Development of the Microstrip Circulator with a Magnetized Ferrite Sphere in Millimeter Wave Band

In this paper, a novel microstrip circulator with a magnetized ferrite sphere is proposed for various millimeter wave communications. A three-dimensional Finite-Difference Time-Domain (FDTD) approach for the analysis of this ferrite sphere based microstrip circulator is first presented. The electromagnetic fields inside the ferrite junction are calculated using special updating equations derived from the equation of motion of the magnetization vector and Maxwell's curl equations in consistency. Frequency dependent insertion loss, isolation and reflection loss of circulator are calculated over a wide band of frequencies with a single FDTD run. Experimental results at Ka band are presented and compared with theoretical simulations. As a result, a good agreement is found between them.     

Analysis of Millimeter Wave Microstrip Circulator with a Magnetized Ferrite Sphere by FDTD Method with Modified Matrix Pencil Method

In this paper, the modified matrix pencil (MMP) method is used in the finite difference time domain (FDTD) method to eliminate the late time instability of time domain responses when analyzing the novel microstrip circulator with a magnetized ferrite sphere. The frequency dependent scattering parameters: reflection, isolation and insertion parameters of the microstrip circulator calculated over a wide band of frequencies with this hybrid method are compared with that obtained by direct FDTD method which agree well with the experimental results.     

CAD of Millimeter Wave Y-Junction Circulators with a Ferrite Sphere

A gradient optimization technique along with a definition of cost function is applied to the CAD of the circulator with a magnetized ferrite sphere for millimeter wave communications. A three-dimensional Finite-Difference Time-Domain (FDTD) approach for the analysis of this ferrite sphere based microstrip circulator is presented. The topology of the structure is enforced at each step of optimization and its physical dimensions are used as optimization variables. The cost function is defined using location of zeros and poles of the circulator's transmission, isolation, and reflection functions. Numerical tests show that the optimization process converges from an arbitrarily selected starting point with the new definition of the cost function.     

Time-Domain Analysis of Millimeter Wave Circulation Around a Magnetised Ferrite Sphere

An efficient numerical method has been devised for the study of wave circulated by a magnetised ferrite sphere. It is a finite-difference time-domain formulation that incorporates Mur's absorbing boundary conditions and a perfectly matched layer. The electromagnetic fields inside the ferrite body are calculated using special updating equations derived from the equation of motion of the magnetization vector and Maxwell's curl equations in consistency. The electromagnetic fields inside ferrite and the power-density distribution on the ferrite's surface normal to the bias external magnetic field are obtained in a wide frequency band with a single time domain run. It is observed that an incident plane wave would circulate around the magnetised ferrite body in an open space as if the ferrite were placed inside a waveguide / microstrip junction circulators.     

Finite-Element Analysis of H-Plane Waveguide Junction with Arbitrarily Shaped Ferrite Post

A numerical approach for solving the problem of H-plane waveguide junctions with Iossy ferrite posts of arbitrary shape is proposed. The junctions are allowed to have arbitrary cross section. The approach is a combination of the finite-element method and the analytical method. To show the validity and usefulness of tbe method, Y-junction circulators with a circular ferrite post are considered. Our results agree well with earlier experimental and theoretical results. The performances of Y-junction circulators with a triangular equilateral ferrite post or a triangular ferrite post having depressed sides are investigated. The influences of the ferrite losses on the performance are examined.     

Application of Preconditioned GMRES Algorithm for Analysis of Millimeter Wave Ferrite Sphere Circulators

The generalized minimal residual (GMRES) iterative method is applied to solve such sparse large non-symmetric system of linear equations resulting from the use of edge-based finite element method. In order to speed up the convergence of GMRES, the symmetric successive overrelaxation (SSOR) preconditioning scheme is applied for the analysis of millimeter wave ferrite circulator. Consequently, this preconditioned GMRES (PGMRES) approach can reach convergence ten times faster than GMRES. The reflection and insertion losses of millimeter wave waveguide circulator are compared with those obtained from literature.     

Application of Preconditioned GMRES Algorithm for Analysis of Millimeter Wave Ferrite Sphere Circulators

The generalized minimal residual (GMRES) iterative method is applied to solve such sparse large non-symmetric system of linear equations resulting from the use of edge-based finite element method. In order to speed up the convergence of GMRES, the symmetric successive overrelaxation (SSOR) preconditioning scheme is applied for the analysis of millimeter wave ferrite circulator. Consequently, this preconditioned GMRES (PGMRES) approach can reach convergence 19 times faster than GMRES. The isolation and insertion losses of millimeter wave waveguide circulator are compared with those obtained from literature.     

Investigation of Waveguide Y-Junction Circulator with a Triangular Ferrite Post

An H-plane waveguide Y-junction circulator with a triangular ferrite post is investigated by a modified analysis of jointly resonance theory and simple field theory. Good agreement between the theoretical obtained performances and experimental results is observed. The circulator exhibits a very low insertion loss and a wide bandwidth.     

A Latching Ring-And-Post Ferrite Waveguide Circulator

This paper presents the performance and normalized design parameters for a latching ring-and-post ferrite circulator in waveguide. A C-band circulator has provided an insertion loss of 0.35 dB and a 20-dB isolation bandwidth of 17 percent. When the circulator was matched for higher maximum isolation (50 dB) but narrower bandwidth (10 percent) at room temperature, the 20-dB isolation bandwidth was 7.8 percent across the -40/spl deg/ to +75/spl deg/C temperature range. Low-loss operation was obtained at pulsed powers up to 7.5 kilowatts, and at least 20 dB of isolation was maintained up to 100 kilowatts. This performance, in conjunction with a switching speed of a fraction of a microsecond, permits the use of these circulators for transmitting-receiving functions in high-reliability RADARs.     

Vector-FEM Analysis of Millimeter Wave Circulator with SOC Truncation Technique

In this paper, the application of the edge-based vector finite element method combined with the short-open calibration (SOC) technique to waveguide junction circulators was presented. By applying permittivity and permeability tensors, the functional formula for tetrahedral vector elements are analytically derived in terms of the electric field strength. And the SOC technique is directly accommodated in the FEM algorithm and used to truncate the computational domain. The SOC technique removes or separates unwanted parasitics brought by the approximation of the impressed voltage source and also the problem of resulting inconsistency between different simulations. Truncation of computational domain by SOC technique makes the iterative solvers for large-sparse linear matrix equations from FEM converge much faster than by perfectly matching layers (PML). The analysis of three 2-port networks is sufficient to form the admittance matrix of the corresponding three-port waveguide junction circulators. To validate the theory, typical three-dimensional numerical results of isotropic dielectric-filled discontinuity are first presented and compared with other hybrid numerical techniques. Further, the ferrite filled waveguide junction circulators are analysed and compared with the measured and available publications. The comparison shows that good agreement is obtained.     

8mm基片集成波导环行器的研究与设计

提出了一种设计毫米波环行器的新方式,以进一步缩小器件体积并维持良好性能。具体方案为:通过SIW使器件具有小体积和高功率;通过弧形SIW将传统的Y字型环行器变为准T字型环行器;通过渐变器将SIW过渡到50Ω的标准微带线上,该渐变器可以内嵌到SIW内使器件体积更小。8mm环行器采用高频层压板和圆柱铁氧体进行设计,并通过高频电磁场仿真软件(HFSS)进行验证,得到工作频带内插入损耗小于0.2dB,隔离度大于20dB,回波损耗大于25dB,驻波小于1.2的结果。按设计得到的产品,其性能测试结果和仿真结果基本吻合,但工作频率有所下降。     

On the Modified Resonance Theory of Waveguide Circulator with Various Ferrite Specimens

A modified resonance theory of waveguide circulator with ferrite specimen is presented. The kernal of this theory is a two-step analysis method of an H-plane Y-junction waveguide circulator. For the first step, the ferrite specimens of Y-junction waveguide circulators are treated as if it were dielectric resonators with no magnetic bias. This simplistic approach is used to design the ferrite specimens of the circulators. Simple formulas are developed for determining the center frequency of the circulators. For the second step, wave circulation is made possible when a pair of degenerate resonance modes experiences different changes when the ferrite specimens are being magnetized. A modified analysis of joint resonance theory and simple field theory is advanced to evaluate the performances of the circulators. Good agreements between the analytically obtained performance and experimental result of various MMW waveguide circulators are observed.     

毫米波成像前端中H面电感膜片波导带通滤波器的精确设计

在H面电感膜片波导带通滤波器的设计中,考虑到加工产生倒角及其产生的频率偏移,总结出带倒角膜片滤波器的精确设计方法,并给出了修正公式。为了验证本文提出的设计方法,利用HFSS对具有不同的中心频率、不同的3 dB带宽(BW)和不同的倒角半径下对这种滤波器进行了仿真,其中心频率分别为18 GHz,26 GHz,34 GHz和42 GHz,对应的带宽对应为2.265%,2.5%,10%,15%和20%,仿真结果表现出了规律性偏移趋势。通过对中心频率和带宽分别为26 GHz、2.5%和34 GHz、2.265%的2种H面波导滤波器进行实测,测试结果与利用修正公式的仿真结果一致。     

毫米波波导成型技术

用活动模芯代替钢带是毫米波波导弯曲成型的有效方法,该工艺的关键是模芯的设计与制造。采用活动模芯弯曲毫米波波导,重点讨论了模芯尺寸、模芯形状和回跳角对波导尺寸和表面粗糙度的影响,并对该工艺制备的样品进行了测定。结果表明:当模芯尺寸与波导内腔实际尺寸差值在0~0.02 mm,不同的弯曲半径和弯曲角度给予不同的回跳角预设值,可以制造出满足设计要求的弯波导。     

A Fast Finite Element Analysis of Millimeter Wave Waveguide Filters

The multifrontal method is applied for solving a large system of linear equations resulting from the use of edge-based finite element method (FEM). The finite element method combined with the perfectly matched layers (PML) is given for simulation of microwave filters and the algorithm of multifrontal method is described in detail. The reflection and insertion losses of millimeter wave filter are analyzed as the examples and the obtained results are compared with those obtained from literature. In order to demonstrate the efficiency of the multifrontal method, the computational time is compared with that of both symmetric successive overrelaxation (SSOR) preconditioned conjugate gradient (PCG) and conjugate gradient methods (CG) for the thick-iris waveguide bandpass filer.     

Analysis of Performances for Broadband Millimeter Wave Folded Waveguide TWTs

On the basis of computation of dispersion and coupling impedance for folded waveguide circuit (FWC), main performances: interact coefficient, saturated gain and output power are analyzed. Computation shows that if FWC is used in MMW amplifier, high power and wide band can be easy reached.     

Efficient Analysis of Millimeter Wave Ferrite Circulators by the GMRES Iterative Algorithm

The finite element method (FEM) combined with the perfectly matched layers (PML) is given for simulation of waveguide ferrite circulators. The generalized minimal residual (GMRES) iterative method is applied to solve such sparse large non-symmetric system of linear equations resulting from the use of edge-based finite element method. The formulation of FEM and the algorithm of GMRES method are described in detail. The reflection and insertion losses of millimeter wave waveguide circulator are analyzed and the results are compared with those obtained from literature.     

Analysis of High Power Millimeter Wave Waveguide Mode Converters with Input Mode Mixture

Based on the coupled mode theory, this paper presents the study on the influence of input mode mixture in circular oversized waveguide mode converters. Three kinds of commonly used waveguide mode converters, including the waveguide mode converters with varying wall radius or small axis perturbations, and the waveguide mode converters with bent structures, are taken as the examples. The results show that the spurious input modes do not simply superimpose onto the output modes, and in some cases they may deteriorate the conversion efficiency for the main output mode. Methods for transforming such spurious input mode mixture simultaneously into the main output mode are also presented in this paper.     

对称加载铁氧体波导差相移式高功率环行器的设计

提出了一种对称加载铁氧体波导差相移式四端环行器，利用HFSS软件的仿真分析和高功率实验研究的方法对该环行器进行了仿真设计和优化，并验证了预期的高功率设计指标给出了仿真分析结果和实验数据，分析了波导中对称加载铁氧体样品对波导巾电磁场分布的影响，并就该环行器的高功率设计考虑作了讨论。