• High-latitude over-the-horizon radar applications

      Theurer, Timothy E.; Bristow, William; Thorsen, Denise; Hawkins, Joseph; Watkins, Brenton (2020-05)
      Over-the-horizon radar (OTHR) systems that operate at high-latitudes often must contend with multipath and pronounced diffusive scattering effects produced by the anisotropic, birefringent, and heterogeneous nature of the ionosphere. In this thesis, radar performance at high-latitudes is quantified and several applications for either mitigating the deleterious effects of multipath and diffusive scattering or deriving information about the state of the ionosphere are proposed. The first application is inspired by adaptive optics techniques in other fields and involves the coherent summation of the received plane wave spectrum in order to improve angular resolution and array gain. The second application involves deriving ionospheric E x B drift from applying spatial correlation analysis to ground clutter echoes. The third application is the development of a new spatial adaptive processing technique designed specifically to preserve the Doppler spectrum of angle-Doppler coupled clutter like that observed at high-latitudes.
    • Ray tracing applications for high-frequency radar: characterizing artificial layers and background density perturbations in the ionosphere

      Theurer, Timothy E. (2012-08)
      In this thesis a numerical method of calculating ground-scattered power from the results of a ray tracing analysis is presented. The method is based on a conservation of energy approach and offers advantages over an alternative method derived from the radar equation. The improved numerical method is used to investigate two different physical phenomena by comparison with measured ground-scattered power observed by a high-frequency (HF) radar located in Kodiak, AK that is part of the Super Dual Auroral Radar Network (SuperDARN). First, the effects of artificial electron density layers on observed ground scatter is studied through a comparison of simulated and measured power profiles. The results demonstrate that the location and spatial dimensions of artificial layers may be estimated by a comparison of the location and amplitude of simulated and measured power enhancements. Second, a Monte-Carlo simulation method is used to characterize the temporal distribution of ground-scattered power. Random processes including background electron density perturbations, polarization, noise, and sample correlation are modeled in simulation and used to estimate statistical moment profiles. The simulated statistical moment profiles are compared to measured profiles as a means of model verification and to roughly approximate background electron density perturbations in the ionosphere.