Characteristics of aperture coupled microstrip antennas on magnetized ferrite substrates

The method of moments in the spectral domain is applied to the full-wave analysis of aperture coupled microstrip antennas in the case where the substrate of the antennas is a layered medium containing magnetized ferrites. The subsectional basis functions used in the analysis make it possible to handle patch antennas and coupling apertures with right angle corners of arbitrary shape. The numerical results obtained show that antennas on ferrite substrates fed by single microstrip lines can radiate both circular and linear polarization, the polarization state being dependent on the orientation of the ferrites bias magnetic field. For a given polarization state, the matching frequency band of the antennas can be tuned over a wide frequency range by adjusting the magnitude of the bias magnetic field. Also, the polarization state can be continuously tuned from circular to linear within the same frequency band by adjusting both the magnitude and the orientation of the bias magnetic field. Some measurements are presented in order to check the validity of the numerical algorithm developed.     

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     

Tunability and bandwidth of microstrip filters fabricated on magnetized ferrites

The method of moments in the spectral domain is applied to the rigorous full-wave analysis of coupled line microstrip filters fabricated on magnetized ferrites. The results show that the center frequency of the filters can be tuned over a wide range by adjusting the magnitude of the bias magnetic field of the ferrite substrates. However, the filters bandwidth is reduced as the tuning frequency increases. This bandwidth reduction is explained in terms of the behavior of the resonant frequencies and quality factors of the resonators included in the filters.     

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     

The RCS of a microstrip antenna on an in-plane biased ferritesubstrate

The numerical solutions for the RCS of a microstrip patch on an in-plane biased ferrite substrate are presented. The peaks in the RCS can be moved with respect to frequency by changing the magnetic bias field. We consider a monostatic RCS with various incident angles and examine all four elements of the cross-section matrix. For the case of an unmagnetized ferrite substrate the cross-polarized RCS components are zero. When the ferrite is magnetized, the cross-polarized RCS components become as significant as do the copolarized RCS components. It is also shown that a loaded patch has the effect of significantly reducing RCS at resonances. The analysis used is based on a full-wave moment method with the exact spectral-domain Green's function     

Resonant modes of circular microstrip patches over ground planeswith circular apertures in multilayered substrates containinganisotropic and ferrite materials

In this paper, the authors analyze how the resonant modes of circular microstrip patch resonators are affected by the presence of circular apertures in the ground plane located under the patches. A rigorous full-wave analysis in the Hankel transform domain (HTD) is carried out in order to obtain the resonant frequencies, quality factors, and radiation patterns of the circular microstrip patch resonators over ground planes with circular apertures. With the use of suitable Green's functions in the HTD, the analysis is performed for the case where the circular patches, as well as the ground planes containing the apertures are embedded in a multilayered substrate consisting of isotropic dielectrics, uniaxial anisotropic dielectrics, and/or magnetized ferrites. The numerical results obtained are compared with experimental results, and good agreement is found. The results show that the circular apertures significantly affect the resonant frequencies of circular microstrip patches     

Dispersion Characteristics of the Dipolar Modes in a Waveguide Partially Filled with a Magnetized Ferrite Column

The electromagnetic wave propagation in a partially filled ferrite waveguide is studied by using both the quasi-static and exact analyses. Here, the ferrite is assumed to be lossless and completely magnetized. The cutoff and resonant frequencies are examined analytically to predict all possible modes, and numerical methods are then used to study the complete dispersion characteristics. Because of the geometrical generality of the problem, the fully filled ferrite waveguide and the ferrite column in free space can be considered as special cases. The classifications of the modes existing in various parametric regions are clarified. The effects of the ratio of the ferrite-to-waveguide radius and the dc axial magnetic field on the behaviors of the modes are studied and discussed. For large values of the phase constant, asymptotic dispersion equations can be derived, and turn out to be the same in both analyses. A comparison between the two sets of results is also made to examine the validity of the quasi-static analysis. The method of analysis used in this present paper is similar to the one used in the corresponding paper on partially filled plasma waveguides published previously.     

The RCS of a microstrip patch on an arbitrarily biased ferritesubstrate

The radar cross section (RCS) of a rectangular microstrip patch on a lossy biased ferrite substrate is investigated. The analysis is based on a full-wave integral equation formulation in conjunction with the method of moments. In the analysis, the direction of the bias field is not prescribed. The RCS characteristics, especially the resonance behavior of a patch with various biasing conditions, are studied and compared to those for an unbiased ferrite. It is found that the resonant frequencies of a patch vary significantly with the change of the bias field, except for those resonant modes which have a dominant magnetic-field component in the direction of the bias field. This phenomenon is explained with a waveguide cavity model, and provides an independent check of the analysis. It is found that the magnetic loss affects the RCS at resonances significantly     

Leaky-wave dispersion behavior on a grounded ferrite slab waveguide

In this letter, leaky-wave dispersion behavior is studied for a grounded biased-ferrite slab waveguide. The full-wave analysis encompasses space-wave leaky modes, surface waves, and magnetostatic modes supported by a ferrite slab as the magnetic bias field varies in strength. In particular, as the bias field increases from a value the TE leaky-wave cutoff frequencies of the isotropic slab split into two cutoff frequencies, resulting in complicated dispersion behavior of the corresponding forward and backward leaky waves. TM modes are unaffected by variation in the strength of the bias field for this orientation.     

Effet ďun champ magnétique sur les modes TMnmo ďune cavité cylindrique circulaire partiellement remplie de ferrite

The resonant modes of a circular cylindrical cavity resonator containing a coaxial circular ferrite rod are investigated. The ferrite sample is partially magnetized by means of a constant external magnetic field applied along its axis. A computer program for deriving the resoant frequencies of this system as a function of the externally applied magnetic field and of the sample radius has been developed. Results for the special cases of the tm₀₁₀ and tm110 modes are presented. The possible application of such a cavity resonator for the remote sensing of magnetic fields is discussed.     

Analysis of partial-height ferrite-slab differential phase-shiftsections

Rectangular waveguide loaded with transversely magnetized ferrite slabs is a classic arrangement used in the construction of high-power differential phase-shift circulators. The characterization of this structure is extended in this paper by using a combined magnetostatic/microwave finite-element method to evaluate propagation characteristics in terms of material parameters, frequency, and bias field. Magnetic flux density was found to vary by typically 20% across a partial-height ferrite slab. Experimental phase-shift data agreed to within 5% of numerical calculations for a 9.25-GHz device. Supplementary design data are presented for the first higher order mode in the cutoff plane, the effect of material properties on phase shift, and to compare below and above resonance operation     

Radiation frequencies of ferrite patch antennas

The radiation frequencies of rectangular microstrip patch antenna deposited on ferrite substrate have been measured. Two different radiation modes were found whose frequencies behaved differently under the application of a biasing magnetic field. These two modes of radiation have been identified with a transverse mode whose radiation frequency increased with increasing magnetic field and a longitudinal mode whose radiation frequency decreased with the applied magnetic field. A theoretical model has been formulated for radiation of these two modes based on a multidomain configuration of the ferrite substrate.<>     

Bragg Interaction of Electromagnetic Waves in a Ferrite Slab Periodically Loaded with Metal Strips

The waveguiding characteristics of electromagnetic TE waves in a ferrite slab periodically loaded with metal strips are investigated. Theoretical formulation by means of the spectral domain approach is employed to obtain the Brillouin diagrams of two types of volume modes and a surface mode. It is found that the nonreciprocal properties of waves depend on the metal strip profile and bias magnetic field strength. Experiments on the magnetic-field dependence of the Bragg frequency and the stop bandwidth are carried out in the millimeter-wave frequencies. Typical results obtained from a polycrystalline YIG slab with periodic gold strips deposited on one surface are stop bandwidth about 2.14 GHz, with return loss about 2 dB at the Bragg frequency of 47.5 GHz, for the bias magnetic-field strength of 5.7 kG. The Bragg frequency can be tuned over the range of 1.39 GHz by varying the bias magnetic field from 0 to 8.2 kG. Experimental results show good agreement with theoretical predictions.     

Magnetic tuning of a microstrip antenna on a ferrite substrate

The operating frequency of a microstrip antenna on a ferrite substrate can be tuned by varying the DC magnetic bias field applied to the ferrite. The letter reports experimental work where a 40% tuning range has been obtained, with usable patterns and return loss over this band     

The absorption and coupling of an electromagnetic wave incident ona microstrip circuit with superstrate

The absorption of an electromagnetic wave incident on a microstrip circuit covered with a dielectric layer is studied. The exact analytical expression for the plane-wave reflection coefficient at the air-superstrate interface of a four-layer model for a superstrate-loaded microstrip circuit is given. Numerical results illustrating the power absorption by the microstrip circuit and the electric and magnetic fields on the surface of the circuit as a function of wave frequency, superstrate thickness, superstrate permittivity, and incident angle are presented. It is found that the power absorption by the circuit at resonant frequencies increases with increasing superstrate permittivity. Higher superstrate thickness and permittivity can both cause more resonant power absorption peaks in the frequency spectrum. Significant intensities of electric or magnetic fields can also exist on the surface of the circuit for almost all the frequencies, which may couple to the circuit and cause malfunctions or interference. Details of the numerical results are presented     

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.     

多层介质覆盖矩形微带天线谐振频率的精确计算

本文将谱域导抗法推广应用于计算多层介质覆盖矩形微带天线的谐振频率，通过引入两种特殊的数值积分方法，解决了二维振荡函数无穷区间积分问题，获得了一些有用的结论。     

Hankel transform domain analysis of dual-frequency stackedcircular-disk and annular-ring microstrip antennas

A theoretical and numerical analysis of the dual-frequency stacked circular-disk and annular-ring microstrip antennas is discussed. The problem is formulated in the Hankel transform domain. First, the Green's function is derived, relating the transformed electric surface currents on the patches and the transformed tangential electric field components on the substrates. Galerkin's method is used with Parseval's relation for Hankel transformation to solve for the resonant frequencies and the unknown currents. The far-zone radiation patterns are expressed in terms of the transforms of the currents. Numerical results obtained for the resonant frequencies and radiation patterns are found to be in excellent agreement with the experimental data available in the literature     

Experimental validation of analysis software for tunable microstrip filters on magnetized ferrites

Measurements are presented for microstrip filters on layered media containing magnetized ferrites. The measurements show that the filters can be tuned by adjusting the magnitude of the magnetic-bias field. The measured results are compared with full-wave numerical results obtained by the authors via the method of moments in the spectral domain. The agreement between experimental and numerical results is reasonably good. The results show that the bandwidth of the filters appreciably decreases as the tuning frequency increases for frequencies located above the magnetostatic waves range (MWR). However, tuning is achieved without substantial bandwidth reduction for frequencies located below the MWR.     

Design of a dual frequency reflectarray using microstrip stackedpatches of variable size

A new stacked microstrip reflectarray, based on patches of variable size, is proposed for dual frequency operation. A progressive phase distribution is achieved for the reflected wave at both frequencies by adjusting the resonant length of the patches in each elementary cell of the reflectarray