Antenna has a split ring resonator. Moreover, the antenna is provided with a first conductor and a second conductor which form, at least in part, an open stub or a short stub which has a predetermined electrical length. With this structure, the antenna can have a plurality of operating frequencies.
1. An antenna having a split ring resonator, wherein:
the antenna comprises a first conductor and a second conductor which form, at least in part, an open stub or a short stub which has a predetermined electrical length, the first conductor and the second conductor forming a transmission line extending over the predetermined electrical length;
the antenna has a plurality of operating frequencies; and
the first conductor and the second conductor are arranged apart from each other in a direction perpendicular to the split ring and are arranged in parallel with each other.
2. The antenna as recited in claim 1 , wherein:
the antenna further comprises a third conductor and a feeding portion;
each of the first conductor, the second conductor, and the third conductor has a first end portion and a second end portion;
the first end portion of the first conductor is connected to the first end portion of the third conductor;
the first end portion of the second conductor is connected to the second end portion of the third conductor;
the second conductor and the third conductor form a split ring;
the second end portion of the second conductor and the first end portion of the third conductor are located apart from each other to form a split portion of the split ring; and
the feeding portion is provided to the second conductor or the third conductor.
3. The antenna as recited in claim 2 , wherein:
the antenna further comprises a fourth conductor which connects the first conductor and the second conductor to each other at the second end portion of the first conductor or a vicinity of the second end portion of the first conductor;
the first conductor, the second conductor, and the fourth conductor form the short stub; and
the predetermined electrical length is at least 0.75 times a wavelength of any one of the operating frequencies.
4. The antenna as recited in claim 2 , wherein:
the first conductor and the second conductor form the open stub; and
the predetermined electrical length is at least 0.5 times a wavelength of any one of the operating frequencies.
5. The antenna as recited in claim 2 , wherein the antenna further comprises a radiation element extending from the third conductor.
6. The antenna as recited in claim 5 , wherein an electrical length of the radiation element corresponds to one fourth of a wavelength of any one of the operating frequencies.
7. The antenna as recited in claim 1 , wherein:
the antenna further comprises a third conductor;
each of the first conductor, the second conductor, and the third conductor has a first end portion and a second end portion;
the first end portion of the first conductor is connected to the first end portion of the third conductor;
the first end portion of the second conductor is connected to the second end portion of the third conductor;
the third conductor forms a split ring; and
the first end portion of the third conductor and the second end portion of the third conductor are located apart from each other to form a split portion of the split ring.
8. The antenna as recited in claim 7 , wherein:
the antenna further comprises a fourth conductor which connects the first conductor and the second conductor to each other at a position distant from the first end portion of the third conductor and the second end portion of the third conductor;
the first conductor, the second conductor, and the fourth conductor form the short stub; and
the predetermined electrical length is at least 0.75 times a wavelength of any one of the operating frequencies.