SIMULATION STUDY OF HIGH-FIDELITY FOLIAGE PENETRATION (FOPEN) AT KU-BAND FREQUENCY
Synthetic aperture radar (SAR) systems use electromagnetic (EM) waveform transmissions to illuminate objects, and images are created from processing reflections or echoes [1]. These technologies have seen many advances in recent decades, and 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. Many studies have developed theoretical, numerical, and computational models for FOPEN behaviors and confirm that lower frequencies in the ultra-high frequency (UHF) and very high frequency (VHF) bands are ideal for FOPEN. This is due to the associated wavelengths being notably larger than tree leaves and most branches, allowing EM transmissions to easily penetrate through. Consequently, many FOPEN studies have used these frequency bands. Other more common frequency bands studied are the P-, L-, S-, C-, and X- bands. A smaller body of research has considered higher frequencies in the K-band (18 – 27 GHz range) and Ka-band (27 - 40 GHz range) with wavelengths on the order of millimeters - the physical dimension of most leaves. These studies have indicated that the smaller wavelengths result in greater EM wave interaction with foliage, increasing scattering and attenuation effects, and decreasing mapping performance