Документ взят из кэша поисковой машины. Адрес оригинального документа : http://www.atnf.csiro.au/projects/askap/techdocs/Design_option.pdf Дата изменения: Thu Sep 30 08:21:28 1999 Дата индексирования: Tue Oct 2 16:51:33 2012 Кодировка:

Luneburg Lens: Electromagnetic Design Options
What do we need to consider to do a design / evaluation:
­ ­ ­ ­ ­ ­ Material requirements Lens structure Constructional aspects Feed Systems Hierarchy Modelling and Design


Material Characteristics
· · · · Low loss materials / loss profile Usable dielectric constant range Homogeneity Compatibility
­ varying density foams ­ loaded foams (artificial dielectrics etc.)


Lens Structure
· Layered Hemisphere
­ ­ ­ ­ gradation and uniformity airgaps and misalignments deformations obstructions

· Ground Plane
­ size and structure ­ discontinuities and imperfections


Constructional Aspects
· · · · Effect Effect Effect Effect of of of of supporting structure feeds and feed network cabling and mechanical control multiple lenses in a station

­ scattering and blockage effects ­ beam / sidelobe structure ­ realistic coverage envelope


Feed Systems
· Wide band line feeds · Line feed arrays (phased / BFN ?)
­ band segments - wideband array design? ­ polarisation ­ imaging

· Multibeaming - multiple line feeds · Spot beams (calibration, interference rejection etc.)


Hierarchy
· Number of lenses per station · Number of independent beams / feeds
­ blockage limitation

· System design
­ ­ ­ ­ ­ optics antenna array and elements electronics sampling fibre-optic data links


Modelling and Design
· Size of problem space for lens modelling
­ resolution to 2 GHz for cell size (eg. FDTD) ­ 0.5 cm resolution = 4 x 109 storage

· Feed array and antenna element design · Ground plane and structural simulation
­ approximation techniques