AIRBORNE INSECT RADAR SCATTERING CHARACTERIZATION USING ELECTROMAGNETIC MODELING

Restricted (Penn State Only)
Author:
Alzaabi, Omar Saleh
Graduate Program:
Electrical Engineering
Degree:
Doctor of Philosophy
Document Type:
Dissertation
Date of Defense:
March 29, 2019
Committee Members:
  • Julio V. Urbina, Dissertation Advisor
  • Julio V. Urbina, Committee Chair
  • James K. Breakall, Committee Member
  • Kenneth Jenkins , Committee Member
  • Michael T. Lanagan , Outside Member
Keywords:
  • Radar Cross Section (RCS)
  • Target Tracking
  • Method of Moments (MoM)
  • FEKO
  • Remote Sensing
  • Bio-electromagnetics
  • numerical methods
Abstract:
Bees are the most important pollinator; therefore, plans for their conservation require an understanding of the dynamics and the spatial scale of scavenging, to better determine their needs in terms of nesting sites and food plants. To investigate airborne insect behavior beyond the visible range, radar now plays a valuable role in entomology, particularly in enabling direct observation of insects without disturbing their natural behavior. However, target identification and classification to discriminate among species of airborne insects has always been a challenge in entomological radar applications, particularly in characterizing their scattering signatures through their Radar Cross Section (RCS). Another limitation hindering entomological radar applications generally is the distinctly differing behavior across varied wave frequencies and polarizations as well as varying viewing angles. This thesis addresses these issues by demonstrating computational electromagnetic tools able to predict the radar scattering characteristics of aerial insects – in this case Honeybee workers (i.e. Apis Mellifera) – and to investigate RCS dependencies on multiple frequencies, polarizations and viewing angles. Knowledge of the Honeybee’s dielectric properties, necessary for RCS analysis, was formed using an X-band system with a frequency range from 8.2 GHz to 12.4 GHz, at room temperature, using rectangular waveguides. By measuring both transmission and reflection parameters, dielectric properties were quantified. The dielectric constant of the Honeybee was found to average between 10.59 to 10.69 across the above frequency range, exhibiting inverse proportionality to frequency. Furthermore, the loss tangent was found to increase from 0.26 to 0.41 for the same frequency range. Based on these findings, the RCS was then simulated and predicted using commercial modeling software FEKO. To produce accurate RCS simulation, an organismal Honeybee model was developed. RCS signatures for both vertical and horizontal polarizations were calculated at multiple frequencies and viewing angles, where the incident angle of the plane wave is θ=〖90〗^° and〖 0〗^°≤φ≤〖180〗^°. The azimuth angle was incremented by 5 degrees. To validate the calculation of backscattering RCS results of the Honeybee model obtained through the FEKO method of moments, the simulated results were compared with laboratory measurements. These measurements of backscattering cross section of Honeybee were performed in the antenna anechoic chamber at the ElectroScience Laboratory (ESL) at The Ohio State University (OSU). The backscattering RCS measurements of the Honeybee were carried out for both horizontal and vertical polarizations over a wide frequency range between 2 and 18 GHz with a frequency step of 6 MHz. These measurements were performed at the incident angle of the plane wave θ=〖90〗^° and 0^°≤φ≤〖360〗^°. The azimuth angle was incremented by 5 degrees. In general, the simulated backscattering cross section of the Honeybee shows very good agreement with the obtained backscattering RCS measurements. As a result, such modeling techniques can be applied for many insect species and birds and will help to discriminate targets of different shapes and sizes, and therefore differentiate among different insect targets.