Time-Division-Multiplexing for AIS on VHF Radio

In this report, a VHF system that is mounted on a mast which carries a radar system on its top. Due to design constraints suffers from bad reception on the mast. As this antenna cannot be situated on the top of the mast it is mounted lower, which results in the mast reflecting or blocking signals to the antenna decreasing the reception area. To solve this problem an alternative solution is proposed in the form of Time Division Multiplexing. This system will divide the frame length of one transmitted symbol across all connected antennae elements and sample the received signal on each antenna. It can then create a unique bitstream per antenna, with the added benefit that measuring the radiation pattern per element and not together does not alter the radiation pattern. To test this solution the mast was modelled in ANSYS HFSS and the calculated antenna radiation patterns were exported to MATLAB in which a communication channel was created to simulate the bit error performance. This resulted after optimisation in a system which requires two antennae to provide sufficient coverage for a circle with a 29 KM radius.