声光可调谐滤光器的原理与应用

本文介绍了声光可调谐滤光器(AOTF)的工作原理和基于AOTF的光谱分析仪器的基本构造、特点,以及AOTF光谱分析仪器的发展应用情况.     

AOTF近红外光谱仪信号源设计

在声光可调滤光器(AOTF)近红外光谱仪系统中,稳定的射频驱动信号源是AOTF实现分光功能的关键.本文根据近红外光谱分析所需的波长范围,利用直接数字频率合成(DDS)技术,设计了驱动AOTF所需的射频信号源.系统包括单片机控制模块、DDS信号发生模块、滤波电路、功率放大模块四部分.经实验测试,系统可在80～150 MHz频段内任意频点输出稳定的正弦信号波形,相对误差在0.45％以内,功率为1W,满足AOTF的工作要求(对应输出波长范围900～1 700 nm).     

凝视型AOTF高光谱成像系统设计

以声光可调谐滤波器(AOTF)为分光元件,集成了一种凝视型AOTF高光谱成像系统.系统硬件由AOTF及其控制器、CCD近红外相机、镜头、计算机组成,系统软件采用VC++2010语言,调用机器视觉算法包HALCON10.0的库文件和AOTF的库文件,实现对AOTF控制器和相机操作的控制及高光谱图像预处理.所集成的AOTF的凝视型光谱成像系统能连续采集被测物体的高光谱图像,光谱段为550～1 000 nm,光谱分辨率为2～6 nm,图像分辨率为1392像素×1 040像素.     

原子荧光光谱分析技术的创新与发展

原子荧光光谱分析技术的应用可以测定以下元素:一是砷,二是镝,三是蹄,四是汞,五是硒等.随后,我国研究人员结合原子荧光光谱分析技术研发出了以下技术:一是空心阴极灯,二是低温点火装置,三是小火焰原子化技术.除此之外,研究人员还研发出以下仪器:一是多通道光谱仪,二是一体化光谱仪.随着社会的快速发展,原子荧光光谱分析技术的应用范围还将不断扩大.但是,原子荧光光谱分析技术还需要不断创新和调整.     

基于CCD的快速光谱测定仪的电路设计

针对光谱分析中多波长快速测量的需要,设计了基于CCD的快速光谱测定仪.该仪器的电路部分采用了线阵CCD进行光谱数据采集,采用USB接口进行通讯和系统供电.这种设计大大提高了光谱测量速度和精度,同时使仪器的小型化和模块化成为可能.     

计算机在原子光谱分析中的应用进展

本文介绍了我国近十年来计算机在原子光谱分析领域的应用概况,所涉及的应用方面包括:仪器、实验设计和分析条件优化、分析数据处理、质量控制和实验室管理、机理研究和教学等.     

电子计算机在光谱分析中的应用

一、概况直读式真空光谱分析仪是一种较新的快速分析仪器。由于它具有准确、快速、高效率以及容易掌握、分析元素多等许多优点,在冶金企业中应用逐渐增多,有着广泛的发展前途。这种仪器过去都靠进口,最近两年我国已成批生产了。我厂自67年引进一套直读式真空光谱分析仪以来,通过近两年的安装、调整、编制程序和试运转,于69年初正式在生产中使用,至今运转良好,为多炼钢、炼好钢作出了一定的贡献。下面介绍一下电子计算机在光谱分析中的应用情况,仅供参考。     

原子吸收分光光度计与微計算机系统联机的自动采样及数据处理程序

原子吸收分光光度计与微计算机的联机使用是目前该仪器进展的主要趋势。国外微计算机已广泛应用于原子吸收光谱分析,实现了分析工作的自动化并提高了数据采集和处理的速度及精度。近期有不少这方面的报导文章。国外商品仪器也普遍采用微计算机,常见的是单板机与仪器的联机。国内目前初见报导文章,一些生产厂正进行这方面的产品设计工作。我们实验室近期初步完成了这方面工作,并已将该程序应用于教学实验和科研工作。     

光学传感器阵列在测定水硬度中的应用

提出一种基于化学计量学方法的水硬度的测量方法。以分光光度法为基础,结合传统的乙二胺四乙酸(EDTA)络合滴定法和现代光电子技术,力求实现水硬度测量的简便和快速。采用单片机控制,以三个特定波长的单色光实现非连续光谱分析,从而实现仪器的小型化和便携性。     

1种基于背景能量曲线的近红外光谱仪器响应函数监控及校准方法

针对近红外光谱分析中普遍存在的模型传递(仪器稳定性)问题,通过建立样品的信号漂移量和背景能量的信号漂移量之间的函数关系,实现了1种对仪器响应函数(状态)进行监控和校准的方法.采用两种不同的处理方式,采用手动调节分析仪器光源能量的方式,对基于阿达玛变换的近红外光谱仪的响应函数进行了模拟监控分析,对比分析了30个汽油样品的研究法辛烷值在校准前后的分析结果,计算结果证明了监控及校准方法的可行性和有效性.     

梳状线可调带通滤波器的设计与仿真

针对现有的微带可调滤波器中心频率调节范围较窄的问题,依据梳状滤波器的原理和变容二极管的特性,设计出一种梳状线可调带通滤波器,经ADS仿真可得其中心频率可调范围达到0．49～5．08GHz、相对带宽仅为6．1％～9．4％,该梳状线可调带通滤波器具有中心频率调节范围很宽、结构简单、易于实现、易于扩展等优点,在工程上具有一定的推广应用价值。     

A widely tunable bandpass filter adopting novel fully tunable resonators

A widely tunable bandpass filter adopting a novel fully tunable resonator is proposed in this letter. The fully tunable resonator is mainly consisted of an open ring, a frequency tuning structure, and a coupling tuning structure. Adopting the fully resonators, the center frequency, the input/output external Q value, and the coupling coefficients can be tuned at the same time. And the tuning range of a tunable filter adopting the novel fully tunable resonators can be expanded. The fully tunable resonators can be combined to achieve more excellent suppression performance. A widely tunable bandpass filter consisted of five fully tunable resonators with 86.5% frequency tuning range is designed, fabricated, and measured. The simulated results are in good agreement with the measured ones.     

Micromachined W-band polymeric tunable iris filter

A tunable filter working in the W-band spectrum has been successfully demonstrated using a combined plastic molding and electroplating process. The prototype filter architecture has two deformable membranes of 1.6 mm in diameter on top of a WR-10 waveguide based, two-cavity, polymeric iris filter. The membranes can be actively adjusted to deform and alter the cavity geometry concurrently for frequency tuning applications. The tunable filter was simulated using High Frequency Structure Simulator and theoretically analyzed using the perturbation method. Experimentally, a prototype band-pass filter has bandwidth of 4.05 GHz centered at 94.79 GHz and a minimum insertion loss of 2.37 dB with return loss better than 15 dB. As a tunable filter, a total of 2.59 GHz center frequency change has been recorded when the membranes deflected from 50 μm into, to 150 μm out of the waveguide. These results imply that the demonstrated tunable filter could be potentially applicable for waveguide-based mm-wave systems.     

High isolation tunable diplexer based on mixed electromagnetic coupling

In this article, a tunable diplexer based on quarter‐wavelength resonators with mixed electromagnetic coupling is designed. Different coupling types are utilized to generate a transmission zero in the stopband of filter, aiming to improve the isolation of diplexer. The meander line tunable filter with a magnetic dominated coupling forms channel 1 of the diplexer, a transmission zero in upper stopband is realized. The tunable filter dominated by electrical coupling constitutes channel 2 of the diplexer, a transmission zero is produced in lower stopband of the filter. Varactor diodes are loaded at quarter‐wavelength resonators for tunability of the center frequency. The proposed diplexer is both demonstrated by simulation and measurement. Experimental results show that the designed tunable diplexer has a frequency range of 0.85‐1.2 GHz and an isolation of greater than 42 dB.     

基于枝节加载多模谐振器的电调微波滤波器设计

针对认知无线电技术对射频微波滤波器的新要求,提出了一种基于枝节加载多模谐振器的电调微波滤波器。该电调微波滤波器由一个枝节加载微带多模谐振器和变容二极管组成,实现了滤波器的小型化。在分析枝节加载微带多模谐振器的基础上,通过在微带谐振器两端和加载枝节上加载变容二极管的方法,设计了枝节加载的电调多模微带谐振器,并提出了复杂微带谐振器谐振特性的分析方法。采用源和负载耦合的方法在通带右边引入一传输零点。通过在源和负载端放置耦合线的方法,提高了滤波器的通带选择性。针对滤波器带外衰减小的问题,引入一种新型的频变馈电结构,改善了滤波器的带外衰减特性。通过优化仿真确定了电调滤波器的尺寸参数。仿真验证了该滤波器的特性,当变容二极管的可调范围为2pf-10pf时,滤波器的频率可调范围为2.10GHz-2.40GHz,频率变化范围为300MHz。     

向列相液晶缺陷光子晶体可调谐滤波器的研究

在一维光子晶体中引入向列相液晶作为缺陷层,用电场改变液晶分子的取向,形成光子晶体可调谐滤波器.用传输矩阵法研究了液晶缺陷光子晶体的可调谐滤波特性,模拟计算了电压和液晶材料参数对滤波器透射谱的影响.结果表明,改变电压能容易改变光子晶体滤波器透射峰的位置、强度、个数和带宽,表现出很好的调谐滤波功能.     

基于电动调谐的波导窄带带阻滤波器的设计与实现

提出了基于电动调谐的可调滤波器设计思想,设计并实现了一种采用步进电机精确控制调谐的可调波导窄带带阻滤波器.该滤波器具有调谐准确,Q值高,功率容量大,易于实现等优点.实验测试结果验证了该设计方案的可行性和有效性.     

An Integrated 800-MHz Coupled-Resonator Tunable Bandpass Filter in Silver With a Constant Bandwidth

This paper presents a fully integrated tunable lumped filter on silicon using a low-temperature silver micromachining process. A prototype 836-MHz bandpass filter with a 3-dB bandwidth of 5.9% and insertion loss of 4.8 dB is demonstrated in a second-order coupled-resonator configuration. Continuous tuning of 50 MHz is achieved by electrostatically actuating the lateral air-gap capacitors of the filter. To control the bandwidth while tuning the center frequency, reconfigurable termination impedance is proposed. As a proof of concept, a low-noise amplifier with tunable input impedance is designed to interface with the bandpass filter. The tunable impedance is realized at the input of the low-noise amplifier using a shunt positive metal–oxide–semiconductor transistor. The fabrication, design, and measurement results of the filter are detailed, and future research directions to improve the performance of such filters are discussed.$hfill$[2009-0031]      

Real-time frequency compensatory filter for adjusting dynamic bandwidth of single-degree-of-freedom sensor system

This paper presents a real-time frequency compensatory filter to control the dynamic bandwidth of a single-degree-of-freedom dynamic system. Especially, the filter is applied to a novel fiber optic accelerometer system to prove its performance. The accelerometer is very profitable for monitoring civil infrastructures; however, it has a limitation such as small dynamic bandwidth. Therefore, it is needed to extend the dynamic bandwidth of the accelerometer by using the frequency compensatory filter. In this paper, the novel fiber optic accelerometer is introduced shortly, and then the compensatory filter is applied to the fiber optic accelerometer to control its natural frequency and damping ratio. Several simulations and experiments are carried out to prove the performance of the compensatory filter. The simulations show particularly the effect of sample rate on the effectiveness of the implemented filter. As a result, it is shown that the presented compensatory filter with a proper sample rate is an efficient way to broaden the dynamic bandwidth of the fiber optic accelerometer.     

A novel symmetrical folding miniaturized substrate integrated waveguide tunable bandpass filter

In order to improve the utilization of spectrum resources, dynamic frequency allocation technology has become a method of spectrum saving. The research of electric tunable filter has received much attention in recent years. Substrate integrated waveguide (SIW) is a new technology of microwave integration in the field. The innovation of this article is to combine the SIW miniaturization technology with tunable technology. In this article, a miniaturized symmetrically folded substrate integrated waveguide (SFSIW) filter is designed. Based on the miniaturization of SIW filter, the center frequency can be adjusted electrically and the measured data show that the tunable filter can achieve eight states under the condition that the bandwidth below ?3 dB remains approximately constant 300 MHz. The center frequency varies from 3.23 GHz to 3.9 GHz. The range of the filter's insertion loss is 1.2 dB to 2.04 dB, and the return loss is higher than 20.9 dB. This filter has practical value in the electronic countermeasures of military communication.