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.
Novel ultrawide-bandwidth Vivaldi antenna with low crosspolarisation
The conventional Vivaldi antenna typically has a bandwidth of less than 3:1, limited by the feed line to radiating slot transition. The antipodal Vivaldi antenna removes this limitation but gives very high crosspolarisation which is undesirable for phased array applications. The Letter describes a new balanced antipodal Vivaldi antenna that retains the wide bandwidth characteristics while reducing the crosspolarisation by 15dB across an 18:1 band. Measurements are presented that compare the performance of existing antenna structures with this novel antenna element.
On the use of the Hardening Soil Small Strain model in geotechnical practice
This article highlights the importance of using advanced constitutive soil models in numerical modelling as daily geotechnical practice. In this context, the Hardening Soil (HS) model is presented as the most advanced soil model implemented in the ZSoil finite element code. The article recalls the basic features of the HS model and it explains their role in numerical simulations. The role of pre-failure non-linear behaviour of soils is also discussed. An application of the HS model is illustrated on typical geotechnical problems such as retaining wall excavation, tunnel excavation and undrained loading followed by consolidation.