Influence of eccentricity on the frequency limitations of circular-pad via-holes

We study the influence of the technologically caused eccentricity of a circular-pad via-hole. We derive an eigenvalue equation using a rigorous method based on a linear transformation of the via-hole polar coordinates. The eigenvalue equation is used to compute the modal resonant frequencies and the modal fields of the eccentric via. It is shown that the via-hole misalignment shifts the modal frequencies and influences its frequency band. The proposed model is verified with published experimental data, and is also compared with results generated with the full-wave simulator Agilent Momentum-2002.     

A parallel-plate waveguide model of lossy microstrip lines

An improved semi-analytical model of a lossy microstrip transmission line is proposed. The model is based on the theory of the fundamental transverse magnetic mode of a lossy parallel-plate waveguide whose dielectric medium is assigned the effective permittivity of the respective lossless microstrip line. The complex propagation constant of the fundamental mode is computed by imposing the Leontovitch boundary condition at the upper and lower plates whose impedances take into account the thickness of the conductors and the current crowding effect. The dielectric loss is computed by perturbation formulas. The proposed model features high accuracy and computational efficiency at frequencies up to 100 GHz.     

Debye relaxation mechanisms of microwave heating of near-critical polar gases

In this work, the average time of slow dielectric relaxation in sub- and supercritical polar gases is considered in terms of a combination of two Debye relaxation mechanisms. Under the assumption of thermal equilibrium, the corresponding relaxation times are theoretically predicted to be proportional to the mean binary collision time and mean translational deceleration time of free molecules with the proportionality factor close to unity. The microwave heating rate for pressurized pure gases and gas mixtures in constant-pressure and constant-density conditions is found from the Poynting formula. Temperature-dependent frequency spectra of the isobaric and isochoric heating rates for sub- and supercritical water are obtained with an allowance for non-Debye high-frequency relaxations. Perceptible temperature effects in the supercritical water heating rates at relaxation frequency are predicted when pressures/densities are high enough and considerable reduction of the heating time for higher pressures/densities is expected.     

Circular-pad via model based on cavity field analysis

An equivalent circuit model of a circular-pad grounding via is proposed based on cavity modal analysis. The modes of the via are derived analytically. Each mode is represented by an equivalent circuit taking into account ohmic losses, as well as losses due to spatial and surface wave radiation. It is shown that the degradation of grounding via characteristics at high frequencies is caused by the multimode effects and radiation. The accuracy of the proposed semi-analytical via model is comparable with that of full-wave analysis up to 75 GHz. It is fast and is easily incorporated in high-frequency circuit simulators.     

Cavity models of planar components grounded by via-holes and their experimental verification

Semianalytical electromagnetic models of grounding via-holes and shorted resonators of different shapes are proposed and experimentally verified. Our models are based on the cavity approach previously used for circular-pad via-holes. For the first time, a model of a square-pad via-hole is developed. By a perturbation approach, an approximate model for slightly rectangular shorted patches is also derived. All our via-hole models are verified experimentally. The influence of the technologically caused eccentricity of the via-hole shape is also modeled and studied by measurements. Additional verification is done by full-wave simulations with Agilent Momentum (2002) and IE3D-10.1. Our models compute the modal resonant frequencies, fields, and equivalent-circuit components of the via-holes. They allow for the study of the frequency limitations of grounding via-holes for high-speed applications, as well as the modes of shorted resonators for printed antennas and filters. The developed models are fast and accurate.