An antenna apparatus, comprising: an antenna radiator comprising a radiator body and a power feeding portion, the radiator body comprising a first end and a second end opposite to the first end, the power feeding portion being disposed at the first end and configured to receive an excitation signal, and the antenna radiator configured to generate an electromagnetic wave signal according to the excitation signal; a support member comprising a first surface defining a horizontal plane and a second surface opposite to the first surface, the first surface disposed more adjacent to the first end than the second surface, the support member further comprising a side surface disposed between the first surface and the second surface and adjacent to the radiator body; and a first extension portion disposed adjacent to the antenna radiator and electrically coupled to the support member through the side surface; the support member and the first extension portion cooperatively constituting a reference ground of the antenna radiator, the first extension portion, the side surface, and the antenna radiator cooperatively defining a gap region, and the gap region constituting at least part of a clearance area of the antenna radiator, wherein the support member and the first extension portion each have a horizontal central plane perpendicular to the radiator body, the horizontal central plane of the first extension portion being located between the horizontal central plane of the support member and the second surface; and wherein the antenna apparatus is configured so that the excitation signal is transmitted on a transmission path defined by the power feeding portion, the first end, a portion of the radiator body between the first end and the second end, the second end, the first extension portion, and the support member in sequence. an antenna radiator comprising a radiator body and a power feeding portion, the radiator body comprising a first end and a second end opposite to the first end, the power feeding portion being disposed at the first end and configured to receive an excitation signal, and the antenna radiator configured to generate an electromagnetic wave signal according to the excitation signal; a support member comprising a first surface defining a horizontal plane and a second surface opposite to the first surface, the first surface disposed more adjacent to the first end than the second surface, the support member further comprising a side surface disposed between the first surface and the second surface and adjacent to the radiator body; and a first extension portion disposed adjacent to the antenna radiator and electrically coupled to the support member through the side surface; the support member and the first extension portion cooperatively constituting a reference ground of the antenna radiator, the first extension portion, the side surface, and the antenna radiator cooperatively defining a gap region, and the gap region constituting at least part of a clearance area of the antenna radiator, wherein the support member and the first extension portion each have a horizontal central plane perpendicular to the radiator body, the horizontal central plane of the first extension portion being located between the horizontal central plane of the support member and the second surface; and wherein the antenna apparatus is configured so that the excitation signal is transmitted on a transmission path defined by the power feeding portion, the first end, a portion of the radiator body between the first end and the second end, the second end, the first extension portion, and the support member in sequence.