Manju Paulson

Compact arrow shaped antenna with embedded rectangular slot for dual frequency dual polarisation operation

A compact arrow shaped microstrip antenna with a rectangular slot is proposed. By embedding a rectangular slot in the patch an additional resonance frequency having opposite polarization compared to the TM/sub 10/ mode is generated This new frequency is much lower than the TM/sub 01/ mode frequency of the patch without a slot. The ratio between the two resonant frequencies can be tuned in a wide range by changing the slot length. These two orthogonal modes can also be combined to achieve circularly polarized radiation. The antenna offers an area reduction /spl sim/75% compared to a rectangular patch antenna designed for the same frequency.

A circular-sided compact microstrip antenna

A microstrip patch with considerable reduction in antenna size is presented. The proposed design uses curved edges so as to increase the effective resonating length. An area reduction of /spl sim/80% compared to a standard rectangular patch is obtained without much reduction in gain. Simple formulae are suggested for calculating the resonant frequency of the new geometry, and its validity is established by experimental results.

QUASI-STATIONARY ELECTRO-THERMAL HEATING MODEL FOR MICROWAVE/HYBRID-PROCESSED MATERIALS USING GREENS FUNCTION TECHNIQUES

A quasi – stationary electro – thermal heating model for microwave and hybrid heating of materials is developed using Greens function technique. The temperature profiles developed inside the materials are calculated by the solution of the non-linear inhomogeneous heat equation imposing Dirichlet boundary condition. Normalised variance (response variable) is calculated as a measure of homogeneity. The effect of lower (2.45 GHz) and higher (24 GHz) frequencies on homogeneity is compared.

PARAMETER OPTIMISATION MODELING USING STATIONARY 1D-ELECTROTHERMAL MODEL TO IMPROVE TEMPERATURE HOMOGENEITY

A parameter optimisation model is developed to find the parameters that have significant effects on homogeneous temperature distribution during microwave processing of materials. Electromagnetic, thermal and processing parameters are collected for a wide variety of materials and the heating profiles are calculated using a stationary 1D-electrothermal model. A measure of temperature homogeneity is obtained from the heating profiles by statistical calculations of normalised variance (the response variable). The processing parameters (power, temperature, size of the material sample) are optimised for all of these materials for a minimum normalised variance which allows maximum change of ± 3% Taverage on the T-distribution to meet most of the industrial process requirements. This mathematical model suggests a group of materials, which requires modifications in processing conditions to achieve uniform heating.