Radio-frequency transmission line structures

An electronic device comprising:

• a slot element having first and second opposing sides formed from conductive structures, wherein the conductive structures include an antenna ground on the second side of the slot element;
• a coaxial cable coupled to the conductive structures across the slot element and having a ground conductor and a signal conductor, wherein the coaxial cable has a segment along which the ground conductor is capacitively coupled to the antenna ground to provide impedance matching for the coaxial cable, the segment is between a first location at which the ground conductor is coupled to a ground antenna feed terminal of the slot element and a second location at which the signal conductor is coupled to a positive antenna feed terminal of the slot element, the first location is a grounding location for the ground conductor closest to an end of the ground conductor along a length of the coaxial cable, and the segment capacitively coupled to the antenna ground extends from the grounding location closest to the end of the ground conductor to the end of the ground conductor;
• and
• a dielectric retention layer that overlaps the segment of the coaxial cable and holds the segment of the coaxial cable in place with respect to the antenna ground.

An electronic device comprising:

• peripheral conductive housing structures having first and second segments separated by a dielectric-filled gap;
• an antenna ground separated from the peripheral conductive housing structures by a slot having an open end at the dielectric-filled gap;
• a radio-frequency transmission line having a signal conductor coupled to a positive antenna feed terminal at the first segment and having a ground conductor coupled to a ground antenna feed terminal at the antenna ground, wherein the radio-frequency transmission line has a segment separated from the antenna ground by a gap to form an impedance matching element using the gap, the antenna ground, and a portion of the ground conductor along the segment, the portion of the ground conductor is between a location at which the ground conductor is coupled to the ground antenna feed terminal and an end of the ground conductor, the location is a grounding location for the ground conductor closest to the end of the ground conductor along a length of the ground conductor, and the portion of the ground conductor extends beyond the grounding location toward the end of the ground conductor;
• and
• a dielectric retention layer that overlaps the segment of the radio-frequency transmission line and the antenna ground and that maintains the gap between the segment of the radio-frequency transmission line and the antenna ground.