“…But the DUT has to be powered up, and this method is susceptible to both non uniform heating and temporal temperature variations, which leads to unreliable sensitivity. Moreover, the acoustic method [10], [11] has excellent long-range diagnostic capability and it is suitable to VOLUME 4, 2016 detect defects on large structures such as pipelines, marine, ships, and aerospace, but it requires heavy data processing and physical contact with the DUT by surface mounting of a large number of sensors, as a result, it makes it impossible to perform scan for small and complex DUTs. Among these techniques, near-field radio frequency (RF) non-destructive evaluation (NDE) offers advantages of single-side access, contactless, low cost, and high measurement speed [12], [13].…”