Transmission characteristics of several kinds of closed groove waveguides for millimeter waves

An advantage of closed groove guide over open groove guide is attended. In this paper, the several kinds of closed groove guides including the trapezoidal-, elliptic- and parabolic-groove guides as new types of millimeter wave transmission lines are presented. Their dispersion and cut-off characteristics of the dominant mode are analysed and compared with ones of the closed V-and circular- groove guides by using the equivalent network method. The obtained results have important meaning in theoretical studies and actual applications of groove waveguides.     

Natural frequency for exponential shaped thermoacoustic resonator

The two-dimensional nonlinear acoustic field of eleven exponential shaped resonators was simulated with a computational fluid dynamics software Fluent.The influence of driving frequency and driving intensity on pressure in resonator as well as its natural frequency was investigated.The relationship between natural frequency and theoretical calculation resonance frequency was also explored.It is found that beating phenomena can be observed in the resonator when the driving frequency deviates from the natural frequency.Moreover,the natural frequency of resonator increases with the increasing of driving intensity,which shows a hard spring effect.However,the driving intensity plays little effect on natural frequency and the natural frequencies are smaller than the theoretical calculation values in any driving intensity.Meanwhile,a formula between the natural frequency and its first-order resonance frequency from theoretical calculation was obtained by linear fitting for all these exponential shaped resonators under consideration.It is also found that the highest pressure amplitude and highest pressure ratio can be obtained from the exponential shaped resonator of m=2.8 under the same driving intensity.Moreover,the relation between natural frequency and the theoretical resonance frequency for m=2.8-tube is slightly different from other tubes in consideration.     

指数型热声谐振管的固有频率

采用计算流体力学软件Fluent模拟研究了11种不同形状参数的指数型热声谐振管内二维非线性声场特性,分析了驱动频率和驱动强度对管内声压演化过程及固有频率的影响,并探索了指数管的固有频率与理论计算谐频之间的关系.研究发现:当驱动频率偏离谐振管固有频率时,管内将出现明显的\     

Untuned resonators for near millimeter waves

A brief account is given of the reasons for revitalizing an old technique for near millimeter wave measurements. The principles of the method are outlined and the scope of its application indicated. The potential importance of the technique for liquid phase and biological material studies is illustrated.     

Dichroic diplexer design for millimeter waves

Metallic plates of finite thickness perforated periodically with circular holes can be used as diplexers, called dichroic, as part of quasioptical multiplexers in the millimetric range. The purpose of this work is to investigate their filtering properties, to provide a method to design dichroic filters in an efficient way and to draw conclusions about their field of application. Computed results are compared to measurements and the design of a diplexer for the breadboard of an atmospheric radiometer is presented.     

A five-channel grating spectrometer for millimeter waves

A five-channel grating spectrometer for use in millimeter wave band (25100GHz) is described with its design theory of optical path, and measured results of insertion loss and resolving power.     

Oversized waveguides and resonators for millimeter waves

If real monolithic systems^* turn out to be impractical at millimeter-wave frequencies, oversized waveguides and resonators are useful alternatives in component and system design. Low losses, high Q factors, and inexpensive manufacturing are their advantages. Starting with an explanation of the term oversized, the loss reductions, Q factors, inherently oversized guides, such as the H-guide and its modifications, excitation of higher-order modes, laterally oversized H-guides, and the effects of coupling are described. A brief consideration of applications concludes the presentation.     

Squeezing millimeter waves into microns

Microstructured metallic devices will play a vital role in the continuing search to manipulate the passage of electromagnetic radiation relevant to optical, microwave, and communication technologies. Here, we investigate the electromagnetic response of a completely novel and ultrathin (< wavelength) structure within which is buried a metal-clad waveguiding layer ("core") of subwavelength width. By removing metal from the core cladding to form a periodic array of slits, radiation is coupled into a standing wave within the layer and the structure resonantly absorbs or transmits radiation of wavelength more than 100 times its thickness. Additionally, such structures display the truly remarkable capability of compressing half of the standing-wave wavelength into a fraction of the expected distance.     

Effective excitation of quasi-optical resonator in millimeter wave

It is described effective excitation of quasi-optical resonator (Q. O. R) in millimeter wave (M. M. W) in this article in which some useful results are obtained.This research work was supported by National Natural Science Foundation of China. (No. 69171027)     

基于同轴TM812模谐振腔的毫米波多注速调管

 研究了群聚电子注穿越同轴TM₈₁₂模谐振腔的换能效率和同轴TM₈₁₂模谐振腔中微波能量的提取方法,论证了其作为毫米波多注速调管的输出腔的可行性。研究结果表明:理想群聚电子注穿越同轴TM₈₁₂模谐振腔的换能效率可达3.29%,一般群聚电子注穿越同轴TM₈₁₂模谐振腔的换能效率可达1.86%;采用同轴TM₈₁₂模谐振腔与沿轴向的同轴线耦合可以实现微波能量的提取;在输出腔工作频率为100.945 GHz,外观品质因数为2 243情形下,根据估算,最大输出功率可达15 kW。     

毫米波赋形聚焦双反射面天线设计

为实现一种具有近场聚焦、斜波束出射能力的偏馈口径天线,采用几何光学方法设计了一种赋形聚焦双反射面天线。基于光线传播的能量守恒定律、Snell定律及光径长度相等三个光学定律开展了天线主反射面赋形设计,副反射面的设计采用 Snell 定理作为约束条件。 通过理论公式和实验测试研究,实现了一种出射波束口径为 110 cm、波束出射方向与竖直方向成 20夹角的赋形聚焦偏馈双反射面天线。在中心频率 95 GHz 下,实测相位实现近场聚焦,出射波束与垂直方向成20夹角。     

毫米波赋形聚焦双反射面天线设计

为实现一种具有近场聚焦、斜波束出射能力的偏馈口径天线,采用几何光学方法设计了一种赋形聚焦双反射面天线。基于光线传播的能量守恒定律、Snell定律及光径长度相等三个光学定律开展了天线主反射面赋形设计,副反射面的设计采用 Snell 定理作为约束条件。 通过理论公式和实验测试研究,实现了一种出射波束口径为 110 cm、波束出射方向与竖直方向成 20夹角的赋形聚焦偏馈双反射面天线。在中心频率 95 GHz 下,实测相位实现近场聚焦,出射波束与垂直方向成20夹角。     

Recent developments in millimeter and submillimeter waves

Millimeter and submillimeter-wave observations provide important information for the studies of atmospheric chemistry and astrochemistry (molecular clouds, stars formation, galactic study, comets and cosmology). But, these observations depend strongly on instrumentation techniques and on the site quality. New techniques or higher detector performances result in unprecedented observations and, sometimes, the observational needs drive developments of new detector technologies, for example, superconducting junctions (SIS mixers) because of their high sensitivity in heterodyne detection in the millimeter and submillimeter wave range (100–700 GHz), HEB (Hot Electron Bolometer) mixers which are being developed by several groups for application in THz observations. For the sub-millimetre wavelengths heterodyne receivers, the local oscillator (LO) is still a critical element. So far, solid state fundamental sources are often not powerful enough for most of the applications at millimetre or submillimetre wavelengths: large efforts using new planar components (HBV) and integrated circuits, or new technics (laser mixing) are now in progress, in a few groups.The new large projects as SOFIA, FIRST, ALMA, … for astronomy; SMILES, EOS-MLS, … for aeronomy and other projects for the planetary science (ROSETTA, Mars Explorer, …), will benefit of the new developments.     

A monopole-dipole resonator for flexural waves in a rod

For flexural waves in a rod, a simplest resonator responding not only displacements but also to the inclination (the derivative of the displacement) of the rod axis is studied. The resonator consists of two springmass systems attached through a rigid (nonbending) bar to the elastic rod in which a flexural wave propagates. One of the springs is oriented perpendicularly to the rod, and the other is parallel to it. It is shown that, at a certain friction, the single monopole-dipole resonator under consideration completely absorbs the incident resonance-frequency flexural wave, which propagates in the elastic rod.     

D波段双球镜准光系统测量低耗介质

采用双球镜准光腔、频谱仪和锁相返波管组建了D波段低损耗介质测试系统,该系统通过频谱仪和外置谐波混频器得到腔体谐振测试数据,并用拟合或积分方法从谐振曲线中求解出准光腔的品质因数。测得双球镜开腔的固有品质因数大于8105,使该系统在工作波段可测量损耗角正切为10-5量级的低损耗介质。用该系统测出的石英、人造金刚石和蓝宝石的介电常数和损耗,与报道的结果一致,并测得4H-SiC在132.07 GHz的介电常数实部为9.598,损耗角正切为6.110-5。     

D波段双球镜准光系统测量低耗介质

采用双球镜准光腔、频谱仪和锁相返波管组建了D波段低损耗介质测试系统,该系统通过频谱仪和外置谐波混频器得到腔体谐振测试数据,并用拟合或积分方法从谐振曲线中求解出准光腔的品质因数。测得双球镜开腔的固有品质因数大于8105,使该系统在工作波段可测量损耗角正切为10-5量级的低损耗介质。用该系统测出的石英、人造金刚石和蓝宝石的介电常数和损耗,与报道的结果一致,并测得4H-SiC在132.07 GHz的介电常数实部为9.598,损耗角正切为6.110-5。