Electronic devices having compact ultra-wideband antennas

An electronic device comprising:

• a substrate;
• a ground plane on a first surface of the substrate;
• conductive traces on a second surface of the substrate, wherein the conductive traces comprise:
• a first antenna arm configured to radiate in a first frequency band,
• a second antenna arm configured to radiate in a second frequency band that is different from the first frequency band, and
• a ring that runs around the first and second antenna arms;
• a first set of conductive vias that couple the ring to the ground plane through the substrate and that short the first antenna arm to the ground plane;
• and
• a second set of conductive vias that couple the ring to the ground plane through the substrate and that short the second antenna arm to the ground plane.

An antenna comprising:

• a ring of conductive traces having first and second segments;
• a first arm having opposing first and second ends, wherein the first end is formed from the first segment of the ring of conductive traces, the first arm being configured to radiate in a first frequency band;
• a first antenna feed coupled to the first arm;
• a second arm having opposing third and fourth ends, wherein the fourth end faces the second end of the first arm, the second arm is configured to radiate in a second frequency band that is higher than the first frequency band, and the third end is formed from the second segment of the ring of conductive traces;
• a second antenna feed coupled to the second arm;
• a ground plane;
• and
• a set of conductive vias that couples the first end of the first arm to the ground plane.