Abstract: A loop antenna adapted for a communication device is provided. The loop antenna includes a feed, a ground, a circular loop, at least one first tuning element, and at least one second tuning element. The circular loop is connected to the feed and the ground. The first tuning element is extended from the circular loop and corresponds to a first frequency band. The second tuning element is extended from the circular loop and corresponds to a second frequency band. Bandwidths of the first frequency band and the second frequency band of the loop antenna are changed by adjusting the first tuning element and the second tuning element, respectively.

Abstract: A loop antenna adapted for a communication device is provided. The loop antenna includes a feed, a ground, a circular loop, at least one first tuning element, and at least one second tuning element. The circular loop is connected to the feed and the ground. The first tuning element is extended from the circular loop and corresponds to a first frequency band. The second tuning element is extended from the circular loop and corresponds to a second frequency band. Bandwidths of the first frequency band and the second frequency band of the loop antenna are changed by adjusting the first tuning element and the second tuning element, respectively.

Abstract: A circuit board having antenna structure for use with portable communication devices includes a substrate and an antenna body provided on the substrate. The substrate has a first, a second and a third surface that adjoin one another, and has a ground metallic element mounted thereon parallel to the third surface. The antenna body includes a radiation portion located on the first and second surfaces, a feed-in portion located on the third surface and connected to the radiation portion, and a ground portion located on the third surface and connected to the radiation portion and the ground metallic element. With these arrangements, the antenna structure provided on the circuit board overcomes the problems of limited antenna position and insufficient antenna area without being hindered by other electronic components or structural elements on the circuit board, and is operable at both higher and lower frequency bands.