Antenna system with full metal back cover

An antenna system, comprising:

• a metal back cover comprising a main body and a plurality of sidewalls extending from the main body, the plurality of sidewalls comprising a first sidewall and a second sidewall opposite to each other;
• a circuit board with a main ground point;
• a first antenna module and a second antenna module electrically connected to the circuit board;
• wherein a first gap is formed between the first sidewall and the main body, and a second gap is formed between the second sidewall and the main body;
• By the first gap and the second gap, the metal back cover is divided into a first metal portion including the first sidewall, a second metal portion including the second sidewall, and a third metal portion between the first metal portion and the second metal portion, which are insulated from each other;
• wherein the first metal portion comprises a top slit penetrating through an edge of the first sidewall and the first gap, and the second metal portion comprises at least one bottom slit penetrating through an edge of the second sidewall and the second gap;
• the second antenna module comprises a diversity antenna unit;
• two bottom slits are formed in the second metal portion, the diversity antenna unit comprises a first feed point;
• the diversity antenna unit comprises a first ground point, the first feed point and the first ground point of the diversity antenna unit are respectively connected to the second metal portion at locations at two opposite sides of a bottom slit adjacent to the first feed point.