Browsing by Author "Sarkkinen, Sakari"

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  • Imaging at 94 GHz for aircraft landing scenarios
    (2023-06-12) Sarkkinen, Sakari
     Sähkötekniikan korkeakoulu | Master's thesis
    Landing an aircraft onto a runway requires sufficient visibilty. Developing a system that could reliably detect the runway in weather conditions such as fog, rain or snowfall would be highly beneficial for the aviation industry. The millimeter wave frequency of 94 GHz has the potential to be suitable for passive or active imaging in these conditions. The thesis starts by evaluating the theoretical range of imaging at 94 GHz by analyzing experimental and simulation data from current research. The feasibility of passive imaging is determined by analyzing the radiometric properties of materials in a typical runway environment, using a Matlab simulation of the radiometric contrast between asphalt and soil covered with vegetation. Finally, antenna systems for imaging are discussed, and a design concept based on a reconfigurable reflectarray is presented with theoretically evaluated performance figures. Research data indicates that propagation at 94 GHz through fog with an optical visibility of up to 100 m is very good, enabling visibility of 18 km at 18 dB total attenuation. Propagation during moderate rainfall is significantly worse. The effect of snow was expected to be less significant than rain, but results were inconclusive. Passive imaging for aviation applications was shown to not be viable in the simulation, due to the radiometrically warm sky at low elevation angles and the resulting poor contrast of a few degrees of K even in best-case scenarios. Active imaging was shown to be more suitable. The design concept is an offset-fed reconfigurable reflectarray antenna, which was shown to achieve a half-power beamwidth of 0.92 degrees with a 400-millimeter diameter reflector and an expected aperture efficiency of 40%. Active imaging with electrical beam steering using either MEMS or PIN diodes for 2-bit discrete phase shifting was expected to achieve video rates of 50x22 pixels at 10 Hz, and 63x22 pixels at 10 Hz respectively. The concept's performance was mostly insufficient, but is noted as a good basis for future development for 94-GHz imaging.
  • Parameter extraction in free-space dielectric spectroscopy
    (2020-12-07) Sarkkinen, Sakari
     Sähkötekniikan korkeakoulu | Bachelor's thesis