Abstract
A radiating system comprises a radiating structure including two or more radiation boosters for transmission and reception of electromagnetic wave signals, a radiofrequency system and an external port. The radiating system is capable of operation in at least a first and second frequency regions which are preferably separated. The radiofrequency system comprises two or more matching networks and a combining structure at which, in transmission, electromagnetic wave signals from the external port are substantially separated and coupled to each radiation booster based on the frequency of the signals; and, in reception, signals from each radiation booster are combined and coupled to the external port. The radiofrequency system provides impedance matching to the radiating structure in the first and second frequency regions at the external port. An advantage of such radiating system is that signals from the first and second frequency regions are fed to and retrieved in one single port.
Claims
1. A radiating system configured to operate in at least a first frequency region and a second frequency region of the electromagnetic spectrum, the radiating system comprising: an external port; a first feeding line including first and second connection points; a second feeding line including first and second connection points; a radiating structure comprising: a ground plane layer including first and second connection points; a first radiation booster including a first booster connection point connected to the first connection point of the first feeding line, the first radiation booster being coupled to the ground player at a first internal port defined between the first booster connection point and the first connection point of the ground plane layer; and a second radiation booster including a second booster connection point connected to the first connection point of the second feeding line, the second radiation booster being coupled to the ground player at a second internal port defined between the second booster connection point and the second connection point of the ground plane layer; and a radiofrequency system to provide impedance matching to the radiating structure in the at least first and second frequency regions at the external port, the radiofrequency system comprising: a combining structure; a first matching network defined between the second connection point of the first feeding line and a point in the combining structure, the first matching network comprising a first transmission line having a width, a gap from the ground plane layer, and a length; and a second matching network defined between the second connection point of the second feeding line and a point in the combining structure, the second matching network comprising a second transmission line having a width, a gap from the ground plane layer, and a length.
2. The radiating system of claim 1, wherein the first and second feeding lines are conductive traces.
3. The radiating system of claim 1, wherein the radiofrequency system further comprises a third matching network defined between a point in the combining structure and the external port.
4. The radiating system of claim 1, wherein a lowest frequency of the second frequency region is higher than a highest frequency of the first frequency region such that the first and second frequency regions are separated.
5. The radiating system of claim 1, wherein the combining structure is a conductive pad.
6. The radiating system of claim 1, wherein, for each of the first and second transmission lines, the width is at least 2.5 times greater than the gap from the ground plane layer.
7. The radiating system of claim 6, wherein, for each of the first and second transmission lines, the width is equal to or greater than 1 mm and less than 3.5 mm.
8. The radiating system of claim 6, wherein, for each of the first and second transmission lines, the gap from the ground plane layer is greater than 0.1 mm and equal to or less than 1 mm.
9. The radiating system of claim 8, wherein, for each of the first and second transmission lines, the width is substantially equal to 1.5 mm and the gap from the ground plane layer is substantially equal to 0.5 mm.
10. The radiating system of claim 1, wherein, for the first and second transmission lines, the gap from the ground plane layer is located along a side of the first and second transmission line that is opposite to a side that is closer to the radiation boosters.
11. The radiating system of claim 1, wherein an impedance measured at the combining structure towards the first radiation booster is greater than 200 ohms for some or all frequencies of one of the first and second frequency regions of operation.
12. The radiating system of 11, wherein an impedance measured at the combining structure towards the second radiation booster is greater than 200 ohms for some or all frequencies of the other of the first and second frequency regions of operation.
13. The radiating system of claim 1, wherein the radiating system has an impedance bandwidth in the first frequency region greater than 10%.
14. The radiating system of claim 13, wherein the radiating system has an impedance bandwidth in the second frequency region greater than 20%.
15. A radiating system configured to operate in at least a first frequency region and a second frequency region of the electromagnetic spectrum, the radiating system comprising: an external port; a first feeding line including first and second connection points; a second feeding line including first and second connection points; a radiating structure comprising: a ground plane layer including first and second connection points; a first radiation booster including a first booster connection point connected to the first connection point of the first feeding line, the first radiation booster being coupled to the ground player at a first internal port defined between the first booster connection point and the first connection point of the ground plane layer; and a second radiation booster including a second booster connection point connected to the first connection point of the second feeding line, the second radiation booster being coupled to the ground player at a second internal port defined between the second booster connection point and the second connection point of the ground plane layer, wherein the first and second radiation boosters are located beyond an edge of the ground plane layer, and wherein, for each of the first and second radiation boosters, a location of the radiation booster is characterized by a location factor defined as a ratio between a width of the radiation booster and a gap that separates the radiation booster from the ground plane layer; and a radiofrequency system to provide impedance matching to the radiating structure in the at least first and second frequency regions at the external port, the radiofrequency system comprising: a combining structure; a first matching network defined between the second connection point of the first feeding line and a point in the combining structure, the first matching network comprising a first transmission line having a width, a gap from the ground plane layer, and a length; and a second matching network defined between the second connection point of the second feeding line and a point in the combining structure, the second matching network comprising a second transmission line having a width, a gap from the ground plane layer, and a length.
16. The radiating system of claim 15, wherein the radiofrequency system further comprises a third matching network defined between a point in the combining structure and the external port.
17. The radiating system of claim 15, wherein the location factor of the first and second radiation boosters is between 0.3 and 3.5.
18. The radiating system of claim 15, wherein, for each of the first and second transmission lines, the width is at least 2.5 times greater than the gap from the ground plane layer.
19. The radiating system of claim 15, wherein: an impedance measured at the combining structure towards the first radiation booster is greater than 200 ohms for some or all frequencies of one of the first and second frequency regions of operation; and the impedance measured at the combining structure towards the second radiation booster is greater than 200 ohms for some or all frequencies of the other of the first and second frequency regions of operation.
20. The radiating system of claim 15, wherein the radiating system has an impedance bandwidth in the first frequency region greater than 10% and an impedance bandwidth in the second frequency region greater than 20%.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
(1) Further characteristics and advantages of the invention will become apparent in view of the detailed description which follows of some preferred embodiments of the invention given for purposes of illustration only and in no way meant as a definition of the limits of the invention, made with reference to the accompanying drawings.
(2) FIG. 1 shows a wireless handheld device, in an exploded view, comprising an exemplary radiating system.
(3) FIG. 2 shows schematically a radiating system according to the present invention.
(4) FIG. 3A and FIG. 3B show exemplary radiating systems with diagrammatic representations of radiofrequency systems.
(5) FIG. 4A and FIG. 4B schematically show examples of matching networks for a radiofrequency system according to the present invention. More particularly, FIG. 4A shows an exemplary matching network comprising a transmission line; and FIG. 4B shows an exemplary matching network suitable for interconnection between the combining structure and the external port of a radiating system.
(6) FIG. 5 shows, in a block diagram fashion, an example of a radiofrequency system according to the present invention.
(7) FIG. 6 shows a possible reflection coefficient measured at the external port of a radiating system which may be included in a wireless device such as FIG. 1.
(8) FIG. 7 shows a table with several transmission line gap and width ratios and the associated characteristic impedances.
(9) FIG. 8A and FIG. 8B show exemplary booster elements according to the present invention.
(10) FIG. 9A and FIG. 9B show a test platform for the electromagnetic characterization of booster elements.
(11) FIG. 10 shows the radiation efficiency and antenna efficiency of a booster element according to the present invention measured with the test platform depicted in FIGS. 9A-9B.
DETAILED DESCRIPTION
(12) In FIG. 1 there is shown a mobile phone in an exploded view, the phone including parts 101, 102, and 103. The mobile phone comprises an exemplary radiating system according to the present invention. The radiating system comprises a radiating structure included in the printed circuit board 102 comprising first radiation booster 104, second radiation booster 105, and ground plane layer 106. The radiating system further comprises the external port 107, and a radiofrequency system which, for clarity, is shown with no components in the matching networks other than first transmission line 108, second transmission line 109, and a combining structure taking the form of conductive pad 110. An example of a complete radiofrequency system is shown in FIG. 5.
(13) Although the device from FIG. 1 is a mobile phone, other wireless handheld or portable devices may include a similar radiating system.
(14) A radiating system according to the present invention is shown schematically in FIG. 2. Said radiating system comprises the radiating structure 201, the radiofrequency system 202, and the external port 203. The radiating structure includes the first radiation booster 204 with a connection point 205, the second radiation booster 206 with a connection point 207, and a ground plane 208 with connection points 209 and 211. A first internal port 210 is defined between the connection point 205 of radiation booster 204 and the connection point 209 of the ground plane 208, and a second internal port 212 is defined between the connection point 207 of radiation booster 206 and the connection point 211 of the ground plane 209. The first radiation booster is connected to a first feeding line through connection point 205, and the second radiation booster is connected to a second feeding line through connection point 207. The radiofrequency system 202 is connected to said first and second feeding lines through connection points 213 and 214 of the feeding lines, and is also connected to the external port 203. The radiofrequency system provides impedance matching to the radiating structure 201 at the external port 203 so that the radiating system is configured to operate electromagnetic wave signals from first and second frequency regions of the electromagnetic spectrum.
(15) The ground plane 208 may be, for instance, a layer of a printed circuit board acting precisely as a ground plane. It may also be formed in more than one layer of a printed circuit board, with several layers being electrically connected; or even be formed in more than one printed circuit board, with the ground plane layers being interconnected.
(16) A radiating system with a schematic radiofrequency system 301 is shown in FIG. 3A. The printed circuit board 302 includes a radiating structure comprising first radiation booster 303 which includes connection point 321 in electrical contact with first feeding line 304 in the form of a conductive trace, second radiation booster 305 which includes connection point 322 in electrical contact with second feeding line 306 in the form of a conductive trace, and a ground plane layer 307 comprising one or more connection points.
(17) The radiofrequency system 301 comprises first matching network 310, second matching network 311, third matching network 312 (matching networks 310, 311 and 312 are shown empty for illustrative purposes only) and combining structure 313 which in this particular example is formed as a conductive pad on the printed circuit board 302. The first matching network is defined between point 314 in the first conductive trace 304 and the combining structure 313, the second matching network is defined between point 316 in the second conductive trace 306 and the combining structure 313, and the third matching network is defined between the combining structure and conductive pad 320. In this example, the external port 319 of the radiating system is defined between conductive pad 320 and the ground plane layer 307. Generally, the matching networks 310, 311, 312 may also be connected to the ground plane 307.
(18) In FIG. 3A there are also shown the width 323 and gap 324 dimensions characterizing radiation booster 303, wherein gap 324 represents the minimum distance of an edge of the conductive part of the radiation booster connected to the conductive trace 304 to the ground plane layer 307, and wherein width 323, in the context of this invention, is taken as the smallest dimension of the radiation booster's footprint on the printed circuit board 302. The ratio between width 323 and gap 324 defines the location factor of the radiation booster. The location factor is preferably greater than 0.3, and/or 0.5, and/or 1.0, and is preferably smaller than 3.5, and/or 3.0, and/or 2.5, and/or 2.0.
(19) In FIG. 3A, the matching networks 310, 311, 312 do not include any component for illustrative purposes only. An example of a suitable matching network for any of the first and second matching networks 310, 311 is shown in FIG. 4A, and an example of a matching network that may be added as the third matching network 312 is depicted in FIG. 4B.
(20) It is readily apparent to the person skilled in the art that radiation boosters 303 and 305 may comprise a booster element like in the form of booster elements 800 and 810 of FIGS. 8A and 8B, or take any other form including the combination of more than one booster element. Therefore the radiation boosters are not limited to the form of polygons 303 and 305 (drawn with dashed lines) of FIG. 3A.
(21) FIG. 3B also shows a radiating system wherein the radiating structure comprises first radiation booster 351 formed by two booster elements, said radiation booster fits in an imaginary sphere having a diameter smaller than of a radiansphere corresponding to the lowest frequency of the first frequency region of the radiating system. The radiation booster 351 is connected to conductive trace 352. The radiating structure further comprises second radiation booster 353 formed by one booster element, and it is connected to conductive trace 354 of the printed circuit board 302. Conductive traces 352 and 354 advantageously separate radiation boosters 351 and 353, respectively, from the ground plane layer 355; said separation may improve the performance of the radiation boosters in terms of impedance bandwidth, and/or efficiency, and/or reflection coefficient. In preferred embodiments, the location factor of radiation boosters is at least 0.3 and less than 3.5, wherein said location factor is defined as the ratio between the width of the radiation booster and the separation between the radiation booster and the ground plane layer.
(22) In the context of the present invention, a first matching network is defined between point 356 in trace 352 and a point in the combining structure 313, a second matching network is defined between point 357 in trace 354 and a point in the combining structure 313, and a third matching network is defined between a point in the combining structure 313 and a point in pad 320, wherein said pad 320 may further define the external port 319 of the radiating system as shown in FIG. 3A. In some cases, a bandwidth target may be achieved at the combining structure and the third matching network may not be necessary, in which case it is also possible that the external port of the radiating system may be defined between the combining structure 313 and the ground plane layer 355.
(23) The first matching network, in addition to other components not drawn in FIG. 3B but shown in FIG. 4A and FIG. 5, comprises a first transmission line 358 characterized by width 360, gap or separation 361 from the ground plane layer 355, and a length. The second matching network, which also comprises other components not represented in FIG. 3B but shown in FIG. 4A and FIG. 5, includes a second transmission line 359 that is also characterized by a width, a gap from the ground plane layer 355, and a length. In this embodiment, both transmission lines 358 and 359 feature the same width 360 and gap 361. The correct election of the lengths of the transmission lines, depending on the given width 360 and gap 361 values, and together with the rest of the components from the respective matching networks, makes the impedance measured at the combining structure 313 towards the first radiation booster 351 to be particularly high for some or all frequencies of the one frequency region (e.g., the second frequency region), and the impedance measured at the combining structure 313 towards the second radiation booster 351 to be particularly high for some or all frequencies of the other frequency region (e.g., the first frequency region). The first and second matching networks also provide impedance matching to frequencies for which the input impedance at the combining structure is not high, namely the frequencies from the other one of the first and second frequency regions. In those cases in which said impedance matching does not achieve a bandwidth target in one or both frequency regions, the third matching network further tunes the impedance for the combined electromagnetic wave signals so as to achieve said bandwidth target; conductive pad 362 may be convenient for allocating part of said third matching network. A circuit that may be suitable for the third matching network may be seen in FIG. 4B and FIG. 5.
(24) A particularity of transmission lines 358 and 359 is that there is no ground plane near the edge of the transmission lines that is closer to radiation boosters 351 and 353, and ground plane is mainly present at the opposite side (the side defining gap 361). Generally, almost no ground plane is present at one side of the transmission lines. In less preferred embodiments, there may be a ground plane layer substantially beneath the transmission lines, such as a layer of a multilayer printed circuit board that may be below said lines. In addition, and even though the lengths of transmission lines 358 and 359 in FIG. 3B is substantially similar, in other embodiments the length of the first transmission line may be different to the length of the second transmission line.
(25) A matching circuit as represented in FIG. 4A may be used in any of the first and second matching networks of a radiofrequency system according to the present invention. Although a particular topology is shown, other topologies may also be used as long as one of the components in the matching network is a transmission line as disclosed in the present invention. In this particular example, point 401 is to be connected to a feeding line such as 352 or 354 in FIG. 3B (corresponding either to point 356 or 357 for example), and point 402 is to be connected to the combining structure like 313 in FIG. 3A or FIG. 3B. In this particular case, the matching circuit comprises four stages: the first stage includes series component 404, the second stage includes two shunted components 405 and 406 which are connected to a ground plane 403, the third stage comprises transmission line 407, and the fourth stage comprises component 408 connected in series between transmission line 407 and point 402. In other embodiments, such a matching circuit may comprise less than four stages or more than four stages.
(26) The matching network is advantageously configured so that the input impedance measured at port 409 is high for part or the totality of the frequencies comprised in one of the first and second frequency regions, thus substantially blocking electromagnetic wave signals from said frequency region, whereas impedance matching at port 409 is partial or total for the other one of said first and second frequency regions.
(27) Regarding FIG. 4B, an exemplary matching circuit suitable for the third matching network of a radiofrequency system is depicted. In this particular circuit, point 411 is connected to the combining structure such as 313 in FIG. 3A or FIG. 3B, and point 412 connects to a pad (such as 320 in FIG. 3A or FIG. 3B) that also defines the external port of the radiating system. The matching circuit comprises three stages, but in other examples it may comprise one, two, or more than three stages. The first stage corresponds to component 413 in series, the component 414 from the second stage is in parallel and connected to ground plane 403, and third stage comprises component 415 also in series. The input impedance or the reflection coefficient achieves a bandwidth target when measured at port 416.
(28) All the circuit components from FIGS. 4A-4B other than the transmission lines may be any of the following, but not limited to: inductors, capacitors, resistors, jumpers, short-circuits, transmission lines, or other reactive or resistive components. The combination of components and topologies of the matching networks depend on the particular characteristics of the radiating system like, for example: the frequency regions of operation of the radiating system; the radiation boosters used and their location in the wireless device; the lengths and shapes of the conductive traces; the dimensions and shapes of the ground plane layers; the width, length and gap parameters of the transmission lines; the electronics and circuitry of the device that are nearby the radiating structure, etc.
(29) FIG. 5 depicts an illustrative example of a radiofrequency system with the first matching network being defined between points 501 (in a first feeding line that connects to a first radiation booster), 502 (in the combining structure), and 503 (in the ground plane); the second matching network being defined between points 504 (in a second feeding line that connects to a second radiation booster), 505 (in the combining structure), and 506 (in the ground plane); and the third matching network being defined between points 507 (in the combining structure), 508 (in a conductive pad that may further define the external port of the radiating system), and 509 (in the ground plane).
(30) Although in this specific embodiment particular matching network topologies and component combinations are represented, it will be readily apparent to the person skilled in the art that other matching networks are also possible according to the teachings of the present invention.
(31) FIG. 6 is a graph representing an exemplary reflection coefficient versus frequency measured at the external port of a radiating system according to the present invention. In this particular graph, the reflection coefficient 601 is equal or lower than 6 dB in the first frequency region 602 ranging from 698 MHz to 960 MHz, and in the second frequency region 603 ranging from 1710 MHz to 2690 MHz. Such performance may be achieved, for example, by the radiating system from FIG. 3B including the radiofrequency system from FIG. 5.
(32) In other embodiments, the reflection coefficient target may be even lower or greater like for instance 4.4 dB; and/or the first and second frequency regions may comprise ranges of frequencies different from the ones shown in FIG. 6.
(33) A table showing pairs of width and gap values of transmission lines is represented in FIG. 7. Specifically, the characteristic impedance (Z0) is indicated for few width-gap pairs when the total width of the transmission line is 2 mm, 3 mm, and 4 mm when no ground plane layer is located beneath the transmission line, although the invention is not limited by the presence or absence of ground plane below the transmission lines.
(34) As represented in the table, the characteristic impedance decreases as the gap is reduced. Accordingly, for given width and gap values that preferably make the transmission line to have a characteristic impedance between 75 and 150, the length of the transmission lines has to be set properly to make the radiating system operable in first and second frequency regions. And for the radiating system to support the tolerances in the PCB manufacturing process, gaps of about 0.5 mm are convenient as slight variations in the fabrication do not have an impact as large as in the case of gaps of 0.2 mm or even 0.1 mm. So for a preferred embodiment with transmission lines featuring a total width of 2 mm, a width of 1.5 mm and a gap of 0.5 mm advantageously make the radiating system operable in two frequency regions by adjusting the lengths of the lines.
(35) Two exemplary booster elements are shown in FIG. 8A and FIG. 8B. The booster element 800 comprises a first conductive surface 801, a second conductive surface 802, a dielectric element or support 803 (shown transparent for illustrative purposes only), and several via holes 804 electrically connecting the first conductive surface 801 with the second conductive surface 802. The first and second conductive surfaces 801 and 802 substantially feature rectangular shapes.
(36) The booster element 810 from FIG. 8B comprises a first conductive surface 811 and a second conductive surface 812, each of which are substantially shaped as squares, although other shapes are possible as well. Said surfaces 811 and 812 are electrically connected by via holes 814 going through the dielectric material 813.
(37) Both booster elements 800 and 810 may be configured to function as a radiation booster in every radiating structure according to the present invention in a single configuration as radiation booster 353 of FIG. 3B, or in a multiple configuration like 351 in FIG. 3B wherein two or more booster elements are connected yet they are configured to function as a single radiation booster.
(38) A connection point (such as 205 and 207 in FIG. 2; or 321 and 322 in FIG. 3A) of booster elements such as 800 and 810 may be located substantially close to one corner of one of the first and second conductive surfaces.
(39) FIG. 9A schematically shows, in a 3D perspective, a test platform for the characterization of booster elements. The platform comprises substantially square conductive surface 901 and connector 902 (for instance an SMA connector) electrically connected to the device or element 900 to be characterized. The conductive surface 901 has sides with a length larger than the reference operating wavelength corresponding to the reference frequency. For instance, at 900 MHz, said sides are at least 60 centimeters long. The conductive surface may be a sheet or plate made of cupper, for example. The connector 902 is placed substantially in the center of conductive surface 901.
(40) In FIG. 9B the same test platform of FIG. 9A is schematically represented in a 2D perspective wherein the conductive surface 901 is partially drawn. In this example, the element that is to be characterized 900 in FIG. 9A corresponds to booster element 800 from FIG. 8A, which is arranged so that its largest dimension is perpendicular to conductive surface 901, and one of the first or second conductive surfaces (801 or 802 of FIG. 8A) is in direct electrical contact with connector 902 (for clearer interpretation of the orientation of booster element 800, via holes 804 connecting the first and second conductive surfaces of booster element are also drawn in FIG. 9B). The booster element 800 lies on a dielectric material (not shown) attached to the conductive surface 901 so as to minimize the distance between booster element 800 and surface 901. Said dielectric material may be a dielectric tape or coating, for example.
(41) FIG. 10 shows an graph of the radiation efficiency and antenna efficiency measured in a test platform like the one shown in FIG. 9A and FIG. 9B, when the element 900 to be characterized is booster element 800. In this particular example, the radiation efficiency measured 1001 (represented with a solid line) at 900 MHz is less than 5%, and the antenna efficiency measured 1002 (represented with a dashed line) at 900 MHz is less than 1%.
(42) The foregoing is merely illustrative of the principles of this invention and various modifications can be made by those skilled in the art without departing from the scope and spirit of the invention.
