Effective Buried Nonlinear Target Detection Under Faulty Antenna Conditions Using Extended DORT Approach

For the detection of buried targets in a dielectric medium, the decomposition of time-reversal operator (DORT) using a multistatic system has been effective in separating multiple targets and imaging their locations. Recently, nonlinear (harmonic) radar-based DORT has been introduced to detect nonlinear targets (NTs) with small radar cross sections (RCSs). However, faulty antennas (i.e., elements unable to transmit or receive signals) can distort the received multistatic response matrix, significantly degrading detection performance and accuracy, necessitating an extension of DORT to address such scenarios. This article presents double scan-DORT (DS-DORT), an extended DORT approach that ensures effective buried NT detection even in the presence of faulty antennas. Unlike conventional DORT, DS-DORT employs two arrays, each performing both transmission and reception, generating two multistatic responses that compensate for distortions caused by faulty antennas. By simultaneously retransmitting two sets of back-propagation signals derived from these responses, DS-DORT minimizes inaccuracies, maintaining robust target detection. Furthermore, DS-DORT offers practical advantages in real-world scenarios, such as hazardous/inaccessible environments, or when antenna failures occur unpredictably, without requiring additional hardware or complex algorithms. Beyond its capability to mitigate faulty antenna effects, DS-DORT also enables the reconstruction of 3-D target locations by leveraging a 2-D antenna array configuration when all antennas function correctly. The proposed approach is validated through numerical simulations and measurements, demonstrating superior detection performance compared with conventional DORT in scenarios involving single or multiple faulty antennas. The results confirm that DS-DORT enables accurate detection of buried NTs even under faulty antenna conditions.