Synthetic aperture radar (SAR) systems use electromagnetic (EM) waveform transmissions to illuminate objects, and images are created from processing reflections or echoes. SAR systems are now widely deployed to support critical remote mapping/sensing capabilities. SAR transmitters are typically installed on moving airborne or satellite platforms to operate at stand-off ranges and collect terrain data measurements. The measured data, collected from multiple passes/scans is interpreted by advanced SAR interferometry algorithms into surface terrain maps to help discriminate (detect) key landscape features, e.g., fault lines, bodies of water, forests and vegetation, glaciers, etc. Some of the most technical tasks include discriminating foliage in mapped terrains, identifying forest types, discerning tree heights, and detecting anomalies or hidden objects beneath foliage - termed the foliage penetration (FOPEN) problem.
Due to the increasing interest in using higher Ku-band frequencies (12-18 GHz) for FOPEN, there is a growing need to quantify the interaction of foliage with Ku-band frequencies for consulting purposes; and to aid with enhanced technology support for applications in both the commercial and military domains. Overall, this important area remains largely unaddressed in the modeling realm today because of the required heavy model detail and substantial computational resources.
This technical paper lays out a FOPEN modeling methodology that introduces a range of new innovations and contributions to address the phenomenology of Ku-band EM wave transmissions through moderate foliage. Two highly detailed computer-aided design (CAD) tree models were created using an open source tree generating software. Due the level of details of tree models, Altair HyperMesh is used for geometry editing and cleaning and then Altair Feko is used for FOPEN computational electromagnetic (CEM) behaviors at L- and Ku-band are characterized.