Resonance Behavior of a Dielectric Target in a Half-Space Using the CNR (Complex Natural Resonance) Method
Due to the advent of short-pulse technology (UWB), there has been a considerable amount of interest shown in the application of the transient or impulse response of a radar target. A typical application for such a system is the use of an UWB illuminating pulse in ground penetrating radar (GPR). However, the detection and identification of buried and subsurface objects still remains a difficult problem, as there is no single sensor or diagnostic tool which can provide sufficient information about the object. The singularity expansion method (SEM) has been used for a long time in the detection and recognition of targets in free space. Whilst this method is usually used to represent the scattered signal from the object in terms of a sum of complex exponentials, it also contains the impulse response of the system which can be obtained via a deconvolution process if the incident signal is known. A similar methodology is very popular in GPR systems in the tracking and identification of buried landmines. Although the resonance behavior of the target occurs in the late time portion of the transient signal, both early and late time portions of the signature are useful for extracting the features of the target. We primarily focus on the late time response of the target as it contains target specific information
The primary objective of this research work is to detect and identify a dielectric target buried below a homogeneous half-space from the backscattered time domain signature. It is well known that the transient scattering of electromagnetic waves from a conducting or dielectric target contains information about the resonance behavior of the target itself as quantified by the complex poles or complex natural resonances (CNR) of the target. The CNRs are theoretically aspect independent, depending only on the shape and electrical properties of the target such as permittivity and conductivity. For a target embedded below an interface, the transient response of target itself can be recovered from the system response using a deconvolution technique. Many deconvolution techniques are described and applied in radar signal processing and image processing fields both in the time domain and frequency domain. However, the time domain approach is found to be superior compared to current frequency domain approaches. Similarly, there are many techniques for extracting the CNRs and, in this context; we use the matrix pencil method to extract the poles from the late time impulse response of target.
KeywordsImpulse Response Ground Penetrate Radar Finite Difference Time Domain Matrix Pencil Resonance Behavior
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