ELECTRONIC DEVICES WITH PARASITIC ANTENNA RESONATING ELEMENTS THAT REDUCE NEAR FIELD RADIATION

• US 20110012794A1
• Filed: 12/07/2009
• Published: 01/20/2011
• Est. Priority Date: 07/17/2009
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: King, Brian M., Li, Qingxiang, Amm, David T., Schlub, Robert W., Leung, Omar S., Jiang, Yi, Gomez Angulo, Rodney Andres, Ayala Vazquez, Enrique, Caballero, Ruben
• Granted Patent: US 8,466,839 B2
• Time in Patent Office: Days
• 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.

2. The electronic device defined in claim 1 further comprising a display on the front surface of the electronic device, wherein the display has an inactive region through which radio-frequency signals are transmitted from the antenna resonating element.

3. The electronic device defined in claim 1 further comprising a display having display panel circuitry that is covered by a transparent dielectric cover member, wherein the antenna resonating element emits radio-frequency signals that pass through the transparent dielectric cover member without passing through the display panel circuitry.

4. The electronic device defined in claim 1 wherein the dielectric antenna window comprises a plastic member mounted in the conductive housing and wherein the parasitic antenna resonating element comprises a capacitive proximity sensor electrode.

5. The electronic device defined in claim 1 further comprising a proximity sensor that detects external objects near the antenna resonating element and dielectric antenna window, wherein the parasitic antenna resonating element comprises a capacitor electrode for the proximity sensor.

6. The electronic device defined in claim 5 wherein the antenna resonating element comprises an inverted-F antenna resonating element formed on a flex circuit.

7. The electronic device defined in claim 6 wherein the parasitic antenna resonating element comprises a rectangular conductive member.

8. The electronic device defined in claim 7 further comprising a capacitor having a first terminal connected to the conductive housing and a second terminal connected to the parasitic antenna resonating element.

9. 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 at least a portion of the conductive housing;

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

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

10. The tablet computer defined in claim 9 further comprising a capacitor connected between the conductive housing and the parasitic antenna resonating element.

11. The tablet computer defined in claim 9 further comprising 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.

12. The tablet computer defined in claim 11 further comprising 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.

13. The tablet computer defined in claim 12 further comprising a capacitor connected between the conductive housing and the parasitic antenna resonating element.

14. The tablet computer defined in claim 13 further comprising a layer of ferrite interposed between the parasitic antenna resonating element and the dielectric antenna window.

15. The tablet computer defined in claim 9 wherein the parasitic antenna resonating element comprises at least two separate metal structures.

16. A portable electronic device comprising:

at least one conductive housing structure to which a ground antenna feed terminal is connected;

an antenna window in the conductive housing structure;

an antenna resonating element formed from conductive traces on a flex circuit to which a positive antenna feed terminal is connected;

radio-frequency transceiver circuitry that is coupled to the positive antenna feed terminal and the ground antenna feed terminal and that transmits radio-frequency signals through the antenna window using the antenna resonating element; and

a parasitic antenna resonating element interposed between the antenna resonating element and the antenna window.

17. The portable electronic device defined in claim 16 wherein the parasitic antenna resonating element comprises a capacitor electrode in a capacitive proximity sensor.

18. The portable electronic device defined in claim 17 further comprising a layer of ferrite tape between the parasitic antenna resonating element and the antenna window.

19. The portable electronic device defined in claim 18 further comprising a capacitor connected between the conductive housing structure and the parasitic antenna resonating element.

20. The portable electronic device defined in claim 19 wherein the electronic device comprises a display and wherein at least some of the radio-frequency signals are transmitted through an inactive portion of the display.

21. The portable electronic device defined in claim 16 wherein the parasitic antenna resonating element comprises a portion of the conductive housing structure that overlaps the dielectric antenna window.