The capacitance of a dielectric coated finite cylindrical duct

A simple formula is presented for the capacitance of a finite-length, perfectly-conducting right-circular cylindrical tube coated with a homogeneous dielectric sleeve. The formula may be used to determine capacitance for all practical aspect ratios (radius/length) and is validated by comparisons with available data calculated from numerical solutions of the coupled set of integral equations.     

Photonic bandgap dielectric waveguide filter

The application of photonic bandgap (PBG) structures as the sidewall of the printed circuit board (PCB) dielectric waveguide filter is investigated. The effect of different PBG parameters on the Q-value of PBG dielectric waveguide resonator is evaluated. A PBG dielectric waveguide three-pole Chebyshev bandpass filter is realized. The measured performance matched well with the calculated results. The newly proposed I/O coupling structure makes the filter much easier for mass production     

Experimental analysis of metal coated dielectric waveguides

This paper concerns the experimental characteristics of metal coated dielectric waveguides with a rectangular surface corrugation. Waveguide are designed to operate at a second Bragg frequency of 90 GHz. The period, height and the duty cycle of a rectangular grating were calculated using the chosen frequency. A metallic layer of aluminum is sputtered on one side of the slab waveguide. The purpose of the metallic layer is to simulate a layer of high density plasma on the surface of the waveguide similar to that obtained by optical excitation of semiconductor structures. Experiments were performed to examine the far field radiation pattern, attenuation constant and the dispersion relation. Due to the presence of the plasma layer there will be an angular shift in the far field radiation pattern. We have observed angular shifts of about 20? in the radiation pattern of the waveguide before and after coating. Measurements are made in the frequency range of 88–95 GHz. This waveguide structure can be used to design an electronically steerable antenna and an electronic phase shifter operating in the millimeter-wave frequency band.     

阶跃阻抗同轴介质滤波器的研究

为了有效减小均匀阻抗同轴滤波器的尺寸,并优化性能参数,设计了阶跃阻抗同轴滤波器。该滤波器基于一种BaO-Nd2O3-Sm2O3-Al2O3-TiO2(BNSTA)五元系高介电常数、低损耗、近零温度系数的微波介质材料,提出阶跃阻抗同轴滤波器的设计流程和方案,采用HFSS高频仿真软件对该滤波器的传输特性进行了整体仿真。结果表明所制滤波器通带特性优异:中心频率为2.01 GHz,带宽为15 MHz,插入损耗小于1.15 dB,带内纹波为0.23 dB。     

The RCS of a cylindrical array antenna coated with a dielectric layer

The scattering properties of dielectric coated waveguide aperture antennas mounted on circular cylinders are investigated. Both the single element antenna and the array case are treated. The array antenna consists of 4 /spl times/ 32 rectangular apertures placed in a rectangular grid on the surface of an infinitely long circular cylinder. The problem is formulated in terms of an integral equation for the aperture fields which is solved with the method of moments using rectangular waveguide modes as basis and test functions. An efficient uniform asymptotic technique is used to calculate the excitation vector and the backscattered far-field. The asymptotic solution is valid for large cylinders coated with thin dielectric layers away from the paraxial (i.e. near axial) region. A similar asymptotic solution is used to calculate the mutual coupling in the nonparaxial region. For the self coupling terms and for the mutual coupling in the paraxial region a planar approximation is used with a corresponding spectral domain technique. Numerical results are presented as a function of frequency, angle of incidence, cylinder radius, and electrical thickness of the coating.     

Creeping wave modes for a dielectric coated cylinder

A new system of poles for the Green's function for a dielectric-coated cylinder has been found. In general, these poles correspond to creeping waves, which are strongly attenuated except for very thick coatings. For radii below a critical value, one of the new poles replaces one of those previously described in the literature and gives rise to a creeping wave of Elliott type with low attenuation     

Scattering of electromagnetic waves from dielectric coated conducting spheres

Several series of rigorous numerical calculations of the backscatter cross section of a conducting sphere with a thin lossless dielectric coating were carried out. The ratio of the radius to wavelength was varied from about 0.02 to 10.0; the dielectric constant of the coating was taken to be 2.56, 4.0, or 6.0; and the thickness of the coating was 0.1 or 0.05 times the outer radius of the coated sphere. Curves of the results are presented which indicate that the backscatter cross section of a coated sphere may be increased by as much as a factor of ten over that of an uncoated sphere of the same size, and, due to interference effects, an even greater decrease may be obtained. Further, small changes (less than one per cent) in the thickness or dielectric constant of the coating, or in the wavelength, may bring about large changes in the cross section. The numerical results are also compared with some experimental measurements, and with predictions of a "creeping-wave" type of analysis carried out by Helstrom.     

A temperature-stable bandpass filter using dielectric resonators

A microstrip bandpass filter has been built with dielectric resonators made of a temperature-compensated material. Its unloaded Q at X band is calculated to be greater than 1200, a four-fold improvement upon conventional printed-on devices. With additional temperature compensation, a temperature coefficient less than 5 ppm/°C is shown to be feasible.     

Electromagnetic scattering from a dielectric coated cylinder using OSRC-GMT

The electromagnetic scattering from a dielectric coated cylinder is analysed based on the generalised multipole technique (GMT) combined with the on-surface radiation condition (OSRC) for separating an open region of inhomogeneous media into the inside region of the homogeneous medium and the outside region of free space. The equivalent multipole sources inside which produce the outside scattered fields, are determined by the OSRC on the outer surface. Some numerical examples for calculating the RCS from the scatterer with concentrically circular or confocally elliptic cross-section are provided.<>     

介质涂覆机翼与下垫粗糙面后向复合散射研究

本文以杏仁体结构的等离子体涂覆机翼为例就等离子体涂覆目标隐身效果做探索性的研究.利用互易性定理结合高频方法的快速混合算法获取锥形波入射下的微粗糙度粗糙面与其上方等离子体涂覆机翼的后向雷达散射截面;数值结果以等离子涂覆机翼与下垫高斯粗糙面为例,讨论了等离子体角频率、电子碰撞频率等的变化对等离子体隐身效果的影响,数值结果为研究等离子体参数对等离子体消隐性能的影响提供了理论参考.     

一种基于插入介质波导的新型滤波结构

提出一种基于插入介质波导的新型滤波结构.采用微带线对插入介质波导进行馈电,使馈电结构更加易于实现.在插入介质波导中引入U形不连续结构,并通过人工神经网络模型算法提取相应的等效集总电路参数,从而实现带通滤波器的设计.最后,设计并实际加工了一款带通滤波器的测试样品.实测结果与设计要求基本吻合,说明了该新型滤波结构是可行的.     

Miniature ridge-waveguide filter module employing moldable dielectric material

The experimental 6-8.6-GHz five-pole bandpass filter being presented is composed of ridge-waveguide resonator segments, evanescent-mode inter-resonator coupling sections, and planar-circuit impedance-matching port networks. To reduce overall filter size, cavities are filled with a low-loss moldable dielectric material that does not shrink during curing. Good agreement is observed between measured and predicted filter response characteristics. Two additional bandpass filter designs with different fractional bandwidths further highlight the versatility of the design methodology that relies entirely on the use of commercially available general-purpose design software.     

900 MHz独块同轴微波介质滤波器的仿真

采用HFSS软件讨论介质滤波器耦合(包括谐振器间的互耦合以及谐振器与外电路的耦合)性能以及中间谐振器谐振长度与其频率的相互关系,得到滤波器外界品质因数与其输入输出端口大小、滤波器级间耦合系数与其耦合孔直径以及中间谐振器谐振长度与其频率之间相互关系曲线,并以此确定所设计的介质谐振器滤波器结构尺寸。根据讨论结果,最终设计出的滤波器性能指标为:中心频率899.5MHz,带宽14MHz,带内波动0.8dB,通带损耗1.5dB,性能满足移动通讯要求。     

双轴同轴型微波介质滤波器的仿真与设计

在介绍双轴同轴型谐振微波介质滤波器结构及工作原理基础上,利用理论公式计算与HFSS10.0三维有限元仿真的混合设计方法,设计了满足性能要求(插入损耗为–3dB以上;–3dB带宽为18MHz以上)的微波介质滤波器。滤波器试样实际测试结果表明,该设计方法正确可行,测试结果与仿真结果有很好的一致性,最终设计出的滤波器插入损耗为–2.83dB,–3dB带宽为35MHz。     

The steady-state performance of a controlled current active filter

An active filter that uses a high-frequency D-class asynchronous switching inverter for power system current distortion compensation is described. The distortion compensation technique involves deriving a signal corresponding to the distortion component of load current, inverting and amplifying this signal, and adding it to the supply current to cancel the load current distortion. A synthetic sinusoid is used to determine the distortion component in the time domain. Extensive computed and experimental results, illustrating the system's steady-state performance and ability to reduce the current harmonic distortion components are presented. An intelligent controller is proposed to maintain the active filter's performance at the optimal operating point under varying load conditions     

COMPUTER-AIDED OPTIMIZATION DESIGN OF BANDPASS FILTER WITH DIELECTRIC RESONATORS

By way of employing a multimode method together with the multimode transmission matrixtechnique based on the theory of planar circuits, the paper presents computer-aided design and optimized de-sign of bandpass fllters with dielectric resonators, and their sample was tested. The experimental result ofthe sample shows a reasonable agreement with the designed one.     

大功率介质腔滤波器设计

针对腔体滤波器在低气压环境下容易发生功率击穿的难题,提出了一种高Q值介质腔滤波器的设计方法,可以有效地提高滤波器低气压功率放电的阈值,按照此方法,设计了一款TM模介质腔滤波器,使用CST、Ansoft Designer软件进行仿真和优化,使用矢量网络分析仪对制作的产品进行了性能测试,测试曲线和仿真曲线完全吻合,此滤波器能够在低气压(13~101 000 Pa)环境中通过20 W的功率信号,且滤波器Q值高,体积小。     

直线型交叉耦合介质窄带滤波器的设计与制作

为了减小滤波器的体积和提高阻带衰减,研究了直线型交叉耦合介质窄带滤波器。介质滤波器由三个TE_(01δ)介质谐振器和两根倾斜45°或135°的金属杆组成,中间谐振器与两端谐振器互相垂直,金属杆位于相邻谐振器之间。分析了两根平行金属杆和正交金属杆产生传输零点的工作原理,并用传输路途相位差的方法来判断零点产生的位置。用HFSS仿真软件详细讨论了谐振频率、耦合系数和外部Qe值与滤波器结构参数的关系,优化了滤波器的结构参数。采用相对介电常数为45的介质陶瓷制作了两个三级介质滤波器,滤波器的中心频率分别为3.76 GHz和3.74 GHz,3 d B带宽分别为50 MHz和64 MHz,插入衰耗分别为0.77 d B和0.51 d B,传输零点分别位于低端和高端,偏离中心频率大约100 MHz,其衰减大于63 d B,测试的各项性能均达到了设计要求。     

介质涂覆电大复杂腔体散射的快速求解

利用腔体涂覆层是薄层损耗介质的情况,引入阻抗边界条件求解腔体的介质涂覆区域.详细推导了快速多极子方法结合迭代物理光学法和阻抗边界条件的混合计算公式.在此基础上利用前后向迭代方法加速收敛.计算结果表明该方法比IPO FMM方法有效地减少了迭代次数,能够对腔体涂覆材料的电磁参数、腔体涂覆部位进行优化设计,对开口腔体的RCS减缩提供理论参考.     

A very small dielectric planar filter for portable telephones

A high performance, high-dielectric stripline filter with the size of 4.5 mm×3.2 mm×2.0 mm has been developed. The filter consists of planar resonators and its structure is made of high permittivity multilayer ceramic in the Bi-Ca-Nb-O system. The performance is distinctive with its attenuation pole. An equivalent lumped circuit is derived to explain the behavior of the attenuation pole quantitatively. A precise design procedure is also described