Antenna development and a stepped-frequency GPR system for landmine detection
A project for developing a compact size GPR system for landmine detection was started. It will be based on stepped-frequency radar system for wider application in various kinds of soil conditions. We have developed a prototype stepped-frequency for fundamental evaluation of the system. This system uses a broadband Vivalidi antenna and operates at 2-6 GHz. The system was tested in laboratory and could be used for imaging buried mine-like targets by high resolution. Series of tests were carried out by using sand with rough surface and inhomogeneous soil. We discuss the ability of GPR for landmine detection.
Comparison of pulsed and stepped frequency continuous wave (SFCW) GPR systems
The use of Ground Penetrating Radar (GPR) in structural investigations is based on the detection of features., embedded objects and flaws that cause a reflection of the transmitted electromagnetic wave. Construction types may vary from concrete to masonry and rock and possible targets include metallic reinforcements., ducts., plastic pipes., air voids., as well as the boundaries of the object itself. While a traditional impulse Ground Penetrating Radar (GPR) system uses time-domain measurements of the reflected waves within the investigated objects., a Stepped-Frequency Continuous-Wave (SFCW) system collects data in the frequency domain and converts the data to time-domain data through computer processing. Until recently., the time-consuming calculations associated with the real-time inverse Fourier transforms in SFCW systems limited its application. Thanks to faster processing capabilities available nowadays., this limitation no longer applies to structural GPR. The experimental work on representative concrete and masonry structures presented in this paper shows a systematic comparison of a new SFCW GPR system with traditional impulse radar systems. The results illustrate that SFCW technology combines the highest resolution in the detection of shallow targets., with a very broad detection range., potentially resolving the resolution/penetration trade-off observed in established structural GPR systems.
The Inca Occupation of the South Coast of Peru
like the others, however; it forks into several nearly parallel ravines of which the largest are Huayuri, Rio Grande-Palpa, Ingenio (called Collao in ancient times), Nasca proper (the ancient Caxamarca), Taruga, and Poroma. Due to peculiarities of the local topography, the irrigated areas in Ica and the ravines of Nasca are located inland, at the foot of the mountains, rather than at the mouths of the rivers as is more usual in Peruvian coastal valleys. No sharp natural or cultural boundary separates the valley of Chincha from the valleys of Cafiete (ancient Huarco and Runahuana), Asia, and Mala, the next valleys going up the coast to the northwest. At the other end of the area we are considering, however, there is a sharp break; beyond Yauca the Andean foothills reach out to the sea, natural conditions are quite different, and there are important differences in the archaeological picture as well. The historical sources which mention the south coast are not particularly helpful, except in so far as they provide us with a few dates. To begin with, no chronicler gives an explicit account of the political organization of the south coast at the time it came into contact with the Incas. It can, perhaps, be inferred from Cabello Balboa's statements about common policy toward the Inca invaders that there was some sort of political connection between the valleys of Mala, Cafiete, and Chincha, but the connection need have been no more than a temporary military alliance. Cabello makes no mention at all of Pisco. The valleys of Ica, Nasca, and 125