Wide-band planar antenna

A wideband planar antenna, comprising:

• a substrate including a first surface and a second surface opposite to the first surface;
• a first radiator disposed on the first surface;
• a second radiator connecting to the first radiator at a connection part, wherein the second radiator is disposed on either the first surface or the second surface;
• a third radiator disposed on either the first surface or the second surface;
• a ground connecting to the third radiator, wherein the ground includes a first ground part and a second ground part, the third radiator includes a shorter side and a longer side, the shorter side connects to the ground, a lengthwise direction of the shorter side is perpendicular to a lengthwise direction of the longer side, the longer side extends toward the first radiator, and the second radiator is disposed between the third radiator and the ground;
• and
• a signal source feeding a high frequency signal including a positive signal and a negative signal, wherein the positive signal is directly fed through the connection part to excite the first radiator and the second radiator to generate a first frequency band mode and a second frequency band mode respectively, and the negative signal couples with the ground to be fed into and excite the third radiator to form a third frequency band mode.