High Accuracy Disbond Thickness Estimation Scheme Employing Multiple-Frequency Near-Field Microwave Measurements

Microwave nondestructive evaluation (NDE) techniques have shown great potential for disbond detection in multi-layer dielectric structures. However, a quantitative disbond thickness estimation scheme has not been introduced yet. In this paper, we propose a maximum-likelihood (ML) disbond thickness estimation scheme utilizing multiple independent measurements obtained at different frequencies. By simulations and experiments, we show that the proposed scheme produces highly accurate disbond thickness estimates