Analysis of cylindrical transmission lines with thefinite-difference time-domain method

In this paper, the finite-difference time-domain (FDTD) method is used to calculate the propagation characteristics of cylindrical transmission lines. An efficient two-dimensional FDTD algorithm is developed by projecting the three-dimensional FDTD cell in the cylindrical coordinates onto the r-φ plane. An effective absorbing boundary condition is employed to truncate the mesh at its outer radial boundary. Numerical results are derived for different cylindrical transmission lines and compared to data available in the literature. Specifically, the newly proposed cylindrical coplanar waveguide is studied both theoretically and experimentally     

FDTD analysis of magnetized ferrites: application to thecalculation of dispersion characteristics of ferrite-loaded waveguides

The finite-difference time-domain (FDTD) method is extended to include magnetized ferrites. The treatment of the ferrite material is based on the equation of motion of the magnetization vector. Magnetic losses are also included in the equation of motion by means of Gilbert's approximation of the phenomenological Landau-Lifschitz damping term. The discretization scheme is based on central finite-differences and linear interpolation. This scheme allows the fully explicit nature of the FDTD method to be maintained. This extension of the FDTD method to magnetized ferrites is applied to the full-wave analysis of ferrite-loaded waveguides. The dispersion curves are calculated by using a recently proposed 2D-FDTD formulation for dispersion analysis which has been adapted to the present problem. The results for both the phase and attenuation constants of various transversely and longitudinally magnetized ferrite-loaded waveguides are compared with the exact values and with those obtained by means of Schelkunoff's method     

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.     

Propagation Characteristics of a Rectangular Waveguide Containing a Cylindrical Rod of Magnetized Ferrite

With an axially magnetized cylindrical ferrite rod inserted into a rectangular waveguide parallel to the E-field of the dominant (TE/sub 10/) mode, the electromagnetic field amplitudes inside the ferrite rod and the transmission and reflection coefficients are numerically obtained by means of a digital computer and their results are shown in figures. At resonance, the distributions of RF magnetization and electric field have good symmetrical patterns in the cross section of the rod. The experimental results of the transmission and reflection coefficients agree well with the theoretical values.     

Theoretical Considerations on the Use of Circularly Symmetric TE Modes for Digital Ferrite Phase Shifters

The effectiveness of using magnetized ferrite toroids in circularly cylindrical guides operating in the TE/sub 01/ mode as elements of a digital phase shifter is investigated. The phase of such a device is controlled by reversing the magnetization of individual ferrite toroids. An analysis of the circularly cylindrical guide containing, coaxially, a ferrite tube is presented for circularly symmetric modes. Some results of computations to determine the optimum tube thickness, mean radius, and effect of frequency and changes in the fundamental constants of the material are included.     

A new Ka-band microstrip Y-junction circulator with a ferrite sphere

A novel microstrip circulator with a magnetized ferrite sphere is proposed for millimetre wave communications. A three-dimensional finite difference time-domain (FDTD) approach for the analysis of this ferrite sphere-based microstrip circulator is presented. The electromagnetic fields inside the ferrite junction are calculated by 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 the Ka-band are presented and compared with theoretical simulation. Good agreement is found between them.     

A Two-dimensional Full-wave Finite-difference Frequency-domain Analysis of Ferrite Loaded Structures

A two-dimensional (2-D) full-wave finite-difference frequency-domain (FDFD) method is presented for analyzing the dispersion characteristics of transversely magnetized ferrite loaded structures. Results for a number of different ferrite loaded structures are presented. The accuracy of the FDFD formulation is verified by comparing the numerical results with analytical results and those obtained using the FDTD method, and very good agreement is obtained.     

Spectral-domain immittance approach for the propagation constantsof unilateral finlines with magnetized ferrite substrate

The admittances of TM and TE modes in a ferrite substrate are given, and the propagation constants for the forward and backward directions of the dominant mode in unilateral finlines with magnetized ferrite substrates are obtained. The solution is obtained by applying the transverse equivalent transmission line in the spectral domain and Galerkin's method. Numerical results are presented which can be used in designing a finline displacement isolator     

Evaluation of the radar cross section of circular microstrippatches on anisotropic and chiral substrates

Galerkin's method in the Hankel transform domain (HTD) is applied to the determination of the radar cross section (RCS) of a circular microstrip patch printed on a substrate which may be an uniaxial anisotropic dielectric, a magnetized ferrite, or a chiral material. The results obtained for circular patches on magnetized ferrites show that the RCS of these patches can be substantially reduced in a tunable frequency band when a bias magnetic field is applied. It is also shown that the results obtained for the RCS of circular patches printed on chiral materials can be substantially different from those obtained when substrate chirality is ignored     

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.     

A simple FDTD model for transient excitation of antennas bytransmission lines

A simple FDTD model is developed for use with antennas that are fed from transmission lines. The model is especially designed for use with transient excitations, where the incident and reflected waveforms within the transmission line are of interest, and the latter is determined directly in the FDTD calculation. The model is verified for both transmission and reception of transient waveforms by comparison with measured results for a cylindrical monopole antenna with a plane reflector     

FDTD treatment of partially magnetized ferrites with a newpermeability tensor model

This paper outlines the finite-difference time-domain (FDTD) treatment of partially magnetized ferrites characterized by a permeability tensor model, which was recently published. Its causal aspect makes this tensor well adapted to time-domain simulations. Validation is demonstrated for a resonant ferrite structure, Numerical and analytical results are compared, showing good agreement     

温度、密度对磁化等离子体光子晶体的影响

为了研究温度、密度对磁化等离子体光子晶体禁带特性的影响,采用在等温近似的条件下,磁化等离子体的分段线形电流密度卷积时域有限差分算法研究了1维磁化等离子体光子晶体的禁带特性。以高斯脉冲为激励源,用算法公式得到的电磁波透射系数来讨论了温度、等离子体层密度对其禁带特性的影响。结果表明,改变温度和等离子体层密度分布可以实现对禁带的控制。     

Full-wave analysis of circular microstrip resonators inmultilayered media containing uniaxial anisotropic dielectrics,magnetized ferrites, and chiral materials

In this paper, Galerkin's method in the Hankel transform domain is applied to the determination of the resonant frequencies, quality factors, and radiation patterns of circular microstrip patch resonators. The metallic patches are assumed to be embedded in a multilayered substrate, which may contain uniaxial anisotropic dielectrics, magnetized ferrites, and/or chiral materials. The numerical results obtained show that important errors can be made in the computation of the resonant frequencies of the resonators when substrate dielectric anisotropy, substrate magnetic anisotropy and/or substrate chirality are ignored. Also, it is shown that the resonant frequencies of circular microstrip resonators on magnetized ferrites can be tuned over a wide frequency range by varying the applied bias magnetic field. Finally, the computed results show that the resonance and radiation properties of a circular microstrip patch on a chiral material is very similar to those of a circular patch of the same size printed on a nonchiral material of lower permittivity     

Composite-Junction Circulators Using Ferrite Disks and Dielectric Rings

Since most junctions do not use the full available magnetic splitting of the ferrite material, it is possible to replace part of it by a dielectric. The theoretical and experimental development of such composite stripline circulators using ferrite disks surrounded by dielectric rings is given in this paper. Theoretical calculations and experimental results on the circulation frequency, gyrator admittance, and split frequencies of such circulators are included. The case of a partially magnetized ferrite disk on a ferrite substrate is treated separately. The suscteptance slope parameter of this circulator geometry is also derived and measured. The results obtained in this paper show to what extent the ferrite disk behaves as a dielectric at the edge of the disk. The geometry leads to considerable saving in ferrite material, which is particularly important in UHF circulators. The experimental results are in good agreement with the theory.     

Finite difference time domain analysis of cylindrical coplanar waveguide circuits

There is a growing interest in using cylindrical transmission line structures in microwave applications. In this paper, the finite difference time domain (FDTD) method is used to characterize several three-dimensional cylindrical coplanar waveguide (CCPW) geometries. Specifically, a CCPW series stub and a three-section CCPW filter are studied both theoretically and experimentally. Moreover, CCPW gap is characterized and the FDTD results are compared to those obtained using conformal mapping techniques. Effective absorbing boundary conditions are employed to truncate the FDTD mesh at the end walls and the outer radial boundary.     

Study of periodic band gap structure of the magnetized plasma photonic crystals

The characteristics of the periodic band gaps of the one dimension magnetized plasma photonic crystals are studied with the piecewise linear current density recursive convolution (PLCDRC) finite-differential time-domain (FDTD) method. In frequency-domain, the transmission coefficients of electromagnetic Gaussian pulses are computed, and the effects of the periodic structure constant, plasma layer thickness and parameters of plasma on the properties of periodic band gaps of magnetized photonic crystals are a...     

The dispersion characteristics of shielded microstrip lines on magnetized ferrite and anisotropic dielectric substrates

The dispersion characteristics of the dominant mode in shielded microstrip lines on magnetized ferrite and anisotropic dielectric substrates have been obtained. The solution is obtained by applying the transverse equivalent transmission line in the spectral domain and Galerkin's method. Numerical results for the frequency-dependent propagation constants are presented which could be used in designing directional couplers and isolators.