Antenna system and mobile terminal

1. An antenna system, comprising: a metal rear cover, a first feeding point and a system ground, wherein a U-shaped slot is arranged at a bottom of the metal rear cover, and the U-shaped slot divides the metal rear cover into a radiation portion and a grounding portion, the grounding portion is connected to the system ground, the radiation portion comprises a first end and a second end, and both the first end and the second end are connected to the grounding portion, a breaking joint is defined at the radiation portion, and the radiation portion is electrically connected to the first feeding point, so as to form a main antenna,

wherein the main antenna has a first working frequency band, a second working frequency band and a third working frequency band, wherein the first working frequency band is 700 MHz-960 MHz, the second working frequency band is 1710 MHz-2700 MHz, and the third working frequency band is 3300 MHz-3800 MHz,

wherein the first feeding point and the breaking joint divide the radiation portion into a first section, a second section and a third section, wherein the first section is a portion of the radiation portion from the first end to the first feeding point, the second section is a portion of the radiation portion from the first feeding point to the breaking joint, and the third section is a portion of the radiation portion from the breaking joint to the second end, and

wherein a main radiator of the first working frequency band comprises the first section and the second section, a main radiator of the second working frequency band comprises the second section and the third section, and a main radiator of the third working frequency band comprises the first section, the second section and the third section.

2. The antenna system according to claim 1 , further comprising an impedance matching circuit, wherein the impedance matching circuit comprises a first branch circuit and a second branch circuit, the first branch circuit has two ends electrically connected to the first feeding point and the radiation portion, respectively, the second branch circuit is connected to the first branch circuit, the second branch circuit is provided with a matching switch and a plurality of different grounding elements, and the matching switch is connectable to at least one of the plurality of different grounding elements.

3. The antenna system according to claim 2 , wherein the plurality of different grounding elements comprises at least one inductance element and a plurality of capacitance elements, or comprises a plurality of inductance elements and at least one capacitance element, and each inductance element or each capacitance element has a value different from one another.

4. The antenna system according to claim 2 , wherein an adjustable capacitance element is provided at a position in the first branch circuit from a connection point with the second branch circuit to the first feeding point.

5. The antenna system according to claim 1 , further comprising a second feeding point, a grounding point, a first switch, and a second switch,

wherein the second feeding point is connected to the third section through the first switch, and the grounding point is connected to the second section through the second switch,

wherein both the first switch and the second switch have a closed state and an open state,

wherein when both the first switch and the second switch are in the open state, the antenna system comprises the main antenna,

wherein when both the first switch and the second switch are in the closed state, the antenna system comprises a first antenna and a second antenna, wherein a main radiator of the first antenna is a portion of the radiation portion from the grounding point to the second end, a main radiator of the second antenna is a portion of the radiation portion from the grounding point to the first end, and both a working frequency band generated by the first antenna and a working frequency band generated by the second antenna are within a range of the second working frequency band and the third working frequency band.

6. The antenna system according to claim 1 , wherein a total length of the first section and the second section is larger than a total length of the second section and the third section.

7. The antenna system according to any one of claim 1 , wherein both the U-shaped slot and the breaking joint have a width within a range of 1.5 mm-3 mm, respectively.

8. The antenna system according to any one of claim 2 , wherein both the U-shaped slot and the breaking joint have a width within a range of 1.5 mm-3 mm, respectively.

9. The antenna system according to any one of claim 3 , wherein both the U-shaped slot and the breaking joint have a width within a range of 1.5 mm-3 mm, respectively.

10. The antenna system according to any one of claim 4 , wherein both the U-shaped slot and the breaking joint have a width within a range of 1.5 mm-3 mm, respectively.

11. The antenna system according to any one of claim 5 , wherein both the U-shaped slot and the breaking joint have a width within a range of 1.5 mm-3 mm, respectively.

12. The antenna system according to any one of claim 6 , wherein both the U-shaped slot and the breaking joint have a width within a range of 1.5 mm-3 mm, respectively.

13. A mobile terminal, comprising the antenna system according to claim 1 .

14. A mobile terminal, comprising the antenna system according to claim 2 .

15. A mobile terminal, comprising the antenna system according to claim 3 .

16. A mobile terminal, comprising the antenna system according to claim 4 .

17. A mobile terminal, comprising the antenna system according to claim 5 .

18. A mobile terminal, comprising the antenna system according to claim 6 .