EP1641077B1

EP1641077B1 - Mobile telecommunication device and planar antenna therefor

Info

Publication number: EP1641077B1
Application number: EP05019902.5A
Authority: EP
Inventors: Ming-Feng Chen
Original assignee: Asustek Computer Inc
Current assignee: Asustek Computer Inc
Priority date: 2004-09-22
Filing date: 2005-09-13
Publication date: 2015-08-19
Anticipated expiration: 2025-09-13
Also published as: CN1753248A; EP1641077A1; CN100544117C

Description

BACKGROUND

Field of the Invention

The invention relates to a planar antenna, and in particular to a mobile telecommunication device with a built-in planar antenna providing multiple frequency bands.

Description of the Prior Art

An antenna is indispensable part of a mobile telecommunication device. A planar inverted-F antenna (PIFA) is commonly built into a mobile telecommunication device. As miniature antennas are commonly built into mobile telecommunication devices, planar inverted-F antennas (PIFA) with EGSM (880 MHz - 960 MHz), DCS (1710 MHz - 1880 MHZ), and PCS (1850 MHZ - 1990 MHz) functions are developed accordingly.
A planar antenna according to the preamble of claim 1 is disclosed in WO 02/078124 A . Similar antennas are described in EP 1 263 079 A1 , US 6 343 208 B1 , US 6 476 769 B1 , and WO 02/078123 A1 .
A dual-frequency planar inverted-F antenna is disclosed by Liu (IEEE transaction on Antennas and Propagation, Vol. 45, pages 1451-1458, Oct. 10, 1997). A dual-band planar inverted-F patch antenna with a branch-line slit is disclosed by Hsiao (Microwave and Optical Technology Letters, Vol. 32, pages 310-312, Feb. 4, 2002). A dual-frequency PIFA with a rolled radiating arm for GSM-DCS operation is further disclosed by Hsiao (IEEE Antennas and Propagation Society International Symposium, pages 103-106, 2003).
Moreover, a series of studies regarding enhancement of operating bandwidth of PIFA have been made by Virga and Rahmat-Samii (Low-profile enhanced-bandwidth PIFA antennas for wireless communications packaging, IEEE transaction on Microwave Theory and Techniques, Vol. 45, pages 1879-1888, Oct 10, 1997).
A PIFA with dual-resonant modes is disclosed by Chen in 2002. The resonant points of the PIFA are at 900MHz and 1900MHz covering frequency bands of DCS and PCS. The PIFA can thus be used in triple-band (GSM/ DCS/PCS) operation (Compact PIFA for GSM-DCS-PCS triple-band mobile phone, IEEE Antennas and Propagation Society International Symposium, pages 528-531, 2002). Accordingly, by cutting a conducting plane in different manners, planar inverted-F antennas (PIFA) with different electromagnetic characteristics can be created. However, when a triple-band PIFA with accurate resonant points is produced, repeated and complex designs are required. Furthermore, when the triple-band PIFA is applied to different mobile telecommunication devices, repeated and complex adjustments are required.
Hence, there is a need for an improved triple-band PIFA built into a mobile telecommunication device. The profiles and relative positions of radiation members in the triple-band PIFA are adequately designed to accomplish triple-band operation for mobile telecommunication.

SUMMARY

A planar antenna according to the invention is specified in claim 1. Optional features of the invention are indicated in the dependent claims. An exemplary embodiment of the invention provides a planar antenna comprising a ground area, a first planar radiation member, a second planar radiation member, and a third planar radiation member. The first planar radiation member opposes the ground area and provides a first resonant frequency. The first planar radiation member comprises a first ground end, a feeding end, and an intermediate portion disposed between the first ground end and the feeding end. The first ground end is connected to the ground area, and the feeding end inputs signals. The second planar radiation member opposes the ground area and comprises a connecting portion and a first free end. The connecting portion is connected to the intermediate portion. The first free end extends to one side of the first planar radiation member and is separated from the first ground end and feeding end by a first gap. The feeding end, intermediate portion, connecting portion and first free end constitute a radiation path providing a second resonant frequency. The third planar radiation member opposes the ground area and provides a third resonant frequency differing from the first and second resonant frequencies. The third planar radiation member comprises a second ground end and a third free end. The second ground end is connected to the ground area. The third free end surrounds the first and second planar radiation members and is separated from the first and second planar radiation members by a third gap. Another exemplary embodiment of the invention provides a mobile telecommunication device according to claim 7, comprising a housing, an antenna base, and a planar antenna. The housing comprises an upper case and a back cover. The antenna base is disposed between the upper case and the back cover and comprises a back surface, a front surface, and a ground area. The back surface faces the back cover, and the front surface faces the upper case. The planar antenna is disposed on the ground area and comprises a first planar radiation member, a second planar radiation member, and a third planar radiation member to emit electromagnetic waves.
In an embodiment of the planar antenna, the first planar radiation member, connecting portion and first free end constitute an enclosed area, and the second free end diverging from the first free end extends into the enclosed area.
In an embodiment of the planar antenna, the first planar radiation member is U-shaped, and the first ground end and feeding end are respectively on both sides of the intermediate portion. One side of the first planar radiation member, the connecting portion and first free end constitute an enclosed area, and the second free end diverging from the first free end extends into the enclosed area. The first ground end is disposed between the feeding end and the second free end. The second free end extending toward the connecting portion is separated from the connecting portion by a second gap.
In an embodiment of the planar antenna, the first, second and third planar radiation members are on the same plane. The third resonant frequency exceeds the first resonant frequency, and the first resonant frequency exceeds the second resonant frequency. Preferably, the first resonant frequency is between 1710 MHz and 1880 MHz, the second resonant frequency is between 880 MHz and 960 MHz, and the third resonant frequency is between 1850 MHz and 1990 MHz.

DESCRIPTION OF THE DRAWINGS

The invention can be more fully understood by reading the subsequent detailed description and examples with references made to the accompanying drawings, wherein:

FIG. 1 is a schematic perspective view of the planar antenna of an embodiment of the invention; and
FIG. 2 is a schematic view of the mobile telecommunication device of an embodiment of the invention.

DETAILED DESCRIPTION

Referring to FIG. 1, the planar antenna 100 comprises a ground area 10, a first planar radiation member 20, a second planar radiation member 30, and a third planar radiation member 40. The first planar radiation member 20, second planar radiation member 30, and third planar radiation member 40 are on the same plane. To simplify the drawings, only a part of the ground area 10 is shown in FIG. 1.
The first planar radiation member 20 opposes the ground area 10 and is separated therefrom by a predetermined distance. The first planar radiation member 20 is U-shaped and provides a first resonant frequency. The first planar radiation member 20 comprises a first ground end 22, a feeding end 24, and an intermediate portion 21. The intermediate portion 21 is disposed between the first ground end 22 and the feeding end 24, or the first ground end 22 and feeding end 24 are respectively disposed on both sides of the intermediate portion 21. The first ground end 22 is connected to a ground point g₁ of the ground area 10 via a first ground conducting element 23. The feeding end 24 is connected to a feeding conducting element 25. The feeding conducting element 25 passes through a through hole al of the ground area 10 and is connected to a feeding point f, to input signals.
The second planar radiation member 30 opposes the ground area 10 and is separated therefrom by a predetermined distance. The second planar radiation member 30 comprises a connecting portion 32, a first free end 34, and a second free end 36. The feeding end 24 and intermediate portion 21 of the first planar radiation member 20 and the connecting portion 32 and first free end 34 of the second planar radiation member 30 constitute a radiation path providing a second resonant frequency. Specifically, the second resonant frequency is less than the first resonant frequency.
Additionally, the connecting portion 32 of the second planar radiation member 30 is connected to the intermediate portion 21 of the first planar radiation member 20. The first free end 34 extends to one side of the first planar radiation member 20 and is separated from the first ground end 22 and feeding end 24 by a first gap d1. The first ground end 22 of the first planar radiation member 20 and the connecting portion 32 and first free end 34 of the second planar radiation member 30 constitute an enclosed area 50. The second free end 36 of the second planar radiation member 30 diverges from the first free end 34, extends into the enclosed area 50, and is parallel to the first ground end 22 and feeding end 24. Accordingly, the first ground end 22 is between the feeding end 24 and the second free end 36. Additionally, the front of second free end 36 is separated from the connecting portion 32 by a second gap d2.
The third planar radiation member 40 opposes the ground area 10 and is separated therefrom by a predetermined distance. The third planar radiation member 40 provides a third resonant frequency differing from the first and second resonant frequencies. Additionally, the third planar radiation member 40 comprises a second ground end 42 and a third free end 44. The second ground end 42 is connected to a ground point g2 of the ground area 10 via a second ground conducting element 43. The third free end 44 surrounds the first planar radiation member 20 and second planar radiation member 30 and is separated therefrom by a third gap d3.
In the planar antenna 100, the third planar radiation member 40 provides a parasitic path and thereby serves as a resonator. The bandwidth of the first planar radiation member 20 is thus enlarged. Accordingly, the third resonant frequency can be greater or less than the first resonant frequency.
In a preferred embodiment of the planar antenna 100, the length of the first, second, and third planar radiation members may approximately be one-fourth of the wavelength at the corresponding resonant point. The first resonant frequency is between 1710 MHz and 1880 MHz (DCS 1800). The second resonant frequency is between 880 MHz and 960 MHz (EGSM 800). The second resonant frequency is between 880 MHz and 960 MHz (PCS 1900). Thus, the planar antenna 100 can be applied to conventional mobile telecommunication systems providing multi-band operation.
FIG. 2 is a schematic view of the mobile telecommunication device 200 of the invention. The mobile telecommunication device 200 can be, for example, a cellular phone.
As shown in FIG. 2, the mobile telecommunication device 200 comprises a housing 110, an antenna base 120, and a planar antenna 100. The housing 110 comprises an upper case 111 and a back cover 112. The antenna base 120 is disposed between the upper case 111 and the back cover 112 and comprises a back surface 124, a front surface 122, and a ground area 10. The back surface 124 faces the back cover 112, and the front surface 122 faces the upper case 111. Specifically, the ground area 10 is also disposed in the planar antenna 100. The first planar radiation member 20, second planar radiation member 30, and third planar radiation member 40 of the planar antenna 100 is capable of emitting electromagnetic waves of different frequency bands.
The first planar radiation member 20 and second planar radiation member 30 constitute a structure with two opposing inverted-F elements. The first ground end 22 is separated from the feeding end 24 by a fourth gap d4. The second free end 36 is separated from the first ground end 22 by a fifth gap d5. The second free end 36 is separated from an intermediate section between the connecting portion 32 and the first free end 34 by a sixth gap d6. Specifically, when the planar antenna 100 is applied to different cellular phones, the resonant frequencies and gain distribution of the planar antenna 100 deviate due to different antenna bases, ground areas, and housings. The width of the fourth gap d4 (conduction area between the first ground end 22 and the feeding end 24) can be adjusted to alter the point and bandwidth of the first resonant frequency, or the position of the second free end 36 in the enclosed area 50 (widths of the fifth gap d5 and sixth gap d6) can be adjusted to alter the point and bandwidth of the second resonant frequency.
Moreover, the third planar radiation member 40 of the planar antenna 100 serves as a resonator. The bandwidth of the first resonant frequency can be adjusted by adjusting the width of the third planar radiation member 40 or third gap d3. Accordingly, the planar antenna 100 can cover three frequency bands of EGSM, GSM 1800, and . GSM 1900, enabling triple-band transmission.
Furthermore, when the profile of the planar antenna 100 remains unchanged, the sizes and widths of the first planar radiation member 20, second planar radiation member 30, and third planar radiation member 40 and gaps therebetween can be adequately adjusted such that the planar antenna 100 can provide other frequency bands and be applied to other telecommunication devices providing dual-band operation, such as IEEE 802.11.b and 802.11.a.

Claims

A planar antenna (100), comprising:
a ground area (10);

a first planar radiation member (20) opposing the ground area and providing a first resonant frequency, wherein the first planar radiation member comprises a first ground end (22), a feeding end (24), and an intermediate portion (21) disposed between the first ground end and the feeding end, the first ground end (22) is connected to the ground area (10), and the feeding end (24) inputs signals;

a second planar radiation member (30) opposing the ground area (10) and comprising a connecting portion (32) and a first free end (34), wherein the connecting portion is connected to the intermediate portion (21), the first free end (34) extends to one side of the first planar radiation member (20) and is separated from the first ground end (22) and feeding end (24) by a first gap (d1), and the feeding end (22), intermediate portion (21), connecting portion (32) and first free end (34) constitute a radiation path providing a second resonant frequency; and

a third planar radiation member (40) opposing the ground area (10) and providing a third resonant frequency differing from the first and second resonant frequencies, wherein the third planar radiation member comprises a second ground end (42) and a third free end (44), the second ground end is connected to the ground area (10), and the third free end is separated from the first and second planar radiation members (20; 30) by a third gap (d3);

characterised in that the second planar radiation member (30) has a second free end (36) which diverges from the first free end (34) to the connecting portion (32) and is separated from the connecting portion by a second gap (d2), and in that the third planar radation member (40) surrounds the first and second planar radiation members (20, 30).
The planar antenna as claimed in claim 1, wherein the first planar radiation member (20), the connecting portion (32) and the first free end (34) constitute an enclosed area (50), and the second free end (36) diverging from the first free end (34) extends into the enclosed area (50)
The planar antenna as claimed in claim 1 or 2, wherein the first planar radiation member (20) is U-shaped, and the first ground end (22) and the feeding end (24) are respectively disposed on both sides of the intermediate portion (21).
The planar antenna as claimed in claim 1 or 2, wherein the first ground end (22) is disposed between the feeding end (24) and the second free end (36).
The planar antenna as claimed in claim 1 or 2, wherein the first, second and third planar radiation members (20, 30, 40) are on the same plane.
The planar antenna as claimed in claim 1 or 2, wherein the third resonant frequency exceeds the first resonant frequency, and the first resonant frequency exceeds the second resonant frequency.
A mobile telecommunication device, comprising:
a housing (110) comprising an upper case (111) and a back cover (112);

an antenna base (120) disposed between the upper case and the back cover and comprising a back surface (124), and a front surface (122), wherein the back surface faces the back cover, and the front surface faces the upper case; and

a planar antenna according to any of the claims 1 to 6, wherein the a ground area (10) is formed on the antenna base (120).
The mobile telecommunication device as claimed in claim 7, wherein the ground area (10) is disposed on the front surface (122)