Ultra wideband radar antenna design for snow measurement applications

Abstract

Creating a high-precision, compact and low cost snow structure and depth sensor has always been the dream of many industries, and yet hard to achieve all together. Snow depth sensors are used in avalanche search and rescue and widely in recreational snow industry, as well as in environmental monitoring systems for snow water equivalence measurements. The use of radar for snow depth measurement is not new and many techniques -such as Frequency Modulated Continuous Wave (FMCW) - have been used but they prove to be costly, bulky, and have relatively low precision. Today with the availability of chip-scale Ultra Wide-Band (UWB) technology, it is possible to create Snow Depth Sensor (SDS) and Snow Water Equivalent (SWE) measuring systems in low cost, small size and possibly mobile devices, with very high precision. One problem that remains at the RF (Radio Frequency) end of the UWB technique in measuring snow parameters is the antenna used in transmitting and receiving UWB pulses. UWB pulses are characterized by an instantaneous fractional energy bandwidth greater than about 0.20-0.25. The FCC has allocated spectrum for UWB use in the 3.1-10.6 GHz band and available chipsets generate pulses in the lower 3-6 GHz band. For creating applications that use UWB in measuring snow parameters such as SWE and snow depth, a UWB antenna is required. A successful UWB radar antenna needs to have high gain, linear phase, low dispersion and low Voltage Standing Wave Ratio (VSWR), and high directivity throughout the entire band. The antennas are to have physically compact design with high gain, linear phase, low VSWR and high directivity for UWB radar applications in the snow measurements industry. This thesis presents several antenna designs for the 3.1-10.6 GHz UWB band and the 3-6 GHz UWB lower band that have the potential to meet these requirements, and show, through laboratory measurements, modeling and simulations, that the required attributes can be achieved.