Coupling between waveguide and hemispherical open resonator

The paper analyzes the summation of the powers of two sources in a hemispherical open resonator (OR) during its tuning. The first higher axially asymmetric TEM10q oscillation mode is excited in the resonator. A circuit with an E- tee waveguide is proposed, which makes it possible to research the summation of the powers using a Gunn diode. Studies of the conducting part of the millimeter range have been undertaken. It is shown that the coefficient of powers summation of two sources in the OR using slot coupling elements does not exceed 72%. The use of one H- polarized diffraction grating, which is in the resonator, does not lead to a significant increase in the summation coefficient when moving it. This is due to the excitation of the first type of TEM10q oscillations in the resonator.

The efficiency of excitation of the axial-asymmetric vibration TEM10q in a quasioptical open resonator of the power combiner (ORSM) by means of the TE20 waveguide wave is investigated. Based on the theory of mirror antennas, the efficiency of excitation of TEM10q oscillations in a hemispherical resonator using a rectangular waveguide with a cross-section in which the TE20 wave propagates is estimated. Based on the calculations, it was concluded that about 87% of the power supplied to the resonator via the waveguide is used to excite the oscillation under consideration. Therefore, such a resonant system should have good selective properties. Additional studies were conducted to confirm this. It was established that with coordinated excitation of oscillations in the VRSP, the latter has angular and frequency spectrum selection. With the correct selection of the transverse dimensions of a rectangular waveguide with a TE20 wave, located in the center of a VRSP flat mirror, the latter will have a single-frequency response in a wide frequency band and a high power stacking factor in the terahertz range can be provided. When placing the sources in each of the two rectangular waveguides that pass into the emitters of the above dimensions, we will get a power adder based on a hemispherical VRSP. An electrodynamic system of two rectangular waveguides of certain cross-sectional dimensions is proposed and investigated, which allows adjusting the amount of coupling between the sources and the resonator. For this purpose, an E-polarized wire diffraction grating is located on the VRSP flat mirror, changing the period of which regulates the connection of the resonator with the sources. It was found that by choosing the parameters of one-dimensional diffraction gratings (E-polarization) in the openings of the communication elements, it is possible to ensure any predetermined connection of individual sources with a resonant volume. Experimental studies of VRSP at a frequency of 130 GHz were carried out. The measured power at its output was within (10...13 dBm), which corresponds to the efficiency of power assembly k=0.76. The results of the conducted research allow us to draw a conclusion about the prospects of using the developed VRSP in highly stable generators of the terahertz range.

Modal analysis and reactive power reserve method are applied in the Entergy electrical system to find the buses and zones prone to voltage instability. In the modal analysis method, weak zones are identified by monitoring the participation factor of the buses in the critical modes. In the reactive power reserve method, reactive power reserves of the zones are monitored for single line outages, generator outages, and double line outages and the zones that have exhausted their reactive power reserves are identified as critical. The critical contingencies resulting in the smallest stability margins are also computed, and are ranked in the order of severity. The voltage stability assessment tool (VSAT) developed by Powertech Labs, is used to determine the weak zones and to determine the critical contingencies.

The method of excitement of the open resonator by the narrow slot on a reflector formed by the waveguide with the highest modes transmitted was experimentally approved. The spectra of such resonator in the range of the frequencies of 85 GHz–110 GHz were received. It is shown that modes with azimuthal variations of the field were most effectively exited. Transformations of spectra by thin dielectric cylinders were researched. A number of parameters of the open resonator, effective in schemes of resonator diagnostics of filamentary objects with small own losses were found.

Voltage stability is an important factor, which needs to be taken into consideration in order to avoid voltage collapse. There are different methods used to study the voltage collapse phenomenon. In this paper, V-Q Sensitivity and Modal analyses methods are implemented on IEEE 14 bus system. Modal analysis method makes use the Jacobian matrix to determine the eigenvalues necessary to evaluate the voltage stability and V-Q Sensitivity method makes use of the diagonal elements of the inverse of reduced Jacobian matrix to a assess this stability. In this paper, our main objective is to apply V-Q Sensitivity and Modal analysis methods by analyzing the effect of neglecting the weak coupling between reactive power Q and voltage angle δ A comparison in terms of the weakest buses is made between the results obtained by taking into account the weak coupling between Q and δ, i.e., by considering the reduced Jacobian matrix and those obtained by neglecting this coupling.

A high-Q hemispherical open resonator is connected to an automatic network analyzer to enable precise and fast determination of the permittivity and loss tangent of low-loss dielectric materials at 100 GHz. Both scalar theory and vector theory with a frequency variation method are used to determine the dielectric properties of low-loss materials which are used in quasioptical components, for example in fusion reactor windows and tenses for millimeter-wave receivers. The uncertainty of the measurement is 0.02% to 0.04% for /spl epsi//sub r/(/spl epsiv//sub r//spl ges/2) and 6-40/spl times/10/sup -6/ for tan /spl delta/(10/sup -4//spl les/tan /spl delta//spl les/10/sup -3/).

A high Q-hemispherical open resonator with W-band vector network analyzer enables a precise and fast determination of the permittivity and loss tangent of low-loss dielectrics near 100GHz. The implemented frequency variation method showed standard deviation in dielectric measurements less than 0.06.

Rectangular waveguide slot arrays are commonly used in several microwave antenna systems. The slots are most often located in the broad wall of the rectangular waveguide, arranged longitudinally parallel with the waveguide axis, because this provides good control of the excitation of each slot over a large dynamic range by adjusting the offset of the slot from the center line of the waveguide. However, longitudinal slots can only radiate electrical fields that are transversely polarized with respect to the waveguide axis. If longitudinal (or dual) polarization is required, the slots (or half of them) must be located transverse to the waveguide axis. Transverse resonant slots in the broad wall are too strongly excited for use in large arrays, so transverse narrow slots in the narrow wall are preferred. In the latter case the slots are not excited unless they are tilted or coupled to tilted parasitic elements like wires or posts inside the waveguide. The purpose of the present paper is to analyse an untilted narrow wall slot excited by two tilted wires. An improved and extended analysis in which the slot extensions into the neighboring two broad walls are included, is described. The virtual cylinder method is applied to the calculation of the external admittances of the slot using wedge dyadic Green's functions and entire-domain basis functions in order to get good convergence of the integrals of the spectral domain formulations.

A hole in a common wall is used to provide coupling between two resonant cavities (k=coefficient of coupling) or between two waveguides (x or b=normalized reactance or susceptance) or between cavity and waveguide (p=loading power factor of cavity). Referring to either side of a thin common wall, the field intensity in the center of a small hole is 1/2 what it would have been at that location on the wall. Between two equal regions, the coupling (k, x or b) by magnetic or electric field is expressed as 1/4 the ratio of the effective volume of the hole over the effective volume of each region, by duality (Booker's principle), the effective volume (related to the polarizability) of an aperture in a thin wall is identified with that of an analogous thin body in a uniform field. For a resonant cavity loaded by coupling to a waveguide, the loading power factor is p=kx; this theorem is proved by reference to an equivalent network. Various cases of coupling by two-dimensional and three-dimensional fields are formulated in terms of area or volume ratios, especially between pillbox resonators (rectangular, circular, or coaxial-circular) and between rectangular waveguides with common side walls or top and bottom walls. The effective area or volume of a small hole in a thin conducting wall is given for various symmetrical shapes, in a magnetic or electric field.

A steady state analysis is applied to study the voltage collapse problem. The modal analysis method is used to investigate the stability of the power system. Q-V curves are used to confirm the obtained results by modal analysis method and to predict the stability margin or distance to voltage collapse based on reactive power load demand. The load characteristics are considered in this research. Different voltage dependent loads are proposed in order to be used instead of the constant load model. The effect of induction machine load is considered in this study. The load is connected to several selected buses.;The analysis is performed for three well-known system; Western System Coordinating Council (WSCC) 3-Machines 9-Bus system, IEEE 14 Bus system and IEEE 30 Bus system. The modal analysis technique is performed for all systems using the constant load model, the voltage dependent load models and induction machine load model. Then, the most critical mode is identified for each system. After that, the weakest buses, which contribute the most to the critical mode, are identified using the participation factor. The Q-V curves are generated at specific buses in order to check the results obtained by the modal analysis technique and to estimate the stability margin or distance to voltage collapse at those buses.

Modal analysis of the influence of freestream on global rotor noise

The open dielectric or gyromagnetic post resonator on the axis of a radial waveguides or at the junction of three rectangular waveguides, is a standard problem region in microwave engineering. The paper introduces a new exact formulation of the passband frequencies of such a symmetrical three-port junction. It is based on recognising that such passbands coincide with the condition for which the impedance of a symmetric mode of the post numerically coincides with the admittance of certain pairs of degenerate modes. This condition is used to determine the frequencies of the first two passbands of the junction in the vicinities of the TM/sub 110//sup m/ and TM/sub 210//sup m/ degenerate pairs of modes. The dominant symmetric TM/sub 010//sup e/ mode is instrumental in defining each of these passbands. The calculations undertaken here are compatible with existing full wave analysis of the geometry under consideration, finite element calculations and measurements.

The absorption efficiency for circular or offset double-clad optical fibers is investigated with modal analysis method. First, calculate the number of all the propagating modes approximately using WKB method and derive the analytic formulas for calculating the number of propagating modes that can't be absorbed by active core. Then the absorption efficiency can be obtained analytically. Comparison of modal method with the ray optics method is made and the condition of using both methods is also discussed.

Slots in rectangular waveguides are often used at elements in linear array antennas. The polarisation of the radiated energy is usually linear. Circular polarisation can be obtained with compound slots in the broad wall. Experiments have shown that circular polarisation can be obtained from certain I-shaped slots in the narrow wall.

Based on the mutual coupling coefficient between two identical structure parallel rectangular waveguides and the scalar integral method for analyzing the mutual coupling factor between two nonparallel waveguides, the coupling characteristic between two nonparallel straight rectangular single mode waveguides is discussed, and a computing instance is introduced for showing the crosstalk characteristic between two nonparallel output rectangular waveguides in the Y branch optical switch. These works provide some theoretical support for ascertaining the fundamental parameters of a Y branch MQW waveguides optical switches.