HAA (High Altitude Airship) belongs to the family of the lighter-than-air craft that could operate at more than 20 kilometers of altitude above the ground. In this study, HAA is considered to be used as a spiral antenna array platform for radar applications. Spiral antennas are usually fed in the center by a balanced signal. However, in some con gurations, like antenna mounted on airship, the center is not accessible. To overcome this issue, studies have been undertaken to move the feeding to the outermost arms. The aim is to obtain radiation characteristics similar to that of a classical center fed spiral antenna with an external feeding. Several solutions of externally fed spiral antennas have been developed. For each case, prototypes have been manufactured and measured to be compared with the modeled antennas. Good agreement is shown between measurement and simulation results. Therefore, the behaviors of the new designs have been validated and they can be used on various shapes that do not allow to feed the spiral in its center.
