The invention discloses an adjustable multi-band antenna
system which is applicable to a mobile terminal with a
metal frame structure. The antenna
system comprises a
metal frame, a PCB (
printed circuit board) and an antenna portion. The
metal frame is designed to be one portion of an antenna radiator, a loop is formed by the metal frame and the antenna radiator together, a single-stage
branch portion is used for debugging low-frequency and high-frequency resonances, and a low-
frequency coupling portion and a high-
frequency coupling portion can be added according to requirements of working bands. The adjustable multi-band antenna
system has the advantages that gaps of the metal frame are formed at the bottom, users are avoided from touching the gaps as much as possible in
actual use, and poor antenna performance is avoided during actual handholding; the working bands of the adjustable multi-band antenna system are 704MHz-960MHz and 1710MHz-2700MHz, and a multi-frequency
broadband is realized; compared with traditional common antennas, the adjustable multi-band antenna system has the advantages of multiple bands and wide bandwidth.