Antenna grounding
An electronic device may have first and second rear-facing displays, a front-facing display, a cover at a front side overlapping the front-facing display, and an antenna that radiates through the cover. The cover may have a three-dimensional curvature. The device may have an inner chassis and an outer chassis. The antenna may include a radiating element and a ground trace on a flexible printed circuit. To maximize wireless performance of the antenna, the ground trace may be electrically coupled to as much conductive material in the vicinity of the antenna as possible. For example, the ground trace may be grounded to conductive structures in the front-facing display via a conductive cavity for the antenna, may be grounded directly to the outer chassis using conductive screws, and/or may be grounded directly to the inner chassis using conductive screws.
1 . An electronic device comprising:
a conductive housing;
a dielectric cover mounted to the conductive housing and having a compound curvature;
an antenna having an antenna resonating element mounted against the dielectric cover and having a ground trace, the antenna being configured to radiate through the dielectric cover; and
a conductive interconnect that couples the ground trace to the conductive housing.
2 . The electronic device of claim 1 , further comprising:
a flexible printed circuit, wherein the ground trace is on the flexible printed circuit and the antenna resonating element includes conductive traces on a portion of the flexible printed circuit, wherein the flexible printed circuit has a tail and the conductive interconnect attaches the tail to the conductive housing.
3 . The electronic device of claim 2 , further comprising:
a first stiffener on a first lateral surface of the tail of the flexible printed circuit; and
a second stiffener on a second lateral surface of the tail of the flexible printed circuit, the conductive interconnect comprising a conductive screw that extends through the first stiffener, the tail of the flexible printed circuit, and the second stiffener.
4 . The electronic device of claim 3 , further comprising:
a screw boss on the conductive housing and configured to receive the conductive screw, wherein the second stiffener comprises an extension that is folded onto a surface of the screw boss.
5 . The electronic device of claim 1 , further comprising:
a conductive frame, wherein the conductive housing surrounds a lateral periphery of the conductive frame;
a dielectric carrier mounted to the conductive frame; and
foam on the dielectric carrier, wherein the foam is configured to press a portion of the antenna resonating element against the dielectric cover.
6 . The electronic device of claim 5 , further comprising:
a conductive rivet that attaches the conductive frame to the conductive housing;
a head strap coupled to the conductive housing;
a first display mounted to the conductive frame and configured to display a left image;
a second display mounted to the conductive frame and configured to display a right image; and
a third display mounted to the dielectric cover and configured to display an image through the dielectric cover.
7 . The electronic device of claim 6 , wherein the third display includes conductive display structures, the electronic device further comprising:
a conductive cavity formed from folded sheet metal, wherein the portion of the antenna resonating element overlaps the conductive cavity, the conductive cavity is electrically coupled to the ground trace, and the conductive cavity is electrically coupled to the conductive display structures.
8 . The electronic device of claim 7 , further comprising a conductive gasket that couples the conductive cavity to the conductive display structures.
9 . The electronic device of claim 7 , further comprising:
a biasing member disposed in the conductive cavity and configured to press the portion of the flexible printed circuit against the dielectric cover.
10 . The electronic device of claim 1 , wherein the dielectric cover comprises an outer glass layer having the compound curvature and a dielectric layer between the antenna resonating element and the outer glass layer, the antenna resonating element comprising a conductive trace patterned onto an interior surface of the dielectric layer.
11 . The electronic device of claim 10 , further comprising:
a radio-frequency connector soldered to the conductive trace; and
a coaxial cable coupled to the radio-frequency connector.
12 . The electronic device of claim 1 , wherein the dielectric cover comprises a glass layer having the compound curvature, the electronic device further comprising:
a plastic layer overlapping the glass layer.
13 . The electronic device of claim 12 , wherein the antenna resonating element is molded within the plastic layer.
14 . The electronic device of claim 1 , wherein the compound curvature has a first non-zero radius of curvature about a first axis and has a second non-zero radius of curvature about a second axis that is non-parallel to the first axis.
15 . An electronic device comprising:
a conductive outer chassis;
a conductive inner chassis, the conductive inner chassis being mounted to the conductive outer chassis and the conductive outer chassis extending around a lateral periphery of the conductive inner chassis;
a cover mounted to the conductive outer chassis and having a three-dimensional curvature;
a flexible printed circuit;
an antenna having an antenna resonating element on a first portion of the flexible printed circuit and having a ground trace on a second portion of the flexible printed circuit, the antenna being configured to radiate through the cover; and
a rigid support mounted to the conductive inner chassis using a conductive interconnect, wherein the conductive interconnect electrically couples the ground trace to the conductive inner chassis.
16 . The electronic device of claim 15 , further comprising:
a biasing member mounted to the rigid support and configured to press the first portion of the flexible printed circuit against the cover.
17 . The electronic device of claim 15 , further comprising:
a conductive rivet that attaches the conductive outer chassis to the conductive inner chassis;
a head strap coupled to the conductive outer chassis;
a logic board mounted to the conductive inner chassis;
a first display mounted to the logic board and configured to display a left image;
a second display mounted to the logic board and configured to display a right image; and
a third display mounted to the cover and configured to display an image through the cover.
18 . A head-mounted device comprising:
a first conductive chassis;
a logic board mounted to the first conductive chassis;
first and second displays mounted to the logic board and configured to display respective left and right images;
a second conductive chassis that extends around the first conductive chassis and the logic board;
a cover mounted to the second conductive chassis opposite the first and second displays, the cover having a third display configured to display images through the cover;
a conductive can mounted to the logic board, wherein the conductive can is electrically coupled to a conductive structure in the third display; and
an antenna having an antenna resonating element interposed between the conductive can and having an antenna ground that includes the conductive can and the conductive structure in the third display.
19 . The head-mounted device of claim 18 , further comprising:
a flexible printed circuit, wherein the antenna resonating element is disposed on the flexible printed circuit and the antenna ground comprises a ground trace disposed on the flexible printed circuit; and
a conductive screw that attaches the flexible printed circuit to the second conductive chassis and that electrically couples the ground trace to the second conductive chassis.
20 . The head-mounted device of claim 18 , wherein the conductive can has a rear wall opposite the antenna resonating element, a sidewall extending from the rear wall towards the cover, and a ledge that extends away from a volume between the conductive can and the antenna resonating element, the electronic device further comprising:
a conductive gasket that is mounted to the conductive ledge and that electrically couples the conductive can to the conductive structure in the third display.