Abstract: Disclosed herein is the structure of a Square Quadrifilar Helical antenna (S-QHA). The structure of the S-QHA includes a square column, four radiation elements, and a feed network. The four radiation elements are formed on the square column. The feed network is disposed at the top or bottom of the square column, and feeds signals to the radiation elements at a phase difference of 90 degrees in a clockwise or counterclockwise direction. As a result, the S-QHA according to the present invention can receive circularly polarized signals.

Abstract: In a multi-band U-slot planar antenna, a limited ground plane is provided. A connector includes a ground terminal connected to the ground plane and a feeding terminal for feeding a signal. A planar radiation device includes a feeding point connected to the feeding terminal, a central U-slot having a symmetrical configuration about a central axis thereof, the central axis extending vertically from the feeding point, and at least one pair of auxiliary U-slots symmetrical with each other about the central axis. In the multi-band U-slot planar antenna, alternatively, at least one auxiliary U-slot may have a symmetrical configuration about the central axis.

Abstract: In a multi-band U-slot planar antenna, a limited ground plane is provided. A connector includes a ground terminal connected to the ground plane and a feeding terminal for feeding a signal. A planar radiation device includes a feeding point connected to the feeding terminal, a central U-slot having a symmetrical configuration about a central axis thereof, the central axis extending vertically from the feeding point, and at least one pair of auxiliary U-slots symmetrical with each other about the central axis. In the multi-band U-slot planar antenna, alternatively, at least one auxiliary U-slot may have a symmetrical configuration about the central axis.