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.     

The Compact Turnstile Circulator

This paper discusses the mode of operation of certain partial height ferrite, Y-junction circulators. It is proposed that such devices operate in a turnstile fashion with modes propagating axially along the ferrite rod. A simple experiment on a 4-GHz circulator substantiates this proposal, and a millimeter-wave device operating in this manner is described.     

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.     

Wide-Band Operation of Microstrip Circulators

Octave bandwidth operation of Y-junction stripline and microstrip circulators is predicted using Bosma's Green's function analysis. The width of the coupling transmission lines is found to be a significant design parameter. Theoretical and experimental results are presented which show that wide lines and a smaller than usual disk radius can be used to obtain wide-band operation. A microstrip circulator is reported which operates from 7-15 GHz. Also presented are an analysis of the input impedance and an approximate equivalent circuit for the Y-junction circulator which shows the relationship between Bosma's equivalent circuit and that of Fay and Comstock.     

The Synthesis of Symmetrical Waveguide Circulators

A method for synthesizing symmetrical waveguide circulators by adjusting the eigenvalues of the scattering matrix is described. This procedure is particularly useful for the design of very compact circulators in the form of waveguide junctions containing ferrite obstacles. Permissible structural symmetries for a circulator are listed, and a standard form for the scattering matrix of a symmetrical circulator is defined. The synthesis procedure is then described in detail, stating the conditions to be imposed on the scattering matrix eigenvalues, and an expression is obtained for the changes in the eigenvalues due to the placing of anisotropic material within the junction. By applying the theory to Allen's 4-port turnstile circulator, it is shown that the use of a matched turnstile junction and a reflectionless Faraday rotator is not essential. The theory is also applied to the design of novel 3- and 4-port circulators, and two 6-port circulators, one of which may be used as a 5-position waveguide switch, are described. Some experimental results are presented for a compact 3-port circulator in the form of an H-plane Y junction, in 1 inch by 1/2 inch waveguide, containing a ferrite post obstacle. This circulator, which operates with a bias field of approximately 25 oersted, has a useful bandwidth of 3 per cent. Greater bandwidths would be expected in a Stripline or a fin-line version of this device.     

Design of a High-Power CW Y-Junction Waveguide Circulator

A junction circulator appears inferior in average power-handling capability, although it is compact and light-weight and has good performance. A new type of 100-kW CW waveguide Y-junction circulator is realized by dividing the junction of the circulator into four equal unit junctions in a so-called "multilayer structure," which is water-cooled easily. This circulator has an insertion loss of 0.18 dB and an isolation of 20 dB, and it is compact and economical to build. The design of 30- and 100-kW CW waveguide Y-junction circulators is presented in this paper, which discusses determination of ferrite dimensions and air gap, considers heat generation in the ferrite, and the influence of dc magnetic-field distribution on its performance. The ferrite dimensions and air gap are determined very easily by using this design method, and these have been confirmed by experiment. It was found that a uniform distribution of internal dc magnetic fieId, obtained by considering the demagnetizing dc magnetic field, gives optimum performance. This is a significant design factor for high-power circulators which require minimum insertion loss.     

The Edge-Guided-Wave Circulator (Short Papers)

A complete study is presented on "edge-guided-wave" circulators (EGC). The fundamental physical principles which underlie EGC's operation are established and exploited to construct a broad-band circulator in the 8-12-GHz band. The performance data are compared to those of a "continuous tracking" circulator (CTC) and a traditional Y-junction circulator.     

Novel filter design incorporating asymmetrical stripline Y-junctioncirculators

Theoretical treatments of an asymmetrical stripline Y-junction circulator have been carried out. These include a formulation of the circulation conditions of an asymmetrical circulator as well as its transmission characteristics under wide-frequency-band consideration. It is found that filter designs incorporating circulators are very plausible and give rise to a narrow transmission band around the desired transmission frequency and a wide stopband extending many times the fundamental transmission frequency. In this design, high order mode excitations inherent in other filter designs are attenuated. In addition, owing to the off-resonance operation of the ferrites, present design could be applied under higher power conditions than traditional resonant ferrite filters     

A Y-Junction Strip-Line Circulator

Summary--The theoretical approach to the three-port symmetrical circulator is reviewed and presented in a form valid for the most general waveguide case. A strip-line Y-junction circulator is described and the performance of different units in the band 800-1600 mc is illustrated. The new type of device described offers, for the low-frequency region of the microwave spectrum, advantages of simple design, light weight, and great compactness with respect to the classical types. When operated with a permanent magnet it gives--in a bandwidth of about 4 per cent--isolation greater than 20 db, insertion loss /spl les/0.4 db, and input VSWR/spl les/1.20.     

Analysis and design of a new type NRD-guide E-plane Y-junction circulator

A new type of E-plane Y-junction circulator has been developed based on the nonradiative dielectric waveguide (NRD-guide) in Ka- band. First, the circulation principle has been analysed by the theory of polarization wave. The field components in the nonreciprocal Y-junction zone and the conclusion of 60° phase difference between clockwise and counterclockwise rotating polarization modes has been obtained. And then, the resonant frequency of the non-dc biased triangle ferrite sample has also been calculated. This kind of structure is benefit to enlarge the bandwidth of the Y-junction circulator. As an example, we had designed and fabricated a circulator in Ka-band. Its operating frequency is 35. 1GHz, the 1.5dB insertion loss and 20dB isolation bandwidth is about 1. 0GHz.     

A Compact Broad-Band Thin-Film Lumped-Element L-Band Circulator

Impedance matrices including magnetic losses are developed for a number of lumped-element ferrite-loaded symmetrical three-port junctions. The scattering matrix eigenvalues corresponding to these matrices are determined as functions of frequency and circuit parameters and are used to analyze these three-ports with emphasis on their properties as circulators. A very compact broad-band thin-film lumped-element circulator is derived from the idealized equivalent circuit. An experimental model approximately represented by this circuit is shown to have a 20-dB isolation bandwidth of greater than 30 percent with an insertion loss of less than 0.6 decibel. A switchable circulator which requires no magnetic-field switching is treated using this same analytical approach. It is suggested that this type of analysis together with additional experimental refinement of equivalent circuits will lead eventually to a computerized design of lumped-element circulators.     

Finite-difference analysis of cyclic H-plane waveguide three-port circulators with an arbitrary-shape lossy ferrite post

A finite difference method (FDM) with an analytical truncation boundary condition is developed for the analysis of cyclic H-plane waveguide three-port circulators with an arbitrary shape ferrite post. The method is based on scalar wave equations and the analytical field distribution in the rectangular waveguides. A general boundary field equation for an arbitrarily shaped ferrite or dielectric interface is derived. To verify the validity of the present method, the eigenvalue phases of the cyclic three-port empty junctions and the characteristics of H-plane waveguide Y-junction circulators with lossless, lossy cylindrical, composite and triangular ferrite post are calculated. Good agreements with previously published experimental and theoretical results have been achieved. The performance of a Y-junction circulator with a hexagonal ferrite post and the characteristics of a cyclic three-port circulator with a ferrite rod are also investigated.     

Theoretical design for 120 GHz semiconductor junction circulators: effects of different numbers of terms in the Green's function

A theoretical analysis of the predicted performance and field distributions for semiconductor junction circulators is based on Bosma's Green's function approach which involves a summation of infinite series in the mathematical derivation. The effects are considered of taking a different number of terms in the series, looking at three different circulators centred at 120 GHz. The narrowband semiconductor circulators show a similar effect to the ferrite junction circulator because the field distributions inside the semiconductor discs can be approximated by only considering the dominant modes. However, there is no dominant mode in the broadband circulator and the higher order modes play an important role in the operation of this circulator. In order to obtain a precise representation of the circulation effects inside both narrowband and broadband circulators, at least up to the 6th term, or 18 terms in all, are required to be added in the summation of Green's functions.     

The Frequency Behavior of Stripline Circulator Junctions

The frequency dependence of the circulation equations for Y-junction stripline and microstrip circulators is investigated, and a new set of design curves is generated for the frequency-independent forms of the circulation condition's roots for both below- and above-resonance cases. Using this new set of curves, the wide-band design predicted by Wu and Rosenbaum and Bosma's narrow-band design are analyzed and compared. Quantitative arguments for the effect of the junction parameters on the bandwidth are given. To support the arguments, the theoretical junction performance of the 7-15 GHz "continuous tracking" circulator reported by Wu and Rosenbaum is calculated and compared with the theoretical performance of a 24 GHz circulator junction designed using the same method. Experimental results also are presented for the 24 GHz design. An analysis for the effect of the ferrite thickness on impedance matching is also included.     

Lightweight Y-Junction Strip-Line Circulator (Correspondence)

In a recent issue, the practical realization of a Y-junction strip-line circulator was described which used disks of yttrium iron garnet located at the junction of the Y, magnetically biased above resonance at approximately 2200 gauss. By using a material with a lower saturation magnetization (magnesium, manganese, aluminum ferrite, 4piM=600) we have reduced the bias field required to approximately 190 gauss for frequencies in the 2-kMc range and to approximately 800° gauss for frequencies in the 1-kMc range, thus reducing considerably the weight of the circulator. If the circulator is to be operated as a switch, the reduced field requirements permit faster switching times or, for a given switching time, a considerable reduction in power supply requirements.     

Millimetric Nonreciprocal Coupled-Slot Finline Components

Promising preliminary results are presented for isolators and a four-port circulator in novel finline structures in the frequency range 26.5-40.0 GHz. The basic configuration is a ferrite-loaded coupled-slot finline with the ferrite magnetized parallel with the direction of propagation. The nonreciprocal effects of the odd mode propagating alone and of the odd and even modes propagating are described. All structures exhibit a 20-dB isolation bandwidth greater than 3.6 GHz. It is suggested that such structures would also be suitable for higher frequencies.     

W Band Circular Waveguide Y-Junction Circulator

In this paper, a new type of W band circular waveguide Y-junction circulator is presented. The structure of this type of Y-junction is a cylindrical cavity connecting with three circular waveguides. The performances of the type of circulator are analyzed by the edge-based vector finite element method hybridized with the modal expansion. The numerical results show that this type of waveguide Y junction circulator has good circulation performance.     

Double Circulation Frequency Operation of Stripline Y-Junction Circulators

The double circulation frequency operation (DCFO) of stripline Y-junction circulators loaded with dielectric-ferrite composites is presented. The dielectric-ferrite composite is made by combining a dielectric puck with a ferrite ring. The DCFO is identified in the mode chart, and it is found that mode 1 and mode 1A, according to Davies and Cohen, play their respective roles in the circulation. Theoretical results of perfect circulation are derived, applying Bosma's Green's function to the junction mode impedances, and then, design and operation of the DCFO are studied. Finally, experimental examples are presented.     

Integrated self-biased hexaferrite microstrip circulators formillimeter-wavelength applications

Planar microstrip Y-junction circulators have been fabricated from metallized 130-μm-thick self-biased strontium hexaferrite ceramic die, and then bonded onto silicon die to yield integrated circulator circuits. The impedance matching networks needed to transform the low-impedance circulator outputs were deployed on low-loss alumina or glass dielectrics to minimize circuit losses. These magnetically self-biased circulators show a normalized isolation and insertion loss of 33 and 2.8 dB, respectively, and a 1% bandwidth for an isolation of 20 dB. Application of small (H<1.5 kOe) magnetic bias fields improved the isolation and insertion loss values to 50 and 1.6 dB, respectively. This design may form the basis for future monolithic millimeter-wave integrated circulator circuits that do not require magnets     

八毫米波段微带集成环行器

本文介绍我们研制成功的8毫米波段微带Y结环行器.说明了设计制作步骤,给出了测试结果.将其一端接匹配负载可构成Y结隔离器.该器件已用于毫米波集成前端中.