Performance of a 2-layer radial hole effective media lens
The outer polyethylene layer of a 8λ0 radius 2-layer polyethylene/cross-linked polystyrene lens was implemented as a radial hole effective media that allows the entire lens to be milled from a single billet of cross-linked polystyrene, simplifying construction by avoiding layer fitting problems. Full wave simulations in a commercially available simulator showed that increasing the number of radial holes to 3000 gave peak directivity within 0.3dB of the original cross-linked polystyrene/polyethylene lens. Both Particle Swarm Optimization and icosahedron based methods were trialed for distributing the holes evenly over the sphere. The latter method produced symmetrical meshes allowing symmetry planes to be used to minimize computational burden, but was bound to the numbers of holes produced by successive triangular face subdivision iterations.
Assessment of Sochacki lenses for autonomous maritime patrol FLAR
Initial numerical and experimental results are given for minimal layer lens antennas for Forward Looking Airborne Radar as the primary sensor onboard small Unmanned Aerial Vehicles adapted for fully autonomous long distance maritime patrol. 27dBi was achieved by a single material lens that is dimensionally compatible with the fuselage of a 6-meter class Unmanned Aerial Vehicle. Numerical results for 2 and 3 layer lenses up to 38dBi directivity were given, been comparable to the reflector antennas presently used in P-3C and P-8A manned maritime patrol aircraft.
Development of Synthetic Aperture Radar onboard unmanned aerial vehicle
Synthetic Aperture Radar (SAR) is well-known as a multi-purpose sensor in all-weather and day-night time. In this research, we are developing Circularly Polarized Synthetic Aperture Radar (CP-SAR) onboard microsatellite under Japanese Ministry of Education and Technology (MEXT) program to observe land deformation on Earth surface etc. The CP-SAR employs elliptical wave propagation and scattering phenomenon by radiating and receiving the elliptically polarized wave, including the specific polarization as circular and linear polarizations. The sensor is designed as a low cost, light, low profile of configuration to transmit and receive left-handed circular polarization (LHCP) and right-handed circular polarization (RHCP). Then these circularly polarized waves are employed to investigate relationship of physical information of scatterer and axial ratio, ellipticity, tilt angle etc. This sensor is also considered to reduce the effect of ionosphere's Faraday rotation. For ground experiment of CP-SAR, we also develop the CP-SAR onboard unmanned aerial vehicle (UAV CP-SAR) that is discussed in this paper.