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111.
文中着重阐述了基于微机电系统(Micro-Electro-Mechanical Systems,MEMS)技术制造的薄膜体声波谐振器/滤波器,简述了它的结构及原理,分析了其主要特征参数和设计方法,并设计了中心频率为2.4GHz,带宽为100MHz的带通滤波器,展示了薄膜体声波谐振器/滤波器的突出性能,为通信MEMS技术的微型化发展提供了更广阔的道路。 相似文献
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谐振式光纤陀螺调相谱检测技术中的光克尔效应 总被引:1,自引:1,他引:1
谐振式光纤陀螺(R-FOG)是基于Sagnac效应产生的谐振频率差来测量旋转角速率的一种新型光学传感器。信号检测技术和系统中存在的各种噪声对系统的检测精度有着重要的影响。基于调相谱检测技术的谐振式光纤陀螺系统中,除顺时针(CW)和逆时针(CCW)光路传播的光强不均匀会引入非互易相位差,使系统出现零漂外,顺时针和逆时针光路的调制系数也会引入系统零漂。光克尔效应引入的系统零漂与系统的真实旋转在测量时是无法区分的,因此成为主要的噪声之一。通过光波场叠加原理,推导得到调相谱检测方案下的谐振式光纤陀螺系统中,光克尔效应引起的系统零漂的解析表达式。依据光克尔效应产生的零漂不随陀螺转速的改变而变化,利用简单的开环系统,对光克尔效应引入的陀螺零漂进行了测试。 相似文献
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A. F. Krupnov M. Yu. Tretyakov V. V. Parshin V. N. Shanin M. I. Kirillov 《International Journal of Infrared and Millimeter Waves》1999,20(10):1731-1737
By the use of Fabry–Perot resonator with quality factor 600 000 and fast precision (down to one Hertz) frequency control of coherent millimeterwave radiation source the 20 Hz accuracy in measurements of the width of resonance curve is obtained. This accuracy corresponds to the detection of 1.8 × 10–3 dB/km absorption in the sample filling the resonator and exceeds the before known sensitivity more than by an order of magnitude. The example of precise measurement of 60 GHz oxygen absorption band in the real atmosphere is presented. The new possibilities of application of precision resonator microwave spectroscopy to the atmospheric problems as well as to the ultra-low absorptions measurements in dielectrics and metal surfaces up to Terahertz frequencies are discussed. 相似文献
118.
Let T be a monad over a category A. Then a homotopy structure for A, defined by a cocylinder P : A A, or path-endofunctor, can be lifted to the category A
T
of Eilenberg–Moore algebras over T, provided that P is consistent with T in a natural sense, i.e. equipped with a natural transformation : T P P T satisfying some obvious axioms. In this way, homotopy can be lifted from well-known, basic situations to various categories of algebras for instance, from topological spaces to topological semigroups, or spaces over a fixed space (fibrewise homotopy), or actions of a fixed topological group (equivariant homotopy); from categories to strict monoidal categories; from chain complexes to associative chain algebras. The interest is given by the possibility of lifting the homotopy operations (as faces, degeneracy, connections, reversion, interchange, vertical composition, etc.) and their axioms from A to A
T
, just by verifying the consistency between these operations and : T P P T. When this holds, the structure we obtain on our category of algebras is sufficiently powerful to ensure the main general properties of homotopy. 相似文献
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Chzhan M Kuppusamy P Samouilov A He G Zweier JL 《Journal of magnetic resonance (San Diego, Calif. : 1997)》1999,137(2):373-378
There has been a need for development of microwave resonator designs optimized to provide high sensitivity and high stability for EPR spectroscopy and imaging measurements of in vivo systems. The design and construction of a novel reentrant resonator with transversely oriented electric field (TERR) and rectangular sample opening cross section for EPR spectroscopy and imaging of in vivo biological samples, such as the whole body of mice and rats, is described. This design with its transversely oriented capacitive element enables wide and simple setting of the center frequency by trimming the dimensions of the capacitive plate over the range 100-900 MHz with unloaded Q values of approximately 1100 at 750 MHz, while the mechanical adjustment mechanism allows smooth continuous frequency tuning in the range +/-50 MHz. This orientation of the capacitive element limits the electric field based loss of resonator Q observed with large lossy samples, and it facilitates the use of capacitive coupling. Both microwave performance data and EPR measurements of aqueous samples demonstrate high sensitivity and stability of the design, which make it well suited for in vivo applications. 相似文献
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