High-Power Ferrite Circulators

The Faraday rotation and insertion loss of various ferrite-loaded waveguide structures have been studied in order to determine their power-handling capacities. A method of measuring insertion loss to within +-0.05 db is described. Two figures of merit containing this information are defied for the various configurations. The first, defined as the rotation per attenuation, indicates for a given value of rotation the efficiency of power transmission through the device, while the second, defined as the dissipative area per power loss, indicates the power handling capacity of the structure. By utilizing this information, the author has described an X-band ferrite circulator which is capable of handling an average power of 1000 watts. In addition, the design of a 2000-watt gyrator type circulator is indicated.     

Design Data for Radial-Waveguide Circulators Using Partial-Height Ferrite Resonators

This paper derives the eigennetworks of radial-waveguide circulators using partial-height ferrite resonators with n=2 Chebyshev characteristics. To obtain a Chebyshev response with such junctions it is necessary to establish the proper phase angles and admittance levels of the three eigennetworks of the device. This paper derives the phase angles for the eigennetworks but relies on experiments to establish the admittance levels. The configurations dealt with include the standard circulators using either half-wave-long ferrite resonators open circuited (OC) at both ends or coupled quarter-wave-long ferrite resonators OC at one end and short circuited (SQ) at the other. It also includes the design of a new single quarter-wave-long version, which is likely to replace the two more conventional arrangements in common usage. It is observed that the eigennetworks of any one of the geometries is sufficient to characterize the other two.     

Design of Waveguide Circulators with Chebyshev Characteristics Using Partial-Height Ferrite Resonators

This paper outlines a step-by-step approach to the design of waveguide circulators using partial-height resonators, which incorporates every linear dimension of the device, The approach used consists of defining the physical variables of the ferrite region in terms of the frequency, VSWR, and bandwidth specification. It also incorporates the definition of the length and admittance level of the radial transformer. The model employed is essentially a two-mode one, with the third mode separately adjusted to exhibit an ideal electric-wall boundary condltion at the terminals of the junction.     

CPW Circulators with Barium Ferrite Thin Films

A miniaturized circulator using barium ferrite films with a coplanar waveguide(CPW) structure is designed and optimized by high frequency electromagnetic field simulations based on finite element methods.The best circulation performance of the film circulator based on 10 μm thick barium ferrite thin films is obtained with an insertion loss of 0.13 dB and an isolation of 22.89 dB around 36.9 GHz.The microwave characteristics of film circulators with CPW and CPW with ground(CPWG) structures have been compared.The influences of the gap between the ground and the signal line,and the ferromagnetic resonance line width on the microwave properties are also studied.     

Computer-aided Design Of Stripline Ferrite Junction Circulators

A general design procedure is presented for stripline Y-junction circulators employing solid dielectric between ground planes. The resonator design and impedance matching are derived in a form suitable for computer evaluation. The procedure is applicable to cases where either the circulator bandwidth or the ground plane spacing is specified. An experimental S-band switching circulator illustrates the technique.     

Design Calculations for UHF Ferrite Circulators (Correspondence)

The recent advances in low-noise amplifier work for communications systems has created an additional demand for circulators; in this case, to prevent receiver noise from returning to the low-noise amplifier. In the range of frequencies greater than 2000 mc, ferrite circulators have been developed in circular and rectangular waveguides. However, in the UHF region, which is a range of frequencies of increasing interest and importance in communications, ferrite circulators present a problem in the sense that ordinary waveguides needed in this range are prohibitively large for practical use. Button of Lincoln Laboratory and Seidel of Bell Telephone Laboratories have pointed a way around this difficulty by considering a TEM structure (a coax) loaded antisymmetrically with dielectric material and ferrite. This configuration provides for the longitudinal component of RF magnetic field necessary for nonreciprocity in the phase constant. The essentially TEM nature of the device allows use of reasonably small, practical cross-sectional areas. The parallel-plate analog analysis presented in Button's paper leads to a transcendental equation for the phase constant which we present below for convenience, together with an example of the structure.     

Reciprocal and Nonreciprocal Switches Utilizing Ferrite Junction Circulators (Correspondence)

The symmetrical ferrite junction circulator has assumed a position of prominence in recent years due to its small physical size and excellent electrical characteristics. The device was described theoretically by Auld, and other investigators have contributed to the design of improved electrical characteristics. Due to their low loss, these circulators have found wide use with parametric and tunnel diode amplifiers. Other applications include duplexers, multiplexer and load isolators.     

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.     

Circulators Using Planar WYE Resonators

An important class of commercial three-port circulator relies for its operation on a junction resonator consisting of the symmetrical connection of three open-circuited transmission lines. A feature of this resonator is that it may be quarter-wave coupled to form a circulator with a moderate specification (25-percent bandwidth to 25-dB return loss points) and physical dimensions of the order of directly coupled conventional circulators (using a disk resonator). For circulators for which the in-phase eigennetwork may be represented by an ideal short-circuit, the equivalent circuit is a one-port network which may be formed from a characterization of the constituent resonator. This feature is used in this paper to study the equivalent circuit of junction circulators using planar WYE resonators. The derivation of the equivalent circuit parameters is supported with the design of a 4-GHz quarter-wave-coupled stripline circulator.     

Design of Partial Height Ferrite Waveguide Circulators (Short Papers)

This short paper presents a design procedure for the widely used three-port waveguide circulator that has a partial height ferrite post in the junction region. Design formulas and curves are derived for two configurations of partial height circulators: one has a short circuit at one end of the ferrite post, while the other has dielectric spacers at both ends. The design method was used to build two circulators for operation at 38 GHz and 60 GHz, respectively. Excellent agreement between theory and experiment was obtained in predicting the center frequency and required matching structure of these devices.     

Suppression of Higher Order Modes in Waveguide-Junction Circulators Using Coupled Open Dielectric Resonators (Letters)

It is well known that some waveguide circulators exhihit an unwanted spurious mode within their passband, which limits their insertion loss and bandwidth. This mode is identified as the TE/sub 0,1,delta/ one in the case of the waveguide junction which relies on the TM/sub 1,1delta,/ mode for its operation. The influence of the saturation magnetization on the separation between the two modes is studied in detail. A mode suppressor is also described which decouples the coupled TE/sub 0,1,delta/ mode without altering the frequency of the circulation ones. This suppressor consists of a thin metal ring placed on the open face of one of the ferrite disks.     

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.     

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.     

Multiple-Frequency Operation of Y-Junction Circulators Using Single-Mode Approximation

The conditions for a Y-junction circulator to operate within more than one frequency band are studied. By taking into account only the dominant resonance mode at each circulation frequency, explicit expressions are obtained which define the properties of the circulator. The results are presented in diagrams and tables which enable rapid evaluation of obtainable performance for some of the most important mode combinations. The validity of the results are experimentally verified.     

Adjustment of In-Phase Mode in Circulators Using Turnstile Junctions

The adjustment of the counter-rotating modes of waveguide circulators using weakly magnetized turnstile junctions is fairly well understood, but some uncertainty about the definition of the in-phase mode still remains. The purpose of this paper is to remedy this situation by experimentally evaluating the in-phase eigenvalue s/sub 0/ for different filling factors and radial wavenumbers of the in-phase resonator. This is done by using the unitary condition to derive four possible relationships between the in-phase and counter-rotating eigenvalues s/sub 0/ and s/sub 1/, and the scattering variable S/sub 11/, and using one or another of them to form s/sub 0/. The situation for which s/sub 0/ is in anti-phase to s/sub 1/ corresporrds to the first classic circulation condition of this class of device and is also derived.     

含有平行铁氧体及介质片的异形波导传输特性

用直线法和横向共振相结合的方法来求含有平行铁氧体及介质片的异形波导的传输特性。计算结果表明,含有铁氧体的脊形波导具有宽频带特性,而含有铁氧体的槽形波导具有较大的差相移,适于做高优值移相器。     

铁酸铋基多铁陶瓷的微观结构和介电性能研究

采用固相反应法制备了(1-x)BiFeO3-xBaTiO3(BF-xBT,0.2≤x≤0.35)多铁陶瓷。研究了二元系固溶体在不同煅烧条件下的相结构和微观形貌,以及不同的BaTiO3(BT)含量对多铁陶瓷性能的影响。研究结果表明,所有的陶瓷样品都具有单一的钙钛矿结构。随着BT含量的增加,固溶体中的杂相呈减少趋势,同时介电常数逐渐增大。另外,当x=0.3时,二元系固溶体在900℃时晶粒增长,但不均匀,在1 000℃时晶界出现融化现象,晶粒间出现孔洞,结果表明,950℃为最适合的烧结温度。