Dual Band Circular Polarization Selective Structures for Space Applications

Satellites are key components in today's modern world, but they are expensive to launch and the orbits are crowded. With use of a dual band circular polarization selective structure (CPSS) the satellites can be improved and the number of reflectors needed to carry out a certain task can be reduced. A dual band CPSS reflects one handedness of circular polarization and transmits the other, over a certain frequency band, and over the other frequency band the opposite occurs. This can be done with use of a CPSS coated reflector or a diplexer type setup. This thesis investigates, through full wave simulations of normal incidence, dierent candidates for dual band reciprocal symmetrical CPSS. The frequency bands of interest in this thesis are 17.7-20.2 GHz and 27.5-30.0 GHz and the goals are: insertion loss and return loss of less than 0.50 dB and an axial ratio of less than 0.78 dB (or 1.74 dB if diplexer setup is considered) for the targeted circular polarization within the frequency band. The dual band CPSS candidates consists of multiple layers of non-resonant metal elements, meander lines and capacitively loaded strips, on substrates inter-spaced by low-permittivity foam sheets. Two meander line designs of 6 and 9 layers fulll the goals specied for the diplexer setup with a bandwidth of 14.73-20.55 GHz (33.0%) and 27.04-30.82 GHz (13.1%) for the 6 layer design, 14.55-20.76 GHz (35.2%) and 27.20-30.31 GHz (10.8%) for the 9 layer design. Moreover the 9 layer meander line design fulll most of the stricter axial ratio requirement with bandwidth of 16.16-20.38 GHz (23.1%) and 28.31-29.53 GHz (4.2%).