An augmented logarithmic spiral antenna structure includes a first conductive layer, a dielectric layer and a second conductive layer. The first conductive layer includes a first spiral arm and a plurality of second spiral arms. The first spiral arm includes a first initial radius. The second spiral arms are disposed around and connected to the first spiral arm, and each of the second spiral arms includes a second initial radius. The dielectric layer has a top surface and a bottom surface, and the top surface is connected to the first conductive layer. The second conductive layer is connected to the bottom surface. A plurality of the second initial radii of the second spiral arms are different from each other, and different from the first initial radius. |