PAGE CONTENTS
Objectives
The objective is to design and manufacture VSAT Waveguide Lens Antennas (WGLA) for the Ku-satellite band, 10.75-14.50 GHz.
The antenna is receiving TV and internet at 10,75-12,75 GHz and transmitting at 13,75-14,50 GHz. This large bandwidth is made possible with a new approach of the geometry of the WGLA compared to previous designs for TVRO application.
The main benefit of using the WGLA compared to a conventional dish is its ability to multi-satellite capture. The antenna systems will provide communication also through wide offset angles. Feed horns especially designed to match the WGLA are being developed which results in increased overall gain of the system.
The WGLA system is seen to be especially beneficial for applications where multi-satellite communication is required. A potential application is to integrate the antenna on a stabilised platform and several satellite links can then be maintained from one single antenna system.
Challenges
The key issue is to achieve sufficient bandwidth for reception and transmission in the Ku satellite band, 10.75-14.50 GHz, with a WGLA. Special care is taken on the antenna geometry for minimised frequency sensitivity.
The side-lobe levels needs to be within strict envelopes and the cross polarisation to be >35 dB. Feed horns are designed to especially match the WGLA and as a result maximise the gain. The manufacturing of the antenna is seen as a key issue as dimensional accuracy is required in order to fulfil the specification for transmission.
Modelling of the antenna with computer codes is also a comprehensive task due to its complexity and high size/wavelength-ratio. Successful antenna simulations with FDTD code have been made using a 72 processor super-computer.
Plan
The project is to be done through a number of cycles. The WGLA’s are designed, simulated and tested in parallel with the feed horns. After tests refinements are done before the final product is completed. Development and optimisation of production methods of the WGLA are done in parallel. The outcome of the project shall be two VSAT antennas with matched feed horns and the system shall concur to present VSAT specifications e.g. Eutelsat type approval.
Current Status
Antenna simulations with FDTD code have been done on a number of different lens variations. An example of simulated radiation patterns of a WGLA is shown below. Two antenna prototypes are now under production and will be field tested during summer 2008. Lab tests at ESTEC for radiation patterns are planned for September 2008.
In FDTD code simulated radiation patterns at 13.75 GHz of a WGLA