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What techniques can enhance the axial ratio in spiral antennas?

I am designing wideband spiral antennas and want to ensure low axial ratio across the operational bandwidth.
I notice that design parameters like arm spacing, feed structure, and substrate choice strongly affect axial ratio.
I want to understand best practices to optimize circular polarization.

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By Gugan Answered 1 year ago

From my experience, axial ratio in spiral antennas can be improved by carefully optimizing the feed geometry, arm spacing, and substrate parameters. I have seen designers introduce slight perturbations in the arms or use a well-matched coaxial or microstrip feed to ensure symmetric excitation. Substrate selection and dielectric thickness also influence the axial ratio, especially at the band edges. I would recommend iterative EM simulation across the full operating bandwidth to verify improvements. In practice, small adjustments to spiral turn spacing or feed point can significantly reduce axial ratio, ensuring stable circular polarization for wideband applications.

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