Design for back lobe improvement of spiral antenna with conical wall

This paper presents design for back lobe suppression of multiband spiral antenna with conical wall. Elliptically bended edge, rolled-up edge and elliptical dual edge to reduce back lobe were considered. The axial ratio of spiral antenna with a newly designed conical wall edge structure was not almost changed to compare with conventional spiral antenna with conical wall. On the other hand, the back lobe of spiral antenna with elliptical dual edge was remarkably suppressed and the gain at boresight was slightly increased.