Abstract: An electronic device may be provided with an antenna resonating element on a first substrate that is mounted to a second substrate. A signal conductor may be coupled to a feed terminal on the antenna resonating element. The signal conductor may include impedance matching structures for the antenna. The impedance matching structures may include an open transmission line stub, a grounded transmission line stub, and a phase shifting segment. The impedance matching structures may configure the antenna to exhibit a wide bandwidth in an ultra-wideband (UWB) frequency band. If desired, the signal conductor may have a phase-shifting segment configured to match a non-50 Ohm impedance of a radio-frequency front end coupled to the signal conductor.

Abstract: An electronic device may be provided with a flexible printed circuit and a rigid printed circuit mounted to the flexible printed circuit using a board-to-board (B2B) connector. The flexible printed circuit may include signal conductors coupled to one or more antennas on the rigid printed circuit through the B2B connector. A given one of the signal conductors may include a phase shifter segment on the flexible printed circuit and/or a thick impedance matching segment on the rigid printed circuit that help to form a smooth impedance transition from the flexible printed circuit to the rigid printed circuit and the antenna(s). The B2B connector may include signal contacts interleaved with a ground contacts. The B2B connector may include ground bars laterally surrounding the signal and ground contacts to maximize the strength of mechanical coupling between the flexible printed circuit and the rigid printed circuit.

Abstract: An electronic device may be provided with a housing and an antenna. The antenna may be on a first substrate mounted to a second substrate. The housing may include a dielectric cover, a conductive plate on the dielectric cover, and a mid-chassis. The second substrate may be mounted to the mid-chassis. The antenna may include a conductive patch extending from a segment of a conductive ring on the first substrate. The conductive plate may have an opening aligned with the conductive patch. The first substrate may be separated from the dielectric cover by an air gap. A conductive gasket may couple the conductive ring to the conductive plate and may laterally surround the air gap and the opening. The antenna may convey ultra-wideband (UWB) signals through the air gap, the opening, and the dielectric cover layer.

Abstract: An electronic device may include an antenna disposed on a substrate. The antenna may include a ring of conductive traces, a fed arm, and an unfed arm. The fed arm and the unfed arm may extend from opposing segments of the ring. The ring may be coupled to ground by fences of conductive vias extending through the substrate. The first arm may have a first radiating edge. The second arm may have a second radiating edge. The first radiating edge may be separated from the second radiating edge by a gap. The first arm may indirectly feed the second arm via near-field electromagnetic coupling across the gap. The first and second arms may collectively radiate in an ultra-wideband (UWB) frequency band.