PAGE CONTENTS
Objectives
Within the ISAS project the design and measurements of low scattering posts for Ku-band DGR antenna applications was addressed. Three companies were involved in this study: the prime contractor HPS GmbH (Germany) and the subcontractors Astrium Les Mureaux (France) and MDA (Canada).
HPS was mainly in charge of the mechanical design and analyses of the low scattering posts, their fabrication and the mechanical measurements. Astrium Les Mureaux was responsible to provide a dual gridded reflector for the measurements and to perform the DGR antenna mechanical analyses. Finally, MDA was responsible for the RF design and measurements of the low scattering posts as well as to perform the antenna RF analyses and measurements.
Two types of low scattering posts have been studied: a dual-band design and a single wideband design. For both a suitable design was assessed in detail and their performances was compared to the ones of a reference conventional post consisting of a dielectric honeycomb sandwich. For the wideband design a RF test campaign was performed in a DGR antenna setup.
The overall objective of this activity was to define and assess novel methods for DGR intercostal posts that minimize the impact on the RF-path i.e. mitigate the reflection, diffraction and blockage induced by them.
Validation of the objective was performed by designing, manufacturing and testing an antenna demonstrator. An assessment of the improvement achieved has been done by comparing RF performance with an antenna implemented using conventional technology. Mechanical analyses showed that RF improvements are obtained while maintaining (and partly improving) the structural properties of the antenna.
Fig: Low scattering posts developed within the ISAS project
Challenges
The challenges addressed in the development of the post were mainly split into two parts: On the one hand the RF functionality development and on the other the structural parts development.
Within the RF development a so called meta-material stack was developed guiding the incidence RF waves around the post. Herein, special care had to be taken on proper RF modelling and prediction in order to elaborate a suitable design considering the structural and mechanical constrains.
For the structural development a post design had to be elaborated incorporating the RF relevant parts and properties but also fulfilling the thermo-mechanical requirements relevant for the performance of the dual gridded reflector. Thereby, special care had been taken regarding requirements such as weight, thermo-elastic behaviour, mechanical capabilities, mechanical integration to the dual gridded reflector, space compliant materials and especially structural integrity of the meta-material stack under space environment (CTE mismatch, cryogenic as well as high temperature capability, adhesion).
Plan
The study was performed in six major work packages:
WP1000 State of the Art and Requirements,
WP2000/3000 Preliminary Design of Antenna and Posts,
WP4000 Critical Technology, Manufacturing and Test of Posts,
WP5000 Antenna Demonstrator Detailed Design,
WP6000 Antenna Demonstrator Manufacturing and Test, and
WP7000 Conclusions and Development Plan.
Current Status
The project was finalized December 2011.