A printed circuit board (PCB) includes a positive differential signal line including first and second segments, a negative differential signal line including third and fourth segments, first and second connecting elements soldered on opposite surfaces of the PCB. The first segment and the fourth segment are located in a first straight line which has a first permittivity. The third segment and the second segment are located in a second straight line which has a second permittivity different from the first permittivity. The first connecting element is connected between the first segment and the second segment. The second connecting element is connected between the third segment and the fourth segment.