Multiband spiral antenna with high gain by conical wall

This paper presents design for high gain spiral antenna with conical wall. To improve the gain of spiral antenna, the angle and length of conical wall is newly designed for the conventional antenna with circular cavity wall. The good axial ratio of 2.4 dB below and the improved gain of 10.5 dBi above are measured by the added conical wall. The measured E-field radiation patterns and main beam directivity toward +z axis direction are agreed well with the simulated results. The proposed antenna will be applied for the NLJD system.