一种新型截止频率可调的滤波器设计

从传统短截线低通滤波器的设计理论出发,推导出新型开关滤波器谐振单元的截止频率和插入损耗计算公式.以频率响应的变化规律为依据,将不同谐振单元级联通过改变并联枝节长度设计任意截止频率的低通滤波器.最后利用PIN管的开关特性,连接不同微带枝节从而改变谐振网络的枝节长度,实现不同截止频率开关滤波器的设计.在同一电路设计了截止频率分别为0.9 GHz、1.5 GHz、2 GHz三波段的低通滤波器,并对其进行了仿真、优化和加工实物测试,验证了理论分析的正确性.     

扫频型接地电阻测量中IIR数字滤波器的设计

为克服传统单一异频法测量精度低的缺点,本文将扫频测量法应用到接地电阻测量中.信号源采用异频扫频电源,测量系统采用IIR数字滤波器进行选频滤波以减弱干扰信号.文中着重介绍了测量系统中IIR数字滤波器的设计,利用Matlab的可视化工具FDATool(Filter Design and Analysis Tool)进行滤波器设计并结合Simulink进行模拟仿真.根据信号源的一系列频率对应设计得到一系列数字滤波器,然后在DSP上编程运算.其特点是可根据设计要求实现可变中心频率的滤波器,进而在高速DsP中实时处理,而且方便调整滤波器参数,直观简便,有利于滤波器的最优化设计.     

Digitally tunable ring laser using ladder filter and ring resonator

We propose a digitally tunable ring laser incorporating a ladder filter and a ring resonator. The widely tunable ladder filter consists of two input-output waveguides and a waveguide array, and it selects one channel from the periodic outputs of the ring resonator. With this device, the passband of the ladder filter is important in terms of obtaining stable lasing operation and it becomes narrower with increasing diffraction order. However, the free-spectral range of the filter is reduced with increasing diffraction order and this induces lasing mode instability. We therefore optimize the diffraction order of the ladder filter. The device is monolithically integrated by using the InP-InGaAsP material system. We achieved 37 channel 1000-GHz spacing digitally tunable laser operation. A promising way of improving the device performance is to use a chirped ladder filter because this filter has one dominant passband.     

基于F-P可调谐滤波器的光纤光栅解调系统设计

针对某结构应力监测系统,提出应用光纤光栅传感原理来测量结构应力,设计了基于光纤标准具的F-P可调谐滤波器光纤光栅解调系统。利用标准具的稳定性来对F-P滤波器进行标定,消除环境温度对F-P滤波器的干扰。利用DDS原理设计了F-P滤波器的驱动源,产生的三角波分辨率可以小于0.42mV,确保解调系统最终的分辨率达到1pm。设计了光电转换电路,实现了微弱光信号的转换和放大,最后转换成易于采集与显示的电压信号。最终,利用本次设计的解调系统可以实现±3000με的应变测量,测量精度可达到2.59%。     

Widely tunable erbium-doped fiber ring laser covering both C-bandand L-band

We demonstrate a widely tunable erbium-doped fiber (EDF) ring laser covering both the conventional wavelength band (C-band) and the long wavelength band (L-band). It features a wide tunable range, high output power, low-coherent, and depolarized output. A tunable range over 80 nm (1520-1600 nm) has been achieved by optimizing the length of the EDF and by using an intracavity fiber Fabry-Perot (FFP) filter     

A broadly tunable erbium-doped fiber ring laser: experimentationand modeling

Broad-band tunability of erbium-doped silica fiber ring lasers in the 1.48-1.62 μm wavelength band is demonstrated through modeling and experiment. Tunability over the erbium-doped fiber amplifier (EDFA) C- and L-bands is achieved with a simple laser design using a single gain medium working in deep saturation. A comprehensive numerical model based on an iterative solution of propagation rate equations and spectrally resolved Giles parameters was used to analyze the impact of various laser variables. The dependence of laser output power on total cavity loss, erbium-doped fiber length, pump power, and lasing wavelength has been investigated. The calculated laser characteristics have been found in good quantitative agreement with the experimentally obtained data. Experimental results concerning wavelength tunability, output power, and lasing wavelength repeatability/stability and spectral purity are also presented     

Tunable optical narrowband filter using a gain-coupled phase-shift-controlled distributed feedback laser

In this paper, we have proposed and analyzed a new tunable optical narrowband filter using gain-coupled phase-shift-controlled distributed feedback (GC-PSC-DFB) laser diode. Coupled-mode equations are solved by using the transfer matrix method (TMM). The GC-PSC-DFB filters offer a stable single-mode bandpass output, similar to that obtained with phase-shifted index-coupled structures. However, GC structures do not suffer from the severe longitudinal spatial hole burning (SHB) that occurs in high-coupling quarter-wave-shifted DFB filters. This SHB can cause multimoded behavior for high-input signal power. Various filter parameters such as wavelength tuning range, side-mode suppression ratio (SMSR), and channel gain deviation have been investigated and discussed. Our results show that the GC DFB structures offer a wider tuning range of 23.3 /spl Aring/ compared with the similar index-coupled DFB structures with nearly steady bandwidth of 12 GHz, while maintaining 41.8-dB constant gain.     

采用改进陷波器的声反馈抑制

声反馈现象普遍存在于各种扩声系统中。声反馈会严重影响声音的清晰度,甚至会产生自激啸叫,而较严重的啸叫可能会使系统中的放大器、扬声器中的高音单元烧毁。所以,声反馈抑制是扩声系统中的一个重要问题。采用多频带FFT算法估计自激频率,估计精度高,鲁棒性强;同时对传统陷波器带宽不变的缺陷进行了改进,使之更适合声反馈的抑制,减少对声音的损伤。仿真结果表明,声反馈得到有效抑制,原始信号被较好的保留。     

High-quality coplanar waveguide tunable band-stop filter using defected ground structure and comb-line resonator with radio frequency microelectromechanical system varactors

A new analog tunable Ka-band band-stop filter is proposed on high resistivity silicon (HRS) substrate using radio frequency microelectromechanical systems (RF MEMS) varactors for satellite and radar applications. The designed filter uses a λ/4 comb-line resonator on the center line of a coplanar waveguide (CPW) with a new uncommon defected ground structure (DGS). Using the DGS in the proposed structure not only decreases the lateral size of the filter but also increases the quality factor. The tuning range of the proposed filter is 29.8–35.6 GHz with a maximum actuation voltage of 44.5 V and a band rejection between 37 and 45 dB. The quality factors of the designed filter in the up and down states of the MEMS varactors are 162 and 292, respectively. The equivalent circuit model of the filter is exactly extracted, and DGS dimensions are optimized. Based on the frequency simulation using ANSOFT HFSS 14, the insertion loss of the designed filter is about 0.51 dB in the 0–20 GHz range and 2 dB in the 0–15 GHz range in, respectively, up and down state of the bridge. The return losses are 0.51 and 0.33 dB at the center frequency for the up- and down-state configuration of the bridge. A step-by-step fabrication process is also proposed for designing the band-stop filter. High quality factor, small size, and improved structure are the advantages of the proposed design.     

Micromachined wavelength tunable laser with an extended feedbackmodel

We present here a miniaturized wavelength tunable laser with an extended feedback model for potential all optical network applications. The feedback model has been developed to study the wavelength tuning characteristics of the micromachined tunable lasers in the weak and medium feedback limits. The miniaturized tunable laser, having a size of 2 mm × 1.5 mm × 1 mm, is an integrated Fabry-Perot diode laser with a surface micromachined mirror and a butt coupled optical fiber. A wavelength tuning range of 16 nm is achieved by moving the micromirror laterally, which is done by driving an electrostatic comb drive attached to the three-dimensional micromachined mirror     

Double-pass fiber Raman laser-a powerful and widely tunable in theultraviolet, visible, and near-infrared fiber Raman laser for biomedicalinvestigations

We present the operating principle, general features, and advantages of a novel concept for the development of powerful and widely tunable fiber Raman lasers (FRL's), based on the high-power pumping of large-core low-loss multimode fibers using a simple double-pass laser arrangement with Littrow-prism-tuned emission. Basic experimental results obtained with various modification double-pass FRL schemes, which provide the generation of both discretely tunable emission in the UV/blue (360-493 nm) at λ_p=355 nm and continuously tunable emission in the visible/near-IR (0.54-1.01 μm) at λ _p=532 nm, are reported. The double-pass FRL schemes permit powerful and widely tunable spectral components to be generated, due to the double passing of nonlinear-converted laser emission through the optical fiber, maximum cavity feedback, the use of multimode fibers, and high-power pumping     

带电压频率正反馈的主动移频式孤岛检测方法

主动移频式孤岛检测(Active Frequency Drift Method,AFD)算法简单、有效,但由于给电流施加了扰动信号,所以输出的电能质量受到影响,同时它的检测盲区(Non-Detection Zone,NDZ)也较大。对AFD算法进行了改进,采用电压频率正反馈,且电流扰动量为改变部分电流幅值的方法。分析了孤岛检测的总谐波特性,采用f 0 normQ?C坐标平面对改进算法的检测盲区进行了描述。仿真实验表明,与传统的主动移频式孤岛检测算法相比,改进的孤岛检测算法提升了检测速度,改善了电能质量,并有效地减小了检测盲区。     

混合耦合电调滤波器设计

设计了一款调谐范围为1200~1800MHz的电调滤波器。在传统梳状线电调滤波器的基础上,通过折叠变化引入了级间电磁场混合耦合使其在传输特性曲线低频端产生了两个传输零点,提高了带外抑制能力。引入的源负载耦合技术使传输零点向通带靠拢,进一步改善了滤波器的带外抑制能力。经测试,该滤波器的带外抑制度达到50dBc(1000MHz)、30dBc(2000MHz)。     

Performance analysis of a time-division-multiplexed fiber Bragggrating sensor array by use of a tunable laser source

The results of an investigation of the performance of a time-division-multiplexed (TDM) fiber Bragg grating (FBG) sensor array using a tunable laser source are reported. The system performance is found limited by the extinction ratio of the optical pulse modulator used for pulse amplitude modulation. Formulas that relate the crosstalk to the extinction ratio of the optical pulse modulator, the modulation parameters of the tunable laser, and the optical path differences among sensing channels are derived. Computer simulation shows that an array of 20 FBG sensors with 3 με resolution can be realized with a commercially available single Mach-Zehnder type optical pulse modulator of -35-dB extinction ratio     

An integrated controller for high‐frequency LCLC resonant inverter with phase‐shifted control and frequency regulation

High‐frequency alternating current has an extensive application as a result of outstanding advantages. The aim of the study is to develop a high‐frequency power source to feed the auxiliary loads of vehicle application such as electric fans, blower motors, and lighting. A feasible implementation of high‐frequency power source is examined by a full‐bridge LCLC resonant inverter. The corresponding control scheme is proposed for the fourth‐order resonant inverter to confront the control challenges of low output harmonics and dynamic nonlinear load. Firstly, an analysis parameter S _r is defined to address the possible impacts of the varying operational frequency to output THD and ZVS features. Secondly, an integrated control scheme is presented to implement pulse‐width control at heavy load and frequency regulation at light load. Lastly, an experimental prototype is accomplished with the peak voltage of 35 V and the output power of 120 W. The accordance of experimental results and theoretical analysis testifies that the proposed control scheme can achieve the low harmonics and high conversion efficiency over a wide scope of operational conditions. Copyright © 2016 John Wiley & Sons, Ltd.     

截止频率为200MHz的LTCC叠层低通滤波器的研制

在对LTCC多层结构电感和电容元件研究的基础上,由对L、C的参数的控制,通过三维场仿真软件HFSS对LTCC滤波器三维结构模型进行仿真模拟和参数提取,设计制作了截止频率为200MHz、在600MHz带外抑制大于25dB的0805尺寸无源集成低通LC型滤波器.仿真结果与样品的测试结果基本吻合.实验证明通过合理的设计,用H...     

Widely tunable DS-DBR laser with monolithically integrated SOA: design and performance

We report recent device characterization results for a fully packaged widely tunable digital supermode (DS) distributed Bragg reflector (DBR) laser which has been monolithically integrated with a semiconductor optical amplifier. This new device gives all of the wide tunability and high side-mode suppression ratio performance previously reported for the DS-DBR laser with the added feature of output powers in excess of 14 dBm in fiber. In addition to output power and basic tuning behavior, we report on linewidth and relative intensity noise measurements for this device in order to investigate the noise characteristics of this laser.