Electronic device with reduced emitted radiation during loaded antenna operating conditions

Patent metadata

Field	Value
Publication number	US-9502750-B2
Application number	US-201313855568-A
Country	US
Kind code	B2
Filing date	Apr 2, 2013
Priority date	Apr 2, 2013
Publication date	Nov 22, 2016
Grant date	Nov 22, 2016

Abstract

An electronic device may have an antenna for providing coverage in wireless communications bands of interest. The wireless communications bands may include a communications band at a first frequency. The antenna may have a parasitic antenna resonating element that supports a low efficiency resonance. In response to operation of the electronic device in free space, the low efficiency resonance will be located at a second frequency that is greater than the first frequency. In response to operation of the electronic device in proximity to a user's body or other external object, the antenna will be loaded and the low efficiency resonance associated with the parasitic antenna resonating element will shift to the communications band at the first frequency. The antenna may include a resonating element formed on a flexible printed circuit or a dielectric carrier such as a plastic support structure.

First claim

What is claimed is:

1. An antenna operable in a communications band at a first frequency, comprising:
an antenna ground;
antenna resonating element, wherein the antenna resonating element comprises an inverted-F antenna resonating element;
a parasitic antenna resonating element, wherein the parasitic antenna resonating element exhibits a resonance at a second frequency greater than the first frequency when the antenna is operated in free space, the resonance shifts to overlap the communications band at the first frequency when the antenna is loaded due to proximity to an object, and the shifted resonance reduces antenna efficiency in the communications band at the first frequency when the antenna is loaded relative to when the antenna is operated in free space; and
a flexible printed circuit having opposing first and second surfaces, wherein the antenna resonating element is formed on the first surface and wherein the parasitic antenna resonating element is formed on the second surface.

2. The antenna defined in claim 1 wherein the parasitic antenna resonating element comprises an L-shaped parasitic antenna resonating element.

3. The antenna defined in claim 1 further comprising a molded plastic carrier, wherein the antenna resonating element comprises metal traces formed on the plastic carrier, and the parasitic antenna resonating element comprises metal traces formed on the molded plastic carrier.

4. The antenna defined in claim 1 wherein the antenna ground comprises a metal electronic device housing.

5. The antenna defined in claim 1 further comprising capacitive proximity sensor circuitry that is electrically coupled to the antenna resonating element.

6. An antenna operable in a communications band at a first frequency, comprising:
an antenna ground;
antenna resonating element, wherein the antenna resonating element comprises an inverted-F antenna resonating element;
a parasitic antenna resonating element, wherein the parasitic antenna resonating element exhibits a resonance at a second frequency greater than the first frequency when the antenna is operated in free space, the resonance shifts to overlap the communications band at the first frequency when the antenna is loaded due to proximity to an object, the shifted resonance reduces antenna efficiency in the communications band at the first frequency when the antenna is loaded relative to when the antenna is operated in free space, and the parasitic antenna resonating element comprises a metal trace; and
an inductor coupled between the metal trace and the antenna ground.

7. An antenna operable in a communications band at a first frequency, comprising:
an antenna ground;
antenna resonating element, wherein the antenna resonating element comprises an inverted-F antenna resonating element;
a parasitic antenna resonating element, wherein the parasitic antenna resonating element exhibits a resonance at a second frequency greater than the first frequency when the antenna is operated in free space, the resonance shifts to overlap the communications band at the first frequency when the antenna is loaded due to proximity to an object, the shifted resonance reduces antenna efficiency in the communications band at the first frequency when the antenna is loaded relative to when the antenna is operated in free space, and the parasitic antenna resonating element comprises a metal trace; and
a capacitor coupled between the metal trace and the antenna ground.

Assignees

• Apple Inc

Inventors

• Yarga Salih
• Li Qingxiang
• Schlub Robert W

Classifications

• H01Q5/378

  Combination of fed elements with parasitic elements · CPC title

• H01Q9/0421

  with a shorting wall or a shorting pin at one end of the element (H01Q9/0414 takes precedence) · CPC title

• H01Q1/243 Primary

  with built-in antennas · CPC title

• H01Q1/245

  with means for shaping the antenna pattern, e.g. in order to protect user against rf exposure · CPC title

• H01Q1/38

  formed by a conductive layer on an insulating support {(patch antennas H01Q9/0407; microstrip dipole antennas H01Q9/065; microstrip slot antennas H01Q13/106; transmission line microstrip antennas H01Q13/206; manufacturing reflecting surfaces using insulating material for supporting the reflecting surface  H01Q15/142)} · CPC title