A communication device includes a circuit board having an upper surface and a lower surface, an upper housing disposed on the upper surface, and a lower housing disposed on the lower surface. The circuit board includes a top metal frame disposed on the upper surface, wherein the top metal frame defines a top cavity; a bottom metal frame disposed on the bottom surface, wherein the bottom metal frame defines a bottom cavity corresponding to the top cavity; a microstrip line disposed on the upper surface and extending into the top cavity; and a side coupler disposed on the lower surface and extending into the bottom cavity. The upper housing includes a depression corresponding to the top cavity, and the lower housing includes an aperture corresponding to the bottom cavity.