A split ring resonator 2. antenna (10, 10A) comprising a main portion (20, 20A) which forms a split ring (21, 21A) with a split portion; the main portion has an upper surface portion, a first fixed portion, a second fixed portion, a third fixed portion, a first reinforcing portion, a second reinforcing portion, a feed portion, a first end portion and a second end portion; each of the first fixed portion, the second fixed portion, the third fixed portion, the first reinforcing portion, the second reinforcing portion and the feed portion extends from the upper surface portion; each of the first fixed portion, the second fixed portion and the third fixed portion is configured to be xed on a circuit board when the antenna is mounted on the circuit board each of the first fixed portion, the second fixed portion and the third fixed portion has a lower end in an up-down direction; the lower ends of the first fixed portion, the second fixed portion and the third fixed portion define an imaginary plane perpendicular to the up-down direction, and wherein the imaginary plane corresponds to an upper surface of the circuit board when the antenna is mounted on the circuit board; the first reinforcing portion is positioned between the first fixed portion and the second fixed portion; the second reinforcing portion is positioned between the second fixed portion and the third fixed portion; each of the first end portion and the second end portion is positioned between the first fixed portion and the third fixed portion; the first end portion and the second end portion form the split portion of the split ring; each of the first reinforcing portion, the second reinforcing portion and the feed portion has a lower end in the up-down direction; and each of the lower ends of the first reinforcing portion, the second reinforcing portion and the feed portion is positioned between the upper surface portion and the imaginary plane in the up-down direction; characterised in that each of the first reinforcing portion and the second reinforcing portion is configured not to be fixed on the circuit board and to be off the circuit board when the antenna is mounted on the circuit board, the main portion, the lower ends of the first reinforcing portion and the second reinforcing portion are configured such that, when the antenna is mounted on the circuit boad and when an external force is applied to the main portion of the antenna, said main portion is deformed and each of the lower ends of the first reinforcing portion and the second reinforcing portion abuts against the circuit board to prevent the main portion from being plastically deformed; a main portion (20, 20A) which forms a split ring (21, 21A) with a split portion; the main portion has an upper surface portion, a first fixed portion, a second fixed portion, a third fixed portion, a first reinforcing portion, a second reinforcing portion, a feed portion, a first end portion and a second end portion; each of the first fixed portion, the second fixed portion, the third fixed portion, the first reinforcing portion, the second reinforcing portion and the feed portion extends from the upper surface portion; each of the first fixed portion, the second fixed portion and the third fixed portion is configured to be xed on a circuit board when the antenna is mounted on the circuit board each of the first fixed portion, the second fixed portion and the third fixed portion has a lower end in an up-down direction; the lower ends of the first fixed portion, the second fixed portion and the third fixed portion define an imaginary plane perpendicular to the up-down direction, and wherein the imaginary plane corresponds to an upper surface of the circuit board when the antenna is mounted on the circuit board; the first reinforcing portion is positioned between the first fixed portion and the second fixed portion; the second reinforcing portion is positioned between the second fixed portion and the third fixed portion; each of the first end portion and the second end portion is positioned between the first fixed portion and the third fixed portion; the first end portion and the second end portion form the split portion of the split ring; each of the first reinforcing portion, the second reinforcing portion and the feed portion has a lower end in the up-down direction; and each of the lower ends of the first reinforcing portion, the second reinforcing portion and the feed portion is positioned between the upper surface portion and the imaginary plane in the up-down direction; characterised in that each of the first reinforcing portion and the second reinforcing portion is configured not to be fixed on the circuit board and to be off the circuit board when the antenna is mounted on the circuit board, the main portion, the lower ends of the first reinforcing portion and the second reinforcing portion are configured such that, when the antenna is mounted on the circuit boad and when an external force is applied to the main portion of the antenna, said main portion is deformed and each of the lower ends of the first reinforcing portion and the second reinforcing portion abuts against the circuit board to prevent the main portion from being plastically deformed;