Radiometric sensor for temperature control of food processing

This paper describes a novel planar antenna sensor created for the purpose of noninvasive temperature measurements using microwave radiometry. In order to improve radiometric measurements in industrial applications, a new generation of sensors is introduced, composed of a metallic sheet. Simulations based upon the method of moments is used both to design and to determine their electromagnetic performances. This paper also describes a radiometric device using these sensors to measure and control the temperature of food products during deep freezing processes. The results and discussions are presented.     

Temperature dependence of electron saturation velocity in GaAs

Electron saturation velocity is determined from the space charge resistance R/sub c/ and microwave impedance Z/sub d/ of GaAs IMPATT diodes under linear conditions. Comparison between experimental measurement and theory is used in a large frequency bandwidth (2-18 GHz) at different temperatures (T>     

Approach to modelling of microstrip-microslot applicator

Microstrip-slot applicators are used for biomedical applications, but their modelling is not easy. We present an approach which considers this type of structure on a lossy medium as a succession of microstrip lines with tuning septums of different sizes. Using a classical spectral-domain approach (SDA) model, calculations of the resonant frequency have been performed and compared with experimental measurements for different simple structures of microstrip-slot applicators.     

Experimental determination of propagation parameters of a microstrip line with tuning septums

The letter refers to the experimental determination of the propagation characteristics of a microstrip line with tuning septums. The purpose of this study is to measure with accuracy the (?, ?) diagram for the two fundamental modes of this line using a crossratio technique.     

Time-domain response of MIS coplanar waveguides for MMICs

An MIS coplanar waveguide propagating a slow-wave mode has been characterised in the time domain. The theoretical analysis proposed to obtain the time-domain response of the line gives results in good agreement with measurements. The circuit analysis used is suitable for the determination of spurious propagation effects, inherent to the use of miniature waveguides encountered in MMICs, such as Schottky contact coplanar lines and coupled microstrip lines laid on MIS substrates.     

Effect of electron-electron interactions on microwave performance of IMPATT GaAs diodes

The effect of electron-electron interactions on the ionisation rate is investigated. It is shown that this effect may be a power and efficiency saturation phenomenon for GaAs IMPATT diodes. This effect may become drastic if too high current densities are used, and this particularly may be the case in the millimetric frequency range.     

Systematic determination of the propagation characteristics ofcoplanar lines on semiconductor substrate

A method allowing the systematic determination of the propagation characteristics of micron-size waveguides and overcoming the influence of feeding access discontinuities is presented. The complex propagation constant and characteristic impedance of a slow-wave Schottky contact coplanar line are determined in the 1 to 26 GHz frequency range under different DC bias conditions. This method is successfully used to characterize the Schottky contact coplanar line of micron size under drastic conditions, that is, high value of slow-wave factor, significant attenuation, dispersive transmission line, and strong mismatches between feeding line and device under test. Comparisons with transmission line model theoretical results show very good agreement, despite the large slow-wave factor, attenuation, and dispersion of the waveguide. The electric schemes of the feeding access discontinuities are also presented     

Comparison of full wave approaches for determination of microstrip conductor losses for MMIC applications

Losses due to ohmic conductors in planar lines are evaluated by two full wave analyses, the first one using impedance surface concept associated with the modified spectral domain approach (SDA) and the second a more accurate mode matching technique. To state the respective validity domain of the two numerical simulations, results are compared to experimental data.<>     

Spectral domain analysis of coplanar superconducting line laid on multilayered GaAs substrate

Shows the influence of superconducting strips on the propagation characteristics of a MIS or a Schottky contact coplanar line laid on a GaAs substrate. The use of superconducting strips instead of metallic strips makes it possible to decrease losses. However the main purpose of the study is t point out the influence of the superconductor on the slowing factor and on the characteristic impedance.<>