antenna-theory.com

[Kitboga]

There's a competition I'm taking part in which involves having to create a dual orthogonal linear polarized antenna array element for observations in the 50-500MHz frequency range.

I've currently tried simulating a Sierpinski fractal bowtie antenna. I chose the bowtie antenna because a central cylindrical hub was required, and the dual polarization would be achieved by just placed two bowtie antennas at 90 degrees to each other. However, reading up on bowtie antennas shows that it really doesn't matter if you create a fractal or not, at least at that frequency. It's back to the drawing board for me - do i improve on my bowtie antennas or do I go with a completely new design? A microstrip antenna might not be that useful because of the competition requirements, and the fact that this is going be a radio array. I think I should go with a bowtie antenna, however if there's any other optimized and unique design then I'm willing to try new things.

I'd love to hear your thoughts on this - what you think might be the best type of antenna. Some more specifications:

(From the official competition requirements:)
1)Dual orthogonal linear polarization reception, using two
separate sub-units with relative orientation of 90 degrees.

2) Efficient radiative coupling over the band from 50 MHz to
500 MHz, with return loss of more than 8 dB over at least
80-320 MHz (i.e. S11 < -8 dB).

3) Total projected span of the structure (Width*Breadth) to be
within 1 square meter, and an extended conducting
reflector below, defining the "ground plane" (for the entire
array), is to be an integral part of the design.

For this, as mentioned above, I've looked at modifying a bowtie antenna with something a little more innovative and optimized. I haven't had much luck, however. Adding a two-layer sierpinski fractal made the simulation result oscillate wildly, and adding log-periodic teeth to it would make it too generic. Is there something _really_ out there and unique that I can do? What would you choose if you had to make an antenna these ways? This is my first time building any sort of radio electronic, and I want to give it my best shot.