# Patent

## Title
Multi-band monopole antenna for a mobile communications device

## Abstract

A multi-band monopole antenna for a mobile communications device includes a common conductor coupled to both a first radiating arm and a second radiating arm. The common conductor includes a feeding port for coupling the antenna to communications circuitry in a mobile communications device. In one embodiment, the first radiating arm includes a space-filling curve. In another embodiment, the first radiating arm includes a meandering section extending from the common conductor in a first direction and a contiguous extended section extending from the meandering section in a second direction.

## Background
CROSS-REFERENCE TO RELATED APPLICATIONS
This patent application is a continuation application of, and incorporates by reference the entire disclosure of, U.S. patent application Ser. No. 12/055,748, which was filed on Mar. 26, 2008 now U.S. Pat. No. 7,675,470. U.S. patent application Ser. No. 12/055,748 is a continuation application of Ser. No. 11/713,324, filed Mar. 2, 2007, now U.S. Pat. No. 7,403,164, issued on Jul. 22, 2008. U.S. Pat. No. 7,403,164 is a continuation application of Ser. No. 11/124,768, filed May 9, 2005, now U.S. Pat. No. 7,411,556, issued on Aug. 12, 2008. U.S. Pat. No. 7,411,556 is a continuation application of International Patent Application No. PCT/EP02/14706, filed on Dec. 22, 2002. This patent application incorporates U.S. patent application Ser. No. 12/055,748, U.S. Pat. No. 7,403,164, U.S. Pat. No. 7,411,556, and International Patent Application No. PCT/EP02/14706 by reference.


BACKGROUND OF THE INVENTION
1. Technical Field of the Invention
This invention relates generally to the field of multi-band monopole antennas. More specifically, a multi-band monopole antenna is provided that is particularly well-suited for use in mobile communications devices, such as Personal Digital Assistants, cellular telephones, and pagers.
2. Description of Related Art
Multi-band antenna structures for use in a mobile communications device are known in this art. For example, one type of antenna structure that is commonly utilized as an internally-mounted antenna for a mobile communication device is known as an “inverted-F” antenna. When mounted inside a mobile communications device, an antenna is often subject to problematic amounts of electromagnetic interference from other metallic objects within the mobile communications device, particularly from the ground plane. An inverted-F antenna has been shown to perform adequately as an internally mounted antenna, compared to other known antenna structures. Inverted-F antennas, however, are typically bandwidth-limited, and thus may not be well suited for bandwidth intensive applications.
SUMMARY OF THE INVENTION
A multi-band monopole antenna for a mobile communications device includes a common conductor coupled to both a first radiating arm and a second radiating arm. The common conductor includes a feeding port for coupling the antenna to communications circuitry in a mobile communications device. In one embodiment, the first radiating arm includes a space-filling curve. In another embodiment, the first radiating arm includes a meandering section extending from the common conductor in a first direction and a contiguous extended section extending from the meandering section in a second direction.
A mobile communications device having a multi-band monopole antenna includes a circuit board, communications circuitry, and the multi-band monopole antenna. The circuit board includes an antenna feeding point and a ground plane. The communications circuitry is coupled to the antenna feeding point of the circuit board. The multi-band monopole antenna includes a common conductor, a first radiating arm and a second radiating arm. The common conductor includes a feeding port that is coupled to the antenna feeding point of the circuit board. The first radiating arm is coupled to the common conductor and includes a space-filling curve. The second radiating arm is coupled to the common conductor. In one embodiment, the circuit board is mounted in a first plane within the mobile communications device and the multi-band monopole antenna is mounted in a second plane within the mobile communications device.



BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a top view of an exemplary multi-band monopole antenna for a mobile communications device;
FIG. 2 is a top view of an exemplary multi-band monopole antenna including one alternative space-filling geometry;
FIGS. 3-9 illustrate several alternative multi-band monopole antenna configurations;
FIG. 10 is a top view of the exemplary multi-band monopole antenna of FIG. 1 coupled to a circuit board for a mobile communications device;
FIG. 11 shows an exemplary mounting structure for securing a multi-band monopole antenna within a mobile communications device;
FIG. 12 is an exploded view of an exemplary clamshell-type cellular telephone having a multi-band monopole antenna;
FIG. 13 is an exploded view of an exemplary candy-bar-style cellular telephone having a multi-band monopole antenna; and
FIG. 14 is an exploded view of an exemplary personal digital assistant (PDA) having a multi-band monopole antenna.



DETAILED DESCRIPTION OF THE DRAWINGS
Referring now to the drawing figures, FIG. 1 is a top view of an exemplary multi-band monopole antenna 10 for a mobile communications device. The multi-band monopole antenna 10 includes a first radiating arm 12 and a second radiating arm 14 that are both coupled to a feeding port 17 through a common conductor 16. The antenna 10 also includes a substrate material 18 on which the antenna structure 12, 14, 16 is fabricated, such as a dielectric substrate, a flex-film substrate, or some other type of suitable substrate material. The antenna structure 12, 14, 16 is preferably patterned from a conductive material, such as a metallic thick-film paste that is printed and cured on the substrate material 18, but may alternatively be fabricated using other known fabrication techniques.
The first radiating arm 12 includes a meandering section 20 and an extended section 22. The meandering section 20 is coupled to and extends away from the common conductor 16. The extended section 22 is contiguous with the meandering section 20 and extends from the end of the meandering section 20 back towards the common conductor 16. In the illustrated embodiment, the meandering section 20 of the first radiating arm 12 is formed into a geometric shape known as a space-filling curve, in order to reduce the overall size of the antenna 10. A space-filling curve is characterized by at least ten segments which are connected in such a way that each segment forms an angle with its adjacent segments, that is, no pair of adjacent segments define a larger straight segment. It should be understood, however, that the meandering section 20 may include other space-filling curves than that shown in FIG. 1, or may optionally be arranged in an alternative meandering geometry. FIGS. 2-6, for example, illustrate antenna structures having meandering sections formed from several alternative geometries. The use of shape-filling curves to form antenna structures is described in greater detail in the co-owned PCT Application WO 01/54225, entitled Space-Filling Miniature Antennas, which is hereby incorporated into the present application by reference.
The second radiating arm 14 includes three linear portions. As viewed in FIG. 1, the first linear portion extends in a vertical direction away from the common conductor 16. The second linear portion extends horizontally from the end of the first linear portion towards the first radiating arm. The third linear portion extends vertically from the end of the second linear portion in the same direction as the first linear portion and adjacent to the meandering section 20 of the first radiating arm 14.
As noted above, the common conductor 16 of the antenna 10 couples the feeding port 17 to the first and second radiating arms 12, 14. The common conductor 16 extends horizontally (as viewed in FIG. 1) beyond the second radiating arm 14, and may be folded in a perpendicular direction (perpendicularly into the page), as shown in FIG. 10, in order to couple the feeding port 17 to communications circuitry in a mobile communications device.
Operationally, the first and second radiating arms 12, 14 are each tuned to a different frequency band, resulting in a dual-band antenna. The antenna 10 may be tuned to the desired dual-band operating frequencies of a mobile communications device by pre-selecting the total conductor length of each of the radiating arms 12, 14. For example, in the illustrated embodiment, the first radiating arm 12 may be tuned to operate in a lower frequency band or groups of bands, such as PDC (800 MHz), CDMA (800 MHz), GSM (850 MHz), GSM (900 MHz), GPS, or some other desired frequency band. Similarly, the second radiating arm 14 may be tuned to operate in a higher frequency band or group of bands, such as GPS, PDC (1500 MHz), GSM (1800 MHz), Korean PCS, CDMA/PCS (1900 MHz), CDMA2000/UMTS, IEEE 802.11 (2.4 GHz), or some other desired frequency band. It should be understood that, in some embodiments, the lower frequency band of the first radiating arm 12 may overlap the higher frequency band of the second radiating arm 14, resulting in a single broader band. It should also be understood that the multi-band antenna 10 may be expanded to include further frequency bands by adding additional radiating arms. For example, a third radiating arm could be added to the antenna 10 to form a tri-band antenna.
FIG. 2 is a top view of an exemplary multi-band monopole antenna 30 including one alternative space-filling geometry. The antenna 30 show in FIG. 2 is similar to the multi-band antenna 10 shown in FIG. 1, except the meandering section 32 in the first radiating arm 12 includes a different space-filling curve than that shown in FIG. 1.
FIGS. 3-9 illustrate several alternative multi-band monopole antenna configurations 50, 70, 80, 90, 93, 95, 97. Similar to the antennas 10, 30 shown in FIGS. 1 and 2, the multi-band monopole antenna 50 illustrated in FIG. 3 includes a common conductor 52 coupled to a first radiating arm 54 and a second radiating arm 56. The common conductor 52 includes a feeding port 62 on a linear portion of the common conductor 52 that extends horizontally (as viewed in FIG. 3) away from the radiating arms 54, 56, and that may be folded in a perpendicular direction (perpendicularly into the page) in order to couple the feeding port 62 to communications circuitry in a mobile communications device.
The first radiating arm 54 includes a meandering section 58 and an extended section 60. The meandering section 58 is coupled to and extends away from the common conductor 52. The extended section 60 is contiguous with the meandering section 58 and extends from the end of the meandering section 58 in an arcing path back towards the common conductor 52.
The second radiating arm 56 includes three linear portions. As viewed in FIG. 3, the first linear portion extends diagonally away from the common conductor 52. The second linear portion extends horizontally from the end of the first linear portion towards the first radiating arm. The third linear portion extends vertically from the end of the second linear portion away from the common conductor 52 and adjacent to the meandering section 58 of the first radiating arm 54.
The multi-band monopole antennas 70, 80, 90 illustrated in FIGS. 4-6 are similar to the antenna 50 shown in FIG. 3, except each includes a differently-patterned meandering portion 72, 82, 92 in the first radiating arm 54. For example, the meandering portion 92 of the multi-band antenna 90 shown in FIG. 6 meets the definition of a space-filling curve, as described above. The meandering portions 58, 72, 82 illustrated in FIGS. 3-5, however, each include differently-shaped periodic curves that do not meet the requirements of a space-filling curve.
The multi-band monopole antennas 93, 95, 97 illustrated in FIGS. 7-9 are similar to the antenna 30 shown in FIG. 2, except in each of FIGS. 7-9 the expanded portion 22 of the first radiating arm 12 includes an additional area 94, 96, 98. In FIG. 7, the expanded portion 22 of the first radiating arm 12 includes a polygonal portion 94. In FIGS. 8 and 9, the expanded portion 22 of the first radiating arm 12 includes a portion 96, 98 with an arcuate longitudinal edge.
FIG. 10 is a top view 100 of the exemplary multi-band monopole antenna 10 of FIG. 1 coupled to the circuit board 102 of a mobile communications device. The circuit board 102 includes a feeding point 104 and a ground plane 106. The ground plane 106 may, for example, be located on one of the surfaces of the circuit board 102, or may be one layer of a multi-layer printed circuit board. The feeding point 104 may, for example, be a metallic bonding pad that is coupled to circuit traces 105 on one or more layers of the circuit board 102. Also illustrated, is communication circuitry 108 that is coupled to the feeding point 104. The communication circuitry 108 may, for example, be a multi-band transceiver circuit that is coupled to the feeding point 104 through circuit traces 105 on the circuit board.
In order to reduce electromagnetic interference from the ground plane 106, the antenna 10 is mounted within the mobile communications device such that the projection of the antenna footprint on the plane of the circuit board 102 does not intersect the metalization of the ground plane 106 by more than fifty percent. In the illustrated embodiment 100, the antenna 10 is mounted above the circuit board 102. That is, the circuit board 102 is mounted in a first plane and the antenna 10 is mounted in a second plane within the mobile communications device. In addition, the antenna 10 is laterally offset from an edge of the circuit board 102, such that, in this embodiment 100, the projection of the antenna footprint on the plane of the circuit board 102 does not intersect any of the metalization of the ground plane 106.
In order to further reduce electromagnetic interference from the ground plane 106, the feeding point 104 is located at a position on the circuit board 102 adjacent to a corner of the ground plane 106. The antenna 10 is preferably coupled to the feeding point 104 by folding a portion of the common conductor 16 perpendicularly towards the plane of the circuit board 102 and coupling the feeding port 17 of the antenna 10 to the feeding point 104 of the circuit board 102. The feeding port 17 of the antenna 10 may, for example, be coupled to the feeding point 104 using a commercially available connector, by bonding the feeding port 17 directly to the feeding point 104, or by some other suitable coupling means. In other embodiments, however, the feeding port 17 of the antenna 10 may be coupled to the feeding point 104 by some means other than folding the common conductor 16.
FIG. 11 shows an exemplary mounting structure 111 for securing a multi-band monopole antenna 112 within a mobile communications device. The illustrated embodiment 110 employs a multi-band monopole antenna 112 having a meandering section similar to that shown in FIG. 2. It should be understood, however, that alternative multi-band monopole antenna configurations, as described in FIGS. 1-9, could also be used.
The mounting structure 111 includes a flat surface 113 and at least one protruding section 114. The antenna 112 is secured to the flat surface 113 of the mounting structure 111, preferably using an adhesive material. For example, the antenna 112 may be fabricated on a flex-film substrate having a peel-type adhesive on the surface opposite the antenna structure. Once the antenna 112 is secured to the mounting structure 111, the mounting structure 111 is positioned in a mobile communications device with the protruding section 114 extending over the circuit board. The mounting structure 111 and antenna 112 may then be secured to the circuit board and to the housing of the mobile communications device using one or more apertures 116, 117 within the mounting structure 111.
FIG. 12 is an exploded view of an exemplary clamshell-type cellular telephone 120 having a multi-band monopole antenna 121. The cellular telephone 120 includes a lower circuit board 122, an upper circuit board 124, and the multi-band antenna 121 secured to a mounting structure 110. Also illustrated are an upper and a lower housing 128, 130 that join to enclose the circuit boards 122, 124 and antenna 121. The illustrated multi-band monopole antenna 121 is similar to the multi-band antenna 30 shown in FIG. 2. It should be understood, however, that alternative antenna configurations, as described above with reference to FIGS. 1-9, could also be used.
The lower circuit board 122 is similar to the circuit board 102 described above with reference to FIG. 10, and includes a ground plane 106, a feeding point 104, and communications circuitry 108. The multi-band antenna 121 is secured to a mounting structure 110 and coupled to the lower circuit board 122, as described above with reference to FIGS. 10 and 11. The lower circuit board 122 is then connected to the upper circuit board 124 with a hinge 126, enabling the upper and lower circuit boards 122, 124 to be folded together in a manner typical for clamshell-type cellular phones. In order to further reduce electromagnetic interference from the upper and lower circuit boards 122, 124, the multi-band antenna 121 is preferably mounted on the lower circuit board 122 adjacent to the hinge 126.
FIG. 13 is an exploded view of an exemplary candy-bar-type cellular telephone 200 having a multi-band monopole antenna 201. The cellular telephone 200 includes the multi-band monopole antenna 201 secured to a mounting structure 110, a circuit board 214, and an upper and lower housing 220, 222. The circuit board 214 is similar to the circuit board 102 described above with reference to FIG. 10, and includes a ground plane 106, a feeding point 104, and communications circuitry 108. The illustrated antenna 201 is similar to the multi-band monopole antenna shown in FIG. 3, however alternative antenna configurations, as described above with reference to FIGS. 1-9, could also be used.
The multi-band antenna 201 is secured to the mounting structure 110 and coupled to the circuit board 214 as described above with reference to FIGS. 10 and 11. The upper and lower housings 220, 222 are then joined to enclose the antenna 212 and circuit board 214.
FIG. 14 is an exploded view of an exemplary personal digital assistant (PDA) 230 having a multi-band monopole antenna 231. The PDA 230 includes the multi-band monopole antenna 231 secured to a mounting structure 110, a circuit board 236, and an upper and lower housing 242, 244. Although shaped differently, the PDA circuit board 236 is similar to the circuit board 102 described above with reference to FIG. 10, and includes a ground plane 106, a feeding point 104, and communications circuitry 108. The illustrated antenna 231 is similar to the multi-band monopole antenna shown in FIG. 5, however alternative antenna configurations, as described above with reference to FIGS. 1-9, could also be used.
The multi-band antenna 231 is secured to the mounting structure 110 and coupled to the circuit board 214 as described above with reference to FIGS. 10 and 11. In slight contrast to FIG. 10, however, the PDA circuit board 236 defines an L-shaped slot along an edge of the circuit board 236 into which the antenna 231 and mounting structure 110 are secured in order to conserve space within the PDA 230. The upper and lower housings 242, 244 are then joined together to enclose the antenna 231 and circuit board 236.
This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to make and use the invention. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art.

## Claims

1. A cellular telephone handset, comprising:
a device housing;
a display;
a keyboard;
a speaker;
a printed circuit board, the printed circuit board comprising:
a ground plane layer;
a feeding point;

a communication circuitry energized by means of a battery;
wherein the communication circuitry is mounted on the printed circuit board;
wherein the communication circuitry is coupled to the feeding point and to the ground plane layer;
an antenna including an antenna element;
wherein the antenna element operates in cooperation with the ground plane layer;
the antenna element comprising:
a common conductor including a feeding port;
a first longer radiating arm connected to the common conductor;
a second shorter radiating arm connected to the common conductor;

wherein the feeding port is coupled to the feeding point;
wherein an orthogonal projection of a footprint of the antenna element on a plane of the printed circuit board overlaps the ground plane layer in less than 50% of an area of said footprint;
wherein the display, the speaker, the printed circuit board, the communication circuitry, and the antenna are arranged inside the device housing; and
wherein the antenna and the cellular telephone handset operate at multiple frequency bands.

2. The cellular telephone handset according to claim 1, wherein the printed circuit board further comprises a plurality of circuit traces; and
wherein a circuit trace of the plurality of circuit traces couples the communication circuitry to the feeding point.

3. The cellular telephone handset according to claim 2, wherein the device housing comprises:
an upper housing, the upper housing including a window;
a lower housing, the lower housing adapted to receive the upper housing;
wherein the display is arranged with respect to the upper housing so as to be visible through the window; and
wherein the keyboard is arranged within the device housing so as to be accessible through the upper housing.

4. The cellular telephone handset according to claim 1, wherein the first longer radiating arm is bent.

5. The cellular telephone handset according to claim 4, wherein:
the first longer arm comprises a first section extending away from the common conductor in a first direction and a second section extending in a second direction; and
wherein the second direction is different from the first direction.

6. The cellular telephone handset according to claim 5, wherein the second direction is substantially opposite to the first direction.

7. The cellular telephone handset according to claim 5, wherein the first section is at least partially shaped as a space-filling curve.

8. The cellular telephone handset according to claim 5, wherein the first section is at least a partially shaped as a substantially periodic meander line.

9. The cellular telephone handset according to claim 1, wherein the communication circuitry comprises a transceiver able to operate at multiple frequency bands.

10. The cellular telephone handset according to claim 1, wherein the cellular telephone handset comprises a mounting structure arranged within the device housing; and
wherein the antenna element is arranged on at least one surface of the mounting structure.

11. The cellular telephone handset according to claim 10, wherein the mounting structure is secured to the printed circuit board.

12. The cellular telephone handset according to claim 10, wherein the mounting structure is secured to the device housing.

13. The cellular telephone handset according to claim 1, wherein the antenna element is fabricated on a surface of a flexible substrate.

14. The cellular telephone handset according to claim 13, wherein:
the flexible substrate comprises an adhesive layer; and
wherein the flexible substrate is affixed to the device housing.

15. The cellular telephone handset according to claim 1, wherein the cellular telephone handset comprises:
a second printed circuit board;
mechanical connecting means; and
wherein the mechanical connecting means enables the second printed circuit board to move with respect to the printed circuit board, so that the cellular telephone handset can be switched between an open configuration and a closed configuration.

16. The cellular telephone handset according to claim 15, wherein the second printed circuit board includes a second ground plane layer; and
wherein the cellular telephone handset comprises electrical connecting means adapted to couple the ground plane layer and the second ground plane layer.

17. The cellular telephone handset according to claim 15, wherein the mechanical connecting means comprises a hinge.

18. The cellular telephone handset according to claim 17, wherein the cellular telephone handset is a clamshell-type cellular telephone handset.

19. The cellular telephone handset according to claim 17, wherein the second printed circuit board includes a second ground plane layer; and
wherein the hinge comprises electrical connecting means adapted to couple the ground plane layer and the second ground plane layer.

20. The cellular telephone handset according to claim 15, wherein an orthogonal projection of the second printed circuit board substantially overlaps the printed circuit board when the cellular telephone handset is in the closed configuration.

21. A smartphone handset, comprising:
a device housing;
a speaker;
a display, the display having an area of at least 60% of an area defined by transversal dimensions of the device housing;
a printed circuit board, the printed circuit board comprising:
a ground plane layer;
a feeding point;

a communication circuitry energized by means of a battery;
wherein the communication circuitry is mounted on the printed circuit board;
wherein the communication circuitry is coupled to the feeding point and to the ground plane layer;
an antenna, the antenna including an antenna element coupled to the feeding point of the printed circuit board and that operates in cooperation with the ground plane layer;
wherein the antenna operates at multiple frequency bands;
wherein an orthogonal projection of a footprint of the antenna element on a plane of the printed circuit board overlaps the ground plane layer in less than 50% of an area of said footprint;
wherein the speaker, the display, the printed circuit board, the communication circuitry, and the antenna are arranged inside the device housing; and
wherein the smartphone handset operates at least three cellular communication services and at least one wireless connectivity service.

22. The smartphone handset according to claim 21, wherein one of the at least three cellular communication services is CDMA2000 or UMTS.

23. The smartphone handset according to claim 21, wherein the at least one wireless connectivity service is an IEEE 802.11 service.

24. The smartphone handset according to claim 21, wherein at least a portion of the antenna element is shaped as a space-filling curve.

25. The smartphone handset according to claim 21, wherein at least a portion of the antenna element is shaped as a substantially periodic meander line.

26. The smartphone handset according to claim 21, wherein the smartphone handset includes an enhanced keyboard comprising at least 19 keys.

27. The smartphone handset according to claim 26, wherein the device housing comprises:
a first housing portion, the first housing portion including a window;
a second housing portion;
mechanical connecting means, the mechanical connecting means enabling the second housing portion to move with respect to the first housing portion, so that the smartphone handset can be switched between an open configuration and a closed configuration;
wherein the display is arranged inside the first housing portion so as to be visible through the window; and
wherein the enhanced keyboard is arranged inside the second housing portion so as to be accessible through the second housing portion.

28. The smartphone handset according to claim 27, wherein the display is substantially rectangular having two long sides and two short sides; and
wherein the enhanced keyboard is adjacent to one of said two long sides of the display when the smartphone handset is in the open configuration.

29. The smartphone handset according to claim 21, wherein the display has an area of at least 75% of the area defined by the transversal dimensions of the device housing;
wherein the smartphone handset comprises a joystick switch button arranged adjacent to a first end of the display; and
wherein the speaker is arranged adjacent to a second end of the display, said second end being opposite to said first end.

30. The smartphone handset according to claim 29, wherein the smartphone handset comprises at least two buttons arranged adjacent to the first end of the display;
and wherein the joystick switch button is substantially centered with respect the at least two buttons.

31. The smartphone handset according to claim 21, wherein the antenna element comprises:
a common conductor including a feeding port;
a first longer radiating arm connected to the common conductor;
a second shorter radiating arm connected to the common conductor; and
wherein the feeding port is coupled to the feeding point.

32. The smartphone handset according to claim 31, wherein the first longer radiating arm is bent.

33. The smartphone handset according to claim 32, wherein the first longer radiating arm comprises a first section extending away from the common conductor in a first direction and a second section extending in a second direction; and
wherein the second direction is different from the first direction.

34. The smartphone handset according to claim 33, wherein the second direction is substantially opposite to the first direction.

35. The smartphone handset according to claim 31, wherein the first longer radiating arm is at least partially shaped as a space-filling curve.

36. The smartphone handset according to claim 31, wherein the first longer radiating arm is at least a partially shaped as a substantially periodic meander line.

37. The smartphone handset according to claim 31, wherein the antenna is a monopole antenna.

38. The smartphone handset according to claim 21, wherein the smartphone handset comprises a mounting structure arranged within the device housing; and
wherein the antenna element is arranged on at least one surface of the mounting structure.

39. The smartphone handset according to claim 38, wherein the mounting structure is secured to the device housing.

40. The smartphone handset according to claim 21, wherein the antenna element is fabricated on a surface of a flexible substrate affixed to the device housing.