A high-temperature superconducting filter with controllable transmission zero

This paper presents a novel microstrip feedline structure to introduce an extra and controllable transmission zero(TZ)with high rejection for a narrowband filter. This structure loads a reconfigurable capacitor at the end of the input feedline without changing the main structure of the filter. The capacitor is recognized by a 2-bit inter-digital capacitor array. The asymmetrical microstrip feedline structure is suitable for multiple-pole filter designs. A low-loss six-pole high-temperature superconducting bandpass filter with a reconfigurable TZ is designed and fabricated. The center frequency of the filter is 5.22 GHz with TZ at the lower stopband. The TZ can be tuned among four different states. The out-of-band rejection at the TZ frequency is higher than 90 d B, and the insertion loss is lower than 0.92 d B. The measured results are consistent with the simulations.     

Microwave photonic filter with negative coefficients based on counter-phase modulation using a single electro-optic phase modulator

A simple photonic approach is proposed for the implementation of a reconfigurable multi-tap microwave filter with negative coefficients. In this scheme, a dual-optical-input intensity modulation module which can perform counter-phase modulation is constructed using a single electro-optic phase modulator. Two inter-complementary microwave signals are experimentally obtained for verification of the function of counter-phase modulation. A reconfigurable four-tap microwave filter with two negative coefficients is implemented by experiment.     

A novel low-loss four-bit bandpass filter using RF MEMS switches

This paper details the design and simulation of a novel low-loss four-bit reconfigurable bandpass filter that integrates microelectromechanical system(MEMS)switches and comb resonators.A T-shaped reconfigurable resonator is reconfigured in a'one resonator,multiple MEMS switches'configuration and used to gate the load capacitances of comb resonators so that a multiple-frequency filtering function is realized within the 7-16 GHz frequency range.In addition,the insertion loss of the filter is less than 1.99 dB,the out-of-band rejection is more than 18.30 dB,and the group delay is less than 0.25 ns.On the other hand,the size of this novel filter is only 4.4 mm×2.5 mm×0.4 mm.Our results indicate that this MEMS reconfigurable filter,which can switch 16 central frequency bands through eight switches,achieves a low insertion loss compared to those of traditional MEMS filters.In addition,the advantages of small size are obtained while achieving high integration.     

滤光轮分光的近红外彩色成像系统

研制了滤光轮分光的近红外彩色成像系统。针对一款光谱响应延伸至近红外波段的CMOS大面阵黑白摄像机,设计加工了大小适合的滤光轮和与光谱匹配的滤光片。根据滤光轮载荷选择了微型电机,并采用由时间同步装置产生的脉冲信号触发滤光轮的转停;采用基于灰度世界理论的RGB融合算法形成彩色图像。室内外的成像实验表明:该系统实现了近红外波段的彩色成像,尤其是夜天光中的近红外辐射,使夜间拍摄的图像亮度得到了明显的提升。     

基于可调高斯型滤波器的光纤光栅振动解调技术研究

 传统的匹配光纤布拉格光栅型光纤光栅波长解调系统具有波长匹配精度低、调节困难和动态测量范围小的缺点。为了克服上述缺点,采用波长可调谐高斯型滤波器代替传统匹配光纤光栅,提出了一种新型的光纤光栅波长解调技术。建立了基于高斯型滤波器的光纤光栅振动解调系统。对不同频率和振幅的周期性振动进行了解调实验。发现当选择合适带宽的滤波器时,透过滤波器的光功率随压电陶瓷上所加电压信号同步且高保真地变化,表明该系统对振动信号实现了有效的解调。该系统同时具有响应速度快、物理结构简单、动态测量范围大的优点。     

Electrically ultra-fast tunable optical filter employing HiBi fiber and phase modulator

An electrically tunable optical filter with ultra-fast tuning time of a few picoseconds is proposed and demonstrated. The filter consists of a phase modulator with HiBi pigtails sandwiched between two polarizers. Tuning of 6.62 nm for a 16.06 nm FSR filter is obtained with an applied voltage of 0.9 V. Tuning speed at 10 Gb/s and risetime of 40 ps is demonstrated with a frequency shift keying modulation experimental setup. Faster tuning speed is potential since the scheme is based on the electro-optic effect of the LiNO₃ crystal with sub-picosecond response time.     

Design and optimization of a microwave photonic filter exploiting differential mode group delay of a multi-mode fiber

Optical Review - A reconfigurable and application-specific tunable microwave photonic filter having finite impulse response is proposed. The filter exploits the differential mode group delays of...     

A tunable and reconfigurable microwave photonic filter based on a Raman fiber laser

A tunable and reconfigurable microwave photonic filter is demonstrated by employing a tunable Mach-Zehnder interferometer (MZI) and a wavelength-controllable Raman fiber laser. The free-spectral-range and spectral response of the microwave photonic filter are tuned and reconfigured by controlling the optical variable delay line in one arm of the MZI and the powers of the pump LDs. Experimental results are given to show the enhanced flexibility of the present microwave photonic filter.     

闭环光纤陀螺滤波算法的分析与改进

为了实现光纤陀螺的工程化,对数字滤波器的结构进行了改进,提出了一种多级抽样率转换器(SRC)与梳状带阻滤波器相结合的滤波算法。把闭环光纤陀螺的信号处理系统分为环内和环外两个部分,环外输出使用了加凯泽-贝塞尔窗的FIR滤波器。介绍了改进算法的优点,给出了新算法的实现方法。使用MATLAB对算法进行了仿真实验。结果表明,改进算法可明显地提高数字信号的处理效率,可保证在采样频率变换的过程中有用信号不会产生混叠,提高了光纤陀螺的精度。     

Experimental realization of a switchable filter based on a dynamically transformable array

We introduce a geometrically reconfigurable metasurface whose artificial "atoms" will reorient within unit cells in response to a thermal stimulus in the microwave spectrum. It can alternate between two contrasting behaviors under different temperatures and serve as a switchable filter that allows the incident energy to be selectively transmitted or reflected with an excess of 10 dB isolation at certain frequencies for both polarizations. The experimental results are consistent with the theoretical simulations, verifying the availability of an innovative method for manipulating electromagnetic waves with the merits of higher controllability for dynamic behavior and greater flexibility in the design process.     

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。     

Tunable and reconfigurable microwave photonic filter based on cascaded modulation for multi-taps generation

In this paper, a theoretical analysis and experiment to obtain the tunable and reconfigurable microwave photonic filter is proposed. The sidebands generated by cascaded modulation serve as the multi-taps, and then the reconfigurability and tunability can be realized by adjusting the operating condition of intensity modulators and the optical phase shifting between modulators.     

Sampling strong tracking nonlinear unscented Kalman filter and its application in eye tracking

The unscented Kalman filter is a developed well-known method for nonlinear motion estimation and tracking. However, the standard unscented Kalman filter has the inherent drawbacks, such as numerical instability and much more time spent on calculation in practical applications. In this paper, we present a novel sampling strong tracking nonlinear unscented Kalman filter, aiming to overcome the difficulty in nonlinear eye tracking. In the above proposed filter, the simplified unscented transform sampling strategy with n+2 sigma points leads to the computational efficiency, and suboptimal fading factor of strong tracking filtering is introduced to improve robustness and accuracy of eye tracking. Compared with the related unscented Kalman filter for eye tracking, the proposed filter has potential advantages in robustness, convergence speed, and tracking accuracy. The final experimental results show the validity of our method for eye tracking under realistic conditions.     

光波导滤波器的理论与最优化设计

本文提出一种新颖光波导滤波器结构,分析其设计理论,并进行最优化设计.该设计的计算方法简便,且可推广到多种介质波导构成的滤波器.其精确度优于通常的等效介电常数法(EDC法).     

一种高选择性可调带通与带阻可切换滤波器

设计了一种高选择性可调带通与带阻可切换微带滤波器。在微带谐振器及枝节末端加载变容二极管实现中心频率的可调;在输入与输出端口馈线之间,利用PIN二极管实现滤波器阻带和通带特性的切换。采用奇偶模的方法对滤波器结构进行分析,通过对奇偶模频率的调节实现了频率调节过程中的恒定绝对带宽。同时,在输入与输出馈线间引入源与负载耦合,使得频带两侧各有一个传输零点,且传输零点在整个频率调谐范围内相对位置几乎不变。因此,在整个频率调节范围内,滤波器实现了高选择性及良好的带外抑制能力。最终设计出的可调带阻滤波器的频率调谐范围为5.58～5.89 GHz,绝对带宽80 MHz±5 MHz,阻带衰减优于14 dB;可调带通滤波器的频率调谐范围为5.42～5.79 GHz,绝对带宽120 MHz±5 MHz,插入损耗1.69～2.25 dB,回波损耗优于13 dB。同时,该滤波器具有0.28λ_g×0.62λ_g（λ_g是可调频率范围中心频率的波长）的紧凑结构尺寸。实验和仿真结果一致性较好。     

基于微米颗粒填充的粉末低通滤波器仿真

粉末滤波器是一种可应用于超导量子计算等低温实验系统的低通滤波器, 随着频率的升高滤波器会对信号产生急剧的有效衰减, 粉末滤波器的填充材料、 中心导线长度、 线径和结构等参数会对它的频率响应特性产生影响. 本文利用 CST 微波工作室基于微米颗粒填充的方式, 首次对不同中心导线结构的粉末滤波器性能进行三维仿真研究, 仿真结果与实测结果对比后的定性一致性, 说明仿真方法的可行性和准确性. 仿真方法的提出可以有效地加快滤波器结构的迭代速度, 从而降低研发周期和成本, 方便可应用于超导量子计算的新一代粉末滤波器的开发.     

Compact tunable three-dimensional polymer optical waveguide comb filter

A compact channel spacing tunable polymeric three-dimensional (3D) comb filter has been designed and fabricated. This comb filter is made of three waveguides laid in two different but parallel layers: one is in the lower layer and the other two are in the upper layer. These two waveguides in upper layer do not cross each other but instead each twice cross over the waveguide in the lower layer. At each crossing point an electrode heater is deposited on the top surface to adjust the coupling ratio between these guides. By supplying power to each heater pair, respectively, the channel spacing can be selected to be either 1.6 nm or 0.8 nm; in addition a flat-top spectral response may be obtained at the 1.6 nm channel spacing if power is supplied to both the heater pairs simultaneously.     

Opto-VLSI-based tunable photonic RF filter

In this paper, an Opto-Very-Large-Scale-Integrated (Opto-VLSI) based tunable photonic radio frequency (RF) filter structure is proposed and numerically simulated. The structure comprises a reconfigurable Opto-VLSI processor capable of arbitrarily steering optical beams of different wavelengths, a diffraction grating for wavelength division demultiplexing, and high-dispersion fibres for true-time delaying RF-modulated wavebands. The proposed structure has the ability to generate arbitrary wavebands and weights for realizing any RF filter responses. The proof-of-concept of the tunable photonic RF signal processor is also experimentally demonstrated by tuning its free-spectral range and altering its shape factor through optical beam steering.     

基于开关电流技术的小波变换的滤波器电路实现

提出基于开关电流技术的小波变换的滤波器电路实现方法. 小波变换的开关电流滤波器实现电路由冲激响应为高斯一阶导数及其膨胀函数的滤波器组构成. 开关电流滤波器的膨胀系数(尺度)通过控制宽长比(W/L)或时钟频率可得到精确地控制. Padé逼近是一种有效的有理逼近，小波函数经过Padé变换可以得到其有理分式逼近，十分利于其开关电流滤波器电路实现. 仿真结果证实了其可行性. 关键词： 小波变换 开关电流 滤波器 Padé逼近     

用多凹槽滤波器控制混沌系统

提出了一种施加多个凹槽滤波器反馈控制混沌系统的方法,使混沌运动转化为规则的运动.多凹槽滤波器控制是一种具有固定参数的线性反馈控制方法,它不影响原系统的参数,截断了系统从倍周期分叉通向混沌的道路.同时,用Melnikov方法进行理论分析,给出了合适的反馈控制器的参数.将多凹槽滤波器应用于典型的混沌系统,其仿真结果表明了该控制方法的有效性与可行性 关键词： 混沌 多凹槽滤波器 Melnikov方法