This book covers all aspects of foliage penetration (FOPEN) radar, concentrating on both airborne military radar systems as well as earth resource mapping radars. It is the first concise and thorough treatment of FOPEN, covering the results of a decade-long investment by DARPA in characterizing foliage and earth surface with ultrawideband UHF and VHF synthetic aperture radar (SAR). Comparisons of the technologies for radar design and signal processing are presented, as are specific design approaches for transmitter design for operation in a dense radio frequency spectrum. Adaptive processing to remove the effects of radio and television signals from the system are also covered. In 10 years, FOPEN systems will find use in crop monitoring, land mine remediation, and creating digital maps under trees. This book will be the foundation for continued research for years to come both for radar and systems engineers in defense and earth resources companies. Government researchers, program managers and planners who have an interest in the unique capabilities of this radar technology, as well as university staff and faculty teaching radar and signal processing will find this book a critical part of their learning for years to come.