Wireless device including a multiband antenna system

Abstract

A wireless handheld or portable device includes an antenna system operable in a first frequency region and a higher, second frequency region. The antenna system comprises an antenna structure, a matching and tuning system, and an external input/output (I/O) port. The antenna structure comprises at least one radiating element including a connection point, a ground plane layer including at least one connection point, and at least one internal I/O port. At least one radiating element of the antenna structure protrudes beyond the ground plane layer. The antenna structure features at any of its internal I/O ports when disconnected from the matching and tuning system an input return loss curve having a minimum at a frequency outside the first frequency region of the antenna system. The matching and tuning system modifies the impedance of the antenna structure and provides impedance matching to the antenna system in the first and second regions.

Claims

1. A wireless handheld or portable device comprising: an antenna system configured to operate within a first frequency region comprising a first frequency band, and within a second frequency region comprising a second frequency band, the first and second frequency regions including a frequency gap in between; the antenna system comprising an antenna structure, a passive matching and tuning system, and an external input/output (I/O) port; the antenna structure comprising: a first radiating element including a first connection point; a second radiating element including a second connection point; a ground plane layer having a perimeter within a ground plane rectangle that is the minimum-sized rectangle that encompasses the ground plane layer, the ground plane layer including at least one connection point; a first internal I/O port defined between the first connection point of the first radiating element and one of the at least one connection point of the ground plane layer and a second internal I/O port defined between the second connection point of the second radiating element and one of the at least one connection point of the ground plane layer; at least one of the first and second radiating elements of the antenna structure extending beyond an edge of the ground plane layer, wherein at least a portion of an orthogonal projection of the at least one of the first and second radiating elements on a plane containing the ground plane layer does not overlap the ground plane layer; the passive matching and tuning system comprising a first I/O port connected to the first internal I/O port of the antenna structure, a second I/O port connected to the second internal I/O port of the antenna structure, and a third I/O port connected to the external I/O port of the antenna system; the antenna structure featuring a first intrinsic frequency at the first internal I/O port above the first frequency region, the first intrinsic frequency featuring a minimum of an input return loss curve of the antenna structure at the first internal I/O port when disconnected from the passive matching and tuning system; the antenna structure featuring at the second internal I/O port a second intrinsic frequency above the second frequency region, the second intrinsic frequency featuring a minimum of the input return loss curve at the second internal port when disconnected from the passive matching and tuning system; the passive matching and tuning system modifying an impedance of the antenna structure and providing impedance matching to the antenna system to transmit and receive electromagnetic wave signals in the first and second frequency bands; wherein at least a portion of at least one of the first and second radiating elements is positioned at a height with respect to the plane containing the ground plane layer; wherein the first and second intrinsic frequencies are outside the first and second frequency regions of operation of the antenna system; wherein a ratio between the first intrinsic frequency at the first internal I/O port of the antenna structure and a highest frequency of the first frequency region is greater than 1.2; and wherein a ratio between the second intrinsic frequency at the second internal I/O port of the antenna structure and a highest frequency of the second frequency region is greater than 2.

2. The wireless handheld or portable device according to claim 1, wherein the orthogonal projections of the first and second radiating elements on the plane containing the ground plane layer do not overlap the ground plane layer.

3. The wireless handheld or portable device according to claim 1, wherein a longest side of a radiator rectangle of the first radiating element has a dimension smaller than one twentieth of a free-space operating wavelength corresponding to a lowest frequency of the first frequency region.

4. The wireless handheld or portable device according to claim 3, wherein a longest side of a radiator rectangle of the second radiating element has a dimension smaller than one twentieth of a free-space operating wavelength corresponding to a lowest frequency of the second frequency region.

5. The wireless handheld or portable device according to claim 1, wherein the radiator contour of at least one radiating element features a complexity factor F21 less than 1.50 and a complexity factor F32 less than 1.50.

6. The wireless handheld or portable device according to claim 1, wherein a major portion of the first and second radiating elements is parallel to the ground plane layer.

7. The wireless handheld or portable device according to claim 1, wherein each radiating element is placed at a height with respect to the plane containing the ground plane layer, the height being not greater than 2% of the wavelength corresponding to the lowest frequency of operation of the antenna system.

8. The wireless handheld or portable device according to claim 1, wherein the first radiating element and the second radiating element are placed respectively, at a first height and at a second height with respect to the plane containing the ground plane layer, the first height being different from the second height.

9. The wireless handheld or portable device according to claim 1, wherein the first radiating element and the second radiating element are positioned at substantially the same height with respect to the plane containing the ground plane layer.

10. The wireless handheld or portable device according to claim 1, wherein at least a portion of the area of the projection of at least one radiating element is at a distance from an edge of the ground plane layer, the distance ranging between 0.6% and 6% of a wavelength corresponding to a highest frequency of a lowest frequency region of operation.

11. The wireless handheld or portable device according to claim 1, wherein the first frequency band extends from 824 MHz to 960 MHz and the second frequency band extends from 1.71 GHz to 2.17 GHz.

12. The wireless handheld or portable device according to claim 1, wherein at least one of the first and second radiating elements comprises a portion having a shape of a parallelepiped with a face being coplanar with the ground plane layer, the portion extending substantially perpendicular to the plane containing the ground plane layer to a predetermined height.

13. The wireless handheld or portable device according to claim 12, wherein a longest side of a radiator rectangle of at least one of the radiating elements comprising a parallelepiped portion has a dimension less than one twentieth of a free-space operating wavelength corresponding to a lowest frequency of the first frequency region.

14. The wireless handheld or portable device according to claim 12, wherein the first and second radiating elements each comprise a portion having a shape of a parallelepiped with a face being coplanar with the ground plane layer; and wherein a radiator box that encloses the first radiating element has a volume larger than a volume of the radiator box that encloses the second radiating element.

15. The wireless handheld or portable device according to claim 12, wherein the first and second radiating elements each comprise a portion having a shape of a parallelepiped with a face being coplanar with the ground plane layer; and wherein a radiator box that encloses the first radiating element has a volume substantially the same as a volume of a radiator box that encloses the second radiating element.

16. The wireless handheld or portable device according to claim 1, wherein the orthogonal projections of the first and second radiating elements on the plane containing the ground plane layer do not overlap the ground plane layer; wherein the projections of the first and the second radiating elements are at a distance from an edge of the ground plane layer, the distance ranging between 0.6% and 6% of a wavelength corresponding to a highest frequency of a lowest frequency region of operation; wherein a portion of each of the first and second radiating element is placed at a height with respect to the plane containing the ground plane layer, the height being not greater than 2% of a wavelength corresponding to a lowest frequency of operation of the antenna system; wherein a ratio between the first intrinsic frequency at the first internal I/O port of the antenna structure and the highest frequency of the first frequency region is greater than 1.2 but less than 2.0; and wherein a ratio between the second intrinsic frequency at the second internal I/O port of the antenna structure and the highest frequency of the second frequency region is greater than 2.0 but less than 4.0.

17. The wireless handheld or portable device according to claim 16, wherein a longest side of a radiator rectangle of the first radiating element has a dimension less than one twentieth of a free-space operating wavelength corresponding to a lowest frequency of the first frequency region.

18. The wireless handheld or portable device according to claim 17, wherein a longest side of a radiator rectangle of the second radiating element has a dimension smaller than one twentieth of a free-space operating wavelength corresponding to a lowest frequency of the second frequency region.

19. The wireless handheld or portable device according to claim 16, wherein the first radiating element and the second radiating element are positioned at different heights with respect to the plane containing a ground plane layer.

20. The wireless handheld or portable device according to claim 16, wherein the first radiating element and the second radiating element are positioned at substantially the same height with respect to the plane containing a ground plane layer.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Embodiments of the invention are shown in the enclosed figures. Herein shows:

(2) FIGS. 1A, 1B and 1C—Block diagrams of three examples of antenna systems according to the present invention.

(3) FIGS. 2A and 2B—Example of an antenna structure for an antenna system, the antenna structure including a radiating element and a ground plane layer: (2A) Perspective view; and (2B) top plan view.

(4) FIGS. 3A, 3B and 3C—Typical radioelectric performance at the internal I/O port of the antenna structure of FIGS. 2A and 2B when disconnected from a matching and tuning system: (3A) Input return loss, (3B) input impedance, and (3C) radiating efficiency.

(5) FIG. 4—Schematic of the matching and tuning system of the antenna system whose antenna structure is shown in FIGS. 2A and 2B.

(6) FIG. 5—Comparison of the typical input return loss at the internal I/O port of the antenna structure of FIGS. 2A and 2B, and at the external I/O port of the antenna system after connecting the matching and tuning system of FIG. 4 to the antenna structure of FIGS. 2A and 2B.

(7) FIGS. 6A and 6B—Radioelectric performance at the internal I/O port of the antenna structure when disconnected from a matching and tuning system as the distance of the radiating element to an edge of the ground plane layer is varied: (6A) Input return loss, and (6B) input impedance.

(8) FIG. 7—Perspective view of a wireless handheld or portable device including a space for the integration of a radiating element, and its corresponding radiator box; and radiator rectangle.

(9) FIGS. 8A and 8B—(8A) Example of a wireless handheld or portable device comprising a ground plane layer included in a PCB, and its corresponding ground plane rectangle; (8B) ground plane rectangle of said wireless handheld or portable device in combination with a radiator rectangle for a radiating element.

(10) FIGS. 9A and 9B—An example of wireless handheld or portable device being held typically by a right-handed user to originate a phone call, and how the feeding point corner of a radiator rectangle of said device may be selected.

(11) FIGS. 10A, 10B and 10C—Example of (10A) a first grid, (10B) a second grid, and (10C) a third grid to compute the complexity factors of a radiator contour.

(12) FIG. 11—Two-dimensional representation of the F32 vs. F21 space.

(13) FIGS. 12A, 12B and 12C—Example of a radiator contour inspired in a Hilbert curve under (12A) a first grid, (12B) a second grid, and (12C) a third grid to compute the complexity factors of said radiator contour.

(14) FIGS. 13A, 13B, 13C and 13D—Computation of the complexity factors of the radiator contour of the radiating element of FIG. 2: (13A) Original radiator contour under a second grid; and modified radiator contour under (13B) a first grid, (13C) a second grid, and (13D) a third grid.

(15) FIG. 14—Perspective view of an example of an antenna structure for an antenna system, the antenna structure including a radiating element having a volumetric geometry.

(16) FIG. 15—Comparison of the typical input return loss at the internal I/O port of the antenna structure of FIG. 14, and at the external I/O port of the antenna system after connecting a matching and tuning system to the antenna structure of FIG. 14.

(17) FIG. 16—Schematic of an example matching and tuning system for an antenna system comprising diplexers.

(18) FIGS. 17A and 17B—Example of an antenna structure for an antenna system, the antenna structure including two radiating elements and a ground plane layer: (17A) Perspective view; and (17B) top plan view.

(19) FIGS. 18A and 18B—(18A) Input return losses at each one of the two internal I/O ports of the antenna structure of FIGS. 17A and 17B when disconnected from a matching and tuning system; (18B) Input return losses at the external I/O port of the antenna system having the antenna structure of FIGS. 17A and 17B and the matching and tuning system of FIG. 19.

(20) FIG. 19—Schematic of the matching and tuning system of the antenna system whose antenna structure is shown in FIGS. 17A and 17B.

(21) FIG. 20—Top plan view of a further example of an antenna structure for an antenna system, the antenna structure including a radiating element and a ground plane layer.

(22) FIGS. 21A, 21B and 21C—Radiator contour of the radiating element in FIG. 20 under (21A) a first grid, (21B) a second grid, and (21C) a third grid to compute the complexity factors of said radiator contour.

(23) FIG. 22A to 22F—Examples of antenna structures comprising two radiating elements suitable for an antenna system according to the present invention.

DETAILED DESCRIPTION

(24) Further characteristics and advantages of the invention will become apparent in view of the detailed description of some preferred embodiments which follows. Said detailed description of some preferred embodiments of the invention is given for purposes of illustration only and in no way is meant as a definition of the limits of the invention, made with reference to the accompanying figures.

(25) FIGS. 1A and 1B show the block diagram of three examples of an antenna system for a wireless handheld or portable device according to the present invention.

(26) In particular FIG. 1A shows an antenna system 100 comprising an antenna structure 105, a matching and tuning system 130 and an external I/O port of the antenna system 140. The antenna structure 105 comprises a radiating element 110, which includes a connection point 112, and a ground plane layer 120, said ground plane layer including also a connection point 121. The antenna structure 105 further comprises an internal I/O port 150 defined between the connection point of the radiating element 112 and the connection point of the ground plane layer 121. The matching and tuning system comprises two I/O ports: a first I/O port 160 is connected to the internal I/O port of the antenna structure 150, and a second I/O port 161 is connected to the external I/O port of the antenna system 140.

(27) Referring now to FIG. 1B, an antenna system 101 comprises an antenna structure 106, which, in addition to a first radiating element 110 and a ground plane layer 120, also includes a second radiating element 111. The antenna structure 106 comprises two internal I/O ports: The first internal I/O port 150 is defined between a connection point of the first radiating element 112 and a connection point of the ground plane layer 121; while the second internal I/O port 151 is defined between a connection point of the second radiating element 113 and the same connection point of the ground plane layer 121.

(28) The antenna system 101 comprises a matching and tuning system 131 including three I/O ports: A first I/O port 160 is connected to the first internal I/O port 150; a second I/O port 162 is connected to the second internal I/O port 151; and a third I/O port 161 is connected to the external I/O port of the antenna system 140.

(29) FIG. 1C depicts a further example of an antenna system 102 having the same antenna structure 105 as in the example of FIG. 1A. However, differently from the example of FIG. 1A, the antenna system 102 comprises an additional external I/O port 141.

(30) The antenna system 102 includes a matching and tuning system 132 having a first I/O port 160 connected to the internal I/O port of the antenna structure 150, a second I/O port 161 connected to the external I/O port 140, and a third I/O port 163 connected to the additional external I/O port 141.

(31) Such an antenna system 102 may be preferred when said antenna system 102 is to provide operation in at least one cellular communication standard and at least one wireless connectivity standard. In one example, the external I/O port 140 may provide the GSM 900 and GSM 1800 standards, while the external I/O port 141 may provide an IEEE802.11 standard.

(32) FIG. 2A shows the antenna structure 200 of an antenna system capable of operating in two separated frequency regions of the electromagnetic spectrum: a first frequency region between 880 and 960 MHz, and a second frequency region between 1710 and 1990 MHz.

(33) The antenna structure 200 comprises a radiating element 201, and a rectangular ground plane layer 202. In this example, the radiating element 201 is substantially planar, said element 201 being placed on the same plane as the one including the ground plane layer 202 (i.e., the radiating element 201 and the ground plane layer 202 are substantially coplanar). Since the radiating element 201 and the ground plane layer 202 are substantially coplanar, they may be embedded in a same PCB of a wireless handheld or portable device.

(34) In accordance to the present invention, the radiating element 201 protrudes beyond the ground plane layer 202. In fact, the projection of the radiating element 201 on the plane of the ground plane layer 202 does not overlap the ground plane layer 202. Moreover, a majority of the area of said projection of the radiating element 201 (in particular more than 80% of said area) is placed at a distance to an edge of the ground plane layer 204 between a 0.6% and a 6% of the wavelength corresponding to the highest frequency of the lowest frequency region of operation (i.e., the first region), obtaining a good compromise between radioelectric performance of the antenna system and integration of the antenna structure 200 within the wireless handheld or portable device.

(35) The radiating element 201 comprises a single radiating arm 205, said arm 205 including a connection point 203 located at one end of the radiating arm 205. The connection point of the radiating element 203 defines together with a connection point of the ground plane layer 202 (not shown) an internal I/O port of the antenna structure.

(36) FIGS. 3A, 3B and 3C presents typical radioelectric performance of the antenna structure 200 at its internal I/O port as a function of the frequency, when the antenna structure 200 is not connected to the matching and tuning system of an antenna system. FIG. 3A shows the input return losses, while FIG. 3B represents the locus of the input impedance on a Smith chart.

(37) In FIG. 3A, the input return loss curve 300 has a minimum at a frequency 301 (around 1.52 GHz), said frequency 301 being the intrinsic frequency of the antenna structure. The intrinsic frequency 301 is advantageously outside the first and second regions of operation of the antenna system, and in particular above said first frequency region. The ratio between the intrinsic frequency 301 and the highest frequency of the lowest frequency region of operation is advantageously larger than 1.4 but smaller than 2.0.

(38) On a Smith chart, in FIG. 3B, frequency 301 corresponds to a point located close to the horizontal axis (i.e., real input impedance), which indicates that the antenna structure 200 is close to resonance at the intrinsic frequency 301.

(39) The input return loss curve 300 of FIG. 3A features also a frequency 302 (around 1.26 GHz), said frequency 302 being lower than the intrinsic frequency 301, at which the absolute value of slope of the curve 300 at said frequency 302 is smaller than the absolute value of the slope of the curve 300 at any other frequency within a non-empty neighborhood centered at said frequency 302. The frequency 302 is therefore the secondary frequency of the antenna structure 200.

(40) Said secondary frequency 302 shows in FIG. 3B as a “bump” in the locus of the input impedance of the antenna structure 200, which is an indication of the coupling of the ground plane layer 202.

(41) In this embodiment, the ratio between the intrinsic frequency 301 and the secondary frequency 302 is larger than 1.0 but smaller than 1.4, which is advantageous to provide adequate radioelectric performance to the antenna system in the two regions of operation once the matching and tuning system is connected to the antenna structure 200.

(42) FIG. 3C shows the radiating efficiency of the antenna structure 200 at its internal I/O port when the matching and tuning system is not connected to it. The antenna structure 200 is efficient around the intrinsic frequency 301, reaching efficiency levels in excess of 50%, and fairly similar throughout its impedance bandwidth.

(43) FIG. 4 depicts a typical matching and tuning system 400 to be used in combination with the antenna structure 200 in FIGS. 2A and 2B in order to transform the input impedance of the antenna structure 200 and provide impedance matching in the first and second regions of operation of the antenna system.

(44) The matching and tuning system 400 comprises a first I/O port 401 for connection with the internal I/O port of the antenna structure 200, and a second I/O port 402 for connection with the external I/O port of the antenna system. The matching and tuning system 400 further comprises a matching network 403, connected to said first and second I/O ports 401, 402.

(45) In this example, the matching network 403 comprises six (6) stages 404-409, although in other examples a matching network 403 could comprise fewer or more stages. The stages 404-409 are arranged forming a ladder structure (i.e., a first stage 404 is laid out in parallel with the first I/O port 401, while a second stage 405 is laid out in series, and so on alternating stages in parallel with stages in series). The last stage 409 is connected to the second I/O port 402.

(46) Moreover, in this example each stage 404-409 comprises each one circuit component. Three stages 404, 406, 407 feature a substantially capacitive behavior in the frequency regions of operation, while three stages 405, 408, 409 feature a substantially inductive behavior.

(47) In FIG. 5 it is shown a comparison between the input return loss at the internal I/O port of the antenna structure 200 (before connecting the matching and tuning system 400), and the input return loss at the external I/O port of the antenna system after connecting said matching and tuning system 400 to the internal I/O port of the antenna structure 200.

(48) Curve 501 (in dashed line in FIG. 5) corresponds to the input return losses at the internal I/O port of the antenna structure 200 when the matching and tuning system 400 is not connected to said internal I/O port, and is the same as the curve 300 in FIG. 3A. Curve 502 (in solid line in FIG. 5) corresponds to the input return losses at the external I/O port of the antenna system, and shows two frequency regions in which the return losses are better than −6 dB: a first frequency region between frequency 503 and frequency 504, which may provide operability for the GSM900 standard; and a second frequency region between frequency 506 and frequency 507, which may provide operability for the GSM 1800 and GSM 1900 standards.

(49) Protruding a radiating element of the antenna structure beyond the ground plane layer is advantageous to adjust the levels of impedance of the antenna structure and enhance its impedance bandwidth. In the embodiment of FIGS. 2A and 2B a major portion of the radiating element 201 is at a distance from an edge of the ground plane layer 204. Varying said distance has an impact on the input impedance of the antenna structure. In FIG. 6, it is represented how the input impedance of an antenna structure such as the one in FIGS. 2A and 2B changes as the distance of the radiating element 201 to said edge 204 is varied.

(50) In particular, FIG. 6A shows the input return loss curves and FIG. 6B the input impedance loci. Curves 602 and 632 (solid lines in FIGS. 6A and 6B) correspond to the case already presented in FIGS. 3A and 3B respectively.

(51) If the distance of the radiating element 201 to the edge 204 is halved with respect to the case depicted in FIGS. 2A and 2B, the input impedance locus 631 becomes larger, which translates into a degradation of the input return loss at the internal I/O port of the antenna structure 601 (dash-dotted lines in FIG. 6A). On the other hand, an increase in said distance results in an input impedance locus 633 smaller, which in turn leads to an input return loss curve 603 with a larger impedance bandwidth, and enhanced radioelectric performance of the antenna system and/or the wireless handheld or portable device including such (dashed lines in FIGS. 6A and 6B).

(52) FIG. 7 shows a perspective view of a wireless handheld or portable device 700 comprising in this particular example only one body. A volume 701 within said device 700 is made available for the integration of the radiating element of an antenna structure. The wireless handheld or portable device 700 also comprises a multilayer PCB. A layer 702 of said PCB serves as a ground plane layer of the antenna structure.

(53) A radiator box 703 is obtained as a minimum-sized parallelepiped that completely encloses the volume 701. In this example, the radiator box 703 has rectangular faces 704-709. According to the present invention, the geometry of the radiating element comes into contact with each of the six (6) faces of the antenna box 704-709 in at least one point of each face. Moreover, the radiating element in the antenna structure of said device 700 has no portion that extends outside the radiator box 703.

(54) A radiator rectangle 710 is obtained as the orthogonal projection of the radiator box 703 along the normal to the face with largest area, which in this case is the direction normal to faces 704 and 705.

(55) FIG. 8A represents a top plan view of the wireless handheld or portable device 700. For the sake of clarity, the volume 701 has been omitted in the figure. A ground plane rectangle 800 is adjusted around the layer 702 that serves as a ground plane layer to the antenna structure of said device 700. The ground plane rectangle 800 is a minimum-sized rectangle in which each of its edges is tangent to at least one point of the perimeter of layer 702.

(56) FIG. 8B depicts the relative position of the ground plane rectangle 800 and the radiator rectangle 710 for the wireless handheld or portable device 700 of FIG. 7. The radiator rectangle has a long side 803 and a short side 804. The ground plane rectangle has a long edge 802 and a short edge 801.

(57) In this particular example, the radiator rectangle 710 and the ground plane rectangle 800 lie substantially on a same plane (i.e., the radiator rectangle 710 and the ground plane rectangle 800 are substantially coplanar). Furthermore, a long side of the radiator rectangle 803 is substantially parallel to a short edge of the ground plane rectangle 801, while in some other embodiments it will be substantially parallel to a long edge of the ground plane rectangle.

(58) In this example, the radiator rectangle 710 is partially overlapping the ground plane rectangle 800. Although in other cases, they can be completely non-overlapping. Moreover, in this example the placement of the radiator rectangle 710 is not symmetrical with respect to a symmetry axis that is parallel to the long edge of the ground plane rectangle 802 and that passes by the middle point of the short edge of said ground plane rectangle 801.

(59) FIG. 2B shows a radiator rectangle 230 fitted around the radiating element 201, and a ground plane rectangle 231 fitted around the ground plane layer of the antenna structure 202.

(60) In this particular example area of the radiator rectangle is advantageously smaller than 0.35% of the square of the wavelength corresponding to the lowest frequency of operation of the antenna system comprising the antenna structure 200.

(61) FIGS. 9A and 9B show a wireless handheld or portable device 900 consisting of a single body being held typically by a right-handed user to originate a phone call while facing a display of said device 901. The wireless handheld or portable device 900 comprises a radiating element and a PCB that includes a layer that serves as a ground plane layer 902 (depicted in dashed line). The radiating element is to be arranged inside a radiator box, whose radiator rectangle 903, 904 is depicted also in dashed line. The radiator rectangle 903, 904 is partially in the projection of the ground plane layer 902. In the case of FIG. 9A, the radiator rectangle 903 is placed substantially in the top part of the body of the device 900 (i.e., above and/or behind a display 901), while in FIG. 9B the radiator rectangle 904 is placed substantially in the bottom part of the body of the device 900 (i.e., below and/or behind a keypad).

(62) For ergonomics reasons, it is advantageous in the examples of the FIGS. 9A and B to select a corner of the radiator rectangle close to the left edge of the device 900. The lower left corner of the radiator rectangle 905 is selected as the feeding point corner in the case of FIG. 9A, while the upper left corner of the radiator rectangle 906 is selected as the feeding point corner in the case of FIG. 9B. In these two examples the corners designated as feeding point corners 905, 906 are also substantially close to a short edge of a ground plane rectangle (not depicted in FIGS. 9A and 9B) that encloses the ground plane layer 902.

(63) FIGS. 10A, 10B and 10C represents an example of a first grid 1001, a second grid 1002 and a third grid 1003 used for the computation of the complexity factors F21 and F32 of a radiator contour that fits in a radiator rectangle 1000. Said radiator rectangle 1000 has a long side 1003 and a short side 1004.

(64) In FIG. 10B, the second grid 1002 has been adjusted to the size of the radiator rectangle 1000. The long side of the radiator rectangle 1003 is fitted with nine (9) columns of cells of said second grid 1002. As far as the number of rows is concerned, the aspect ratio of the radiator rectangle 1000 in this particular example is such that a cell aspect ratio closest to one is obtained when the short side of the radiator rectangle 1004 is fitted with five (5) rows of cells of said second grid. Therefore, the radiator rectangle 1000 is perfectly tessellated with 9 by 5 cells of the second grid 1002.

(65) FIG. 10A shows a possible first grid 1001 obtained from grouping 2-by-2 cells of the second grid 1002. In this example, the upper left corner of the radiator rectangle 1000 is selected as the feeding point corner 1005. A first cell of the first grid 1006 is placed such that said cell 1006 has a corner being the feeding point corner 1005 and is completely inside the radiator box 1000. In the example of FIG. 10A, the radiator rectangle 1000 spans five (5) columns and three (3) rows of cells of the first grid 1001.

(66) Since the radiator rectangle 1000 is tessellated with an odd number of columns and rows of cells of the second grid. An additional column 1008 and an additional row 1009 of cells of the second grid 1002 are necessary to have enough cells of the first grid 1001 to completely cover the radiator rectangle 1000. Said additional column 1008 and additional row 1009 meet at the lower right corner of the radiator rectangle 1007 (i.e., the corner opposite to the feeding point corner 1005).

(67) FIG. 10C shows the third grid 1003 obtained from dividing each cell of the second grid 1002 into four (4) cells. Each cell of the third grid 1003 has a cell width and cell height equal a half of the cell width and cell height of a cell of the second grid 1002. Thus, in this example the radiator rectangle 1000 is perfectly tessellated with eighteen (18) columns and ten (10) rows of cells of the third grid 1003.

(68) FIG. 11 shows the two-dimensional space 1100 defined by the complexity factors F21 and F32. The radiator contour of a radiating element of a device is represented as a point 1101 of coordinates (F21, F32) in said two-dimensional space 1100.

(69) FIGS. 12A, 12B and 12C provide an example to illustrate the complexity factors that feature two radiating elements radically different: A rectangular radiating element that occupies the area of a radiator rectangle 1200 for a wireless handheld or portable device; and a radiating element whose contour is inspired in a Hilbert curve 1210 that fills the available space within the radiator rectangle 1200. These two radiating element examples help to show the relevance of the two complexity factors.

(70) FIGS. 12A, 12B and 12C show said radiating element 1210 inside the radiator rectangle 1200 under a first grid 1201, a second grid 1202, and a third grid 1203. In this example, the radiator rectangle 1200 is perfectly tessellated with nine (9) columns and five (5) rows of cells of said second grid 1202 (FIG. 12B). The radiating element 1210 has a connection point 1211 used for feeding purposes, located substantially close to the lower left corner of the radiator rectangle 1205 (being thus the feeding point corner).

(71) In FIG. 12A, there are fifteen (15) cells of the first grid 1201 at least partially inside the radiator rectangle 1200 and that include at least a point of the radiator contour of radiating element 1210 (i.e., N1=15). In FIG. 12B, there are forty-five (45) cells of the second grid 1202 completely inside the radiator rectangle 1200 and that include at least a point of the radiator contour of the antenna 1210 (i.e., N2=45). Finally in FIG. 12C, there are one hundred eighty (180) cells of the third grid 1203 completely inside the radiator rectangle 1200 and that include at least a point of the radiator contour of the radiating element 1210 (i.e., N3=180). Therefore, in the present example, a radiating element whose contour is inspired in the Hilbert curve 1210 features F21=1.58 (i.e., smaller than 2.00) and F32=2.00.

(72) On the other hand if the process of counting the cells in each of the three grids is repeated for a rectangular radiating element whose contour is the radiator rectangle 1200 then N1=12, N2=24 and N3=52, which results in F21=1.00 and F32=1.12 (i.e., larger than 1.00).

(73) These results illustrate that complexity factor F21 is geared more towards discerning if the radiator contour of a particular radiating element distinguishes sufficiently from a rectangular radiating element rather than capturing the complete intricacy of said radiator contour, while complexity factor F32 is predominantly directed towards capturing if the degree of complexity of said radiator contour approaches to that of a highly-convoluted curve such as a Hilbert curve.

(74) FIG. 13A provides an example to illustrate the complexity factors that feature the radiator contour 1301 of the radiating element 201 of the antenna structure 200 in FIGS. 2A and 2B.

(75) FIG. 13A shows said radiator contour 1301 inside the radiator rectangle 1300 under a second grid 1302. In this example, the radiator rectangle 1300 is perfectly tessellated with nine (9) columns and three (3) rows of cells of said second grid 1302. The radiator contour 1301 comprises a portion in which a first edge 1303 and a second edge 1304, said second edge 1304 not being adjacent to said first edge 1303, are placed at a distance d smaller than the cell width of said second grid 1302. Therefore, said portion of the radiator contour 1301 does not substantially distinguish from a zero-width line 1307 placed at the middle distance between said edges 1303 and 1304. Similarly, the radiator contour 1301 comprises another portion in which two non-adjacent edges 1305 and 1306 are also placed at a distance d. Therefore, said other portion of the radiator contour 1301 can also be replaced by a line 1308 at the middle distance between said edges 1305 and 1306.

(76) As a result of the modification of the radiator contour 1301, the radiator rectangle 1300 has to be resized, and a first, a second and a third grid fitted to said radiator contour 1301.

(77) FIG. 13B-D show a modified radiator contour 1321 inside its radiator rectangle 1320 under a first grid 1331, a second grid 1332, and a third grid 1333. In this example, the radiator rectangle 1320 is tessellated with nine (9) columns and three (3) rows of cells of said second grid 1332 (FIG. 13C). The radiator contour 1321 has a connection point 1322 used for feeding purposes of the radiating element 201, located substantially close to the bottom left corner of the radiator rectangle 1323 (being thus the feeding point corner).

(78) In FIG. 13B, there are six (6) cells of the first grid 1331 at least partially inside the radiator rectangle 1320 and that include at least a point of the radiator contour 1321 (i.e., N1=6). In FIG. 13C, there are eleven (11) cells of the second grid 1332 completely inside the radiator rectangle 1320 and that include at least a point of the radiator contour 1321 (i.e., N2=11). Finally in FIG. 13D, there are twenty three (23) cells of the third grid 1333 completely inside the radiator rectangle 1320 and that include at least a point of the radiator contour 1321 (i.e., N3=23). Therefore, in the present example, the radiator contour 1321, corresponding to the radiating element 201 in FIGS. 2A and 2B, features F21=0.9 (i.e., smaller than 1.2) and F32=1.1 (i.e., smaller than 1.2). Such low complexity factors are an indication of the geometrical simplicity of the radiating element 201, which is advantageous to provide a single path to the electric currents flowing on said radiating element 201 to excite a radiation mode with enhanced radioelectric performance.

(79) FIG. 14 presents another embodiment of an antenna system according to the present invention based on a modification of the antenna structure shown in FIGS. 2A and 2B.

(80) Antenna structure 1400 comprises a radiating element 1401 and a ground plane layer 202. The radiating element 1401 includes a radiating arm formed by a first portion 1406 protruding substantially perpendicularly to an edge of the ground plane layer 204, and a second portion 1405 arranged substantially parallel to said edge 204. The first portion 1406 includes a connection point 1403 on one end, and is connected to the second portion 1405 on the opposite end.

(81) The first portion 1406 is substantially coplanar to the ground plane layer 202, while the second portion 1405 features a volumetric geometry. Said second portion 1405 has the shape of a parallelepiped with a face being coplanar to the ground plane 202 and extending upwards (i.e., substantially perpendicular to the plane containing the ground plane layer 202) a height t. In this particular embodiment, the radiating element can be confined in a radiator box having a height t being at least 2.0% of the wavelength corresponding to the lowest frequency of operation of the antenna system.

(82) FIG. 15 presents the input return losses at the internal I/O port of the antenna structure 1400 (before connecting a matching and tuning system) compared with the input return losses at the external I/O port of the antenna system after connecting said matching and tuning system to the internal I/O port of the antenna structure 1400.

(83) Curve 1501 (in dashed line in FIG. 15) corresponds to the input return losses at the internal I/O port of the antenna structure 1400. When a matching and tuning system comprising a six-stage matching network is connected to said internal I/O port, curve 1502 (in solid line in FIG. 15) is obtained at the external I/O port of the antenna system. Curve 1502 shows two frequency regions in which the return losses are better than −6 dB: a first frequency region between frequency 1503 and frequency 1504, which may provide operability for the GSM 850 and GSM900 standards; and a second frequency region between frequency 1505 and frequency 1506, which may provide operability for the GSM 1800, GSM 1900 and UMTS standards.

(84) The use of the antenna structure 1400 in which the radiating element 1401 has a volumetric geometry is advantageous in enhancing the radioelectric performance of the antenna system, in particular increasing the impedance bandwidth in both the first and second frequency regions with respect to the example of FIGS. 2A and 2B, making it possible for the wireless handheld or portable device to operate five communication standards.

(85) FIG. 16 shows an example matching and tuning system comprising a first diplexer 1603 to separate the electrical signals of a first and a second frequency regions of operation of an antenna system, a first matching network 1605 to provide impedance matching in said first frequency region, a second matching network 1606 to provide impedance matching in said second frequency region, and a second diplexer 1602 to recombine the electrical signals of said first and second frequency regions.

(86) The first diplexer 1603 is connected to a first I/O port 1601, while the second diplexer 1604 is connected to a second I/O port 1602. In an antenna system, an internal I/O port of an antenna structure may be connected to said first I/O port 1601, while an external I/O port of the antenna system may be connected to said second I/O port 1602.

(87) The use of diplexers in the matching and tuning system is advantageous to separate the electrical signals of different frequency regions and transform the input impedance characteristics in each frequency region independently from the others.

(88) FIGS. 17A and 17B present a further example of an antenna structure for an antenna system according to the present invention. The antenna system is to operate in a first frequency region from 824 to 960 MHz and a second frequency region between 1.71 and 2.17 GHz.

(89) In this example, the antenna structure 1700 includes a first radiating element 1701, a second radiating element 1702 and a ground plane layer 1703. A major portion of the radiating elements 1701, 1702 is substantially parallel to the ground plane layer 1703. Moreover, a major portion of said elements 1701, 1702 is placed at a height with respect to the plane containing the ground plane layer 1703 not larger than 2% of the wavelength corresponding to the lowest frequency of operation of the antenna system. In this particular example, the first radiating element 1701 and the second radiating element 1702 are placed at different heights with respect to the ground plane layer 1703, although in other examples said heights can be substantially equal. Setting the height of each radiating element independently allows to modify the input impedance characteristics of the antenna structure (such as for instance to increase the impedance bandwidth) selectively in certain frequency regions.

(90) The first and second radiating elements 1701, 1702 protrude beyond the ground plane layer 1703. In particular, the orthogonal projection of the radiating elements 1701, 1702 on the plane containing the ground plane layer 1703 does not overlap said ground plane layer 1703. Moreover, a majority of the area of said projection of the radiating elements 1701, 1702 is at a distance from an edge of the ground plane layer 1704 between a 0.6% and a 6% of the wavelength corresponding to the highest frequency of the lowest frequency region of operation (i.e., the first region). In other preferred embodiments, the orthogonal projection of radiating elements 1701, 1702 on the plane containing the ground plane layer 1703 might overlap at least partially said ground plane layer 1703.

(91) The first radiating element 1701 comprises a first connection point 1705. Said element 1701 is arranged with respect to the ground plane layer 1703 in a way that its connection point 1705 is substantially close to a first end of edge 1704. The second radiating element 1702 comprises a second connection point 1706. Said element 1702 is arranged with respect to the ground plane layer 1703 in a way that its connection point 1706 is substantially close to a second end of edge 1704, opposite to said first end.

(92) In some embodiments, the space between radiating elements 1701 and 1702 might be advantageously used to integrate one or more components of the wireless device, such as for instance but without limitation: a camera or a CCD sensor, a speaker, an earpeace, a microphone, a vibrating module, an electronic connector, or a shield can.

(93) The first radiating element 1701 can be fitted in a radiator box, whose radiator rectangle 1731 has an area smaller than 0.3% of the square of the wavelength corresponding to the lowest frequency of operation of the antenna system. Analogously, the second radiating element 1702 features a radiator rectangle 1732 having an area smaller than 0.2% of the square of said wavelength.

(94) The first connection point 1705 defines together with a connection point of the ground plane layer 1703 (not depicted in the figure) a first internal I/O port of the antenna structure 1700. Similarly, the second connection point 1706 defines together with said connection point of the ground plane layer 1703 a second internal I/O port of the antenna structure 1700.

(95) The input return losses at each one of the two internal I/O ports of the antenna structure 1700 when not connected to a matching and tuning system are presented in FIG. 18A.

(96) Curve 1801 (in solid line in FIG. 18A) corresponds to the input return losses at the first internal I/O port (i.e., the one connected to the first radiating element 1701). Curve 1801 has a minimum at a frequency around 1.3 GHz, said frequency being the intrinsic frequency of the first internal I/O port of the antenna structure 1700. Said intrinsic frequency is advantageously outside the first and second regions of operation of the antenna system, and in particular above said first frequency region. The ratio between the intrinsic frequency of the first internal I/O port of the antenna structure 1700 and the highest frequency of the lowest frequency region of operation is advantageously larger than 1.2 but smaller than 2.0.

(97) Curve 1801 features also a frequency around 1 GHz, said frequency being lower than the intrinsic frequency of the first internal I/O port of the antenna structure 1700, at which the absolute value of slope of the curve 1801 at said frequency is smaller than the absolute value of the slope of the curve 1801 at any other frequency within a non-empty neighborhood centered at said frequency. Therefore, said frequency is the secondary frequency of the first internal I/O port of the antenna structure 1700.

(98) In this embodiment, the ratio between the intrinsic frequency and the secondary frequency of the first internal I/O port of the antenna structure 1700 is advantageously larger than 1.0 but smaller than 1.4.

(99) Curve 1802 (in dashed line in FIG. 18A) corresponds to the input return losses at the second internal I/O port (i.e., the one connected to the second radiating element 1702). Curve 1802 has a minimum at a frequency larger than 2.3 GHz, said frequency being the intrinsic frequency of the second internal I/O port of the antenna structure 1700. Said intrinsic frequency is advantageously outside the first and second regions of operation of the antenna system, and in particular above said first and second frequency regions. The ratio between the intrinsic frequency of the second internal I/O port of the antenna structure 1700 and the highest frequency of the lowest frequency region of operation is advantageously larger than 2.2 but smaller than 4.0.

(100) Curve 1802 features also a frequency around 1.4 GHz, said frequency being lower than the intrinsic frequency of the second internal I/O port of the antenna structure 1700, at which the absolute value of slope of the curve 1802 at said frequency is smaller than the absolute value of the slope of the curve 1802 at any other frequency within a non-empty neighborhood centered at said frequency. Therefore, said frequency is the secondary frequency of the second internal I/O port of the antenna structure 1700.

(101) In this embodiment, the ratio between the intrinsic frequency and the secondary frequency of the second internal I/O port of the antenna structure 1700 is advantageously larger than 1.2 but smaller than 2.4.

(102) FIG. 19 presents a schematic of a matching and tuning system 1900 to be connected to the two internal I/O ports of the antenna structure 1700 in order to transform the input impedance of the antenna structure 1700 and provide impedance matching in the first and second regions of operation of the antenna system.

(103) The matching and tuning system 1900 comprises two I/O ports 1901, 1902 to be connected respectively to the first and second internal I/O ports of the antenna structure 1700, and a third I/O port 1903 to be connected to a single external I/O port of the antenna system.

(104) The matching and tuning system 1900 also comprises a first matching network 1904 connected to I/O port 1901, providing impedance matching within the first frequency region; and a second matching network 1905 connected to I/O port 1902, providing impedance matching within the second frequency region.

(105) The matching and tuning system 1900 further comprises a first band-pass filter 1906 connected to said first matching network 1904, and a second band-pass filter 1907 connected to said second matching network 1905. The first band-pass filter 1906 is designed to present low insertion loss in the first frequency region and high impedance in the second frequency region of operation of the antenna system. Analogously, the second band-pass filter 1907 is designed to present low insertion loss in said second frequency region and high impedance in said first frequency region.

(106) Said first and second band-pass filters 1906, 1907 comprise each at least two stages, and preferably at least one of said at least two stages includes an LC-resonant circuit.

(107) The matching and tuning system 1900 additionally includes a combiner/splitter 1908 to combine (or split) the electrical signals of different frequency regions. Said combiner/splitter 1908 is connected to the first and second band-pass filters 1906, 1907, and to I/O port 1903.

(108) In some examples, the combiner/splitter 1908 can be advantageously constructed by directly connecting in parallel the two band-pass filters 1906, 1907 to I/O port 1903.

(109) In FIG. 18B it is shown the input return loss at the external I/O port of an antenna system comprising the antenna structure 1700 connected to the matching and tuning system 1900.

(110) The curve in FIG. 18B shows two frequency regions in which the return losses are better than −6 dB: a first frequency region below frequency 1831, which may provide operability for the GSM 850 and GSM 900 standards; and a second frequency region between frequency 1832 and frequency 1833, which may provide operability for the GSM 1800, GSM 1900 and UMTS standards.

(111) FIG. 20 shows another antenna structure 2000 for an antenna system capable of operating in two separated frequency regions of the electromagnetic spectrum when an appropriate matching and tuning system is connected to said antenna structure 2000.

(112) The antenna structure 2000 includes a radiating element 2001, and a rectangular ground plane layer 2002. The radiating element 2001 comprises a single radiating arm 2003, said arm 2003 including a connection point 2004 located at one end of the radiating arm 2003.

(113) FIGS. 21A, 21B and 21C show the radiator contour 2110 of the radiating element 2001 inside the antenna rectangle 2100 under a first grid 2101, a second grid 2102, and a third grid 2103. In this case, the radiator rectangle 2100 is perfectly tessellated with nine (9) columns and five (5) rows of cells of said second grid 2102 (FIG. 21B). The radiating element 2001 has a connection point 2004 located substantially close to the bottom left corner of the radiator rectangle 2105 (being this the feeding point corner). In this particular example, the radiator contour 2110 comprises curve segments.

(114) As for the radiator contour 2110 of FIG. 21A, there are thirteen (13) cells of the first grid 2101 at least partially inside the radiator rectangle 2100 and that include at least a point of the radiator contour 2110 (i.e., N1=13). In FIG. 21B, there are twenty-six (26) cells of the second grid 2102 completely inside the radiator rectangle 2100 and that include at least a point of the radiator contour 2110 (i.e., N2=26). Finally in FIG. 21C, there are fifty-seven (57) cells of the third grid 2103 completely inside the radiator rectangle 2100 and that include at least a point of the radiator contour 2110 (i.e., N3=57). Therefore, in the present example, the radiating element 2001 features F21=1.0 (i.e., smaller than 1.2) and F32=1.1 (i.e., smaller than 1.2).

(115) FIG. 22A-f present some further examples of antenna structures 2210, 2220, 2230, 2240, 2250, 2260 for an antenna system according to the present invention. As in the example described in connection with FIGS. 17A and 17B, these antenna structures comprise two radiating elements and a ground plane layer 2200.

(116) FIGS. 22A and 22B show two examples in which a first and second radiating elements feature a volumetric geometry. The first radiating element 2211, 2221 and the second radiating element 2212, 2222 comprise a portion having the shape of a parallepiped (and more preferably the shape of a cube) with a face being coplanar with the ground plane layer 2200 and extending upwards (i.e., substantially perpendicular to the plane containing the ground plane layer 2200) a predetermined height. Said height may be the same for both the first and second radiating elements 2211, 2212, 2221, 2222, or may be different.

(117) In FIG. 22A, the radiator box of the first radiating element 2211 has a volume larger than the volume of the radiator box of the second radiating element 2212, while in FIG. 22B the volume of the radiator box of the first radiating element 2221 is substantially the same as that of the radiator box of the second radiating element 2222.

(118) FIGS. 22C and 22D show two examples in which a first and second radiating element are substantially planar. The first radiating element 2231, 2241 and the second radiating element 2232, 2242 comprise a portion having the shape of a rectangle (and more preferably the shape of a square) and are located on the same plane as the one containing the ground plane layer 2200 (i.e., the first and second radiating elements 2231, 2232, 2241, 2242 and the ground plane layer 2200 are substantially coplanar).

(119) In FIG. 22C, the radiator rectangle of the first radiating element 2231 has an area larger than the area of the radiator rectangle of the second radiating element 2232, while in FIG. 22D the area of the radiator rectangle of the first radiating element 2241 is substantially the same as that of the radiator rectangle of the second radiating element 2242.

(120) FIGS. 22E and 22F show two further examples in which a first and second radiating elements are substantially planar. The first radiating element 2251, 2261 and the second radiating element 2252, 2262 comprise a single radiating arm that defines a geometry with a radiating contour having a plurality of segments. In these examples, the radiator contour of the radiating elements 2251, 2252, 2261, 2262 has more than 10 segments but advantageously less than 20 segments in order to keep the geometrical complexity low. Also, although in these examples the number of segments of the radiator contour of the radiating elements 2251, 2252, 2261, 2262 appears to be the same, in other cases they may be different.

(121) In some cases, as in the example in FIG. 22E, the sum of the length of the segments of the radiator contour of the first radiating element 2251 and that of the radiator contour of the second radiating element 2252 are different. In other cases, such as in the example of FIG. 22F, the sum of the length of the segments of the radiator contour of the first radiating element 2261 and that of the radiator contour of the second radiating element 2262 are substantially equal.