Dissipative Parameters in Ferrites and Insertion Losses in Stripline Y Circulators Below Resonance (Letters)

Extensive microwave loss measurements have been performed at the frequency of 1.3 GHz on below resonance stripline Y circulators loaded with aluminum doped YIG. Extemal x' have been measured on the same compositions. Also, dielectric loss measurements have been carried out. A relation is found which correlates insertion loss in stripline circulators with loss parameters x' and tan /spl delta/.     

Dielectric Resonator in a Waveguide Below Cutoff

A structure is considered consisting of a waveguide 2 below cutoff, connected to waveguides above cutoff, 1 and 3, by means of suitable junctions. A dielectric resonator is introduced in waveguide 2. Its effect on the transmission curve of the structure is evaluated in the limit epsilon/sub r/spl rarr/spl infin/. Theoretical results are compared with experiment.     

Ferromagnetic Resonance in Planar Ferrites (Correspondence)

Attention is called to the fact that most planar ferrites are not adequately described by a single crystalline anisotropy constant. The presence of higher order terms in the anisotropy is important if resonance with the static field out of the easy plane is considered.     

Insertion Loss and Misalignment Tolerance in Multimode Tapered Waveguide Bends

Experimental measurements of laterally tapered multimode waveguide bends fabricated photolithographically on FR4 printed circuit board establish that the product of the mean insertion loss (in linear units) and the mean source misalignment tolerance is a constant which depends only on the taper ratio TR (input width/output width) and not on the radius of curvature R. The minimum loss of 0.78 dB occurs in the special case of TR = 0.8, R = 14 mm. Together, these form waveguide layout design rules for board-to-board and chip-to-chip optical interconnects.     

High Power Ferromagnetic Resonance at X-Band in Polycrystalline Garnets and Ferrites

Resonance experiments have been performed at X-band on spherical samples of polycrystalline yttrium garnet, yttrium-gadolinium garnet, yttrium-holmium garnet and nickel-cobalt ferrite. The RF field strength extended up to 60 Oersted. In the case of yttrium garnet the samples differed considerably in density and hence in Iinewidth. At fairly low power levels the susceptibility at resonance varies linearly with the square of the RF magnetic field strength. At high power levels the susceptibility is inversely proportional to the amplitude of the microwave magnetic field. The "spin-wave Iinewidth" Delta H/sub k/ is inferred by extrapolation from the behavior at very high powers. It is found that Delta H/sub k/ is, to a large extent, independent of the Iinewidth Delta H/sub k/ observed by the usual low power experiments. In particular Delta H/sub k/ was found to be essentially the same (approximately 4 Oe) for all yttrium iron garnets (single crystals and polycrystals with linewidth varying between 1.8 Oe and 450 Oe). On the other hand, Delta H/sub k/ increases very rapidly if the yttrium is partially substituted by holmium (Delta H/sub k/~11 Oe for 1 per cent substitution.)     

10kV及以下配电线路线损计算与降损措施

文章主要探讨了配电网络电能损失计算、配电变压器电能损失计算和无功补偿电容计算,并由此提出了降损措施。降损可以从几方面着手：加强营销管理,堵塞各种漏洞;建立同步抄表制度,减少因抄表时间差造成的线损波动;减少抄表误差,抄表要到位,杜绝估抄、漏抄和错抄等现象;加强电量、电价、电费的核算管理,积极推广计算机核算工作,减少核算差错,确保电量、电价、电费正确无误;加强用电检查工作,防止窃电和保证正确计费。     

Propagation Constant Below Cutoff Frequency in a Circular Waveguide with Conducting Medium

Exact and approximate propagation characteristics of normal modes in the cutoff region of a circular waveguide surrounded by a medium of finite conductivity are discussed. An exact solution is obtained by numerical analysis, and an approximate one is derived by expanding the characteristic equation considering the finite conductivity of the cylinder wall. The computed values are compared with experimental ones. It is shown that the attenuation of TM/sub 01/ mode at frequencies that are much lower than the cutoff frequency is constant, i.e., independent of frequency and the material constants of the external medium, and this mode is the most suitable one for realizing a precision circular piston attenuator.     

Dielectric Losses in an H-Plane-Loaded Rectangular Waveguide (Short Papers)

The attenuation constant due to dielectric losses in a rectangular waveguide loaded with a dielectric slab in the H-plane is calculated. Results for the dominant LSM/sub 11/ mode are presented graphically.     

ZnO对MnZn铁氧体磁导率和损耗温度特性的影响

采用氧化物陶瓷工艺制备MnZn功率铁氧体.通过对铁氧体断面微观形貌的表征及密度、电阻率和磁特性的测试,研究了ZnO含量对低损耗MnZn功率铁氧体起始磁导率(μ1)和损耗温度特性的影响.结果表明,随着ZnO摩尔分数的增加,室温下MnZn功率铁氧体的μi、饱和磁感应强度Bs、密度及电阻率均先增大后减小,损耗先减小后增大,居里温度一直降低.当x(ZnO)=14.5%时,室温下铁氧体的μ1、Bs、密度及电阻率均达到最大值,而磁滞损耗(Ph)、涡流损耗(Pe)及总损耗(Pcv)达到最小值.同时,铁氧体的μiT曲线Ⅱ峰及最低损耗所对应的温度点向低温移动.Ph-T曲线与μi-T曲线呈相反的变化趋势;Pe-T曲线与经典涡流损耗不一致,主要是由于与磁滞损耗有关的附加涡流损耗(Pe,exc)对总的涡流损耗有一定贡献.最终,当x(ZnO)=14.0%时,MnZn铁氧体材料的室温μi为3180,在25～120℃温度范围总损耗(Pcv)为280～350 kW/m3,具有优秀的宽温低损耗特性.     

Analysis of an Inhomogeneously Loaded Rectangular Waveguide with Dielectric and Metallic Losses

A dieletric loaded rectangular guide (Fig. 1) is analyzed taking into account the losses of the line, the substrate, and the metallic shield. For this study, Schelkunoff's method is used in considering the propagation modes as a convenient combination of coupled modes of the empty waveguide. Computations and experimental measurements are made for two different lines.     

Resonance Measurements on Nickel-Cobalt Ferrites as a Function of Temperature and on Nickel Ferrite-Aluminates

The variation of line width (Delta H) and effective g factor (g/sub eff/) with cobalt content and with temperature is studied in a series of ferrites of composition Ni/sub 1- alpha/Co/sub alpha/Mn/sub 0.02/Fe/sub 1.9/O/sub 4+-/. Here alpha lies between 0 and 0.09; temperatures range from 20° to 340° C. A minimum in Delta H is observed at alpha=0.027; g/sub eff/ decreases with increasing alpha. The temperature dependence of each is qualitatively that which would be expected on the basis of the temperature dependence of the anistrophy of the mixed ferrite. Above room temperature Delta H and g/sub eff/ increase or decrease, depending on the cobalt content. It is also shown that the shape of the resonance line is determined by the sign of the anisotropy constant. For negative K/sub 1/ the line is steeper on the low-field side of resonance--for positive K/sub 1/ it is steeper on the high-field side. Resonance data are presented on several nickel-cobalt ferrite-aluminates, of composition Ni/sub 1_alpha/Co/sub alpha/Mn/sub 0.02/Fe/sub 2-t/Al/sub t/O/sub 4+-/, with alpha varying from 0 to 0.025 for t=0.3, 0.4, 0.5, and 0.6. The reduction of Delta H and g/sub eff/ expected from anisotropy considerations is observed.     

Propagation Losses of Guided Modes in an Optical Graded-Index Slab Waveguide with Metal Cladding

Analytical results for propagation Iosses of guided modes in a graded-index slab waveguide (GISW) with metal cladding are presented. When the permittivity in the guiding layer decreases linearly away from the metal surface, the attenuation constant alpha/sub G/ of well-guided modes, TE and TM, is approximately proportional to only the ratio (Delta epsilon/sub i/ / epsilon/sub 0/) / d/sub i/, where Delta epsilon/sub i/ is the increment in the permittivity at the metal surface in the direction of the polarization of optical waves, d/sub i/i is the diffusion depth in this direction, and epsilon/sub 0/ is the permittivity of free space.     

Measurement of Two-Mode Discontinuities in a Multimode Waveguide by a Resonance Technique

The deliberate use of two or more propagating modes in a multimode waveguide, and a knowledge of associated control elements, has assumed renewed importance, particularly for millimeter wavelength applications. This paper presents a resonance measurement technique for the precise evaluation of the equivalent network for a lossless shunt discontinuity coupling two nondegenerate modes in a multimode waveguide. The discontinuity structure is placed into a cavity closed by adjustable plungers, and the data consists of those plunger positions which render the cavity resonant in the two modes of interest. This multipoint data is then transformed to permit an analysis of the two-port network in the discontinuity plane by conventional techniques. Computations and experimental results obtained at S band illustrative of the procedure are presented for shunt discontinuities coupling the E/sub 01/ and H/sub 01/ modes in circular waveguide. The accuracy achieved is comparable to that obtained in single mode precision measurements.     

Theoretical and Experimental Driving-Point Impedance Results of Resonance Circuits in a Gunn Waveguide Oscillator

The frequency tuning range of waveguide oscillator and its stability depend sensitively on the dimension of the resonance cap. Therefore the driving-point impedances with the various dimensions of the resonance cap are calculated by using HFSS(High Frequency Simulation System). In this paper the comparisons between theoretical results of the driving-point impedances as a function of frequency and that of experimental results are described. The oscillation frequency range could be predicted by using the theoretical evaluation methods which are proposed. It shows that resonance cap size and disc height have an effect on the frequency tuning characteristics of Gunn oscillator.     

A Catalog of Low Power Loss Parameters and High Power Thresholds for Partially Magnetized Ferrites

The low power loss and high power threshold properties have been measured on a number of candidate ferrite phase-shifting materials. The low power loss is characterized by /spl mu//sub 0/', the imaginary part of the diagonal component of the permeability tensor for the completely demagnetized state. /spl mu/sub 0/' was measured from 3.0 to 16.8 GHz. The high power properties are characterized by the parallel pump threshold at a bias field correspontig to H/sub i/ /spl equiv/ 0 and to 4/spl pi/M /spl equiv/ 4/spl pi/M/sub s/. The threshold was measured between 3.0 and 16.8 GHz. For the purposes of computer calculation /spl mu//sub 0/' and h/sub crit/ were fit to an equation of the form A (/spl gamma/4/spl pi/M/sub s/ / /spl omega/)/sup N/. Translating /spl mu//sub 0/' and h/sub crit/ to /spl Delta/H/sub eff/ and /spl Delta/H/sub k/ gives the YIG plus Al as the lowest loss and lowest threshold materials followed by the Gd garnets and MgMn spinels. The Ni spinels are very Iossy.     

A Comparison of the Attenuation of High-Order Mode in Coaxial Waveguide due to Inner and Outer Conductor Losses

In this paper, comparison studies of mode attenuation in coaxial waveguides due to inner and outer conductor losses are carried out analytically. Numerical results for some typical high-order modes are presented. This study is helpful for guiding the loading of distributed losses in coaxial gyrotron traveling wave amplifiers.     

T-Equivalent Circuit Parameters of a Variable-Length Cylindrical Post in a Rectangular Waveguide

A simple expression for the series reactance of a solid variable-length cylindrical post in a rectangular waveguide is determined from an approximate field analysis. Results are shown to be in excellent agreement with experimental measurements. When used in conjunction with an existing analysis for determining the shunt reactance, it is shown that accurate results can be calculated for the complete T-equivalent circuit.     

Modal Gain Analysis of Transverse Bragg Resonance Waveguide Lasers With and Without Transverse Defects

We use a transfer matrix method to analyze the modal gain of transverse Bragg resonance (TBR) structures. We show that these TBR structures can support two types of modes characterized by different modal angles: small mode angle (SMA) modes and TBR modes. We discuss the origin, modal properties and field distributions of both the TBR modes and SMA modes. Three different feedback mechanisms are proposed to select the desired TBR modes.