基于SIR的同轴腔体带通滤波器设计

基于阶跃阻抗谐振器SIR(stepped impedance resonators)的基本原理,采用λg/4型SIR作为基本谐振单元,设计了一款小型化同轴腔体带通滤波器.仿真结果显示,相比实际长度λg/4该滤波器尺寸压缩了56.7%,通带内回波损耗小于-17.5 dB,插入损耗小于0.1 dB,带外抑制度达到了-38.8 dB,满足了现代通信系统对滤波器小型化、低插入损耗、高选择性的要求,能够广泛应用于现代移动通信系统.     

Ultra-wideband bandpass filter with multiple notch-bands on multilayer liquid crystal polymer substrate

Novel compact ultra-wideband (UWB) bandpass filters (BPFs) with single or multiple notch-bands to avoid interference from existing radio systems are presented. A compact UWB BPF is proposed and designed based on broadside-coupled stepped impedance resonators (SIRs) at first, and then notch-bands are generated by embedding open-circuit stubs into broadside-coupled SIRs. Because of the harmonic suppression behaviour of SIRs, the proposed UWB BPFs have a wide stopband and high rejection level. The characteristic of the proposed notch-structure was investigated by full-wave simulations. Multilayer liquid crystal polymer (LCP) technology was used to implement the designed UWB BPFs. In the experiments, a UWB BPF with excellent stopband performance was designed to meet the Federal communications commission-defined indoor limits at first, and then UWB BPFs with single, double and triple notch-bands were designed to demonstrate the flexible notch-band, high-selectivity and wideband harmonic suppression performances of the proposed filter. The designed BPFs were fabricated by a multilayer LCP lamination process and measured using a vector network analyser. Good agreement between the predicted and measured results was obtained as presented here.     

Combination of highly nonlinear fiber, an optical bandpass filter, and a Fabry-Perot filter to improve the signal-to-noise ratio of a supercontinuum continuous-wave optical source

We present a theoretical study of a supercontinuum (SC) continuous-wave (cw) optical source generation in highly nonlinear fiber and its noise properties through numerical simulations based on the nonlinear Schr?dinger equation. Fluctuations of pump pulses generate substructures between the longitudinal modes that result in the generation of white noise and then in degradation of coherence and in a decrease of the modulation depths and the signal-to-noise ratio (SNR). A scheme for improvement of the SNR of a multiwavelength cw optical source based on a SC by use of the combination of a highly nonlinear fiber (HNLF), an optical bandpass filter, and a Fabry-Perot (FP) filter is presented. Numerical simulations show that the improvement in modulation depth is relative to the HNLF's length, the 3-dB bandwidth of the optical bandpass filter, and the reflection ratio of the FP filter and that the average improvement in modulation depth is 13.7 dB under specified conditions.     

Liquid-crystal bandpass filter based on the optical rotatory dispersion effect

A bandpass spectral filter and the test measurement results are presented and described. The filter is developed and constructed by use of a ferroelectric liquid-crystal polarization rotator in combination with dispersive quartz optical rotators, and its wavelength selection is mechanically tunable and electrically switchable.     

Widely tunable optical bandpass filter by use of polymer long-period waveguide gratings

We report the design and fabrication of a widely tunable optical bandpass filter based on using two identical long-period gratings formed along a polymer channel waveguide with a section of the waveguide core removed. The peak transmission of the passband of the fabricated filter is approximately 60% and the bandwidth of the passband is approximately 6 nm. The filter is thermally tunable over the C + L band (1520-1610 nm) for both TE and TM polarizations with a temperature control of approximately 30 degrees C.     

Markov-chain Monte Carlo approach to the design of multilayer thin-film optical coatings

We reconsider the problem of locating the globally optimal solution of a multilayer-optical-coating design problem, within some predetermined space of parameters, with the aim of obtaining a robust technique that requires a minimum of user intervention. The approach we adopt centers on exploring the space of the parameters of interest by using a Markov-chain Monte Carlo sampling algorithm. This technique enables one to locate the global optimum automatically with high confidence and without the need for a good starting design. It also allows the trivial inclusion of prior constraints on the variables and provides a natural means for investigating the robustness of the optimal solution.     

Band-notched ultra-wideband bandpass filter design using combined modified quarter-wavelength tri-section stepped-impedance resonator

This study presents a new band-notched ultra-wideband (UWB) bandpass filter (BPF) that is designed using a new structure-shared multi-mode resonator (MMR). The MMR is formed by combining two quarter-wavelength (λ/4) tri-section stepped-impedance resonators (TSSIRs) in a proper fashion to exhibit both λ/4 and half-wavelength (λ/2) types of resonance. With the first two resonant frequencies of the inherent λ/4 TSSIR, the first two of the parasitic λ/2 SIR and the coupling peaks of the input/output interdigital parallel-coupled lines properly located in the UWB passband, a six-transmission-pole UWB BPF can be realised. In this filter design, besides obtaining a uniform in-band transmission response, a notched band centred around 5.5 GHz is created by embedding L-shaped open-end slots in the TSSIR and loading the TSSIR with closely coupled winding-type resonators (WTRs) to filter out the 5-GHz wireless local-area network radio signal interferences. In addition, spur-lines are embedded in the TSSIR to sharpen the passband skirts for selectivity improvement.     

Miniature bandpass microwave filter with interference suppression by more than 100 dB in a wide rejection band

A new planar resonator design in which a single conductor is replaced by three parallel stripe conductors located one above the other on a suspended two-layer substrate is proposed. It is shown that the resonator longitudinal sizes can be significantly reduced and, at the same time, the resonator intrinsic Q factor and frequencies of higher oscillation modes can be increased. A fourth-order bandpass filter with a central frequency of the transmission band (relative width 5%) of 1 GHz has been developed and fabricated. This filter has a ?100-dB rejection band up to frequencies exceeding 10 GHz. The filter is enclosed in a metallic case with an internal size of 38 × 12 × 7.5 mm. It is shown that a similar filter fabricated in accordance with low-temperature cofired ceramic (LTCC) technology has a ?40-dB rejection band up to 30 GHz, with sizes reduced to 5.0 × 4.25 × 1.24 mm.     

Kinoform filter for an incoherent optical processor

Fabrication and testing of a kinoform filter is described, for use in a real-time incoherent optical processor designed for track recognition in high-energy physics experiments. Composition of the filter as a mosaic of kinoforms with different random diffusers improves the quality of the restoration.     

应用于蓝牙技术发展的LTCC——AlN多层布线工艺

现代IT产业的发展催生了蓝牙技术的发展。而蓝牙技术的发展迫切需要发展高性能三维功能衬底技术。AlN陶瓷具有优良的综合性能。研究了AlN流延坯和Ag导体浆料的低温共烧技术 ,比较了在AlN成瓷基板上的各种金属化工艺。     

Highly sensitive optical length measurement by using a microwave photonic filter with multi-passband

In this paper, a method for optical length measurement that employs a multi-passband microwave photonic filter (MPF) is analysed and demonstrated experimentally. The MPF consists of a sliced broadband light source, a phase modulator, a dual-parallel dispersion medium and a photodetector (PD). By cascading two Mach–Zehnder interferometers (MZIs) with different arm length difference, the MPF with eight passbands has been obtained. The variation of the length difference of MZI will lead the change of the free spectral range (FSR) of the interference spectrum, as well as the frequency of the passbands. By changing the arm length of the MZI, a high length measuring sensitivity of ?2.420?GHz/mm has been achieved. The MPF has broad application prospects in the field of multi-parameter sensing. Moreover, the sensor reveals the advantages of highly sensitive, easy to implement and is able to overcome the influence of the environmental perturbation, for example temperature.     

Synthesis of ultra-wideband bandpass filter employing parallel-coupled stepped-impedance resonators

To design an ultra-wideband (UWB) bandpass filter with the fractional bandwidth (FBW) up to 110% (3.1%10.6%GHz), a new filter prototype consisting of multi-stage parallel-coupled stepped-impedance resonators (SIRs) is synthesised based on the transmission-line theory rather than the conventional multi-mode property. Asymmetrical SIRs are employed instead of the conventional symmetrical/quasi-symmetrical ones, so that an extra degree of freedom is introduced in circuit parameter selection. As a result, the minimum dimension of the coupling gaps between the adjacent SIRs is successfully enlarged to be more than 0.1%mm, which alleviates the requirement on fabrication precision. A simple equivalent circuit for this filter prototype is represented in the form of distributed parameters and the corresponding Chebyshev filtering function is derived as well. The relation between the number of poles in passband, N _p, and the stage of the filter, n, is summarised to be N _p=3n+2. To validate the newly derived synthesis theory, a one-stage UWB filter is first synthesised to compare with the previously published results obtained by the electromagnetic (EM) simulator. Furthermore, a two-stage filter is synthesised to successfully meet the Federal Communications Commission (FCC)+s indoor/outdoor spectrum specifications. The fabricated UWB filter exhibits a compact size of 26.58+mm in total length, low insertion loss (0.9+dB at 6.85+GHz), flat group delay (0.5+0.1+ns), good stopband characteristics (+S21+++40+dB at 1+2+GHz) and steep skirt property (+28+dB/GHz) as well. It should be noted that the proposed filter prototype can be also used to realise aUWB filter with an FBW even greater than 110+.     

Realization of an optical communication tunable filter using a diffraction-based optical system

Optical bandpass tunable filters are key elements for dense WDM optical communication systems. Recently, a realization of optical linear transformation using a spatial diffraction optical system was presented and theoretically analyzed [J. Opt. Soc. Am. A21, 732 (2004)]. We present an optical bandpass tunable filter based on this optical system and a spatial light modulator. The mathematical analysis and additional computer simulations for testing the filter's basic parameters using the Fresnel diffraction theory are presented. Some newly obtained laboratory experimental results of the device in the optical visible spectrum will be shown.     

基于FPGA的多通道CIC滤波器设计

数字信号处理中运用CIC滤波器进行采样率转换非常普遍.考虑到实际应用,传统的CIC滤波器存在一些不足.采用多级级联方法降低了对硬件运算速度的要求,有利于实时处理;采用余弦滤波器改善了阻带衰减不足;内插二阶多项式滤波器补偿了CIC滤波器通带内的衰减;抗混叠低通滤波器减小了混叠影响.通过仿真实验验证了FPGA硬件平台的可行性.     

基于仿真技术的动力装置优化设计技术研究

针对传统动力装置设计方法中存在计算复杂、动态性能难以计算等问题，提出利用动力装置仿真系统来设计船舶动力装置的方法。首先，利用模块化建模原理建立了动力装置各组成部件的数学模型，然后利用C＋＋语言编写了各模型的仿真程序，并建立了动力装置仿真系统。利用该仿真系统对某型船舶的全燃动力装置进行了详细设计，设计过程及结果表明，采用仿真系统来设计动力装置可以准确计算动力装置的动态性能，同时对动力装置各部件的性能参数进行优化。     

强化自组装技术在多层复合分离膜领域的应用

强化自组装技术是近年来被发展的一种制备聚电解质复合物多层膜的新方法,该法巧妙地利用外加力与聚合物间作用力的协同效应,强化组装过程,简化成膜程序,提高膜分离性能.总结了近年来课题组在这一领域的研究进展.     

Iterative WLS design of SAW bandpass filters

It has been demonstrated by several authors that the well-known weighted least squares (WLS) approximation can be equiripple if a suitable weighting function is applied. In the present paper, the WLS algorithm is generalized to SAW filter synthesis with prescribed magnitude and phase specifications. Several weighting techniques producing quasi-equiripple designs are presented. The frequency sampling technique is used for SAW filter frequency response approximation to reduce the number of optimized variables. The WLS algorithm rapidly converges both for linear and nonlinear phase SAW filters. Typically, no more than 5-10 iterations are required to obtain the WLS solution to accuracy better than 0.5-1 dB in the stopband when compared with the optimum Chebyshev approximation. Moreover, it is shown that the WLS technique can be effectively applied for second-order effect compensation.