Electronic devices with parasitic antenna resonating elements that reduce near field radiation

• US 8,466,839 B2
• Filed: 12/07/2009
• Issued: 06/18/2013
• Est. Priority Date: 07/17/2009
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Schlub, Robert W., Amm, David T., Leung, Omar S., King, Brian M., Li, Qingxiang, Ayala Vazquez, Enrique, Gomez Angulo, Rodney Andres, Jiang, Yi, Caballero, Ruben
• Primary Examiner(s): DUONG, DIEU HIEN
• Application Number:
  US12/632,697
• Publication Number:
  US 20110012794A1
• Time in Patent Office: 1,289 Days
• Field of Search: 343/702, 343/872, 343/873
• US Class Current: 343/702
• CPC Class Codes: H01Q 1/243 with built-in antennas
• CPC Class Codes: H01Q 1/245 with means for shaping the antenna pattern, e.g. in order to protect user against rf exposure
• CPC Class Codes: H01Q 1/44 using equipment having another main function to serve additionally as an antenna , e.g. means for giving an antenna an aesthetic aspectH01Q1/27 - H01Q1/34 take precedence
• CPC Class Codes: H01Q 5/378 Combination of fed elements with parasitic elements
• CPC Class Codes: H03K 17/955 using a capacitive detector

Abstract

Antennas are provided for electronic devices such as portable computers. An electronic device may have a housing in which an antenna is mounted. The housing may be formed of conductive materials. A dielectric antenna window may be mounted in the housing to allow radio-frequency signals to be transmitted from the antenna and to allow the antenna to receive radio-frequency signals. Near-field radiation limits may be satisfied by reducing transmit power when an external object is detected in the vicinity of the dielectric antenna window and the antenna. A proximity sensor may be used in detecting external objects. A parasitic antenna resonating element may be interposed between the antenna resonating element and the dielectric antenna window to minimize near-field radiation hotspots. The parasitic antenna resonating element may be formed using a capacitor electrode for the proximity sensor. A ferrite layer may be interposed between the parasitic element and the antenna window.

Claims

1. An electronic device having front and rear surfaces, comprising:

a conductive housing;

a dielectric antenna window in the conductive housing;

an antenna resonating element mounted in the conductive housing so that radio-frequency signals are transmitted through the dielectric antenna window; and

a parasitic antenna resonating element located between the antenna resonating element and the dielectric window, wherein the parasitic antenna resonating element comprises a capacitive proximity sensor electrode, wherein the capacitive proximity sensor electrode serves as a part of a capacitive proximity sensor and as at least a part of the parasitic antenna resonating element.

2. The electronic device defined in claim 1 wherein the dielectric antenna window comprises a plastic member mounted in the conductive housing.

3. A tablet computer comprising:

a conductive housing;

a dielectric antenna window in the conductive housing;

radio-frequency transceiver circuitry;

an antenna with which the radio-frequency transceiver circuitry transmits radio-frequency signals in at least one cellular telephone band, wherein the antenna comprises;

an antenna ground formed from a portion of the conductive housing;

an antenna resonating element mounted adjacent to the dielectric antenna window;

a parasitic antenna resonating element formed from a planar metal member that is interposed between the antenna resonating element and the dielectric antenna window;

a capacitive proximity sensor that detects when an external object is in the vicinity of the antenna, wherein the parasitic antenna resonating element comprises a capacitor electrode in the capacitive proximity sensor

a display mounted to the conductive housing, wherein the conductive housing forms a planar rear surface for the tablet computer, and wherein the display has a cover glass with an inactive region through which the radio-frequency signals are transmitted

a capacitor connected between the conductive housing and the parasitic antenna resonating element; and

a layer of ferrite interposed between the parasitic antenna resonating element and the dielectric antenna window.

4. The tablet computer defined in claim 3 wherein the parasitic antenna resonating element comprises at least two separate metal structures.