Radiation Loss from Open-Circuited Dielectric Resonators (Short Papers)

The Q factor of an open-circuited resonator is influenced by dielectric, conductor, and radiation losses. This short paper discusses these losses and shows that insight into the radiation loss can be obtained by an extension to the analysis given by Lewirt. This shows that the radiation loss is a maximum for the dominant mode and that provided the permittivity is not less than 9.0 the radiation losses are at a minimum for the second mode. It is suggested that these results may be applied to the design of filters based on dielectric resonators. The application of the results to stripline resonators in which the dielectric extends past the termination of the upper conducting strip is more difficult, and it is suggested that experimental work is required to investigate postulated improvements. Finally, some of the radiation patterns of the open-circuited dielectric resonators, obtained in this paper, show interesting directional properties which may be applied to the design of antenna systems.     

Conduction and Radiation Losses in Microstrip (Short Papers)

Losses in microstrip on fused-silica and alumina substrates have been experimentally evaluated for various values of stripwidth. Radiation losses in circuits, commonly used for measuring losses in microstrips, depend on the dimensions of the circuit and affect the total losses considerably. Radiation and conduction losses of open-ended line resonators have been separately determined. These measurements have also drawn attention to discrepancies between published theories and our experiments. The effect of surface roughness upon conduction losses has been measured.     

Comparison Method of Measurement Q of Microwave Resonators (Short Papers)

A method for the measurement of the quality factor of microwave resonators is given. It is based on the comparison of the transmitted power of the measured resonator with that of a reference resonator. The characteristics obtained by simultaneous display of the transmitted powers of the two resonators in Cartesian coordinates are analyzed. The relationship between the shape of the resulting curve and the parameters of the reference and measured resonators is discussed. The principal scheme of the X-band measuring microwave set and the measurement procedure are described. Some verification of the measurement results are presented. The method described is especially convenient for measuring small relative changes in the quality factor. It can be utilized for measuring the microwave loss tangent of materials by perturbation resonator methods.     

Loss Considerations for Microstrip Resonators (Short Papers)

The influence of radiation losses on the Q of microstrip resonators is shown for a variety of frequencies, characteristic impedances, substrate materials, and thicknesses. Radiation becomes a dominant factor at higher frequencies, especially for low-impedance lines and thick substrates with a low dielectric constant.     

Computations of Frequencies and Intrinsic Q Factors of TE/sub 0nm/ Modes of Dielectric Resonators (Short Papers)

The Rayleigh-Ritz method is described, which is used to calculate the resonant frequencies and intrinsic Q factors due to dielectric losses of quasi TE/sub onm/ modes of dielectric resonators. Electromagnetic fields of an auxiliary post dielectric resonator are taken as an electrodynamics basis for approximate solutions of this problem. The method provides upper bounds for true resonant frequencies. Numerical results are compared with previously published complementary calculations. The influence of a dielectic substrate on resonant frequencies and intrinsic Q values is demonstrated.     

End Effects of Half-Wave Stripline Resonators (Short Papers)

The end effects of an open-circuited TEM transmission line make the line electrically longer than its physical length. In this short paper a half-wave resonator of a balanced strip transmission line has been analyzed and the required foreshortening of the line to achieve a prescribed resonance frequency has been calculated. Also the decrease in the characteristic impedance of the stripline caused by the end effects has been determined. The theory is in reasonably good agreement with measurements performed, especially for narrow stripline resonators.     

Mode Chart for Microstrip Ring Resonators (Short Papers)

A universal mode chart for the microstrip ring resonator, based on a radial waveguide model, is presented. The resonant frequency is related to the width of the ring conductor. Experimental results from 4 to 16 GHz are shown to be in good agreement with the theory.     

Simdified 12-GHz Low-Noise Converter with Mounted Planar Circuit in Waveguide (Short Papers)

A 12-GHz low-noise converter consisting of a planar circuit mounted in waveguide is described. This circuit consists of a metal sheet with proper patterns that is inserted in the middle of a waveguide parallel to the E plane. All circuit elements required for the converter are pressed or etched. This circuit is very useful for low-cost mass production and good performance. A measured noise figure of 4.5 dB was obtained with a 12-GHz signal frequency and a 420-MHz intermediate frequency.     

On the Theory of Coupling Between Finite Dielectric Resonators (Short Papers)

The coupling coefficients between open dielectric resonators in three useful dielectric-filter configurations, calculated from an electric rather than from a magnetic excitation of the fields, are given. The limitations of the latter method are pointed out and experimental results are given which supports the first method and shows that the differences cannot always be neglected.     

Q Degradation in Varactor-Tuned Oscillators (Short Papers)

A general analysis of varactor-tuned negative-resistance oscillators is presented to show the varactor loading effect on the oscillator Q. The external Q of the varactor loaded circuit normalized with respect to the unperturbed external Q is plotted as a function of the tuning range for several values of the varactor Q and the capacitance ratio.     

Equivalent Circuit of Reentrant Cavity (Short Papers)

In order to develop a design formula for a reentrant cavity, as it changes from the very flat to very long form, the admittance of the cavity at the gap is derived. For the resonant frequency of an air-filled cavity, the theoretical value by the formula derived here agrees well with the experimental value.     

Ridged Waveguide for Planar Microwave Circuits (Short Papers)

A TE-mode planar transmission line is analyzed. It has a cross section as a ridged waveguide where the ridges are very thin. It is easily fabricated by photoetching of copper-clad dielectric boards, but can also be made without dielectrics for low-loss applications. Thus, it can be integrated together with other planar transmission lines like, for example, striplines. Besides the simplicity in feeding by stripline, the guide can be made smaller than an ordinary rectangular waveguide. It has applications in filters, resonators, balun-transitions, antenna feeds, etc. The characteristic impedance of the transmission line and its free-space cutoff wavelength are calculated and given in a diagram.     

New Method for Computing the Resonant Frequencies of Dielectric Resonators (Short Papers)

A new method is develop for accurately predicting resonant frequencies of dielectric resonators used in microwave circuits. By introducing an appropriate approximation in the field distribution outside the resonator an analytical formulation becomes possible. Two coupled eigenvalue equations thus derived are subsequently solved by a numerical method. The accuracy of the results computed by the present method is demonstrated by comparison with previously published data.     

Dielectric Losses in an H-Plane-Loaded Rectangular Waveguide (Short Papers)

The attenuation constant due to dielectric losses in a rectangular waveguide loaded with a dielectric slab in the H-plane is calculated. Results for the dominant LSM/sub 11/ mode are presented graphically.     

The Electric-Dipole Resonances of Ring Resonators of Very High Permittivity (Short Papers)

The lowest confined mode in a coaxial ring resonator is investigated. Data are given about the Q of the mode, the eigenelectric dipole at resonance, and the structure of the electric field surrounding the resonator. The data are valid for high, but finite values of epsilon/sub r/.     

Planar Circuit Analysis of Microstrip Radial Stub (Short Paper)

Radial-line stubs have been found to work better than low-impedance rectangular stubs when an accurate localization of a zero-point impedance is needed. In this paper, microstrip radial-line stubs are analyzed using a planar circuit technique and characterized for design purposes. Experiments performed on various structures are in excellent agreement with the theory and confirm the suitability of such a structure as an altenative to a conventional straight stub.     

A Design Method of Bandpass Filters Using Dielectric-Filled Coaxial Resonators (Short Papers)

Design formulas for capacitively coupled bandpass filters using dielectric-filled coaxial resonators are derived and experimentally verified. The most important advantage of this filter is its ability to provide wide stopband characteristics for harmonics suppression. Its features can be obtained from the configuration using both quarter-wavelength uniform impedance resonators (UIR's) and stepped impedance resonators (SIR's).     

Behavioral Suppression by 383-MHz Radiation (Short Papers)

The heads of two rhesus monkeys were irradiated in a 383-MHz resonant cavity immediately before and during performance of a four-choice forced-choice serial reaction task. CW radiation at integral dose rates of 0.001 -17.5 W were delivered to the head. No effects were observed below a critical dose level (/spl ap/23 W/kg) derived from integral dose rate and body mass. Above this level, behavioral suppression occurred, i.e., correct response rate was profoundly altered. The effect was completely reversible and repeatable in one of the subjects---the other subject did not recover completely and was sacrificed for histological examination which revealed no gross or microscopic damage. The nature of the effect suggests a neurochemical rather than an electrical or mechanical basis for the results.