Accurate complex permittivity measurement of a microwave low loss dielectric combining waveguide reflection and transmission on a rectangular structure

The metrological use of a slab-loaded rectangular guide driven at a frequency corresponding to an integral number of half wavelengths in the sample is discussed. A simple swept reflectometer technique leads to the determination of the permittivity with an uncertainty of a few promille at X band. A similar technique is combined with a transmission method to determine low losses. An accuracy of a few tens of microradians has been achieved for loss angle.Anglai

Signal Reduction by tree leaves in Low-THz Automotive Radar

In this study, the attenuation of 300 GHz signal propagating through a layer of leaves which can built upon the antenna radome is investigated. Three set of leaves (Lauren, Birch, Willow) are chosen in this measurement as likely obscurants which can stick to automotive radar radome and cause signal degradation. Transmissivity through uniform layer of the leaves with different water contents is measured. The water content is estimated in leaves drying gradually. The complex permittivity of the leaves with different water contents is estimated and these values are used to calculate the transmissivity through the uniform layer of leaves. Comparison of transmissivity in equivalent water layer with that of leaves having the same water content is made. Measured transmissivity through leaves is compared with that obtained by theoretical model.</p

Microwave processing of lunar soil for supporting longer-term surface exploration on the Moon

The future of human space exploration will inevitably involve longer-term stays and possibly permanent settlement on the surfaces of other planetary bodies. It will, therefore, be advantageous or perhaps even necessary to utilise local resources for building an infrastructure for human habitation on the destination planetary body. In this context human lunar exploration is the next obvious step. Lunar soil is regarded as an ideal feedstock for lunar construction materials. However, significant gaps remain in our knowledge and understanding of certain chemical and physical properties of lunar soil, which need to be better understood in order to develop appropriate construction techniques and materials for lunar applications. This article reviews our current understanding of the dielectric behaviour of lunar soil in the microwave spectrum, which is increasingly recognised as an important topic of research in the Space Architecture field. Although the coupling between the lunar soil and microwave energy is already recognised, considerable challenges must be overcome before microwave processing could be used as a main fabrication method for producing robust structures on the Moon. We also review the existing literature on the microwave processing of lunar soil and identify three key research areas where future efforts are needed to make significant advances in understanding the potential of microwave processing of lunar soil for construction purposes