Tunable loop antennas

摘要

Electronic devices are provided that contain wireless communications circuitry. The wireless communications circuitry may include radio-frequency transceiver circuitry and antenna structures. A parallel-fed loop antenna may be formed from portions of a conductive bezel and a ground plane. The antenna may operate in multiple communications bands. The bezel may surround a peripheral portion of a display that is mounted to the front of an electronic device. The bezel may contain a gap. Antenna feed terminals for the antenna may be located on opposing sides of the gap. A variable capacitor may bridge the gap. An inductive element may bridge the gap and the antenna feed terminals. A switchable inductor may be coupled in parallel with the inductive element. Tunable matching circuitry may be coupled between one of the antenna feed terminals and a conductor in a coaxial cable connecting the transceiver circuitry to the antenna.

主权项

1. A parallel-fed loop antenna in an electronic device having a periphery, comprising:
an antenna feed that includes first and second antenna feed terminals; a conductive loop coupled between the first and second antenna feed terminals, wherein the conductive loop is formed at least partly from conductive structures disposed along the periphery; and a variable inductor that bridges the first and second antenna feed terminals, wherein the variable inductor is coupled in parallel between the first and second antenna feed terminals, wherein the variable inductor comprises:
a first segment, wherein the first segment forms a part of a transmission line path with a first inductance and a first length; anda second segment, wherein the second segment and the first segment form part of a second transmission line path with a second inductance and a second length that is different from the first length.