合肥光源横向束流反馈系统中矢量运算单元和光纤陷波滤波器的研制

 合肥光源横向束流反馈系统已经建成,着重介绍了系统中矢量运算单元和光纤陷波滤波器的研制。矢量运算单元中使用混频器控制信号的衰减,调节控制电压的大小以控制反馈信号的相位;光纤陷波滤波器创新性地提出用光纤延时制作陷波滤波器,很好地滤除了信号中的回旋频率分量,节省了反馈功率。     

具有陷波电路结构的P波段低温低噪声放大器

该文的工作是设计和制作了一种具有陷波电路结构的P波段低温低噪声放大器。在低温75K环境下,工作频段为250-350MHz的范围内,该低温低噪声放大器具有优异的性能,噪声系数小于0.4dB,增益为14.4dB,增益平坦度小于0.05dB,输入反射损耗S11<-20dB,输出反射损耗S22<-20dB。同时在工作频段外的高温超导滤波器寄生通带内,该低温低噪声放大器成功实现了传输陷波响应,加强了系统对前端高温超导滤波器产生的寄生通带的衰减和抑制。     

强激光束在柱面镜空间滤波器中的传输特性

为了解决空间滤波器滤波针孔堵孔问题,提出了一种新型柱面镜空间滤波器,新型柱面镜空间滤波器由柱面镜和狭缝构成。利用线性传输理论,对高功率激光束在新型柱面镜空间滤波器中的传输特性进行了数值模拟。结果表明:新型柱面镜空间滤波器的焦斑面积比传统滤波器大,而焦斑功率密度较小;新型柱面镜空间滤波器的滤波效果与传统滤波器相同,近场均匀性也相同。因此新型柱面镜空间滤波器能够抑制空间滤波器堵孔效应,可以缩短空间滤波器系统透镜焦距,从而提高功率装置的整体性价比。由此,采用新型柱面镜空间滤波器替换传统球面镜空间滤波器具有可行性。     

VHF波段变容管调谐式超导陷波器

设计制作了一款VHF波段变容管调谐式超导陷波器,该陷波器采用一种结构紧凑的电容加载的矩形回路谐振器,谐振器与主线之间的耦合形式为混合耦合。通过调节加载在谐振器上变容二极管的反偏电压,实现带阻滤波器中心频率可调。测试表明,陷波器中心频率可调范围为251~360MHz,陷波器中心频点抑制40dB,3dB带宽9dB,插入损耗0.5dB。     

自适应陷波滤波器应用研究

本文介绍自适应陷波滤波器的基本理论,提出了设计极窄带自适应陷波器和滤波器的方法,介绍了用作相位估计器的概念。作者证明自适应相位估计器是理想条件下的最大似然比相位估计器,计算机仿真研究和硬件实验结果均表明该估计器有良好的性能,它的显著优点是同时完成了信号的检测和相位差的估计。     

基于Sagnac环可调谐光梳状滤波器特性研究

提出了一种基于Sagnac环干涉结构的光梳状滤波器。该结构利用保偏光纤双折射效应产生梳状滤波响应,通过控制Sagnac环内相位调制器的驱动信号实现光学滤波器陷波深度与滤波波长的独立调谐。利用Jones矩阵对所提出的Sagnac环光滤波器的滤波响应函数进行研究,通过分析得到光滤波器的陷波深度和滤波波长分别与射频信号和直流偏压之间的关系。在此基础上构建实验链路,验证了系统的理论分析,实现了光滤波器陷波深度在0dB~30dB范围内的灵活控制;通过设置直流偏压在0~12V范围内变化,实现了光滤波器滤波波长在一个自由光谱范围(0.5nm)内的连续可调,波长调谐效率为0.043nm/V。     

格结构在晶体梳状滤波器设计中的应用

利用数字信号处理中的格滤波器理论,研究了晶体梳状滤波器的设计方法.当传输函数满足对称和功率互补时,分析指出滤波器的阶数是奇数,N阶滤波器只需要(N+1)/2个波片,且所用波片的厚度比为1∶2∶2…2或2∶2…2∶1；提出了对半带滤波器传输函数作谱分解得到光梳状滤波器传输函数的方法.在此基础上总结出根据应用要求设计晶体梳状滤波器传输函数和结构参量的方法,通过设计一个7阶滤波器,表明提出的方法设计过程简单,且设计结果符合梳状滤波特征.     

声表面波陷波器与梯形结构相结合的滤波器

用单端对SAW谐振器取代LC低通滤波器中的电容可构成宽通带陷波器。它具有频率选择性好，通带插损低，对陷波频点抑制较高的优点。将这种陷波器与梯形滤波器结合，能实现一种在通带具有低插损，而在特定频段达到高抑制的滤波器，从而可用于双工器中。本文首先分析了这种组合结构的构成原理及实现方法；然后进行理论模拟，并进行了实验验证。     

基于半导体光放大器的通带与阻带相互切换的全光微波滤波器

为了满足光纤射频链路和相位阵列人线应用要求,提出并实验验证了基于半导体光放大器(SOA)的全光微波滤波器,该结构利用SOA的放大自发辐射的交义增益调制(XGM)原理,可以实现通带和阻带的相互切换.它是基于由SOA和可调谐窄带光学滤波器构成的光纤延时环,利用SOA的放大自发辐射谱的交义增益调制产生负系数.当可调谐窄带光学滤波器的中心波长对准激光器的波长时,可获得一个高Q的带通滤波器频率响应;当可调谐窄带光学滤波器的中心波长偏离激光器波长一定量时,可获得陷波宽度较窄和通带相对较平的陷波滤波器频率响应.此结构通过调节可调谐窄带滤波器的中心波长可实现高Q与通带相对较平的陷波频率响应的切换.     

一种新型高效光子晶体多信道下载滤波器的设计

采用二维正方排列的光子晶体,根据微腔缺陷模和波导模共振耦合原理,设计了一种新型的多信道下载滤波器,该滤波器通过主波导、90°弯波导和共振微腔的组合,提高了各个信道下载波导的下载效率。利用二维时域有限差分法模拟了滤波器的传输特性,并理论分析了影响下载效率的因素,进一步对滤波器进行了优化,使得各信道下载波导的下载效率均在91%以上。模拟结果表明该滤波器能有效地实现光波的分波下载,传输谱信道波长间隔约为20nm,中心波长误差为±2nm,传输谱的最大半宽度为3.2nm,有良好的波长选择性,证实了增大下载波导和共振微腔的耦合区域可以有效地提高滤波器的下载效率。     

Self-coupled dual-mode ring resonator with turning transmission zeros in microwave bandpass filter for planar metamaterial: analysis and design

An H-shape dual-mode closed resonator with self-coupled segments is reported. The self-coupling between ring segments renders an equivalent mode perturbation effect as the normal ways of adding stub, cutting notch, or varying line impedance to the ring resonator. The mode perturbation and transmission-zero generation from the self-coupling effect and step-impedance were analyzed using the even–odd mode theory. By regulating the impedance ratio and coupling coefficients of self-coupled sections, the self-coupled ring resonator can produce either the capacitive or inductive perturbation. The input and output positions affect the number and locations of transmission zero. The positions of input and output ports are properly selected. In the capacitive perturbation case, when the two transmission zeros are located on both sides of the passband, and bring about a pseudo-elliptic bandpass response. The analysis of finding optimized taping positions of input and output ports is proposed. Comparing to the regular uniform ring resonator, the H-shaped self-coupled ring resonator has shorter ring length, is easily to be folded and does not destroy the dual-mode characteristics. The feature of compact size is favorable in the design of a bandpass filter. A 2.45-GHz bandpass filter based on the H-shaped self-coupled ring resonator was performed to verify the proposed theory. A schematic bandpass filter was implemented with a compact size which is only 20% of the conventional dual-mode bandpass filter.     

基于双SSLR的小型化双通带带通滤波器设计

设计了一种新的具有良好选择性的小型化的双模双通带带通滤波器。该滤波器的谐振结构由两个短路枝节加载谐振器(SSLR)连接到同一个接地金属柱构成。首先通过奇偶模分析方法分析单个SSLR的谐振频率,得到谐振频率的变化规律;然后为了实现滤波器的小型化,将两个SSLR连接到同一个金属柱上并且折叠微带线,通过调节枝节长度分析滤波器通带的变化;设计中使用双枝节分别对谐振器馈电的结构,并且引入了源与负载耦合,可以在上阻带多提供一个传输零点,以提高阻带抑制;最后对滤波器的传输零点进行分析,提高滤波器的选择性。通过上述的分析,对该滤波器进行仿真、加工以及测试,得到最后实物的测试结果与软件的仿真结果较为一致。     

自适应陷波器在机抖激光陀螺信号处理中的应用

首先利用极零点受限自适应陷波器对二频机械抖动激光陀螺输出信号利用预处理,然后再进行低通滤波器处理的方法,不仅有效地消除了抖动输出,而且减小了由FIR滤波器引起的时间延迟。     

适用于3G移动通讯的高温超导窄带滤波器

研制了一种适用于3G移动通讯基站接收机的高温超导窄带带通滤波器.其中心频率为1949.85兆赫兹,带宽为9.7兆赫兹.为了实现极高性能,理论设计了12阶准椭圆(quasi-elliptic)函数型滤波器,引入了3对传输零点.滤波器的计算机仿真是用Sonnet软件完成的.此滤波器是在直径为2英寸、厚度约为0.5毫米的氧化镁双面超导薄膜上制作的.实测表明,达到了极高的性能要求:相对带宽0.49%,带边陡度>150dB/MHZ,带外抑制>60dB,插入损耗<0.2dB,反射损耗<-14dB.     

感应电压叠加装置中角向传输线阻抗计算

在进行感应电压叠加装置设计时, 为了使初级脉冲形成与传输系统产生的快前沿高压脉冲均匀耦合到次级传输线, 需要建立感应腔的二维电路模型对电磁波在角向传输线中的传播过程进行分析, 并基于电路计算结果优化设计角向传输线阻抗分布规律,使次级传输线中电流能够均匀分布。由于角向传输线结构复杂, 没有精确求解阻抗值的解析公式, 介绍了一种基于电报方程和瞬态电磁场仿真求解复杂结构传输线阻抗值的方法, 采用该方法对等宽度和变化宽度两种结构角向传输线阻抗值进行了评估。研究结果表明,相比于三平板传输线阻抗计算公式, 采用微带传输线阻抗计算公式对角向传输线阻抗值进行求解结果更加精确。     

Phase,zeros and poles of the transmission in quantum waveguides with an attached resonator and waveguide superlattices

This work reports on a study of electron transport in two-dimensionally-defined waveguide superlattices modeled by a lateral quantum waveguide with different numbers of attached quantum stubs. It is found that for the system with a single stub, the transmission amplitude exhibits pairs of zeros and poles in the complex-energy plane and the phase of the transmission coefficient drops sharply by π when the transmission passes a zero. This co-occurrence phenomenon of the transmission zero and the phase discontinuity is identical to the feature observed in a recent double-slit-like experiment by Schusteret al.[Nature385, 417 (1997)]. When two or more quantum stubs are attached to the quantum waveguide, each transmission zero seen in the single-stub structure develops into a group of zeros and the phase of the transmission coefficient shows, in correspondence to the group of zeros, a multiple-drop structure. However, not all poles of the waveguide superlattices are found to be paired with zeros and poles that are not paired with zeros are found to be located, in the complex energy plane, at the two sides of a multiple-zero region.     

Auditory filter asymmetry in the hearing impaired

Thresholds for 2-kHz sinusoidal signals were determined in the presence of a notched-noise masker, for six normal-hearing listeners and 12 listeners with cochlear hearing losses. Following Patterson and Nimmo Smith [J. Acoust. Soc. Am. 67, 229-245 (1980)], conditions were used where the notch was placed both symmetrically and asymmetrically about the signal frequency. The auditory filter shape for both the low- and high-frequency side of the filter was calculated using the rounded-exponential form of the filter. In six hearing-impaired listeners, the auditory filter shape showed a shallow low-frequency skirt indicating pronounced susceptibility to the upward spread of masking. In two hearing-impaired listeners, the filter shape showed a shallow high-frequency skirt, indicating pronounced susceptibility to the downward spread of masking. Two other listeners with mild threshold losses had steeper and more symmetric filters than normal, suggesting either a small conductive loss or an attenuation factor of sensorineural origin not associated with a degradation of frequency resolution. In the remaining two listeners, the auditory filter had too little selectivity for its shape to be reliably determined.     

Magnon nanometric filters in quasi-one-dimensional cluster chains

In the frame of the discrete dipole approximation, the propagation of magnons in quasi-one-dimensional resonant structures made of nanometric magnetic clusters is examined theoretically. These resonant structures, composed of a nanometric magnetic cluster chain and adsorbed clusters near the chain, may exhibit sharp peaks (dips) in the magnon transmission spectrum. Stop bands and sharp resonant magnonic states in the gaps can be created with an appropriate choice of the geometrical or magnetic parameters of the structure. These resonant states result from an internal resonance of the structure when such a resonance is situated in the vicinity of a zero of transmission or placed between two zeros of transmission. This model may have potential applications in constructing magnon filter devices.     

新型透射式全息窄带带阻滤光器的光谱特性分析

滤光器在光谱学、光学测量和激光物理中有着极其重要的应用。全息滤光器是一种新型滤光器,特别是利用重铬酸明胶(DCG)记录的全息透射式窄带滤光器,其主要特点为对主谱线有很窄的带宽。文章主要用紫外-可见分光光度计测定用DCG记录的透射式全息窄带带阻滤光器的光谱特性,测量结果分析表明,滤光器在可见光区域(400～800 nm)对其中心波长的相对透射率小于2%,其他谱线的相对透射率大于85%。且滤光器有较窄的带宽,其半宽度小于12 nm,十分之一宽度小于15 nm。对氩离子激光(Ar+)主谱线514.5 nm有优良的滤光特性。     

General IIR optical notch filter based on Michelson Gires–Tournois interferometer

A general IIR optical notch filter design is presented from a digital filter design perspective for Michelson Gires–Tournois Interferometer structure. Optical notch filter with arbitrary notch frequency, notch point number, and 3 dB rejection bandwidth can be designed easily. According to the spectral requirement of desired notch filter, in frequency domain we firstly calculate the transfer function of desired allpass filter. Then the numbers of reflectors in Gires–Tournois etalon can be determined. We calculate the transfer function of this multi-cavity Gires–Tournois etalon by using Z-transform. By making the transfer function of allpass filter in frequency domain equal to that of the multi-cavity Gires–Tournois etalon, the notch filter can be directly realized. Different design examples are given in detail in the paper. The change of output spectrum is also investigated for the reflectance of the reflectors and the distance between the reflectors deviating from the ideal value. The results show that the notch filter has the tunability of notch frequency and 3 dB rejection bandwidth. The chromatic dispersion characteristic of the notch filter is analyzed finally. It shows that the notch filter has excellent chromatic dispersion characteristic.