Evolution of electromagnetic field in resonator with nonlinear paramagnetic filling

The problem deals with the evolution of the electromagnetic field inside resonator with the paramagnetic filling is considered. The complex magnetic susceptibility obtained from the Bloch equations has been presented in a form of power series intensity of the electromagnetic field. The solution of evolution equations describing the time dependence of the electromagnetic field inside the resonator under the conditions of harmonical excitation is obtained.     

Eigen Q-factor of electromagnetic oscillations of E-type in waveguide junction of plane waveguides with anisotropic dielectric

The electrodynamic and numerical analysis of eigen Q-factor of electromagnetic modes of E-type in waveguide junction of plain waveguides, fulfilled with anisotropic dielectric in depending on a permittivity tensor components and dielectric loss have been carried out in the paper. The recommendations on using of waveguide junctions for measurement of dielectric losses of the materials are given.     

Hybrid surface magnetoplasma oscillations in the layered semiconductor-dielectric resonator

Theoretical and numerical studies of the electromagnetic properties of the layered semiconductor-dielectric structure in the external constant magnetic field is carried out. It is shown that due to removal of frequency degeneration the intertype coupling arises and as the result two new surface oscillations with near resonance frequencies arrear, their fields are orthogonal and modulated along interface semiconductor — dielectric of the orthogonal envelopes.     

Approximate 3D model of electromagnetic modes in waveguide cross-shaped junctions with dielectric filling

Athree-dimensional electrodynamic model of hybrid electromagnetic modes in a waveguide junction of cylindrical and rectangular waveguides with dielectric filling of a cylindrical waveguide is proposed in this study. To solve the vector problem, the mode matching technique (MMT) is applied with the separation of the common waveguide junction region and the representation of the field in this region in the form of superposition of the fields of the partial eigenwaves of waveguides. Classification of eigenmodes is carried out: intrinsic resonances of junction based on transcendental modes and resonances of a waveguide-dielectric type. The investigated structure can be used for measuring the electrical parameters of dielectric samples of both cylindrical and rectangular cross-section shape. Since the spectral characteristics of the junction are determined mainly by the size of the central coupling region of the waveguides and the electrical parameters of the dielectric in the junction, the measurements are of a local nature.     

椭圆波导中的本征模

在椭圆波导的应用中,场量和场图是非常有用的。本文采用将马丢函数展成傅里叶级数的方法,讨论了椭圆波导中的场分布,给出了偏心率E＝0．75时前100个模的场图。这些具有完整电磁力线的场图是严格的和标准的,力线的疏密程度正比于该处的场强。     

Dual electric and magnetic frequency tuning of coupled oscillations in a composite magnetodielectric resonator

The possibility of dual magnetic and electric tuning of resonance frequencies of the electrodynamic structure consisting of dielectric resonator and the epitaxial film of Yittrium-Iron Garnet (YIG)- lead zirconate titanate (LZT) heterostructure has been shown. The coupled electromagnetic-andspin oscillations of dielectric resonator and epitaxial YIG film were theoretically and experimentally investigated. The experiments revealed the possibility of implementing the electric frequency tuning of coupled oscillations of a composite magnetodielectric resonator. This possibility is determined by induced elastic stresses in the epitaxial YIG film. A theoretical model is proposed for calculating the frequency shift of coupled oscillations caused by the electric field applied to the piezodielectric layer. It is shown that the basic Q-factor of composite resonator and the range of electric frequency tuning of hybrid oscillations increase with the reduction of the magnetic bias field.     

The theory of propagation of electromagnetic waves in a waveguide with a magnetoactive anisotropic modulated filling

Propagation of electromagnetic waves in a waveguide with an arbitrary cross section is considered. The waveguide is filled with a magnetoactive anisotropic medium periodically modulated in space and time. The wave equations for the potentials of transverse electric (TE) and transverse magnetic (TM) fields are derived. Expressions for the TE and TM waveguide fields observed in the region of weak interaction between the signal wave and the modulation wave are found in the first approximation for small modulation indexes of the filling. The frequency near which strong (resonance) interaction between the signal wave and the modulation wave develops is expressed in an analytic form. The propagation of TE and TM waves in the strong-interaction region is investigated.     

Polarization oscillations in coupled quantum wells-a scheme forgeneration of submillimeter electromagnetic waves

It is shown that, in a specially designed coupled quantum-well (QW) system, it is possible to prepare an initial nonstationary electronic state selectively by interband photoexcitation in one of the wells. Excited electrons oscillate between the two wells, giving rise to an oscillating electric dipole moment. In a stacked system of identical QW pairs, these dipoles add up, producing a tangible alternating voltage which can be used to modulate the incident radiation intensity. Therefore, with a properly designed positive feedback loop connecting the coupled QW system and the light modulator, it is possible to generate self-excitation of dipolar oscillations. This provides a new method of generating submillimeter electromagnetic waves, accompanied by ultrashort optical pulses at terahertz frequencies     

Generation of high-frequency electromagnetic and acoustic oscillations in a semiconductor in low-frequency electric field

The effect of generation of high-frequency electromagnetic and acoustic oscillations is theoretically predicted and experimentally found in a piezoelectric semiconductor in an alternating electric field with the frequency corresponding to the `synchronism? conditions (i.e. when the period of the field is equal to the double transit time of a sound through the specimen).     

An analytical model for generation of the second harmonic in a nonlinear resonator based on an electromagnetic crystal

An electromagnetic crystal formed by an infinite along one coordinate lattice of metal cylinders placed inside a planar waveguide is considered. A resonator formed by introduced defects in the form of lumped nonlinear capacitors connected into the metal cylinders in internal infinite rows of the of the electro-magnetic crystal is studied. The effect of generation of the second harmonic in such a resonator excited by the fundamental mode of the planar waveguide is analyzed. An approximate analytical model of the structure, which is based on expansion of vectors of capacitor voltages in terms of eigenvectors of the matrix of mutual admittances, is proposed. The zero-order approximation to an analytical solution of the problem is obtained and then refined in the first-order approximation. Numerical results obtained with the help of the proposed model are discussed.     

Diffraction of a plane electromagnetic wave by a two-layer finite array of small bodies of revolution

A three-dimensional vector problem of plane-wave diffraction by a two-layer finite array of perfectly conducting bodies of revolution is considered. The problem is solved under the assumption that the sizes of the elements of the array are small as compared to the wavelength. The approach proposed was tested by comparing the far-field patterns of an array with a small number of elements, calculated by two different methods. Angular dependences of the far-field patterns of arrays of elements in the form of spheres, oblate spheroids, and superellipsoids of revolution are constructed. Dependences of the plane-wave reflection and transmission coefficients on the angle of incidence for single-row finite and infinite arrays are presented.     

THE MEASUREMENT OF COMPLEX PERMITTIVITY OF ANISOTROPIC DIELECTRICS BY MEANS OF AN ELECTROMAGNETIC OPEN RESONATOR

By applying the perturbation method and the complex-source-point theory, the theoretical research of measurement of complex permittivity of uniaxial anisotropic materials by means of an electromagnetic open resonator has been made, and the double refraction phenomenon due to anisotropy of measured dielectric materials has been quantitatively analyzed. Finally, measurements have been made on some single-crystal quartz specimens using an automated open resonator measurement system at 8mm band.     

Chaos in pulse-excited resonator with self feedback

A novel nonautonomous chaotic oscillator based on an active series LC resonator is reported. Excitation is provided by a bipolar pulse-train voltage-source and self feedback via a comparator is employed. The high-dimensional nature of the oscillator is clarified.     

Dielectric resonator filters with wide stopbands

Dielectric resonators used in filter networks present a model spectrum with undesired, or spurious, resonances in close proximity to the desired one. Through the use of evanescent mode bandpass irises tuned to the filter center frequency, the resonator spurious modes are suppressed, resulting in N-section filters with stopbands clean to at least (N-1) times the individual iris stopband levels. The problem of achieving a wide stopband is reduced to the problems of realizing the resonating capacitance required in an evanescent bandpass filter and computing the junction susceptance occurring at the interface between a larger evanescent section (the resonator enclosure) and the smaller iris opening. The technique results in high-Q resonator filters with stopbands clean to at least -55 dBc, out to at least 1.7 times the filter center frequency     

Tunable dielectric resonator with ferroelectric element

A method for electrical tuning of a dielectric resonator using a Ba_xSr_(1-x)TiO₃ thick film grown on a metal substrate is described. The results show that by incorporating a ferroelectric element, fast resonant frequency tuning of a dielectric resonator, while maintaining a useful Q-factor, is possible     

Micromechanical resonator with ultra-high quality factor

A 6.3 MHz Lame-mode square resonator with fully differential drive and sense electronics, exhibiting quality factor (Q) values over 1 million in ambient pressures as high as 200 Pa is reported. A maximum Q value of 1.6 million was experimentally measured for the resonator designed for this study. It was also experimentally observed that the Q value for the designed bulk mode resonator was relatively independent for pressures below 200 Pa, suggesting that the Q is pressure limited for pressure higher than 200 Pa.     

Generation of high-frequency oscillations by electromagnetic shock wave on transmission lines on the basis of multilayer heterostructures

The possibility of the direct effective transformation of a videopulse into a radiopulse with high filling frequency (of the order of 100÷300 GHz) because of evolution of an electromagnetic shock wave structure on dispersive transmission lines with nonlinear components on the basis of multilayer heterostuctures (MLHS) with hysteretic (asymmetric MLHS) and single-valued functional (symmetric MLHS) capacitance — voltage characteristics has been investigated. The requirements on the MLHS and dispersion characteristics for effective generation of the train of oscillations are discussed.     

遗传算法在矩阵特征值求解中的应用

遗传算法进行全空间并行搜索,并将搜索重点集中于性能高的部分,从而使效率提高且不易陷入局部极小。具有固有的并行性,通过对种群的遗传处理可处理大量的模式,并且容易并行实现。重点研究遗传算法以及混合遗传算法在传统数学中的应用:解决矩阵特征值问题。通过大量的实验研究,证明遗传算法在传统数学的研究问题中有很高的应用价值。     

Bias of a resonator fiber optic gyro composed of apolarization-maintaining fiber ring resonator with the photoinducedbirefringent grating

A theoretical study of the polarization-fluctuation induced bias of an resonator fiber optic gyro (R-FOG), which employs a polarization-maintaining fiber ring resonator with a photoinduced birefringent grating, is presented. The polarization conversion due to the photoinduced birefringent grating can stabilize the resonator output, which result in the reduction of the bias in the R-FOG output. The influences of the parameters, such as the fluctuation of the input polarization, the resonator finesse, and the photoinduced index change of the dielectric tensor, on the bias in the gyro-output have been investigated. Our results show that with the help of a photoinduced birefringent grating the bias in the gyro-output can be limited around 10^-7 rad/s (0.02 deg/hr), a typical specification for the aircraft-navigation