Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01Q—ANTENNAS, i.e. RADIO AERIALS
  • H01Q1/00—Details of, or arrangements associated with, antennas
  • H01Q1/52—Means for reducing coupling between antennas; Means for reducing coupling between an antenna and another structure
  • H01Q1/521—Means for reducing coupling between antennas; Means for reducing coupling between an antenna and another structure reducing the coupling between adjacent antennas
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01Q—ANTENNAS, i.e. RADIO AERIALS
  • H01Q1/00—Details of, or arrangements associated with, antennas
  • H01Q1/12—Supports; Mounting means
  • H01Q1/22—Supports; Mounting means by structural association with other equipment or articles
  • H01Q1/24—Supports; Mounting means by structural association with other equipment or articles with receiving set
  • H01Q1/241—Supports; Mounting means by structural association with other equipment or articles with receiving set used in mobile communications, e.g. GSM
  • H01Q1/242—Supports; Mounting means by structural association with other equipment or articles with receiving set used in mobile communications, e.g. GSM specially adapted for hand-held use
  • H01Q1/243—Supports; Mounting means by structural association with other equipment or articles with receiving set used in mobile communications, e.g. GSM specially adapted for hand-held use with built-in antennas
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01Q—ANTENNAS, i.e. RADIO AERIALS
  • H01Q9/00—Electrically-short antennas having dimensions not more than twice the operating wavelength and consisting of conductive active radiating elements
  • H01Q9/04—Resonant antennas
  • H01Q9/16—Resonant antennas with feed intermediate between the extremities of the antenna, e.g. centre-fed dipole
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01Q—ANTENNAS, i.e. RADIO AERIALS
  • H01Q9/00—Electrically-short antennas having dimensions not more than twice the operating wavelength and consisting of conductive active radiating elements
  • H01Q9/04—Resonant antennas
  • H01Q9/30—Resonant antennas with feed to end of elongated active element, e.g. unipole
  • H01Q9/42—Resonant antennas with feed to end of elongated active element, e.g. unipole with folded element, the folded parts being spaced apart a small fraction of the operating wavelength

Definitions

• the present description is directed, generally, to multiple-element antennas and, more specifically, to systems and methods employing components to reduce the effects of mutual coupling between and among multiple antenna elements.
• Some antenna systems employ antenna elements placed above a ground plane.
• the antenna elements can induce currents in the ground plane that travel to other antenna elements and increase undesired coupling.
• various techniques have been devised. For example, one solution has been to split the ground plane so that two antennas that might interfere are not connected by a continuous ground plane.
• PCB Printed Circuit Board
• Such structures are analogous to Photonic Band Gap (PBG, used in optics) structures and generally act as bandstop filters and can be designed to cancel specific, unwanted signals.
• PBG Photonic Band Gap
• Such systems are expensive in terms of both space and money because of the complexity of the three- dimensional shapes of the structures.
• PBG Photonic Band Gap
• Various embodiments of the invention are directed to systems and methods that include a coupling element in a multiple-element antenna system.
• a coupling element is placed between two antenna elements.
• the shape of the coupling element is designed so that it cancels out the current that is due to direct coupling of the elements.
• the coupling element can be quite small, thereby offering economy of space.
• various embodiments are much less complex than PBG-inspired designs and, thus, are cheaper to manufacture than prior art systems that use PBG-inspired isolation elements.
• FIGURE 1 is an illustration of an exemplary antenna system, adapted according to one embodiment of the invention.
• FIGURE 2 is an illustration of an exemplary antenna system, adapted according to one embodiment of the invention.
• FIGURE 3 is an illustration of an exemplary system, adapted according to one embodiment of the invention.
• FIGURE 4 is an illustration of an exemplary system, adapted according to one embodiment of the invention.
• FIGURE 5 is an illustration of an exemplary system adapted according to one embodiment of the invention.
• FIGURE 6 shows exemplary antenna arrays, adapted according to embodiments of the invention.
• FIGURE 7 is an illustration of an exemplary USB dongle, adapted according to one embodiment of the invention.
• FIGURE 8 is an illustration of an exemplary method adapted according to one embodiment of the invention.
• FIGURE 1 is an illustration of exemplary antenna system 100, adapted according to one embodiment of the invention.
• System 100 includes antenna elements 101 and 102, as well as coupling element 103.
• antenna element 101 is driven by a Radio Frequency (RF) feed, and the current in antenna element 101 is l ⁇ xated-
• the total current in antenna element 102 that is due to mutual coupling with antenna element 101 is ⁇
• Region 110 is where coupling element 103 does not lie between antenna elements 101 and 102. In other words, in region 110, each antenna element 101 and 102 is in the other's line of sight.
• Region 120 is similar to region 110.
• coupling element 103 is positioned between antenna elements 101 and 102.
• regions 110 and 120 there is direct coupling between antenna elements 101 and 102.
• the current due to direct coupling is referred to in this example as , and it is equal to ⁇ l ⁇ xcited, wherein ⁇ is a constant that is affected by distance between antenna elements
• antenna elements 101 and 102 are not direct. Instead, in region 130, antenna elements 101 and 102 each couple with coupling element 103, rather than with each other. Antenna element 101 couples with coupling element 103, thereby inducing a current in coupling element 103 that is in the opposite direction of ⁇ Direct- The current that is induced in coupling element 103 then induces a current (Icancei) in antenna element 103 that is shifted by approximately 180 degrees again.
• the phase of ⁇ cancei is in a direction opposite that o ⁇ l D ⁇ rect and Icancei can be expressed as ⁇ Incited, where ⁇ is a constant that depends on the distances between antenna elements 101 and 102 and coupling element 103 as well as on the size of coupling element 103. In this example, ⁇ is approximately equal to ⁇ , so that lcoupled ⁇ Zer ⁇ .
• antenna elements 101 and 102 are shown as dipole elements, which are generally ⁇ /2 in length.
• the total length of coupling element 103 including both the vertical and horizontal components, is also ⁇ /2 as well.
• the constant ⁇ is affected by the length of the vertical portion (i.e., parallel to antenna elements 101 and 102) of coupling element 103.
• the horizontal portion (i.e., perpendicular to antenna elements 101 and 102) of coupling element 103 has very little, if any, effect on ⁇ . Instead, the horizontal portion is present so that the total length of coupling element 103 is ⁇ /2.
• FIGURE 2 is an illustration of exemplary antenna system 200, adapted according to one embodiment of the invention.
• FIGURE 2 shows an antenna system design with dimensions (in mm) thereon and also provides graphs 250 and 260 to explain the performance of antenna system 200.
• Antenna system 200 is built on Printed Circuit Board (PCB) 205, and it includes antenna elements 201 and 202, coupling element 203, and ground plane 204.
• antenna elements 201 and 202 are Planar Inverted F Antenna (PIFA) elements. Due to their proximity to each other, antenna elements 201 and 202 experience mutual coupling. Coupling element 203 reduces or eliminates the effects of mutual coupling, thereby improving the performance of antenna system 200.
• PIFA Planar Inverted F Antenna
• FIGURE 1 shows a coupling element of total length ⁇ /2
• the total length of the coupling element is also ⁇ /4.
• antenna elements that have resonant lengths of ⁇ /4 include, e.g., monopoles and PIFAs.
• antenna system 200 which uses PIFAs as antenna elements 201 and 202
• coupling element 203 has a length of ⁇ /4.
• Graph 250 shows the simulated and measured performance of an antenna system similar to that of antenna system 200, but without coupling element 203.
• graph 260 shows simulation and measurement results for system 200.
• graph 250 at 2.45 GHz there is -8 dB of coupling.
• Graph 260 shows -30 dB of coupling at 2.45 GHz, indicating an improvement of over -20 dB of isolation. The improvement is impressive, considering that -30 dB means that for every one thousand units of energy only one unit is coupling. For real world systems, it is very difficult to achieve zero coupling; however, embodiments of the invention can improve isolation such that the effects of coupling is near zero (as in graph 260).
• FIGURE 2 shows that the coupling length (i.e., not the total length) of coupling element 203 is two millimeters.
• the coupling length can be adjusted to tune the performance of the system by affecting ⁇ . In fact, differing lengths can be simulated and/or tested to arrive at an optimal length.
• FIGURE 2 While dimensions are given in FIGURE 2, the invention is not so limited. Any of a variety of designs and structures can be used, and each system can be adapted to perform in specific bands and employ different dimensions. In fact, any dimensions given in this description are illustrative and exemplary but not limiting.
• System 200 has directional diversity, in that antenna elements 201 and 202 radiate in different directions. Because of the diversity in antenna system 200, antenna system 200 can be adapted for use in MIMO applications. Coupling element 203 between antenna elements 201 and 202 enhances the performance of antenna system 200 by reducing the effects of coupling between the diverse resonating elements.
• FIGURE 3 is an illustration of exemplary system 300, adapted according to one embodiment of the invention.
• Various embodiments of the invention include Three- Dimensional (3D) structures, such as the embodiment shown as system 300.
• System 300 includes dipole antenna elements 301 and 302 and coupling element 303.
• Antenna system 300 is deigned for performance in the band around 2.4 GHz.
• Graph 310 shows simulation results for antenna system 300 with and without coupling element 303. As can be seen, the presence of coupling element 303 increases isolation around the resonant frequency of system 300.
• FIGURE 4 is an illustration of exemplary system 400, adapted according to one embodiment of the invention.
• System 400 is a MIMO antenna that provides performance at 2.4 GHz and 5 GHz.
• System 400 is built on PCB 405 and includes PIFA elements 401 and 402, coupling element 403, and ground plane 404.
• Coupling element 403 includes two coupling portions: The portion including 403a and 403c and the portion including 403b and 403c.
• Each coupling portion 403a plus 403c and 403b plus 403c has a different coupling length (i.e., a different ⁇ ) as well as a different effective total length, thereby giving each coupling portion 403 a plus 403 c and 403b plus 403 c a different operating band.
• coupling element 403 provides isolation to antenna system 400 at 2.4 GHz and 5 GHz.
• system 400 can be built on a form factor that is roughly the size of a flash "memory stick" and included in a Universal Serial Bus (USB) dongle, such as exemplary dongle 700 of FIGURE 7.
• USB Universal Serial Bus
• system 400 can be connected to a computer through a USB interface to provide wireless Local Area Network (LAN) connectivity.
• LAN Local Area Network
• FIGURE 5 is an illustration of exemplary system 500 adapted according to one embodiment of the invention.
• System 500 includes antenna elements 501-504 and coupling elements 511-514.
• Coupling element 511 provides isolation between antenna elements 501 and 502; similarly, coupling element 513 provides isolation between antenna elements 503 and 504.
• Coupling elements 512 and 514 provide isolation between antenna elements 502 and 503, as well as 501 and 504, respectively.
• Embodiments of the invention can be adapted for use in any of a variety of antenna systems.
• embodiments can be adapted for use in systems employ dipoles, monopoles, PIFAs, and any other kind of grounded or ungrounded antenna element.
• various embodiments can be adapted for use in many different arrays, such as 2D, 2.5D, and 3D arrays.
• FIGURE 6 shows exemplary antenna arrays 610, 620, 630, 640, and 650, adapted according to embodiments of the invention.
• Coupling elements such as those shown above in FIGURES 1-5, can be used to increase isolation between antenna elements in the arrays of FIGURE 6.
• FIGURE 8 is an illustration of exemplary method 800 adapted according to one embodiment of the invention. Method 800 can be performed on embodiments, such as those described above in FIGURES 1-7.
• a first current is excited in the first antenna element.
• the first antenna element is driven by a Radio Frequency (RF) module.
• the current can be in any RF band, including bands used in WiFi (IEEE 802.11) applications, cellular telephone applications, and other RF applications that are too numerous to list herein.
• the first current directly induces a second current in the second antenna element. An example of the first current directly inducing a second current is explained above with respect to FIGURE 1 , wherein lExcited induces loirect-
• a third current is induced by the first current in the coupling element.
• a fourth current is induced by the third current in the second antenna element. The fourth current is out of phase with the second current and reduces the effects of the mutual coupling between the first and second antenna elements by at least partially cancelling the second current.
• method 800 is shown as a series of discrete steps, various embodiments of the invention are not so limited. Some embodiments may add, modify, rearrange, and/or omit one or more actions. For instance, from a human's perspective, it will appear that actions 801-804 occur simultaneously and continuously during operation of the antenna system. Furthermore, other methods may include such features as canceling the effects of mutual coupling in two or more operating bands, canceling the effects of mutual coupling between more than one pair of antenna elements, and the like.

Landscapes

• Engineering & Computer Science (AREA)
• Computer Networks & Wireless Communication (AREA)
• Variable-Direction Aerials And Aerial Arrays (AREA)
• Details Of Aerials (AREA)

Priority Applications (2)

Applications Claiming Priority (1)

Publications (1)

Family

ID=42004772

Family Applications (1)

Country Status (2)

Cited By (30)

Families Citing this family (8)

Citations (4)

• 2008
  • 2008-09-11 WO PCT/CN2008/072335 patent/WO2010028521A1/en active Application Filing
  • 2008-09-11 CN CN200880000128.0A patent/CN101821902B/zh not_active Expired - Fee Related

Patent Citations (4)

Non-Patent Citations (1)

Also Published As

Similar Documents

Legal Events