Abstract
An antenna includes at least two radiating arm structures made of or limited by a conductor, superconductor or semiconductor material. The two arms are coupled through a region on first and second superconducting arms such that the combined structure forms a small antenna with broadband behavior, multiband behavior or a combination thereof. The coupling between the two radiating arms is obtained via the shape and spatial arrangement thereof, in which at least one portion on each arm is placed in close proximity to each other (e.g., at a distance smaller than 1/10 of the longest free-space operating wavelength) to allow electromagnetic fields in one arm to be transferred to the other through close proximity regions. The proximity regions are spaced from the feeding port of the antenna (e.g., greater than 1/40 of the free-space longest operating wavelength) and specifically exclude the feeding port of the antenna.
Claims
1. An apparatus comprising: an antenna arranged within the apparatus and operable at a first frequency band, a second frequency band higher in frequency than the first frequency band, and a third frequency band higher in frequency than the second frequency band, the antenna comprising: a ground plane; a first radiating structure fed through a feeding terminal, the first radiating structure having a first length extending along a first non-straight path from a first end at the feeding terminal to a second, open end and having a first width perpendicular to the first non-straight path; and a second radiating structure connected to the ground plane through a grounding terminal, the second radiating structure having a second length extending along a second non-straight path from a first end at the grounding terminal to a second, open end and having a second width perpendicular to the second non-straight path, wherein the second length is shorter than the first length, the second radiating structure being arranged separated from the first radiating structure by a distance that is non-constant over an extent of the first and second radiating structures, wherein: the first and the second radiating structures are folded to provide coupling between the first radiating structure and the second radiating structure at least at the second and the third frequency bands; and the first width varies over an extent of the first radiating structure, and the second width varies over an extent of the second radiating structure.
2. The apparatus of claim 1, wherein a portion bounding the first radiating structure is formed by at least ten connected segments, each of the segments forming an angle with neighboring connected segments, the angle being less than 180 degrees, and the segments being shorter than of a longest free-space operating wavelength in the first frequency band.
3. The apparatus of claim 2, wherein a portion bounding the second radiating structure is formed by at least ten connected segments, each of the segments forming an angle with neighboring connected segments, the angle being less than 180 degrees, and the segments being shorter than 1/10 of a longest free-space operating wavelength in the second frequency band.
4. The apparatus of claim 1, wherein the first radiating structure includes at least one sub-branch.
5. The apparatus of claim 4, wherein the second radiating structure includes at least one sub-branch.
6. The apparatus of claim 1, wherein a folding of the first radiating structure is formed by a 90 angle.
7. The apparatus of claim 1, wherein a distance between at least a first point in the first radiating structure and at least a second point in the second radiating structure is smaller than a distance between the feeding terminal and the grounding terminal.
8. An apparatus comprising: an antenna arranged within the apparatus and having a multi-band behavior, the antenna comprising: a ground plane; a first radiating structure fed through a feeding terminal, the first radiating structure having a length extending along a first non-straight path from a first end at the feeding terminal to a second, open end and having a first width perpendicular to the first non-straight path, the first width varying over an extent of the first radiating structure; and a second radiating structure connected to the ground plane through a grounding terminal, the second radiating structure having a second length extending along a second non-straight path from a first end at the grounding terminal to a second, open end and having a second width perpendicular to the second non-straight path, the second width varying over an extent of the second radiating structure, the second radiating structure being separated from the first radiating structure by a distance that is non-constant over an extent of the first and second radiating structures, wherein: the first and second radiating structures and the spacing between the first and second radiating structures are configured to enable the antenna to operate at a first frequency band, a second separate frequency band higher in frequency than the first frequency band, and a third frequency band higher in frequency than the second frequency band; the spacing between the first and second radiating structures is configured to transfer electromagnetic fields from the first radiating structure to the second radiating structure at least at the second frequency band; and the second length is shorter than the first length and the second length is configured to provide a bandwidth required for the antenna to operate in at least the second frequency band.
9. The apparatus of claim 8, wherein the first radiating structure includes at least one sub-branch.
10. The apparatus of claim 9, wherein the second radiating structure includes at least one sub-branch.
11. The apparatus of claim 8, wherein a portion bounding the first radiating structure is formed by at least ten connected segments, each of the segments forming an angle with neighboring connected segments, the angle being less than 180 degrees, and the segments being shorter than of a longest free-space operating wavelength in the first frequency band.
12. The apparatus of claim 11, wherein a portion bounding the second radiating structure is formed by at least ten connected segments, each of the segments forming an angle with neighboring connected segments, the angle being less than 180 degrees, and the segments being shorter than 1/10 of a longest free-space operating wavelength in the second frequency band.
13. The apparatus of claim 8, wherein a folding of the first radiating structure is formed by a 90 angle.
14. The apparatus of claim 8, wherein a distance between the first end of the second radiating structure and the feeding terminal of the first radiating structure is less than a distance between the second, open end of the second radiating structure and the feeding terminal of the first radiating structure.
15. An apparatus comprising: an antenna arranged within the apparatus and configured to operate in at least first, second, and third frequency bands, the antenna comprising: a ground plane; a first radiating structure fed through a feeding terminal, the first radiating structure having a first length extending along a first non-straight path from a first end at the feeding terminal to a second, open end; and a second radiating structure connected to the ground plane through a grounding terminal, the second radiating structure having a second length extending along a second non-straight path from a first end at the grounding terminal to a second, open end, the second radiating structure being separated from the first radiating structure by a distance that is non-constant over an extent of the first and second radiating structures, wherein: the first and the second radiating structures are folded to form a close proximity region between the first and the second radiating structures, an orthogonal projection of the close proximity region onto a plane of the ground plane does not intersect the ground plane; the distance between the first and the second radiating structures is configured to provide coupling from the first radiating structure to the second radiating structure at least at the third frequency band; the second frequency band has higher operating frequencies than the operating frequencies of the first frequency band, and the third frequency band has higher operating frequencies than the operating frequencies of the second frequency band; and the second radiating structure is configured to increase the resulting bandwidth of the antenna at the second and third frequency bands in relation to a bandwidth provided by only the first radiating structure.
16. The apparatus of claim 15, wherein the second length is shorter than the first length.
17. The apparatus of claim 15, wherein the first radiating structure is non-planar.
18. The apparatus of claim 17, wherein the second radiating structure is non-planar.
19. The apparatus of claim 15, wherein the first radiating structure includes at least one sub-branch.
20. The apparatus of claim 19, wherein the second radiating structure includes at least one sub-branch.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0027] For a better understanding of the present invention, reference will now be made to the appended drawings in which:
[0028] FIGS. 1A, 1B and 1C show different prior-art configurations. FIG. 1A shows a conventional active monopole (unbalanced antenna connected to a feed point) with a parallel parasitic element, whereas FIG. 1B shows a conventional active monopole (unbalanced antenna connected to a feed point) with four conventional straight parasitic elements, all of them parallel to the active monopole. FIG. 1C shows a very well-known prior-art configuration known as Yagi-Uda, used mainly for terrestrial communications. With this Yagi-Uda configuration, several parasitic elements are placed in parallel to the active element and at the same distance to each other.
[0029] FIGS. 2A and 2B show two basic structures for what is covered with this invention. FIG. 2A shows two arms, one of them is fed, and the other one is directly connected to ground. It can be seen that there is a close proximity region between them. Both arms are folded in this example. FIG. 2B shows another configuration for the two arms, wherein the arm that is fed is straight, whereas the parasitic arm is folded so as to form a close proximity region with said first arm.
[0030] FIGS. 3A to 3F show several basic examples of different configurations for coupled antennas, where the arms that are connected to the feeding point (active arms) are straight, whereas the parasitic arms are folded so as to form a close proximity region with the active arms.
[0031] FIGS. 4A to 4F show a series of more complex examples of coupled antennas, where the arms that are connected to the feeding point (active arms) are straight, whereas the parasitic arms can be folded with space-filling curves.
[0032] FIGS. 5A to 5F shows that not only the parasitic arms can be folded so as to form a close proximity region, but also the active arms, that is, the arms that are connected to ground plane. Basic configurations are shown in these figures.
[0033] FIGS. 6A to 6F show alternative schemes of coupled antennas. FIGS. 6A to 6C are examples of coupled antennas where either one of two arms have parts acting as stubs, for better matching the performance of the antenna to the required specifications. FIGS. 6D to 6F show examples of how coupled-loop structures can be done by using the present invention.
[0034] FIGS. 7A to 7F show that several parasitic arms (that is, arms that are not connected to the feeding port) can be placed within the same structure, as long as there is a close proximity region as defined in the object of the invention.
[0035] FIGS. 8A to 8F show different configurations of arms formed by space-filling curves. As in previous examples, no matter how the arms are built, the close proximity region is well defined.
[0036] FIGS. 9A to 9F show another set of examples where arms include one or several sub-branches to their structure, so as to better match the electrical characteristics of the antenna with the specified requirements.
[0037] FIGS. 10A to 10F show several complex configurations of coupled antennas, with combinations of configurations previously seen in FIGS. 1A to 9F.
[0038] FIGS. 11A to 11F show that any shape of the arm can be used, as long as the coupled antennas are connected through a close proximity region.
[0039] FIGS. 12A to 12F show a series of complex examples of coupled antennas. FIGS. 12A and 12B show that arms can also be formed by planar structures. FIG. 12C shows an active armformed by a multilevel structure. FIG. 12D shows a spiral active arm surrounding the parasitic arm. FIG. 12E shows another example of planar arms folded. Not only linear or planar structures are covered within the scope of the present invention, as seen in FIG. 12F, where two 3D arms are positioned so as to form a close proximity region.
[0040] FIGS. 13A and 13B show that not only monopoles can feature a close proximity region, but also slot antennas, such as the ones showed in FIGS. 13A and 13B.
[0041] FIGS. 14A and 14B show a coupled antenna mounted on a chip configuration.
[0042] FIGS. 15A to 15C show more examples of applications where coupled antennas can be mounted. FIGS. 15A and 15C show basic configurations of coupled antennas mounted on handheld PCBs. FIG. 15B shows a clamshell handheld configuration (folded PCB) and how the coupled antenna could be mounted on that.
[0043] FIG. 16 shows another configuration for coupled antennas, where those are connected in a car environment.
[0044] FIG. 17A shows a PIFA structure that is also covered within the scope of the present invention, since it features a close proximity region between the two arms (in this case, two planar patches) of the structure. FIGS. 17B to 17D show a series of dipole structures (balanced feeding structure) that also feature a close proximity region.
DETAILED DESCRIPTION
[0045] In order to construct a coupled antenna system according to embodiments of the invention, a suitable antenna design is required. Any number of possible configurations exists, and the actual choice of antenna is dependent, for instance, the operating frequency and bandwidth, among other antenna parameters. Several possible examples of embodiments are listed hereinafter. However, in view of the foregoing description, it will be evident to a person skilled in the art that various modifications may be made within the scope of the invention. In particular, different materials and fabrication processes for producing the coupled antenna system may be selected, which still achieve the desired effects.
[0046] FIG. 1A shows in a manner already known in prior-art an antenna system formed by two monopoles, one acting as the active monopole (100) and the other acting as the parasitic monopole (101). The feed point (102), represented with a circle in all the drawings in the present invention, can be implemented in several ways, such a coaxial cable, the sheath of which is coupled to the ground plane, and the inner conductor of which is coupled to the radiating conductive element (100). Parasitic element (101) is connected to ground plane through (103). In this configuration, there is no close proximity region, since both (100) and (101) are in parallel. The radiating conductive element (100) is usually shaped in prior art like a straight wire, but several other shapes can be found in other patents or scientific articles. Shape and dimensions of radiating element (100) and parasitic element (101) will contribute in determining the operating frequency of the overall antenna system.
[0047] FIG. 1B shows also in a manner known in prior-art an antenna system formed by a radiating element (100) and several parasitic monopoles (104). In this configuration, there is no close proximity region, since both the radiating element (100) and the parasitic elements (104) are in parallel.
[0048] FIG. 1C shows a prior-art configuration known as Yagi-Uda. With this structure, the distance between any pair of dipoles is generally constant, that is, all the dipoles (105, 106, 107) are parallel and no proximity region is included to strength the coupling between dipoles. The object of such a parallel dipole arrangement in the Yagi-Uda antenna is to provide an end-fire, directive radiation pattern, whereas in the present invention the radiating arms are arranged together with the close proximity region to reduce the antenna size yet providing a broadband or multiband behavior.
[0049] Unlike the prior art structures illustrated in FIG. 1A to 1C, the newly disclosed coupled antenna system shown in FIG. 2A is composed by a radiating element (110) connected to a feeding point (represented by (102)) and a parasitic element (111) connected to the ground plane (112) through (103). It is clear in this configuration the close proximity region (200) between folded subpart arms (108) and (109). That is, Ws<Wd. Feeding point (102) can be implemented in several ways, such a coaxial cable, the sheath of which is coupled to the ground plane (112), and the inner conductor of which is coupled to the radiating conductive element (110). Shape and dimensions of radiating element (110) and parasitic element (111) will contribute in determining the operating frequency of the overall antenna system. For the sake of clarity but without loss of generality, a particular case is showed in FIG. 2B. It is composed by a radiating element (100) connected to a feeding point (102), and a parasitic element (113) connected to the ground plane (112) through (103). It is clear in this configuration also that the close proximity region (201) between (100) and (113) contributes to the enhanced performance of the antenna system, and that Ws<Wd. It is clear to those skilled in the art that these configurations in FIGS. 2A and 2B could have been any other type with any size, and being coupled in any other manner as long as the close proximity region is formed, as it will be seen in the following preferred embodiments. For the sake of clarity, the resulting monopole structures are lying on a common flat ground plane, but other conformal configurations upon curved or bent surfaces for both the coupled antennas and the ground planes could have been used as well. The ground-plane (112) being showed in the drawing is just an example, but several other ground plane embodiments known in the art or from previous patents could have been used, such as multilevel or space-filling ground planes, or Electromagnetic Band-Gap (EBG) ground planes, or Photonic Band-Gap (PBG) ground planes, or high-impedance (Hi-Z) ground planes. The ground-plane can be disposed on a dielectric substrate. This may be achieved, for instance, by etching techniques as used to produce PCBs, or by using a conductive ink.
[0050] In some preferred embodiments, such as the ones being showed in FIGS. 3A to 3F, only the parasitic elements (114, 115, 116, 117, 118, 119) are folded so as to form a close proximity region between radiating elements (100) and parasitic elements (114, 115, 116, 117, 118, 119). Basic configurations (FIGS. 3A to 3F) are being illustrated in these figures, where folding of the parasitic elements (114, 115, 116, 117, 118, 119) is formed by 90-degree angles. The described embodiments of these figures are presented by way of example only and do not limit the invention. Having illustrated and described the principles of the invention in several preferred embodiments thereof, it should be readily apparent to those skilled in the art that the invention can be modified in arrangement and detail without departing from the close proximity region principle.
[0051] Some embodiments, like the ones being showed in FIGS. 4A to 4F, where space-filling curves are coupled, are preferred when a multiband or broadband behavior is to be enhanced. Said space-filling arrangement allows multiple resonant frequencies which can be used as separate bands or as a broadband if they are properly coupled together. Also, said multiband or broadband behavior can be obtained by shaping said elements with different lengths within the structure. Space-filling curves is also a way to miniaturize further the size of the antenna. For the sake of clarity but without loss of generality, particular configurations are being showed in these figures, where the active elements (that is, the radiating arms) are straight, whereas the space-filling properties have been utilized in the parasitic elements. However, the same space-filling principle could have been used to the radiating elements, as it will be shown in other preferred embodiments described later in this document.
[0052] In some preferred embodiments, such as the ones being showed in FIGS. 5A to 5F, both the parasitic elements (121, 122, 123, 125, 127, 129) and the radiating/active elements (120, 124, 126, 128) are folded so as to form a close proximity region between said radiating elements (120, 124, 126, 128) and said parasitic elements (121, 122, 123, 125, 127, 129). Basic configurations (FIGS. 5A to 5F) are being illustrated in these figures, where folding of the parasitic elements (121, 122, 123, 125, 127, 129) and radiating elements (120, 124, 126, 128) is formed by 90-degree angles. The described embodiments of these figures are presented by way of example only and do not limit the invention. Having illustrated and described the principles of the invention in several preferred embodiments thereof, it should be readily apparent to those skilled in the art that the invention can be modified in arrangement and detail without departing from the close proximity region principle.
[0053] For the preferred embodiments showed in FIGS. 6A, 6B and 6C, the arms are being formed by means of using inductive stubs (130, 131, 132, 133, 134). The purpose of those is further reduce the size of the antenna system. The position of said stubs can be placed and distributed along the radiating or the parasitic arms.
[0054] In some preferred embodiments, loop configurations for the coupled antennas further help matching the operating frequencies of the antenna system, such as the ones showed in FIGS. 6D, 6E and 6F. From these drawings it can be seen that the overall shape of the antenna system forms an open loop, yet still being within the scope of the present invention without departing from the close proximity region principle.
[0055] To illustrate that several modifications of coupled antenna systems can be done based on the same principle and spirit of the present invention, other preferred embodiment examples are shown in FIGS. 7A to 7F. FIG. 7A shows a structure where two parasitic elements (135, 136) are included, and a close proximity region is being formed between the active element and the parasitic subsystem. FIGS. 7B to 7F show other preferred configurations where several parasitic elements with different shapes have been placed in different locations and distribution.
[0056] Some embodiments, like the ones being showed in FIGS. 8A to 8F, where space-filling curves are coupled, are preferred when a multiband or broadband behavior is to be enhanced. Said space-filling arrangement allows multiple resonant frequencies which can be used as separate bands or as a broadband if they are properly coupled together. Also, said multiband or broadband behavior can be obtained by shaping said elements with different lengths within the structure. Space-filling curves is also a way to miniaturize further the size of the antenna. For the sake of clarity but without loss of generality, particular configurations are being showed in these figures, where the both the active elements (that is, the radiating arms) and the parasitic elements are being formed by means of space-filling curves.
[0057] In some preferred embodiments, sub-branches to the parasitic and the active elements need to be added so as to match the frequency response of the antenna to the required specifications. FIG. 9A shows a configuration where a branch (137) has been added to the active element, and another branch (138) has been added to the parasitic element. The shape and size of the branch could be of any type, such as linear, planar or volumetric, without loss of generality. FIGS. 9B to 9F show other examples of coupled antennas with a branch-like configuration.
[0058] It is interesting to notice that the advantage of the coupled antenna geometry can be used in shaping the radiating elements and the parasitic elements in very complex ways. Particular examples of coupled antennas using complex configuration and designs are being showed in FIGS. 10A to 10F, but it appears clear to any skilled in the art that many other geometries could be used instead within the same spirit of the invention.
[0059] The shape and size of the arms could be of any type, such as linear, planar or volumetric, without loss of generality. FIGS. 11A to 11F show several examples of coupled antennas where shape of both radiating and parasitic elements varies within the same element.
[0060] FIGS. 12A to 12F show that not only linear structures can be adapted to meet the close proximity region principle defined in the scope of this invention. FIG. 12A shows an example of two planar elements (143, 144). FIG. 12C shows an example of a multilevel structure acting as the radiating element. FIG. 12D shows a spiral active arm surrounding the parasitic arm. FIG. 12E shows another example of planar arms folded. Not only linear or planar structures are covered within the scope of the present invention, as seen in FIG. 12F, where two 3D arms are positioned so as to form a close proximity region.
[0061] FIGS. 13A and 13B show that not only monopoles or dipoles can feature a close proximity region, but also slot antennas, such as the ones showed in FIGS. 13A and 13B. Both drawings are being composed by a conventional solid surface ground-plane (151) that has been cut-out so as to have some slots on it (152, 156, 158). The feed point (155) can be implemented in several ways, such as a coaxial cable, the sheath (153) of which is connected to the external part of (151), and the inner conductor (154) of the coaxial cable is coupled to the inner radiating conductive element, as shown in FIG. 13A. In the case of FIG. 13B, the inner conductor of the coaxial cable would be connected to (157).
[0062] Another preferred embodiment of coupled antennas is the one being showed in FIGS. 14A and 14B. The Drawings represent a coupled antenna being placed in an IC (or chip) module, and is composed by a top cover (159), by a transmit/receive IC module (163), by bond wires (162), by the lead frame of the chip (164), and by a coupled antenna, being formed by an active element and a parasitic element (160, 161). Any other type of chip technology could been used without loss of generality.
[0063] FIGS. 15A to 15C show different configurations of handheld applications where coupled antennas, as described in the present invention, can be used. FIG. 15A shows a PCB (167) of a handheld device (for instance, a cell phone) that acts as ground plane. Just for the sake of clarity, the antenna system in this example is formed by two arms, one acting as active (165), that is, connected to the feeding point and the other one acting as parasitic (166). FIG. 15B shows a clamshell configuration (also known as flip-type) for a cell phone device, and where the antenna system presented in this invention could be located at. FIG. 15C shows a PCB (172) of a handheld device (for instance, a cell phone} that acts as ground plane. The antenna system in this example is formed by two arms that are, in this specific case, 3D structures, once acting as the active arm (171) and the other one acting as the parasitic arm (170). Here, the arms (170, 171) of the antenna system are presented as a parallelepipeds, but any other structure can be obviously taken instead.
[0064] Another preferred embodiment is the one shown in FIG. 16, where the coupled antenna system (173, 174) is mounted on or in a car.
[0065] FIG. 17A shows a PIFA structure that is being composed by an active element formed by ground plane (176), a feeding point (177) coupled somewhere on the patch (178) depending upon the desired input impedance, a grounding or shorting point connection (175), and a radiator element (178). Also, the system is being formed by a parasitic element (179) that is connected to ground plane as well (181). In FIG. 17A it can be clearly seen that the close proximity region is formed by elements (178) and (179). PIFA antennas have become a hot topic lately due to having a form that can be integrated into the per se known type of handset cabinets. Preferably, for this type of antenna system, the antenna, the ground plane or both are disposed on a dielectric substrate. This may be achieved, for instance, by etching techniques as used to produce PCBs, or by printing the antenna and the ground-plane onto the substrate using a conductive ink. A low-loss dielectric substrate (such as glass-fibre, a Teflon substrate such as Cuclad or other commercial materials such as Rogers 4003 well-known in the art) can be placed between said patches and ground-plane. Other dielectric materials with similar properties may be substituted above without departing from the intent of the present invention. As an alternative way to etching the antenna and the ground plane out of copper or any other metal, it is also possible to manufacture the antenna system by printing it using conductive ink. The antenna feeding scheme can be taken to be any of the well-known schemes used in prior art patch or PIFA antennas as well, for instance: a coaxial cable with the outer conductor connected to the ground plane and the inner conductor connected to the patch at the desired input resistance point; a microstrip transmission line sharing the same ground-plane as the antenna with the strip capacitively coupled to the patch and located at a distance below the patch, or in another embodiment with the strip placed below the ground-plane and coupled to the patch through a slot, and even a microstrip transmission line with the strip co-planar to the patch. All these mechanisms are well known from prior art and do not constitute an essential part of the present invention. The essential part of the present invention is the shape of the proximity close region, which contributes to reducing the size with respect to prior art configurations, as well as enhancing antenna bandwidth, VSWR, and radiation efficiency.
[0066] FIGS. 17B to 17D show configurations of coupled antennas as described in the object of the present invention, but with balanced feeding points (183).
[0067] The above-described embodiments of the invention are presented by way of example only and do not limit the invention. Having illustrated and described the principles of our invention in several preferred embodiments thereof, it should be readily apparent to those skilled in the art that the invention can be modified in arrangement and detail without departing from such principles.
