Dispersion analysis of multilayer cylindrical transmission lines containing magnetized ferrite substrates

Abstract

Recently, there has been a growing interest in using cylindrical transmission lines that contain magnetized ferrite material in a variety of applications. In this paper, the finite-difference time-domain (FDTD) method (in cylindrical coordinates) and the spectral-domain analysis (SDA) are used to calculate the propagation characteristics of cylindrical transmission lines that contain magnetized ferrite material. The magnetization can be either in the longitudinal or azimuthal directions. Specifically, the cylindrical microstrip line, and the cylindrical coplanar waveguide printed on magnetized ferrite substrate are analyzed. Both the FDTD and SDA results are in very good agreement. In addition, the results are compared to those of planar structures by taking the radius of the substrate to be large enough such that the curvature effect is negligible. Index Terms-Circular waveguide, coplanar waveguide, FDTD methods, ferrite loaded waveguides, microstrip, spectral-domain analysis. I. INTRODUCTION T HERE IS A growing interest in antennas that are printed on cylindrical substrates. These antennas may find applications in aircraft, missiles, and wireless communications due to their features of conformability, light weight, small size, and the geometrical compatibility to the vehicle they are mounted on. The use of ferrite substrates also adds more flexibility to the design of cylindrical antennas due to the effect of the applied dc magnetic field on the performance of the antenna. Ferrite materials are widely used in microwave applications, such as isolators, circulators, and phase shifters. Recently, there has been an increasing interest in studying cylindrical structures (circular waveguide and cylindrical microstrip antennas) containing magnetized ferrite media [1]-[6]. Specifically, the effects of anisotropy of ferrite coating on the radiation characteristics of cylindrical structures excited by elementary electric or magnetic dipoles have been investigated in [1]-[3]. The main advantage of a ferrite substrate is that the electrical parameters can be controlled by an externally applied magnetic field. Recently, the finite-difference time-domain (FDTD) technique has been extended to study the dispersion characteristics Manuscript received March 25, 2001.

Full-wave analysis of azimuthally magnetized ferrite-loaded circular structures using the one-dimensional finite difference frequency domain method

“…As an example of using eqs. (17)- (19) to determine Db, Figure 10 shows the way of finding the constant A from (17). From (17), it is clear that A is practically constant for different values of a at fixed r n , which means that this curve represents the approximation curve for all the values of A(a).…”

“…(17)- (19) to determine Db, Figure 10 shows the way of finding the constant A from (17). From (17), it is clear that A is practically constant for different values of a at fixed r n , which means that this curve represents the approximation curve for all the values of A(a). As seen from (17) and (19) and Figure 10 that the constant C can be found directly by multiplying any value of A with its corresponding r n , which means the area of any arbitrary rectangle: abcd, afgh, or aejk which is a constant value as have been proposed for this scheme in [28].…”

“…Different researchers studied and solved for the propagation characteristics of ferrite-loaded circular structures as in [13][14][15][16]. In [17], Dib and Omar presented a full wave dispersion analysis of multilayer cylindrical transmission lines containing (azimuthally and longitudinally) magnetized ferrite material using 2D-FDTD method and spectral domain analysis (SDA). The electromagnetic wave propagation in transversely magnetized ferrite filled circular waveguide was completely analyzed in cylindrical coordinates in [18].…”

Designs and Analyses of Some Rf/Microwave Passive Elements on Cylindrical CPWS

“…Since these type transmission lines are quite flexible they can be especially applied in aircraft, missiles, and mobile communication applications in order to feed printed antennas around a non-planar surface like an elliptical or a cylindrical surface where the planar realization is not feasible as mentioned in [1,2]. It is possible to construct cylindrical and/or elliptical transmission lines using appropriate dielectric materials easily.…”

“…It is possible to construct cylindrical and/or elliptical transmission lines using appropriate dielectric materials easily. Up to date there are some studies about non-planar transmission lines to evaluate characteristic parameters of them analytically and accurately [1][2][3][4][5]. In addition, various planar and cylindrical CPW discontinuities have been analyzed in [6][7][8] …”