Hybrid electromagnetic-spin oscillations in the ferrite-dielectric structure with single-crystal hexaferrite in domain region

Hybrid electromagnetic-spin oscillations in ferrite-dielectric structure consisting of a single-crystal BaFe₁₂O₁₉ platelet and a dielectric disk-shaped resonator in multidomain state of ferrite have been investigated by experiment. Experiments were conducted with different types of domain structures, and the frequency-field spectra were measured at tangent magnetization. It was shown that the effective hybridization of electromagnetic and magnetostatic modes in such resonator could implement such excitation regime, where one electromagnetic mode of dielectric resonator is split into three hybrid quasi-electromagnetic oscillations even in the absence of external magnetizing fields.     

Ferromagnetic tridisk-coupled resonator and magnetically tunablestripline Y circulator

A ferromagnetic tri-disk-coupled (TDC) resonator is constructed by placing three YIG ferrite disks mutually attached on the circular center conductor. The EM fields in one of the disks is described in terms of expanded circular harmonics with an approximated transformation of derivative, and the EM fields in a TDC resonator is synthesized from the respective constituent fields of the disks, by sum-transformation, regarding three eigenjunctures of the TEC resonator. The synthesized fields include coefficients A, B, and D, which are described as functions of the radis ratio r₀ /r and azimuthal angle φ. The special case in which A=D=0 is treated. Two conditional equations of perfect Y circulation are calculated. Magnetically tunable operation is theoretically analyzed using the conditional curves, and the magnetically tunable operation is examined experimentally with theoretical analysis     

Increased dielectric quality factor in planar resonators byselective dielectric removal

A means for increasing the effective dielectric quality factor by selective removal of dielectric from a microstrip resonator is discussed. Methods for determining the impedance and effective dielectric constant are included. The reduction in loss compared with an equivalent microstrip resonator is presented     

A New Type of Isolator for Millimeter-Wave Integrated Circuits Using a Nonreciprocal Traveling-Wave Resonator

A nonreciprocal traveling-wave resonator critically coupled to a waveguide becomes an isolator with high isolation. The dielectric image-line isolator with a magnetized ferrite pillbox as the nonreciprocal traveling-wave resonator is described. The validity of the theory is verified by experiments earned out at the 50-GHz range. The theoretical and experimental estimations of the coupling coefficient between a pillbox resonator and a straight dielectric waveguide are also included.     

Resonant frequency and quality factors of a silver-coatedλ/4 dielectric waveguide resonator

In this paper, resonant frequency, radiation loss, conductor loss, and dielectric loss of a silver-coated λ/4 dielectric waveguide resonator are investigated. Leakage of the electromagnetic field from the open-end face of the resonator is the only source of radiation, which also affects the resonant frequency. New theoretical expressions are devised to calculate resonant frequency, conductor quality (Q) factor, dielectric Q factor, and radiation Q factor. Effective conductivity of the silver-coated resonator is estimated from experimental unloaded Q factor. The theoretical analysis is validated by the experimental result and the data obtained using the finite-difference time-domain (FDTD) technique. Finally, we have designed and fabricated a dual-mode bandpass filter using this resonator     

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.     

EMI antenna calibration on an absorber-lined ground plane to determine free-space antenna factor

Theoretical and experimental investigations are carried out on the establishment of a quasi-free-space environment for electromagnetic interference antenna calibration using ferrite-tile absorbers at the test site. Numerical techniques are developed to evaluate the accuracy of the free-space antenna factor obtained on the absorbers when the ferrite-tile material constants are known. In addition, the antenna impedance measurement on a tuned dipole antenna is proposed for evaluating the calibration error caused by the unwanted ground reflection. Experiments confirm the validity of the numerical techniques and demonstrate that commercially available ferrite tiles can drastically reduce ground reflection even in a lower very-high-frequency (VHF) range. It is concluded that the standard antenna method can yield free-space values of the antenna factor for the entire VHF region with an error of less than 0.3 dB, if ferrite tiles are placed on a metal ground plane greater than 8.7/spl times/8.7 m/sup 2/ and if the antenna under calibration is positioned at a height of about 3 m.     

Dielectric resonator with discrete electromechanical frequency tuning

A novel approach for discrete frequency tuning of dielectric resonators based on electromechanical actuators such as the microelectromechanical system is presented. The concept is based on the intermodal coupling between the TE/sub 01/spl delta// mode of a cylindrical dielectric resonator and the radially arranged planar slotline resonators. The resonance frequency of the dielectric resonator is changed by switching a resistive load at the open end of each quarter-wave slotline resonator leading to a variation of the coupling between the slotline resonator mode and the TE/sub 01/spl delta// mode of the dielectric resonator. As a consequence, the resonance frequency of the TE/sub 01/spl delta// mode changes. Based on this novel tuning concept, discrete tuning by 5 MHz in 0.25-MHz frequency steps was demonstrated for a test resonator at 2 GHz. The unloaded quality factor is about 12000 and the measured switching time is about 1 ms.     

Measurement of Low-Loss Dielectric Materials Using Dielectric Rod Resonator

To obtain the complex permittivity of low-loss dielectric materials at 60 GHz, a measurement method is developed. Using a dielectric rod resonator excited by a dielectric waveguide, effective conductivity of conducting plates for short circuiting the resonator is determined. The complex permittivity of the dielectric rod is determined by the resonant frequency and unloaded quality factor of the TE_0m1-mode resonator. Moreover, the complex permittivity of single crystal sapphire, polycrystalline ceramics, and cordierite has been investigated in virtue of numerical simulation. For all the measured specimens in this study, the proposed method is seen to provide much better accuracy for values.     

A new method developed in measuring the dielectric constants of metallic nanoparticles by a microwave double-cavity dielectric resonator

A microwave double dielectric resonator is implemented to measure the dielectric constants of nano-metallic powders. The metallic nanoparticles prepared by vacuum evaporation in inert gas are collected and mixed with alumina powder to fill the inner hole of a sapphire disc by which the resonant frequency and Q factor are measured at the TE/sub 011/ mode to derive the complex dielectric constant.     

Approximate Determination of the Characteristic Impedance of the Coaxial System Consisting of an Irregular Outer Conductor and a Circular Inner Conductor

An elementary formula is presented for the determination of the characteristic impedance of a coaxial transmission line consisting of a circular inner conductor and an irregular outer conductor. In this approach, the irregular outer conductor is replaced by an eccentric circular enter conductor which has the same "shield factor" as an irregular one at the extreme of a small wire, and the same formnla is adapted for outer conductors of different shapes by determining values of eccentricity of the equivalent eccentric coaxial lines. The validity of the formula is confirmed by numerical results.     

Submillimeter-wave dielectric measurements using an open-resonator

The open resonator method for dielectric measurements is developed in the submillimeter-wave region. This method, different from usual laser methods is based on the sweeping of resonator length. The conventional theory developed in the millimeter-wave region is improved so as to make measurements possible with resonable precision even in this frequency region and the design criterion of an optimum resonator at around 890 GHz (λ₀=337μm) is presented. Finally, the measurements are performed for several kinds of low loss material and it is confirmed that the present method becomes a useful one in the submillimeter-wave region.     

Approximate approach to the design of shielded dielectric diskresonators with whispering-gallery modes

An analytical method is presented for calculating the resonant frequency and the Q-factor of shielded dielectric disk resonators excited in whispering-gallery modes. The method is based on a single-mode representation of electromagnetic fields in partial regions of the resonator. For high order modes with high degree of energy concentration in the dielectric this method gives a good agreement with experimental results obtained for different sapphire disks at both room temperature and cryogenic temperatures     

Spinwave Linewidth Measurements with Low-Power RF Sources (Correspondence)

This correspondence describes a perturbation technique for obtaining the spinwave linewidth of polycrystalline garnet spheres with large values of /spl Delta/H/sub k/. Conventions waveguide cavity techniques require power levels in the kilowatt region to excite the parallel-pump instability. By using a dielectric resonator, large RF magnetic field intensities can be generated using relatively low-power levels, and the presently available low-loss dielectric materials enable high Q-values to be attained in the resonator. Since the sensitivity of cavity perturbation techniques depend on high Q-values, the ferrite sphere can be made small enough so that perturbation assumptions apply. Results are presented for some representative polycrystalline samples. The largest spinwave linewidth measurement required a RF magnetic field intensity of approximately 27.0 Oe.     

Spectral Domain Analysis of an Elliptic Microstrip Ring Resonator (Short Paper)

The quasi-static capacitance of an elliptic microstrip ring resonator is evaluated with the spectral domain technique. The effect of fringing of fields associated with the structure is determined using this capacitance value in terms of the effective eccentricities of the inner and outer ellipses, the effective values of the ratio of the semimajor and semiminor axes, and the effective dielectric constant. The resonant frequency of the even TM /sub c110/ mode, calculated utilizing them, is in good agreement with the experiment. Mode charts for the dominant and higher order even and odd TM/sub cm10/ resonance modes are also presented.     

Tunable Dielectric Resonator Bandpass Filter With Embedded MEMS Tuning Elements

This paper presents a novel approach for constructing a tunable dielectric resonator bandpass filter by using the microelectromechanical system (MEMS) technology. The tunability is achieved by unique MEMS tuning elements to perturb the electrical and magnetic fields surrounding the dielectric resonators. The use of such elements as a tuning mechanism results in a wide tuning range at a relatively low tuning voltage and fast tuning speed. A three-pole tunable dielectric resonator bandpass filter is designed, fabricated, and tested. The experimental filter has a center frequency of 15.6 GHz, a 1% relative bandwidth, and an unloaded Q of 1300. A tuning range of 400 MHz is obtained by using MEMS tuning elements with 2 mmtimes2 mm tuning disks. The measured results demonstrate the feasibility of the proposed concept     

A novel quasi-optical resonator for the surface near-millimeterwaves

The theory and experimental investigations are presented for a new type of quasi-optical near-millimeter-wave prismatic resonator, which provides frequency selective transformation of the plane waves into the surface waves. Theoretical expressions are obtained for the Q-factor and finesse, which consider dielectric loss and the effect of prism finite aperture. The theoretical evaluations are verified by experimental measurements in the frequency range 300-500 GHz using a prismatic resonator made from the optical quality fused silica glass. The increase of intensity of surface waves by a factor of 10-25 is demonstrated for the prismatic resonator made from an extremely low-loss dielectric     

Magnetically tunable microstrip resonator based on polycrystallineferrite

A conventional microstrip ring resonator consisting of a polycrystalline ferrite substrate is demonstrated. This resonator produces improved tunability compared with other available versions. Resonators with tunability approaching 31% at a minimum insertion loss of 11.17 dB in a magnetic field of 3 kG applied longitudinally along wave propagation have been demonstrated using LiZiTi ferrite composition. Tunability of 31% is the best reported for any tunable structure     

2200 MHz圆环形介质谐振器的研制

讨论了TE011谐振模式的圆环形介质谐振器的研制过程。固定ZnO添加量为质量分数1.00%,考察了WO3改性剂对(Zr0.8Sn0.2)TiO4微波陶瓷介电性能的影响。当w(WO3)为0.25%时,可得到εr为38.0、Q值大于5800(7GHz)、τf小于2.0×10–6/℃的瓷料。以该瓷料为原料制作谐振器,研究了制作工艺和支撑物高度对谐振器性能的影响。发现采用冷等静压成型工艺所制谐振器的Q值比采用干压成型工艺提高了4%。获得了谐振频率为2200MHz的高Q值、高功率、高稳定性圆环形介质谐振器,完全满足设计要求。     

The Magnetic-Dipole Resonances of Ring Resonators of Very High Permittivity

The lowest magnetic-dipole mode with symmetry of revolution is investigated in a coaxial ring resonator of height L, inner radius b, and outer radius a. Theoretical data are given about the Q of the mode, the eigen magnetic dipole at resonance, and the structure of the fields (electric and magnetic) inside and outside the resonator. The variables are the dielectric constant epsilon/sub r/ = N/sup 2/ and the dimensionless ratios b/a and L/2a. The data are valid in the limit of very high epsilon/sub r/. Experiments show them to be already useful at epsilon/sub r/ = 35.