Patent Publication Number: US-8988288-B2

Title: Tri-band antenna for noncellular wireless applications

Description:
FIELD 
     The specification relates generally to antennas, and specifically to a tri-band antenna for non-cellular wireless applications. 
     BACKGROUND 
     Current mobile electronic devices, such as smartphones, generally have different antennas implemented to support different types of wireless protocols, such as GPS (Global Positioning System), GLONASS (Globalnaya Navigatsionnaya Sputnikovaya Sistema), WIFI of different types, such as WiFi a, WiFi b. WiFi g and WFi n, as well as Bluetooth™. In other words, each wireless protocol has different bandwidth requirements and current mobile electronic devices have different antennas to support the different bandwidth requirements. 
    
    
     
       BRIEF DESCRIPTIONS OF THE DRAWINGS 
       For a better understanding of the various implementations described herein and to show more clearly how they may be carried into effect, reference will now be made, by way of example only, to the accompanying drawings in which: 
         FIG. 1  depicts a left perspective view of a tri-band antenna, according to non-limiting implementations. 
         FIG. 2  depicts a front perspective view of the tri-band antenna of  FIG. 1 , according to non-limiting implementations. 
         FIG. 3  depicts a graph of return loss characteristics of the tri-band antenna of  FIG. 1 , according to non-limiting implementations. 
         FIG. 4  depicts the tri-band antenna of  FIG. 1  integrated into a housing, according to non-limiting implementations. 
         FIG. 5  depicts a top view of the tri-band antenna of  FIG. 1 , according to non-limiting implementations. 
         FIG. 6  depicts an electrical model of the tri-band antenna of  FIG. 1  at a second and third frequency band, according to non-limiting implementations. 
         FIG. 7  depicts an electrical model of the tri-band antenna of  FIG. 1  at a first frequency band higher than the second and third frequency bands, according to non-limiting implementations. 
         FIG. 8  depicts a top view of an alternative tri-band antenna, according to non-limiting implementations. 
         FIG. 9  depicts a side view of an antenna feed of the tri-band antenna of  FIG. 1 , according to non-limiting implementations. 
         FIG. 10  depicts a schematic diagram of a device into which the tri-band antenna of  FIG. 1  has been integrated, according to non-limiting implementations. 
         FIG. 11  depicts a top view of another alternative tri-band antenna, according to non-limiting implementations. 
         FIG. 12  depicts a top view of yet a further alternative tri-band antenna, according to non-limiting implementations. 
     
    
    
     DETAILED DESCRIPTION 
     An aspect of the specification provides a tri-band antenna comprising: a first radiating arm enabled for generating a first resonance in a first frequency band, the first radiating arm further enabled for connection to an antenna tuning circuit; the first radiating arm comprising a capacitive coupling structure; a coupling arm separated by a gap from the first radiating arm; a second radiating arm enabled for generating a second resonance in a second frequency band lower than the first frequency band, the second radiating arm connected to the coupling arm such that the second radiating arm is capacitively coupled to the first radiating arm; and a third radiating arm enabled for generating a third resonance in a third frequency band lower than the second frequency band, the third radiating arm connected to the coupling arm such that the third radiating arm is capacitively coupled to the first radiating arm. 
     The first frequency band can comprise one or more of: about 5 GHz to about 6 GHz; and a WiFi a,n band. 
     The second frequency band can comprise one or more of: about 2 GHz to about 2.5 GHz; and a WiFi b,g band; a Bluetooth™ band. 
     The third frequency band can comprise one or more of: about 1 GHz to about 2 GHz; and a GPS (Global Positioning System) band; a GLONASS (Globalnaya Navigatsionnaya Sputnikovaya Sistema) band. 
     The capacitive coupling structure can comprise one of an L-shaped capacitive coupling structure and a U-shaped capacitive coupling structure. The coupling arm one of: extends along a long arm of the L-shaped capacitive coupling structure and ends prior to a short arm of the L-shaped capacitive coupling structure; and, extends between long arms of the U-shaped capacitive coupling structure. 
     The capacitive coupling structure can comprise a planar structure. 
     The first radiating arm can comprise one or more of an antenna feed and a contact area for connecting to the antenna tuning circuit. The antenna feed can comprise a three dimensional feed extending from the capacitive coupling structure to the contact area. 
     At least one of the second radiating arm and the third radiating arm can be adapted to extend along a housing of a mobile electronic device. At least one of the first radiating arm, the second radiating arm and the third radiating arm are located at a position at the housing to reduce combined SAR (specific absorption rate) at the mobile electronic device. 
     The second radiating arm can be in a same plane as the first radiating arm and the third radiating arm can be in another plane about perpendicular to the same plane. 
     The second radiating arm and the third radiating arm can be about parallel. 
     The second radiating arm and the third radiating arm can be about perpendicular to the coupling arm. 
     The second radiating arm and the third radiating arm can extend in a same direction. 
     The second radiating arm and the third radiating arm can extend in opposite directions. 
     The tri-band antenna can further comprise an antenna tuning circuit for independent tuning of each the first frequency band, the second frequency band and the third frequency band, the antenna tuning circuit connected to the antenna feed. 
     A further aspect of the specification provides a device comprising a housing enabled to house components of the device; a tri-band antenna comprising an antenna feed; a first radiating arm enabled for generating a first resonance in a first frequency band; the first radiating arm comprising a capacitive coupling structure; a coupling arm separated by a gap from the first radiating arm; a second radiating arm enabled for generating a second resonance in a second frequency band lower than the first frequency band, the second radiating arm connected to the coupling arm such that the second radiating arm is capacitively coupled to the first radiating arm; and a third radiating arm enabled for generating a third resonance in a third frequency band lower than the second frequency band, the third radiating arm connected to the coupling arm such that the third radiating arm is capacitively coupled to the first radiating arm; and, a communication interface comprising an antenna tuning circuit connected to the first radiating arm, the antenna tuning circuit for independent tuning of each the first frequency band, the second frequency band and the third frequency band. 
     At least one of the second radiating arm and the third radiating arm are adapted to extend along the housing. 
     The first frequency band can comprise one or more of: about 5 GHz to about 6 GHz; and a WiFi a band; the second frequency band can comprise one or more of: about 2 GHz to about 2.5 GHz; a WiFi b,g band; and a Bluetooth™ band; and the third frequency band can comprise one or more of: about 1 GHz to about 2 GHz; a GPS (Global Positioning System) band; and a GLONASS (Globalnaya Navigatsionnaya Sputnikovaya Sistema) band. 
       FIGS. 1 and 2  respectively depict left and front perspective views of a tri-band antenna  100  comprising: a first radiating arm  101 , a second radiating arm  102 , a third radiating arm  103 , and a coupling arm  105 , according to non-limiting implementations. First radiating arm  101  is generally enabled for generating a first resonance in a first frequency band. First radiating arm  101  is further enabled for connection to an antenna feed  107 ; indeed, in depicted implementations, tri-band antenna  100  further comprises antenna feed  107  connected to first radiating arm  101 . First radiating arm  101  further comprises a capacitive coupling structure  108 : in other words, the shape of first radiating arm  101  is such that first radiating arm  101  can be capacitively coupled to coupling arm  105  and in turn capacitively coupled to second radiating arm  102  and third radiating arm  103 . It is further appreciated that coupling arm  105  is hence separated by a gap  109  from the first radiating arm  101  such that the capacitive coupling occurs via gap  109 . Second radiating arm  102  is generally enabled for generating a second resonance in a second frequency band lower than the first frequency band, second radiating arm  102  connected to coupling arm  105  such that second radiating arm  102  is capacitively coupled to first radiating arm  101 . Third radiating arm  103  is generally enabled for generating a third resonance in a third frequency band lower than the second frequency band, third radiating arm  103  connected to coupling arm  105  such that third radiating arm  103  is capacitively coupled to first radiating arm  101 . 
     Attention is next directed to  FIG. 3  which depicts a graph  200  showing a frequency response of tri-band antenna  100  according to non-limiting implementations. Specifically, graph  200  comprises return loss (i.e. S-parameter in decibels) of tri-band antenna  100  as a function of frequency (in GigaHertz (GHz)), return loss being a measure of the effectiveness of power delivery from a transmission line to tri-band antenna  100 . For example, graph  200  depicts three peaks  201 ,  202 ,  203  respectively corresponding to the first frequency band of first radiating arm  101 , the second frequency band of the second radiating arm  102  and the third frequency band of the third radiating arm  103 . Specifically, first peak  201  (i.e. the first frequency band) is in the range of about 5 GHz to about 6 GHz, and further corresponds to a WiFi a, n band. Second peak  202  (i.e. the second frequency band) is in the range of about 2 GHz to about 2.5 GHzm and further corresponds to one or more of a WiFi b, g band and a Bluetooth™ band. Third peak  203  (i.e. the third frequency band) is an a range of about 1 GHz to about 2 GHz, and further corresponds to one of more of a GPS (Global Positioning System) band and a GLONASS (Globalnaya Navigatsionnaya Sputnikovaya Sistema) band. 
     Tri-band antenna  100  is therefore enabled for communicating in at least three different bands and on at least three different protocols. For example, tri-band antenna  100  can be used to communicate on the WiFi a,n band of 5.170 GHz to 5.835 GHz, the WiFi b,g and Bluetooth™ bands of 2.4 GHz to 2.5 GHz, as well as the GPS band of about 1.575 GHz and the GLONASS band of about 1.602 GHz. Hence, tri-band antenna  100  can replace a plurality of respective antennas for each of these bands in a mobile electronic device. 
     For example, attention is next directed to  FIG. 4  which depicts tri-band antenna  100  integrated into a housing  401  of a mobile electronic device. It is appreciated that housing  401  can comprise an internal housing: for example, housing  401  can be internal to a mobile electronic device. From  FIG. 4 , it is appreciated that: first radiating arm  101  is located at a planar side  403  of housing  401 , for example a back side; second radiating arm  102  extends along an edge of housing  401 ; and third radiating arm  103  extends along a sidewall  405  of housing  401 . Further, each of second radiating arm  102  and third radiating arm  103  are adapted to extend along housing  401 : for example, the depicted sidewall  405  comprises various physical contours, and both of second radiating arm  102  and third radiating arm  103  are contoured accordingly. The contours of second radiating arm  102  and third radiating arm  103  are also visible in  FIGS. 1 and 2 . 
     It is yet further appreciated that at least one of first radiating arm  101 , second radiating arm  102  and third radiating arm  103  are located at a position at housing  401  to reduce combined SAR (specific absorption rate) at the mobile electronic device. 
     It is yet further appreciated from  FIGS. 1 ,  2 , and  3  that first radiating arm  101  and second radiating arm  102  are located in a same plane for example along planar side  403 , and third radiating arm  103  is in another plane about perpendicular to the plane of that first radiating arm  101  and second radiating arm  102 . In other words, a lateral axis of third radiating arm  103  is about perpendicular to a lateral axis of second radiating arm  102 . 
     Attention is next directed to  FIG. 5  which depicts a top view of tri-band antenna  100 . From  FIG. 5  it is appreciated capacitive coupling structure  108  of first radiating arm  101  comprises a planar structure. Further capacitive coupling structure  108  of first radiating arm  101  comprises a U-shaped capacitive coupling structure and coupling arm  105  extends between long arms of the U-shaped capacitive coupling structure. 
     From  FIG. 5  it is further appreciated that second radiating arm  102  and third radiating arm  103  are about parallel, and further that second radiating arm  102  and third radiating arm  103  are about perpendicular to coupling arm  105 . 
       FIG. 5  also indicates dimensions of first radiating arm  101 , second radiating arm  102 , third radiating arm  103 , gap  109  and a gap between second radiating arm  102  and third radiating arm  103 . Specifically, it is yet further appreciated that the “U” shape of capacitive coupling structure is not symmetrical, with one long side of the “U” having a length “L 1   a ” which is longer than an opposite long side having a length “L 1   b ”. Specifically, “L 2 ” indicates the length of second radiating arm  102 , and “L 3 ” indicates the length of third radiating arm  103 . Further the distance between capacitive coupling structure  108  and coupling arm  105  (i.e. the size of gap  109 ) is indicated by “d 1 ”. Similarly, the distance between second radiating arm  102  and third radiating arm  103  is indicated by “d 2 ”. 
     It is further appreciated that gap  109  can be adjusted to change the capacitive coupling between first radiating arm  101  and coupling arm  105 . For example, the capacitance between capacitive coupling structure  108  and coupling arm  105  is as follows: C˜1/d 1 , where “C” is the capacitance and “d 1 ” is the size of gap  109 , as indicated in  FIG. 5 . 
     For example, attention is next directed to  FIG. 6  which depicts an electrical model of second radiating arm  102  and third radiating arm  103  of tri-band antenna  100 . Specifically, at  6 -I of  FIG. 6 , second radiating arm  102  of length L 2 , and third radiating arm  103  of length L 3  are shown electrically connected to a capacitive resistance XC, which is the capacitive resistance of gap  109 . It is appreciated that capacitive resistance XC is in turn connected to antenna tuning circuit, and further that capacitive resistance XC is due to the capacitive feeding of second radiating arm  102  and third radiating arm  103 . XC may be determined from XC=1/(ωC), where C is the capacitance of gap  109  and w is the frequency at which second radiating arm  102  and/or third radiating arm  103  are radiating (e.g. see  FIG. 2 ). 
       FIG. 6  further depicts the equivalent circuit of second radiating arm  102  and third radiating arm  103  at  6 -II. Specifically, second radiating arm  102  can be modelled as a radiation resistance Rs 2  in series with an inductive resistance XL 2 ; similarly, third radiating arm  103  can be modelled as a radiation resistance Rs 3  in series with an inductive resistance XL 3 . The total resistance for each of second radiating arm  102  and third radiating arm  103  is hence, respectively, Rs 2 +XL 2 , and Rs 3 +XL 3 . Further, each inductive resistance XL 2 , XL 3  in part compensates for capacitive resistance XC. Furthermore, coupling between second radiating arm  102  and third radiating arm  103  can be modelled as a capacitive resistance Xd 2 , indicating that coupling can be decreased by increasing d 2 . 
     Attention is next directed to  FIG. 7 , which depicts an electrical model of first radiating arm  101  of tri-band antenna  100 . Specifically, at  7 -I it is appreciated that first radiating arm  101  is connected to the antenna tuning circuit without capacitive coupling. However, the long arms of capacitive coupling structure  108 , having lengths L 1   a , L 1   b , are acting as part of an antenna radiator due to their electrical length (and not as part of the coupling structure). In other words, the coupling between capacitive coupling structure  108  and second radiating arm  102 /third radiating arm  103  is not high in the frequency range of about 5 GHz to about 6 GHz such that that XC approaches 0. Rather the long arms of capacitive coupling structure  108  having lengths L 1   a  and L 1   ba  act as radiators when the mechanical length is in the range of ¼ the resonance wavelength. While second radiating arm  102  and third radiating arm  103  are still capacitively coupled to capacitive coupling structure  108  in the in the frequency range of about 5 GHz to about 6 GHz, the effect is minimal such the resonance of L 1   a  and L 1   b  is not affected in their respective frequency ranges. 
     Hence, the electrical model in  FIG. 7  shows a respective radiation resistance, Rs 1   a , Rs 1   b  of each of the long arms of capacitive coupling structure  108  having lengths L 1   a  and L 1   ba  connected in parallel. It is further appreciated that the radiation resistance, Rs 1   a , Rs 1   b  of each of the long arms of capacitive coupling structure  108  having lengths L 1   a  and L 1   ba  are connected in parallel to an antenna tuning circuit. It is further assumed that any radiation resistance loss of capacitive coupling structure  108  is much less than either of radiation resistance, Rs 1   a , Rs 1   b , at least in the frequency range of about 5 GHz to about 6 GHz. 
     A successful prototype of tri-band antenna  100  is now described. In the successful prototype, with respect to first radiating arm  101 , L 1   a  was about 9.5 mm L 1   b  was about 7.3 mm and d 1  of gap  109  was about 0.5 mm. Furthermore, second radiating arm had a length L 2  of about 18.5 mm, third radiating arm had a length L 3  of about 26 mm, with a gap there between of d 2  about 0.8 mm. Furthermore, a width of each of first radiating arm  101 , second radiating arm  102  and third radiating arm  103  were each about 1.2 mm. In particular, the dimensions of the successful prototype are compatible with laser direct structuring techniques and were manufactured therewith. 
     It is yet further appreciated that the shape of first radiating arm  101  is not limited to U-shaped capacitive coupling structures. For example, attention is next directed to  FIG. 8  which depicts top view of an alternative tri-band antenna  100   a , according to non-limiting implementations. Tri-band antenna  100   a  is substantially similar to tri-band antenna  100  with like elements having like numbers but with an “a” appended thereto. Hence, tri-band antenna  100   a  comprises a first radiating arm  101   a  comprising a capacitive coupling structure  108   a  capacitively coupled to a coupling arm  105   a , which is in turn connected to a second radiating arm  102   a  and a third radiating arm  103   a . First radiating arm  101   a  comprises an antenna feed  107   a . Gap  109   a  separates first radiating arm  101   a  and coupling arm  105   a . Hence, tri-band antenna  100   a  is substantially similar to tri-band antenna  100  except that capacitive coupling structure  108  of first radiating arm  101   a  comprises an L-shaped capacitive coupling structure and coupling arm  105   a  extends along a long arm of the L-shaped capacitive coupling structure and ends prior to a short arm of the L-shaped capacitive coupling structure. Gap  109   a  is adjusted relative to gap  109  to account for the change in capacitive coupling due to the change in capacitive coupling structure there between as described above. 
     Attention is next directed to  FIG. 9 , which depicts a side view of detail of first radiating arm  101  and antenna feed  107  when integrated into a mobile electronic device. Specifically, antenna feed  107  comprises a three dimensional feed extending from capacitive coupling structure  108  to a contact area  901 , antenna feed  107  comprising contact area  901 . Hence, antenna feed  107  is enabled to extend into a mobile electronic device to connect with an antenna tuning circuit  903 ; in depicted implementations, the connection between contact area  901  and antenna tuning circuit  903  comprises a biased flexible C-clip, however, in other implementations the connection can be made using any other suitable electrical connector. For example, antenna feed  107  need not be three-dimensional and a connection between capacitive coupling structure  108  and antenna tuning circuit  903  can comprise a conducting wire. However, the biased flexible C-clip  705  can be conveniently to obviate soldering the conducting wire to capacitive coupling structure  108  and antenna tuning circuit  903 . 
     It is yet further appreciated that, in other implementations, antenna tuning circuit  903  and tri-band antenna  100  can be provided as an integrated unit. For example, tri-band antenna  100  can comprise antenna tuning circuit  903 , wherein antenna tuning circuit  903  is enabled for independent tuning of each the first frequency band, the second frequency band and the third frequency band. Any suitable antenna tuning circuit  903  is within the scope of present implementations, but generally comprises an impedance matching circuit for matching first radiating arm  101 , second radiating arm  102  and third radiating arm  103  to one or more radiators enabled to radiate in each of the first frequency band, the second frequency band and the third frequency band. 
     Attention is next directed to  FIG. 10  which depicts a schematic diagram of a mobile electronic device  1001 , referred to interchangeably hereafter as device  1001 . Device  1001  comprises: housing  401  enabled to house components of device  1001 ; tri-band antenna  100 ; and a communication interface  1014  comprising antenna tuning circuit  903  connected to antenna feed  107  of tri-band antenna  100  as described above. As described above, in device  1001 , at least one of second radiating arm  102  and third radiating arm  103  are adapted to extend along housing  401 . 
     Device  1001  can be any type of electronic device that can be used in a self-contained manner to communicate with one or more communication networks using tri-band antenna  100 . Device  1001  includes, but is not limited to, any suitable combination of electronic devices, communications devices, computing devices, personal computers, laptop computers, portable electronic devices, mobile computing devices, portable computing devices, tablet computing devices, laptop computing devices, desktop phones, telephones, PDAs (personal digital assistants), cellphones, smartphones, e-readers, internet-enabled appliances and the like. Other suitable devices are within the scope of present implementations. 
     It should be emphasized that the structure of device  1001  in  FIG. 10  is purely an example, and contemplates a device that can be used for both wireless voice (e.g. telephony) and wireless data communications (e.g. email, web browsing, text, and the like). However,  FIG. 1  contemplates a device that can be used for any suitable specialized functions, including, but not limited, to one or more of, telephony, computing, appliance, and/or entertainment related functions. 
     Device  1001  comprises at least one input device  1028  generally enabled to receive input data, and can comprise any suitable combination of input devices, including but not limited to a keyboard, a keypad, a pointing device, a mouse, a track wheel, a trackball, a touchpad, a touch screen and the like. Other suitable input devices are within the scope of present implementations. 
     Input from input device  1028  is received at processor  1020  (which can be implemented as a plurality of processors, including but not limited to one or more central processors (CPUs)). Processor  1020  is configured to communicate with a memory  1022  comprising a non-volatile storage unit (e.g. Erasable Electronic Programmable Read Only Memory (“EEPROM”), Flash Memory) and a volatile storage unit (e.g. random access memory (“RAM”)). Programming instructions that implement the functional teachings of device  1001  as described herein are typically maintained, persistently, in memory  1022  and used by processor  1020  which makes appropriate utilization of volatile storage during the execution of such programming instructions. Those skilled in the art will now recognize that memory  1022  is an example of computer readable media that can store programming instructions executable on processor  1020 . Furthermore, memory  1022  is also an example of a memory unit and/or memory module. 
     Processor  1020  can be further configured to communicate with display  1026 , and microphone  134  and speaker  132 . Display  1026  comprises any suitable one of, or combination of, CRT (cathode ray tube) and/or flat panel displays (e.g. LCD (liquid crystal display), plasma, OLED (organic light emitting diode), capacitive or resistive touchscreens, and the like). Microphone  134 , comprises any suitable microphone for receiving sound data. Speaker  132  comprises any suitable speaker for providing sound data, audible alerts, audible communications from remote communication devices, and the like, at device  1001 . In some implementations, input device  1028  and display  1026  are external to device  1001 , with processor  1020  in communication with each of input device  1028  and display  1026  via a suitable connection and/or link. 
     Processor  1020  also connects to interface  1014 , which can be implemented as one or more radios and/or connectors and/or network adaptors, configured to wirelessly communicate with one or more communication networks (not depicted) via tri-band antenna  100 . It will be appreciated that interface  1014  is configured to correspond with network architecture that is used to implement one or more communication links to the one or more communication networks, including but not limited to any suitable combination of USB (universal serial bus) cables, serial cables, wireless links, cell-phone links, cellular network links (including but not limited to 2G, 2.5G, 3G, 4G+, UMTS (Universal Mobile Telecommunications System), CDMA (Code division multiple access), WCDMA (Wideband CDMA), FDD (frequency division duplexing), TDD (time division duplexing), TDD-LTE (TDD-Long Term Evolution), TD-SCDMA (Time Division Synchronous Code Division Multiple Access) and the like, wireless data, Bluetooth links, NFC (near field communication) links, WiFi links, WiMax links, packet based links, the Internet, analog networks, the PSTN (public switched telephone network), access points, and the like, and/or a combination. 
     Specifically, interface  1014  comprises radio equipment (i.e. a radio transmitter and/or radio receiver) for receiving and transmitting signals using tri-band antenna  100 . It is further appreciated that interface  1014  comprises antenna tuning circuit  903  as described above. 
     It is yet further appreciated that device  1001  comprises a power source, not depicted, for example a battery or the like. In some implementations the power source can comprise a connection to a mains power supply and a power adaptor (e.g. and AC-to-DC (alternating current to direct current) adaptor). 
     It is yet further appreciated that device  1001  further comprises an outer housing which houses components of device  1001 , including housing  403 . 
     In any event, it should be understood that a wide variety of configurations for device  1001  are contemplated. 
     Persons skilled in the art will appreciate that there are yet more alternative implementations and modifications possible. For example, attention is next directed to  FIG. 11  which depicts top view of an alternative tri-band antenna  100   b , according to non-limiting implementations. Tri-band antenna  100   b  is substantially similar to tri-band antenna  100  with like elements having like numbers but with a “b” appended thereto. Hence, tri-band antenna  100   b  comprises a first radiating arm  101   b  comprising a U-shaped capacitive coupling structure  108   b  capacitively coupled to a coupling arm  105   b , which is in turn connected to a second radiating arm  102   b  and a third radiating arm  103   b . First radiating arm  101   b  comprises an antenna feed  107   b . Gap  109   b  separates first radiating arm  101   b  and coupling arm  105   b . However, while tri-band antenna  100   b  is substantially similar to tri-band antenna  100 , each of second radiating arm  102   b  and third radiating arm  103   b  are in the same plane as first radiating arm  101 . 
     Yet a further alternative tri-band antenna  100   c  is depicted in  FIG. 12 , according to non-limiting implementations. Tri-band antenna  100   c  is substantially similar to tri-band antenna  100   b  with like elements having like numbers but with a “c” appended thereto rather than a “b”. Hence, tri-band antenna  100   c  comprises a first radiating arm  101   c  comprising a U-shaped capacitive coupling structure  108   c  capacitively coupled to a coupling arm  105   c , which is in turn connected to a second radiating arm  102   c  and a third radiating arm  103   c . First radiating arm  101   c  comprises an antenna feed  107   c . Gap  109   c  separates first radiating arm  101   c  and coupling arm  105   c . However, while tri-band antenna  100   c  is substantially similar to tri-band antenna  100   b , second radiating arm  102   c  and third radiating arm  103   c  extend in opposite directions from coupling arm  105   c.    
     In any event, a versatile tri-band antenna is described herein that can replace a plurality of antennas at a mobile electronic device. A first radiating arm radiating in a first band is connected to an antenna tuning circuit, and a second and third radiating arm radiating in respective second and third bands at frequencies less than the first band are capactively coupled to the antenna tuning circuit via the first radiating arm. 
     A portion of the disclosure of this patent document contains material which is subject to copyright protection. The copyright owner has no objection to the facsimile reproduction by any one of the patent document or patent disclosure, as it appears in the Patent and Trademark Office patent file or records, but otherwise reserves all copyrights whatsoever. 
     Persons skilled in the art will appreciate that there are yet more alternative implementations and modifications possible, and that the above examples are only illustrations of one or more implementations. The scope, therefore, is only to be limited by the claims appended hereto.