Can a loop antenna be designed to avoid polarisation?

Yes — but not with a single ordinary loop. A single loop always has a defined polarization response, so a signal with the “wrong” polarization can suffer a deep null.

If by “avoid polarisation” you mean receive signals regardless of their polarization, there are several good approaches:

  • Two loops at 90° to each other: mount two identical loops orthogonally and use separate receiver channels or combine them appropriately. One loop will respond when the other is near a polarization null. This is probably the simplest solution.
  • Three mutually perpendicular loops: X, Y and Z loops form a vector magnetic-field antenna. This comes closest to being polarization-independent because at least one/two loops will respond regardless of the incoming field orientation.
  • Crossed loops with 90° phasing: two perpendicular loops combined in quadrature can produce sensitivity to circular/elliptical polarization. Depending on the combining arrangement, you can receive both polarization components.
  • Sum the detected powers rather than the RF voltages: for radio astronomy this is particularly attractive. Receive two orthogonal loops independently, measure their powers, then calculate something like \(P=P_X+P_Y\). This avoids the cancellation problems that can occur when simply connecting two loops together.

By Admin

Leave a Reply

Your email address will not be published. Required fields are marked *


This site uses Akismet to reduce spam. Learn how your comment data is processed.