s simply composed by symmetrically loading periodical metal diaphragms on each wall of a square waveguide. The influences of insert sizes and loading periods on the overall BPF performances are analyzed. Experimental results agree well with those predicted. 6 GHz pass-band with insert loss less than 1 dB, 2.5 GHz stop-band and larger than 25 dB polarization isolation can be obtained. The BPF can be applied in dual-polarized waveguide-based antenna-feed systems.

Design of UWB Band-pass Filters with GPS Band Rejection

这份报纸论述一个协议极端宽带( UWB )用一个高通行证的过滤器和一个低通行证的过滤器的通带过滤器，并且有我们的建议通带过滤器的 Iumped elements.The 结构的共鸣器很简单，背叛地面结构( DGS )结构被用来让低通行证的过滤器 characteristics.This 建议通带过滤器能比串联类型 filter.As 小得多模拟的结果，插入损失是在整个 2.2 GHz10.6 GHz 的通带的不到 0.3 dB ，当时

Widening DGD Dynamic Range of DOP-based PMD Monitor Using Band-pass Filter

The theoretical and experimental analyses of widening the differential group delay (DGD) dynamic range of degree of polarization(DOP)-based polarization mode dispersion monitor using a band-pass filter are presented. The experiment shows that the maximum DGD same time, DOP sensitivity has a little change. The experimental results are in accordance with the numerical ones.

A tunable dual-narrowband band-pass filter using plasma quantum well structure

A tunable dual-narrowband pass-band filter is designed. A one-dimensional photonic crystal （1D PC） is comprised of alternate dielectric layer and vacuum layer. Two quantum wells （QWs） as defects can be constructed by sandwiching two plasma slabs symmetrically in the 1D PC, and a dual-narrowband pass-band filter is formed. The conventional finite- difference time-domain （FDTD） method and piecewise linear current density recursive convolution （PLCDRC）-FDTD method are applied to the dielectric and plasma, respectively. The simulation results illustrate that the dual-narrowband frequencies can be tuned by changing the plasma frequency. The pass band interval and the half-power bandwidths （-3-dB band widths） are related to the space interval between two QWs.

一种提高变流器弱电网适应能力的虚拟阻抗控制策略

弱电网下较大的电网等值电感可能引起并网变流器失稳,为此,首先,建立了并网变流器的阻抗模型,根据阻抗比判据分析了电网等值电感对并网变流器稳定性的影响;其次,针对并网变流器对感性电网阻抗适应能力较低的问题,提出了一种基于带通滤波的虚拟阻抗控制策略,并研究了虚拟电阻值对变流器弱电网适应能力的影响,给出了虚拟电阻的选取原则;最后,搭建了系统仿真模型,仿真结果验证了文中理论分析的正确性和控制策略的有效性。

基于文氏桥振荡器的CCCⅡ带通滤波器

为了得到一个最简单、最经济的电流模式高Q带通滤波器,根据传统的文氏桥振荡器和伴随网络理论,设计了一个电流模式/跨导模式的CCCⅡ带通滤波器。通过调整CCCⅡ的偏置电流,电路的极点频率和品质因数能够被独立地电调谐,当满足IB3=2IB4,电路还能产生正弦振荡。由于电路使用4个CCCⅡ和2个接地电容,因此电路适宜集成。计算机仿真结果表明设计方法正确。

自适应差分阈值的心电信号R峰检测算法

针对传统差分阈值算法的不足,设计了一种自适应差分阈值算法实现对R峰的准确检测。该算法能够依据R峰高幅值、高斜率的特征自适应更新信号检测阈值,并且根据R-R峰之间的心率间隔特征,设计回溯判定机制提升算法的灵敏度和适用范围。文中选用MIT-BIH心率失常数据库中的心电数据作为信号样本,采用带通滤波和小波变换相结合的方法完成对心电信号的去噪,依据自适应阈值检测实现对心电信号的R峰特征提取。从实验结果来看,自适应后的差分阈值法将心电信号的检测准确率提高到了99.59%,灵敏度达到了99.64%,减少了R峰检测过程中漏检、误检情况的出现,提高了检测的准确性。

基于改进EMD-Kurtogram法的滚动轴承早期故障诊断研究

实现滚动轴承早期故障准确诊断的关键是得到故障部位有效振动信息,但实际工程中所采集到的轴承振动信号常含有噪声、干扰成分,给有效信息的选择带来了困难。带通滤波是解决该问题的有效方法之一,但不合理的滤波器参数会降低诊断结果的准确性。为此,提出一种基于改进EMD-Kurtogram法的滚动轴承早期故障诊断方法。该方法首先对EMD方法处理后的采样信号进行重构,再根据快速谱峭度图得到带通滤波器所需要的最优参数,最后经过带通滤波及时频域分析得到故障频率。通过实验平台验证及相关算法的对比得出,所提方法得到的故障倍频信息更加充分、清晰,所含噪声干扰更少,证明了该方法的有效性和先进性。

传输零点对称可调的调谐滤波器的设计

为改善滤波器的带外抑制效果,设计了一款微带平面结构的电调带通滤波器,可以实现滤波器中心频率的调谐和一个传输零点的对称可调。由于采用Doublet型耦合结构,传输零点的对称可调是通过调整谐振器的谐振频率实现的,不需要调整与端口间的耦合系数。采用微带结构,不仅使结构简单,也实现了两个谐振器与端口的耦合系数的单独控制。文中对Doublet型耦合结构进行了详细的研究,总结出了其产生有限位置传输零点的条件和特点。设计采用基于耦合矩阵的设计方法,文中详细描述了设计过程。实际设计、加工并测试了一款滤波器,中心频率调整范围为1,24GHz~1.36GHz,传输零点在左侧的调谐范围为1,225GHz~1.345GHz,右侧为1,225GHz~1.375GHz,回波损耗保持为-20dB左右。测试结果与仿真结果基本吻合,证明了所提滤波器及其设计方法的有效性。

基于电磁混合耦合的SIW宽阻带带通滤波器设计

为实现阻带一段范围内依然具有良好的抑制能力,提出了电磁混合耦合的基片集成波导(Substrate Integrated Waveguide,SIW)宽阻带带通滤波器(Bandpass Filter,BPF)。根据模式的本征抑制和电磁混合耦合理论,合理地设置外部馈电端口、内部耦合窗口及内部耦合圆孔阵列,抑制了频率低于TE_(105)和TE_(501)之前的所有高次模,并且使得工作模式TE101电耦合很好地传输。仿真与实测结果均显示,该滤波器的中心频率f_(0)=5.94 GHz,插入损耗为−3.46 dB,相对带宽为2.44%,当阻带宽度延伸至3.85 f0时,抑制深度优于20 dB。与经典的四阶SIW宽阻带带通滤波器相比,拥有相同的带宽时,该双层层叠的方式更加紧凑,有利于集成到微波电路系统中。

Passive optimization of pump noise transfer function by narrow band-pass filtering in femtosecond fiber lasers

Fluctuation of pump power is one of the major sources of temporal and intensity noise in femtosecond fiber lasers.In this work,the transfer functions between the relative intensity noise(RIN)of the pump laser diode(LD)and the output RIN,between the RIN of the pump LD and timing jitter of femtosecond fiber lasers are systematically studied.It is demonstrated,for the first time to our knowledge,that the amplitude of the pump RIN transfer function can be effectively decreased by an intra-cavity narrow band-pass filter.In particular,for normal-dispersion lasers,the 3-d B bandwidth of the transfer function can also be narrowed by two-thirds,with a steeper falling edge.Furthermore,with the narrow band-pass filtering,the transfer function is almost independent of the net intra-cavity dispersion due to amplifier similariton formation.The proposed scheme can effectively isolate the pump-induced noise without the need of complex active pump LD control and intra-cavity dispersion management,thus providing an easy way for practical high-power,high-stability femtosecond fiber laser design and related high-precision applications outside the laboratory.

A Microwave Ceramic Band-Pass Filter for Mobile Communications with New Coupling Structure

A surface mounted device （SMD） microwave ceramic band-pass filter for mobile communication with a new coupling structure is reported in this paper. In this filter, the external and internal coupling structures are fabricated on an alumina substrate and both resonators and coupling structures are placed into a metal house to cut off its radiation. The relationship between the coupling structures and the performance of the filter is analyzed by high frequency structure software （HFSS） and the filter with a center frequency of 836.5 MHz, bandwidth of 40.0 MHz, pass-band ripple of 0.1 dB and insertion loss of 1.5 dB has been successfully designed and fabricated. The measured results show a good agreement with the simulation results.

基于优化暂态零序方向与改进首半波的综合决策选线方法

针对现有小电流接地选线判据适应性较差、选线精度较低的问题,提出了基于优化暂态零序方向与改进首半波的综合决策选线方法,通过带通数字滤波器的设计及暂态首半波特性分析,综合利用首半波短窗、首半波长窗以及带通滤波数据窗内极性满足特性的采样点统计,确定各自相关系数,形成综合选线判据。基于该综合决策选线方法开发了对应的选线保护装置,并进行了RTDS动模测试及真型试验。结果表明,该选线方法能适应各种系统运行方式及故障条件,验证了其有效性和可靠性。

优化脉振高频信号注入的PMSM无位置传感器控制方法

针对基于脉振高频信号注入法的永磁同步电动机(PMSM)无位置传感器控制策略中,使用带通滤波器(band pass filter, BPF)会增加系统相位延迟,造成观测性能不佳的问题,提出一种采用双二阶广义积分器(second order-second order generalized integrator, SO-SOGI)的优化脉振高频信号注入法无位置传感器控制策略。首先,设计了采用SO-SOGI观测PMSM转子位置和转速信息的方法。其次,分析了所采用的SO-SOGI在中心频率处的幅频特性,验证了SO-SOGI具有较好的基波提取能力和内环负反馈调节机制,可以输出特定的频率信号而不存在相位延迟。最后,MATLAB/Simulink的仿真验证结果表明:在静态运行时转子位置估计的精度提高约0.7 rad,证明了该方法拥有良好的位置估算精度,提高了系统的可靠性;在动态运行时转速估计误差减小了62.5%左右,该方法能有效适应低速下转速变化,提高了系统的抗扰动性。