Multipath mitigation techniques based on time reversal concept and superresolution algorithms for inverse synthetic aperture radar imaging

Abstract

Radar imaging based on static high-resolution coherent radar is widely known as inverse synthetic aperture radar (ISAR) imaging. This 'all-weather' system is able to provide slant-range -Doppler images of non-cooperative targets whose motion is unknown. Conventional ISAR systems are designed for imaging targets with a direct line of sight of sensors. For this reason, they have a reduced performance in today's complex scenarios -such as urban environments -where secondary returned waveforms are added to directly reflected echoes coming from targets. They are known as ghost artefacts since they obscure true targets when using the standard range-Doppler algorithm (RDA). In this study, an innovative multipath mitigation technique is presented, in which 'time reversal (TR)' concept is implemented in ISAR images, leading to 'TR-ISAR algorithm'. For this purpose, a pre-processing algorithm is previously needed so as to solve the geometric problem related to multipath. Finally, superresolution algorithms provide us with the tools to mitigate the spurious component that arises during the averaging process carried out by TR-ISAR. The authors' conclusion is that imaging quality after employing superresolution approaches is clearly improved. As a proof-of-concept, real data from high-resolution radar have been used to verify the proposed method.

Locating Ships Using Time Reversal and Matrix Pencil Method by Their Underwater Acoustic Signals

“…TR calculates the position of a target in an inhomogeneous medium, using information from many sensors validating mathematical properties in the solution of the wave equation. The use of TR ranges from the location of electromagnetic phenomena, such as lighting discharges [8], to the monitoring of structural health problems [9], going by linear networks analysis [10] and in aperture radar imaging [11]. Specifically, on underwater acoustic applications, it is used in the detection of multidimensional signals in aquatic environments [12] and in processing information for UWA communication processes [13,14].…”

Modelado y Mitigación de Fenómenos de Multitrayecto en Imágenes Radar mediante Técnicas basadas en Inversión Temporal

“…Una vez presentados todos los modelos matemáticos que dan soporte al algoritmo final (junto con sus correspondientes simulaciones), como prueba de concepto, se pretende mostrar su efectividad haciendo uso de datos experimentales [Arr12a,Arr12b,Arr12c]. Es muy importante recalcar la gran relevancia que supone el poder justificar y validar los modelos teóricos simulados mediante el uso de datos medidos en entornos reales.…”

“…Ésta es la razón por la que tales algoritmos pueden englobarse dentro de las denominadas técnicas de post-procesado. Cabe destacar el interés de las conclusiones fruto de este estudio, y su consiguiente difusión en dos prestigiosas revistas de carácter internacional [Arr12b,Arr12c].…”