An antenna includes a grounding conductor, a feed conductor, a resonant conductor, and a radioactive conductor. The feed conductor is disposed apart from the grounding conductor. The resonant conductor having a resonant width is disposed along the grounding conductor and disposed apart from the grounding conductor by a resonant-ground distance. The resonant conductor connects to the feed conductor. The radioactive conductor has a radioactive width. One end of the radioactive conductor connects to one end of the resonant conductor with the feed conductor, and another end of the radioactive conductor is disposed apart from the grounding conductor. The radioactive conductor is disposed along the resonant conductor and disposed apart from the resonant conductor by a resonant-radioactive distance. The resonant conductor is positioned between the radioactive conductor and the grounding conductor. A proportion of the resonant-ground distance, the resonant width, the resonant-radioactive distance, and the radioactive width is a fixed proportion.