Developing an Interference-Free Non-Destructive Microwave Testing System for Liquid Samples

摘要

Non-destructive testing (i.e., NDT) techniques are exploited in various fields to detect internal properties of materials. In this work, an interference-free scheme for NDT microwave system is proposed. A testing-bed using off-the-shelf equipment has been implemented. The microwave radiation pattern is optimized to overlap with the middling sample between the transmitter and the receiver. The received power is then measured to characterize different samples. A software is developed using MATLAB to handle the acquisition, processing, and analysis of the received power data. A pure water sample is utilized as a standard sample. The system is, then, designed to eliminate the environment interference by performing an initial testing for the standard sample, prior any actual measurement, and process the two reads by the developed software. First, testing experiments are conducted using a single microwave frequency for different samples and a data-base for material classifications is created. A fixed RF frequency of 2650 MHz is used. Second, the testing experiments were conducted over the 1700 MHz to 2600 MHz microwave frequency range to evaluate liquid samples with controlled/contaminated properties. These include gasoline with different octane number samples and mixtures of milk and water samples. It is shown that the properties of the controlled (or contaminated) under-test sample can be successfully detected by calculating the average of the received power with respect to the measurement frequency range. The developed system is interference-free, made of off-the-shelf equipment, and is compatible with any personal computer or smart display.