介电常数微弱变化的高灵敏度测试技术

提出了一种测量介电常数微弱变化的新型传感器。该传感器利用幅度相同、相位相反的两路信号的相互抵消作用,来消除背景噪声,达到提高灵敏度的作用。此装置主要包括两个相同的威尔金森功分器、一个同相巴伦和一个180°反相巴伦。通过对去离子水与不同浓度乙醇溶液之间介电常数的差异的测量可知,该传感器能够探测到的介电常数的最小绝对变化和相对变化分别为1.68%和2.07% ,与微波湿度传感器相比,所提出的传感器的灵敏度更高。     

固体电介质微波介电参数的耦合器测量技术

论述了微带分支线耦合器非破坏性测量固体电介质复介电常数的方法,阐明了3dB分支线耦合器用于介电常数测量的原理,提出的分支线耦合器的输出与耦合端口各连接一段终端开路的微带线,待测物放在其中的一条线上。待测物的介电常数可通过测量两端口的散射参数的幅度进行计算。运用提出的方法,在2.45GHz下测量了特氟龙、聚丙烯等固体电介质的复介电常数,其结果与文献相吻合。     

固体电介质微波介电参数的耦合器测量技术

论述了微带分支线耦合器非破坏性测量固体电介质复介电常数的方法,阐明了3dB分支线耦合器用于介电常数测量的原理,提出的分支线耦合器的输出与耦合端口各连接一段终端开路的微带线,待测物放在其中的一条线上。待测物的介电常数可通过测量两端口的散射参数的幅度进行计算。运用提出的方法,在2.45GHz下测量了特氟龙、聚丙烯等固体电介质的复介电常数,其结果与文献相吻合。     

第二讲 阻抗式传感器(上)

一、电阻式传感器电阻式传感器是利用电阻元件把待测的物理量如力、位移、形变及加速度等量变换成电阻阻值,从而通过对电阻阻值的测量达到测量该物理量的目的。电阻式传感器按其工作原理可分为以下二类: 1.电位计式电阻传感器 2.应变式电阻传感器电位计式传感器工作于电阻阻值变化较大的状态,适宜测量被测对象参数变化较大的场合,由于此类传感器与一般电位计相同,故不再赘述。应变式电阻传感器工作于电阻阻值变化极小的状态,灵敏度较高,以下作专题介绍。 (一) 应变式电阻传感器原理     

测量低损耗薄膜材料介电常数的标量法

依据被测介质性质,在现有实验设备条件下,提出了一种标量法测量低损耗薄膜介质介电常数的新方法.该方法利用传输线法测量原理,先测量待测介质损耗,间接得到反射系数,由反射系数与介电常数关系式,推导得出待测介质的介电常数.该方法有样品容易制作,测量简单准确等特点.通过测量实例的误差分析,指出标量法测量薄膜材料介电常数的不足,提出相应的改进措施.     

铁电材料介电常数的测量方法研究

描述了一种基于同轴谐振腔技术测量铁电材料介电常数的原理和方法。将待测样品放置在1/4波长的同轴谐振腔的开路端,通过设计制作尺寸合适的同轴谐振腔以保证在测量频率范围内只存在横向电磁场(TEM)基波,并根据测量的同轴谐振腔TEM基波的谐振频率,计算出相应的样品介电常数以及介电常数随电压的变化。为了精确采样待测样品和同轴谐振腔开路端之间部分所形成的等效电容,分析了电容边缘效应并结合边界元数值算法计算该等效电容。针对主要误差来源(气膜),采用在样品上用导电胶制作电极从而减小气膜对测量的误差影响。实验结果表明这是一种简便而有效的测量铁电材料介电常数的方法。     

基于双开口环型的太赫兹超材料传感器设计

设计了一款可用于检测材料折射率及厚度的双开口环型太赫兹超材料传感器,其结构由双开口方环与圆环嵌套的超材料结构和聚酰亚胺衬底两部分构成.当太赫兹波垂直入射超材料表面时,该传感器结构在0.8～1.8 THz范围内形成三个高Q值谐振峰(中心频率分别为f1,f2和f3).通过探讨超材料结构表面电流分布与三个谐振峰形成的关系,观察到超材料结构对入射太赫兹波的不同响应特性导致产生不同的表面电流分布.此外,还对该传感器在折射率传感和厚度传感方面的应用进行了探究.在待测物厚度一定的情况下,该传感器在谐振频率f1,f2和f3处的传感灵敏度分别可达170,103和119 GHz/RIU,均具有优越的传感特性,可利用其多谐振峰进行高灵敏度折射率传感.这种高灵敏度的多谐振峰折射率传感器可以检测到待测分析物的微小变化,在生物化学检测领域具有广阔的应用前景.     

用于介电常数测量的小型化微波传感器的设计

本文提出了一种基于慢波结构的半模基片集成波导的介电常数微波传感器。该传感器将新型互补开口谐振环加载到半模基片集成波导上,用于低损耗介质的介电常数的测量。在半模基片集成波导上加载金属化盲孔阵列,将大部分电场集中在上基板上,实现电场和磁场的有效分离,从而实现横向和纵向尺寸的同时减小,并表现出典型的慢波效应现象。传感器通过在介质平面上加载带有“T”字型枝节的互补开口谐振环,可以获得更均匀、更集中的电场,从而增强传感器的灵敏度。仿真和实验结果表明,每单位介电常数的谐振频率偏移量达到124 MHz,灵敏度达到2.76%。用该传感器测量已知标准值的待测材料的介电常数时,实部相对误差小于2%,虚部相对误差小于0.005。     

用于天线阵馈电的新型三等分功分器设计

为了解决传统三等分功分器输出支路跨接隔离电阻实现困难的问题,基于Wilkinson功率分配器设计理论,通过引入二分之一波长微带传输线,提出了一种新型微带三等分功率分配器的设计方法.基于此方法,设计了一款应用于海事卫星通信频段的对称结构三等分功分器.实测结果表明该功分器在整个设计频带内各端口匹配好,各输出支路等分度好、隔离度高.该功分器已成功应用于天线阵馈电网络的设计.     

RCWA方法设计阶梯形光学生物分子检测探针

设计了一种阶梯形光学生物分子检测探针,并利用严格耦合波分析（RCWA）法计算了此探针的反射光谱的反射效率。模拟结果表明,此探针的反射谱中特定峰值处,探针周围的待测物折射率与探针的入射角间呈线性变化,且探针反射效率与待测物折射率和入射角均符合左半高斯型曲线分布。所以,既可应用入射角来反映待测物折射率的变化,也可利用反射效率的变化反映待测物折射率的变化。基于此研究的方法和结果可广泛应用于生物传感器和生物分析等研究领域。     

A waveguide-based two-step approach for measuring complex permittivity tensor of uniaxial composite materials

A rectangular waveguide-based two-step approach for measuring the complex permittivity tensor of uniaxial highly lossy nonmagnetic composite materials in the S-band is presented. In the proposed scheme, two independent sets of reflection and transmission coefficient data for each material-under-test (MUT) are measured by aligning the electric field vector of the dominant TE/sub 10/ mode in the rectangular waveguide parallel and perpendicular to the fiber orientation of the uniaxial sample, respectively. The complex permittivity tensor of the MUT is determined from these measured scattering data in two successive steps. The first step uses the newly proposed analytical approach, which can resolve the ambiguity problem, commonly encountered with samples of electrical length larger than a wavelength. In the second step, nonlinear least square optimization algorithms are employed, where the material parameters using the first step are now used as the initial guess. The proposed two-step approach is valid for multilayered structures, and the local minima problem commonly encountered with optimization routines are also avoided. A number of carbon-fiber composite materials along and, transverse to the fiber orientation are measured using the proposed method. Finally, a brief uncertainty analysis, to study the effect of air-gaps on waveguide measurements, is carried out.     

基于空间时频分布的高效DOA估计

提出了一种利用信号空间时频特征的高效波达方向（DOA）估计方法。通过计算参考阵元输出与其它阵元输出之间的互时频分布,构造出新的时频域数据矩阵模型,然后在时频面上不同的能量聚集区域内选择时频点,构造空间时频分布矩阵,然后对进行矩阵奇异值分解来实现波达方向估计。与直接构造空间时频分布矩阵的方法相比,该方法构造矩阵的计算量大大减小,并且能处理相干信号。仿真结果验证了算法的有效性。     

A production insensitive compact power divider

Power dividers are inevitable components in most microwave systems. Well known topologies like Wilkinson power divider are widely studied in the literature. An “all 50 ohm power divider” is another topology presented in the some works. In this study, an all 50 ohm structure is taken as the basis and a compact-easy to implement modification the power divider is proposed. A sample structure is designed, implemented and measured to prove the topology. The decreased sensitivity to production tolerances is demonstrated by various design modifications. Comparisons with well-known topologies are given for reference.     

Compact Dual-Band Equal Power Divider Circuit for Large Frequency-Ratio Applications

A novel design of compact dual-band equal power divider circuit for large frequency-ratio (greater than 3) applications is proposed in this paper. Topology of the circuit consists of two-section transmission-line transformers and a series RLC network for isolation. This power divider provides an equal power-dividing at two arbitrary frequencies which feature high center frequency-ratio. Besides, this power divider achieves good port matching and isolation. Theoretical derivations are presented and verified by measuring a 3-dB microstrip power divider operating at both 1 GHz and 4 GHz.     

使用GaAs MMIC技术的X波段微波频率检测器

The design, fabrication, and experimental results of an MEMS microwave frequency detector are presented for the first time. The structure consists of a microwave power divider, two CPW transmission lines, a microwave power combiner, an MEMS capacitive power sensor and a thermopile. The detector has been designed and fabricated on GaAs substrate using the MMIC process at the X-band successfully. The MEMS capacitive power sensor is used for detecting the high power signal, while the thermopile is used for detecting the low power signal. Signals of 17 and 10 dBm are measured over the X-band. The sensitivity is 0.56 MHz/fF under 17 dBm by the capacitive power sensor, and 6.67 MHz / μV under 10 dBm by the thermopile, respectively. The validity of the presented design has been confirmed by the experiment.     

Microwave frequency detector at X-band using GaAs MMIC technology

The design,fabrication,and experimental results of an MEMS microwave frequency detector are presented for the first time.The structure consists of a microwave power divider,two CPW transmission lines,a microwave power combiner,an MEMS capacitive power sensor and a thermopile.The detector has been designed and fabricated on GaAs substrate using the MMIC process at the X-band successfully.The MEMS capacitive power sensor is used for detecting the high power signal,while the thermopile is used for detecting the low power signal.Signals of 17 and 10 dBm are measured over the X-band.The sensitivity is 0.56 MHz/fF under 17 dBm by the capacitive power sensor,and 6.67 MHz//μV under 10 dBm by the thermopile.respectively.The validity of the presented design has been confirmed by the experiment.     

Dual-frequency power divider with isolation stubs

A novel dual-frequency power divider with isolation stubs is presented. To reduce the parasitic effects between the two stubs that are connected by the isolation resistor in traditional Wilkinson power dividers, a structure consisting of isolation stubs is proposed. The corresponding design equations are obtained to calculate the design parameters of the desired dual-frequency power divider. Finally, this design concept is validated by experimental results on a 0.95/2.09 GHz dual-frequency power divider.     

基于中值观测的自适应变步长MPPT算法研究

提出一种应用于光伏发电系统中的基于中值观测的自适应变步长MPPT方法。该MPPT方法以中值法为观测基础,具有自适应且变步长的优势,跟踪过程不需要人为干涉与寻找初值和优值,在具有高效率的同时具有很高的适用性。在Matlab/Simulink平台验证了此MPPT控制算法,其模型避免用到除法器,有利于加快运算速度与减小电路规模。     

多路宽带带状线功率分配器设计分析

宽带功率分配器是电子系统的重要部件。提出了宽带带状线功率分配器的设计方案,详细论述了二功分器、八功分器的设计方法,研究了该方法在工程中存在的问题及解决办法。应用电路与电磁场仿真软件进行了仿真,制作了一个3～10 GHz的功率分配器样件,对样件进行了指标测试,详细分析了测试结果与仿真结果存在差异的原因。