Communication device and method for designing multi-antenna system thereof

A method for designing a multi-antenna system suitable for a communication device, the method comprising:

• disposing a multi-antenna system in a communication device comprising a ground conductor portion, wherein the ground conductor portion comprises at least a first radiating edge and a second radiating edge, and the multi-antenna system comprises at least a first resonant portion and a second resonant portion;
• disposing the first resonant portion on the first radiating edge, wherein the first resonant portion has a loop resonant structure or an open-slot resonant structure, and the first resonant portion has a first resonant path, the first resonant portion comprising a first electrically coupling portion and a first switch, the first switch is disposed on the first resonant path, the first electrically coupling portion makes the length of the first resonant path less than or equal to 0.18 times the wavelength of the lowest operating frequency of the multi-antenna system, thereby exciting the first radiating edge to form a strong surface current distribution, and generating a first effective radiating energy and at least one first resonant mode covering at least one first operating band, and the first effective radiating energy generated has a first strongest radiation direction;
• disposing the second resonant portion on the second radiating edge of the ground conductor portion, wherein the second resonant portion has a loop resonant structure or an open-slot resonant structure, and the second resonant portion has a second resonant path, the second resonant portion comprising a second electrically coupling portion and a second switch, the second switch is disposed on the second resonant path, the second electrically coupling portion makes the length of the second resonant path less than or equal to 0.18 times the wavelength of the lowest operating frequency of the multi-antenna system, thereby exciting the second radiating edge to form a strong surface current distribution, and generating a second effective radiating energy and at least one second resonant mode covering at least the first operating band, the second effective radiating energy generated having a second strongest radiation direction;
• disposing a first control circuit respectively electrically coupled to the first resonant portion and the second resonant portion through a plurality of signal lines, the first control circuit switching a signal source to electrically couple to one of the first resonant portion or the second resonant portion, and generating the first strongest radiation direction or the second strongest radiation direction, or controlling the signal source to concurrently and electrically couple to the first resonant portion and the second resonant portion, and generating a third effective radiating energy having a third strongest radiation direction;
• and
• disposing a second control circuit respectively and electrically coupled to the first switch and the second switch through a plurality of signal lines, the second control circuit switching the first switch to a conducting state when the signal source is electrically coupled to the first resonant portion, and switching the second switch to the conducting state when the signal source is electrically coupled to the second resonant portion.