Kavitha Arunachalam

Inverse problem solutions in NDE can be broadly classified as model-based approach and system-based approach. In model-based approach an accurate forward model is used in an iterative framework to provide a defect shape that minimizes the error between the measured signal and a simulated signal. However this approach results in repeated executions of a three dimensional forward model in each iteration, making it computationally demanding. This paper presents a direct approach to inversion using principles of time reversal. The feasibility of the approach is demonstrated via application to microwave NDE data. A two-dimensional finite difference time domain model for simulating the propagation of forward and time reversed wave fields is first developed. The key advantage of the approach is that it provides a model-based inversion method that is not iterative. Simulation and experimental results validating the approach are presented. © 2011 American Institute of Physics.

The feasibility of non-contact and non-destructive evaluation (NDE) of planar aerospace dielectric composites using microwave is examined in this paper. Free space microwave measurement set up includes spot focusing horns to gather the scattering parameters of the composites with the help of (Gated-thru reflect line) G-TRL calibration. The dielectric properties are studied from the measured scattering parameters to characterize the material's defective and non-defective region. Particulate reinforced composite with an air gap of 0.1 mm thickness and 10 mm width is used for validation of the technique.

Non-contact measurement of the level of molten glass is demonstrated in an engineering scale induction-heated glass melter using microwaves. The microwave sensor is a corrugated horn used in mono static RADAR (RAdio Detection and Ranging) mode operating over 20 to 24 GHz with 20 dB gain. The ability to measure the level of the glass melt is demonstrated using an off-centered port in an induction glass melting furnace.

Medical microwave radiometry is a passive non-invasive technique for measuring tissue temperature gradient in the human body. Design and evaluation of a medical microwave radiometer centered at 1.3 GHz with 330 MHz bandwidth is presented here. An active noise source with noise equivalent temperature of 303 K is used for temperature calibration. Radiometer characterization results are presented for matched load maintained at thermal steady state and hot spot in a tissue phantom. Radiometer measurements recorded using a dielectric loaded waveguide and substrate integrated waveguide (SIW) antenna with a slot demonstrated the ability to measure the temperature gradient at depth.

A non-contact microwave measurement technique to measure the change in conductivity profile of glass mixture with temperature (30-700°C is presented here. Mono static radio detection and ranging (RADAR) signals from the glass melts recorded using a corrugated horn are processed to identify the relative change in material conductivity with respect to temperature.

The feasibility of non-contact and non-destructive evaluation (NDE) of planar aerospace dielectric composites using microwave is examined in this paper. Free space microwave measurement set up includes spot focusing horns to gather the scattering parameters of the composites with the help of (Gated-thru reflect line) G-TRL calibration. The dielectric properties are studied from the measured scattering parameters to characterize the material's defective and non-defective region. Particulate reinforced composite with an air gap of 0.1 mm thickness and 10 mm width is used for validation of the technique.