Abstract:
A multi-band antenna for use in a wireless communications network provides frequency support for different wireless technologies in a single structure. This substantially reduces installation costs and can be the only solution in limited space installation sites. In one instance, the multi-band antenna has two serial feedlines carrying respective anode and cathode components of RF signals. Each, comprising serial feedline is coupled to two or more different length dipole elements. Each dipole element of a given length attached to the first serial feedline has a corresponding dipole element of approximately equal length attached to the second serial feedline and oriented, with respect to the first dipole element so as to form a dipole. Thus, at least two dipoles of differing lengths are formed, enabling performance in two different bands by the antenna. The gain of the antenna for any particular band is determined by the number of dipoles corresponding to that band contained within the antenna.

Description:
RELATED APPLICATIONS 
       [0001]    This application is related to co-pending and co-assigned U.S. applications entitled “MULTI-RESONANT MICROSTRIP DIPOLE ANTENNA,” client reference 900.US, filed on Jun. 16, 2006 and assigned Ser. No. ______ and “MULTI-BAND RF COMBINER,” client reference 872.US, filed on Jun. 16, 2006 and assigned Ser. No. ______. The above-noted applications are incorporated herein by reference. 
     
     BACKGROUND 
       [0002]    Wireless telephones and other wireless devices have become almost the defacto standard for personal and business communications. This has increased the competition between wireless service providers to gain the largest possible market share. As the marketplace becomes saturated, the competition will become even tougher as the competitors fight to attract customers from other wireless service providers. 
         [0003]    As part of the competition, it is necessary for each wireless service provider to stay abreast of technological innovations and offer their consumers the latest technology. However, not all consumers are prepared to switch their wireless devices as rapidly as technological innovations might dictate. The reasons for this are varied and may range from issues related to cost to an unwillingness to learn how to use a new device or satisfaction with their existing device. 
         [0004]    However, certain technological innovations may require different antenna technologies in order to deliver service to the wireless customer. For example, although Wide Band Code Division Multiple Access (WCDMA) and Global System for Mobile communications (GSM) technologies typically operate on different frequencies, and they may require separate antennas, a wireless provider may have customers using both types of technologies. In many areas, simply leasing or buying new antenna space for the new technology may be economical. However, in many areas, particularly in urban areas, the cost of obtaining additional leases as well as zoning and other regulatory issues can make retaining old technologies while introducing new technologies cost prohibitive. 
         [0005]    Thus, it is desirable to have an antenna capable of simultaneously radiating and receiving signals from both technologies (i.e., a multi-band antenna). One attempted solution is the Kathrein brand multi-band omni antenna which was developed for E911 Enhanced Observed Time Difference (EOTD) deployments to measure adjacent cell sites downlink messaging for determining a mobile location. However, the Kathrein brand antenna design has limited RF performance due to its unique antenna element design which limits gain to unity. 
       SUMMARY 
       [0006]    The following presents a simplified summary of the subject matter in order to provide a basic understanding of some aspects of subject matter embodiments. This summary is not an extensive overview of the subject matter. It is not intended to identify key/critical elements of the embodiments or to delineate the scope of the subject matter. Its sole purpose is to present some concepts of the subject matter in a simplified form as a prelude to the more detailed description that is presented later. 
         [0007]    The subject matter provides a multi-band antenna for use, for example, in a wireless communications network. Instances of the multi-band antenna provide frequency support for different wireless technologies in a single structure. This substantially reduces installation costs and can be the only solution in limited space installation sites. In one instance, the multi-band antenna has two serial feedlines carrying respective anode and cathode components of RF signals. Each serial feedline is coupled to two or more different length dipole elements. Each dipole element of a given length attached to the first serial feedline has a corresponding dipole element of approximately equal length attached to the second serial feedline and oriented, with respect to the first dipole element so as to form a dipole. Thus, at least two dipoles of differing lengths are formed, enabling performance in two different bands by the antenna. The gain of the antenna for any particular band is determined by the number of dipoles corresponding to that band contained within the antenna. 
         [0008]    To the accomplishment of the foregoing and related ends, certain illustrative aspects of embodiments are described herein in connection with the following description and the annexed drawings. These aspects are indicative, however, of but a few of the various ways in which the principles of the subject matter may be employed, and the subject matter is intended to include all such aspects and their equivalents. Other advantages and novel features of the subject matter may become apparent from the following detailed description when considered in conjunction with the drawings. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]      FIG. 1  is a block diagram of a multi-band antenna system in accordance with an aspect of an embodiment. 
           [0010]      FIG. 2  is a side view of a multi-band antenna in accordance with an aspect of an embodiment. 
           [0011]      FIGS. 3A and 3B  illustrate the two sides of the multi-band antenna in accordance with an aspect of an embodiment. 
           [0012]      FIG. 4  is a side view of the multi-band antenna oriented ninety degrees away from the view depicted in  FIG. 2  in accordance with an aspect of an embodiment. 
           [0013]      FIG. 5  is a diagram of an alternate embodiment of a dual band antenna in accordance with an aspect of an embodiment. 
           [0014]      FIG. 6  is a diagram illustrating a symmetric embodiment of a multi-band antenna in accordance with an aspect of an embodiment. 
           [0015]      FIG. 7  is a diagram illustrating a multi-band antenna encased in a radome in accordance with an aspect of an embodiment. 
           [0016]      FIG. 8  is radiation patterns of a multi-band antenna with and without a parasitic element in accordance with an aspect of an embodiment. 
           [0017]      FIG. 9  is a system diagram illustrating a communication system in accordance with an aspect of an embodiment. 
       
    
    
     DETAILED DESCRIPTION 
       [0018]    The subject matter is now described with reference to the drawings, wherein like reference numerals are used to refer to like elements throughout. In the following description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the subject matter. It may be evident, however, that subject matter embodiments may be practiced without these specific details. In other instances, well-known structures and devices are shown in block diagram form in order to facilitate describing the embodiments. 
         [0019]    In  FIG. 1 , a block diagram of a multi-band antenna system  100  in accordance with an aspect of an embodiment is shown. The multi-band antenna system  100  is comprised of a multi-band antenna  102  that can transmit and/or receive multiple bands of frequencies from frequency band transceivers  1 -N  104 - 108  that can receive and/or send frequency bands  1 -N respectively, where N is an integer from one to infinity. In this manner, a single multi-band antenna  102  can replace multiple antennas that can only operate at a given frequency and/or can increase communication frequency bands when antenna installation space is limited. This provides a very cost effective and space effective alternative to multiple antenna installations. 
         [0020]    Looking at  FIG. 2 , a side view of a multi-band antenna  200  in accordance with an aspect of an embodiment is illustrated. Multi-band antenna  200  can be implemented as, for example, one of the plurality of towers  930  depicted in  FIG. 9 . Multi-band antenna  200  is a microstrip multi-band collinear array with dipole elements  201 - 206 ,  210 - 215 , and  220 - 225  arranged on both sides of microstrips  230  and  232  and on both sides of a dielectric substrate  250 . The microstrips  230  and  232  and the dipole elements  201 - 206 ,  210 - 215 , and  220 - 225  are constructed from an electrically conducting material (e.g., copper). The elements  201 - 203 ,  210 - 215 , and  230  on a first side of the multi-band antenna  200  are illustrated with solid lines and the elements  204 - 206 ,  220 - 225 , and  232  on the second side of the multi-band antenna separated from the first side by a dielectric substrate  250  are represented by dashed lines in  FIG. 2 . 
         [0021]    The multi-band antenna  200  comprises large and small dipoles each of which corresponds to one of the bands of the antenna. The large dipoles comprise corresponding dipole elements  201  and  204 ,  202  and  205 , and  203  and  206 . The small dipoles comprise corresponding dipole elements  210  and  220 ,  211  and  221 ,  214  and  224 ,  215  and  225 ,  212  and  222 , and  213  and  223 . Each dipole contains a dipole element on the first side of the dielectric substrate  250  and a second dipole element on the second side of the dielectric substrate separated from each other by the dielectric substrate  250  such as, for example the dipole which contains a dipole element  201  on the first side of the dielectric substrate  250  and a dipole element  204  on the second side of the dielectric substrate  250 . The dielectric substrate  250  can be any RF dielectric such as, for example, a PTFE (polytetrafluoroethylene)/fiberglass composite. 
         [0022]    The two bands of operation from the multi-band antenna  200  can be, for example, cellular 850 MHz and PCS (personal communications service) 1900 MHz Frequency bands where the larger dipole elements, such as, for example, dipole element  201 , radiate the 850 MHz signal and the smaller dipole elements, such as, for example, dipole element  210 , radiate the 1900 MHz signal. The distance between successive dipoles of the same band should be no less than ½ the wavelength (λ) and should not be greater than one λ. However, between these two extremes, the separation distance can be varied to optimize the antenna  200  for maximum performance. 
         [0023]    The impedance of the dipoles created from dipole elements  201 - 206 ,  210 - 215  and  220 - 225  should match the impedance of free space, e.g. 377 ohms. The physical length of each dipole element  201 - 206 ,  210 - 215 , and  220 - 225  is determined by the frequency that each dipole is intended to radiate. The ratio of the number of shorter dipoles to the longer dipoles is variable and depends upon the gain desired at each frequency. The number of dipoles of each type is determined by the amount of gain that is desired. For example, doubling the number of dipoles of one type results in a 3 dB signal gain at the frequency of interest. 
         [0024]    The coaxial ground and center conductor signals received, typically via a coaxial cable, from a transmitter (not shown) are placed on respective microstrip feedlines for microstrips  230  and  232 . The impedance of the feedlines  230  and  232  should match the impedance of the coaxial cable and/or other transmission medium that feeds the signal from the transmitter to the feedlines for microstrips  230  and  232 . For a coaxial cable, this impedance is typically around 50 ohms. A feed structure for feeding ground and pin signals from an RF combiner can be designed to be, for example, a microstrip, a stripline, or a coax design with a single RF connector at one end of the multi-band antenna  200 . The multi-band antenna  200  can also have a cylindrical radome  240  placed over the antenna structure for weather proofing. 
         [0025]    In one modification to the multi-band antenna  200 , the shorter dipoles can be laid out so that they are on both sides of the main feedlines for microstrips  230  and  232 , and the longer dipoles can also be laid out so that they are on both sides of the main feedlines for microstrips  230  and  232 . An example of such a modification can be achieved by replacing shorter dipole elements  210 - 211  and  220 - 221  with a single larger set of corresponding dipole elements of substantially equivalent size as dipole elements  201  and  204 ; replacing longer dipole elements  202  and  205  with two pairs of corresponding shorter dipole elements similar to dipole elements  214 - 215  and  224 - 225 ; and replacing shorter dipole elements  212 - 213  and  222 - 223  with a pair of corresponding longer dipole elements. Such a modification can provide a more omni radiation pattern. 
         [0026]    With reference to  FIGS. 3A-3B , the two sides of the multi-band antenna  200  are depicted in accordance with an aspect of an embodiment.  FIG. 3A  depicts side  1  on the multi-band antenna  200 .  FIG. 3B  depicts side  2  of the multi-band antenna  200 . Both the views in  FIG. 3A  and  FIG. 3B  are from the same side, but represent a different cross-section of multi-band antenna  200 . In between the two cross-sections shown in  FIG. 3A  and  FIG. 3B  is a layer of dielectric material  250 . The pattern of the microstrips  230  and  232 , and the dipole elements  201 - 206 ,  210 - 215 , and  220 - 225  is etched or otherwise formed in a dielectric substrate  250  and a electrically conductive material such as, for example, copper is deposited onto each side of the dielectric substrate  250  to form the multi-band antenna  200 . Alternatively, a reverse mask acid etch can be performed in order to form the appropriate pattern of feedlines and dipole elements. It can be appreciated that although only two microstrips are provided in this example, more than two microstrips can be utilized to create additional frequency bands for the multi-band antenna  200 . 
         [0027]    With reference now to  FIG. 4 , a side view of the multi-band antenna  200  oriented ninety degrees away from the view depicted in  FIG. 2  is shown in accordance with an aspect of an embodiment. In this view, it is more readily apparent that microstrips  230  and  232  as well as associated dipole elements connected to microstrips  230  and  232  are separated from each other by the dielectric material  250 . 
         [0028]    With reference now to  FIG. 5 , a diagram of an alternate construction of the multi-band antenna  200  is illustrated. Antenna  500  is similar to multi-band antenna  200  depicted in  FIGS. 2-4  and is shown from the same perspective as the perspective of  FIG. 4 . However, dipole elements  501 - 506 , which correspond to dipole elements  201 - 206  in  FIGS. 2-4 , have been bent away at approximately 90 degrees from the plane of a surface of the dielectric material  250  in which the microstrips  230 ,  232  and dipole elements  501 - 506  were formed. Bending dipole elements  501 - 506  away from the surface of the dielectric material  250  reduces the interference between the dipoles formed by dipole elements  210 - 213  and the dipoles formed by dipole elements  501 - 506 . 
         [0029]    With reference now to  FIG. 6 , a diagram illustrating a symmetric embodiment of a multi-band antenna is depicted in accordance with an aspect of an embodiment. The multi-band antenna depicted in  FIG. 2  is an asymmetric configuration of a dual-band antenna. However, alternatively, a symmetric configuration of a dual-band (or higher order multi-band) antenna can be constructed. Antenna  600  is an example of a symmetric dual-band antenna. In this embodiment, the dipole elements  610 - 617  are arranged such that on one side of the microstrip  650  and within the plane of the microstrip  650  is a mirror image dipole element of the dipole element on the other side of the microstrip  650  and in the plane of microstrip  602  (which is beneath microstrip  650  when viewed as depicted in  FIG. 6 ). Thus, for example, two short dipoles are formed on either side of microstrip  650  by dipole elements  610 - 613  (e.g., the pair of elements  610  and  611  form a dipole and the pair of elements  612  and  613  form a dipole) and two short dipoles are formed on either side of microstrip  650  by dipole elements  614 - 617  (e.g., the pair of dipole elements  614  and  615  form a dipole and the pair of elements  616  and  617  form a dipole). Two longer dipoles are formed by elements  620 - 623  (e.g. the pair of dipole elements  620  and  621  from one dipole and the pair of dipole elements  622  and  623  form a second dipole). All of the elements  602 ,  610 - 617 ,  620 - 623 , and  650  are formed within a dielectric material  660 . The dielectric material  660  also physically separates elements  610 ,  612 ,  614 ,  616 ,  620 ,  622 , and  650  from elements  602 ,  611 ,  613 ,  615 ,  617 ,  621 , and  623 . 
         [0030]    With reference now to  FIG. 7 , a diagram illustrating a multi-band antenna encased in a radome is depicted in accordance with an aspect of an embodiment. Antenna  704  is a multi-band antenna such as, for example, multi-band antenna  200  in  FIG. 2  and is encased within a radome  706  having a parasitic element  702  attached to the outside. Without the parasitic element  702 , the radiation pattern of antenna  704  is more elliptical and similar to a radiation pattern  804  depicted in  FIG. 8 . However, with the addition of parasitic element  702 , the radiation pattern produced by antenna  704  becomes more circular and omni-directional as depicted by radiation pattern  802  in  FIG. 8 . 
         [0031]    The antennas depicted in  FIGS. 2-6  are examples of multi-band antennas with dual bands. Dual-band antennas have been shown for simplicity of explanation. However, these antennas are presented and intended only as examples of a multi-band antenna and not as architectural limitations. It is appreciated that the instances presented above can be extended to antennas having three, four, or more operation bands by adding additional dipole elements of lengths corresponding to the additional bands desired. 
         [0032]    In order to provide additional context for implementing various aspects of the embodiments,  FIG. 9  and the following discussion are intended to provide a brief, general description of a suitable communication network  900  in which the various aspects of the embodiments can be performed. It can be appreciated that the inventive structures and techniques can be practiced with other system configurations as well. 
         [0033]    In  FIG. 9 , a system diagram illustrating a communications network  900  in accordance with an aspect of an embodiment is depicted. The communications network  900  is a plurality of interconnected heterogeneous networks in which instances provided herein can be implemented. As illustrated, communications network  900  contains an Internet Protocol (IP) network  902 , a Local Area Network (LAN)/Wide Area Network (WAN)  904 , a Public Switched Telephone Network (PSTN)  909 , cellular wireless networks  912  and  913 , and a satellite communication network  916 . Networks  902 ,  904 ,  909 ,  912 ,  913  and  916  can include permanent connections, such as wire or fiber optic cables, and/or temporary connections made through telephone connections. Wireless connections are also viable communication means between networks. 
         [0034]    IP network  902  can be a publicly available IP network (e.g., the Internet), a private IP network (e.g., intranet), or a combination of public and private IP networks. IP network  902  typically operates according to the Internet Protocol (IP) and routes packets among its many switches and through its many transmission paths. IP networks are generally expandable, fairly easy to use, and heavily supported. Coupled to IP network  902  is a Domain Name Server (DNS)  908  to which queries can be sent, such queries each requesting an IP address based upon a Uniform Resource Locator (URL). IP network  902  can support 32 bit IP addresses as well as 128 bit IP addresses and the like. 
         [0035]    LAN/WAN  904  couples to IP network  902  via a proxy server  906  (or another connection). LAN/WAN  904  can operate according to various communication protocols, such as the Internet Protocol, Asynchronous Transfer Mode (ATM) protocol, or other packet switched protocols. Proxy server  906  serves to route data between IP network  902  and LAN/WAN  904 . A firewall that precludes unwanted communications from entering LAN/WAN  904  can also be located at the location of proxy server  906 . 
         [0036]    Computer  920  couples to LAN/WAN  904  and supports communications with LAN/WAN  904 . Computer  920  can employ the LAN/WAN  904  and proxy server  906  to communicate with other devices across IP network  902 . Such communications are generally known in the art and are described further herein. Also shown, phone  922  couples to computer  920  and can be employed to initiate IP telephony communications with another phone and/or voice terminal using IP telephony. An IP phone  954  connected to IP network  902  (and/or other phone, e.g., phone  924 ) can communicate with phone  922  using IP telephony. 
         [0037]    PSTN  909  is a circuit switched network that is primarily employed for voice communications, such as those enabled by a standard phone  924 . However, PSTN  909  also supports the transmission of data. PSTN  909  can be connected to IP Network  902  via gateway  910 . Data transmissions can be supported to a tone based terminal, such as a FAX machine  925 , to a tone based modem contained in computer  926 , or to another device that couples to PSTN  909  via a digital connection, such as an Integrated Services Digital Network (ISDN) line, an Asynchronous Digital Subscriber Line (ADSL), IEEE 802.16 broadband local loop, and/or another digital connection to a terminal that supports such a connection and the like. As illustrated, a voice terminal, such as phone  928 , can couple to PSTN  909  via computer  926  rather than being supported directly by PSTN  909 , as is the case with phone  924 . Thus, computer  926  can support IP telephony with voice terminal  928 , for example. 
         [0038]    Cellular networks  912  and  913  support wireless communications with terminals operating in their service area (which can cover a city, county, state, country, etc.). Each of cellular networks  912  and  913  can operate according to a different operating standard utilizing a different frequency (e.g., 850 and 1900 MHz) as discussed in more detail below. Cellular networks  912  and  913  can include a plurality of towers, e.g.  930 , that each provide wireless communications within a respective cell. At least some of the plurality of towers  930  can include a multi-band antenna allowing a single antenna to service both networks&#39;  912  and  913  client devices. Wireless terminals that can operate in conjunction with cellular network  912  or  913  include wireless handsets  932  and  933  and wirelessly enabled laptop computers  934 , for example. Wireless handsets  932  and  933  can be, for example, personal digital assistants, wireless or cellular telephones, and/or two-way pagers and operate using different wireless standards. For example, wireless handset  932  can operate via a TDMA/GSM standard and communicate with cellular network  912  while wireless handset  933  can operate via a UMTS standard and communicate with cellular network  913  Cellular networks  912  and  913  couple to IP network  902  via gateways  914  and  915  respectively. 
         [0039]    Wireless handsets  932  and  933  and wirelessly enabled laptop computers  934  can also communicate with cellular network  912  and/or cellular network  913  using a wireless application protocol (WAP). WAP is an open, global specification that allows mobile users with wireless devices, such as, for example, mobile phones, pagers, two-way radios, smart phones, communicators, personal digital assistants, and portable laptop computers and the like, to easily access and interact with information and services almost instantly. WAP is a communications protocol and application environment and can be built on any operating system including, for example, Palm OS, EPOC, Windows CE, FLEXOS, OS/9, and JavaOS. WAP provides interoperability even between different device families. 
         [0040]    WAP is the wireless equivalent of Hypertext Transfer Protocol (HTTP) and Hypertext Markup Language (HTML). The HTTP-like component defines the communication protocol between the handheld device and a server or gateway. This component addresses characteristics that are unique to wireless devices, such as data rate and round-trip response time. The HTML-like component, commonly known as Wireless Markup Language (WML), defines new markup and scripting languages for displaying information to and interacting with the user. This component is highly focused on the limited display size and limited input devices available on small, handheld devices. 
         [0041]    Each of Cellular network  912  and  913  operates according to an operating standard, which can be different from each other, and which may be, for example, an analog standard (e.g., the Advanced Mobile Phone System (AMPS) standard), a code division standard (e.g., the Code Division Multiple Access (CDMA) standard), a time division standard (e.g., the Time Division Multiple Access (TDMA) standard), a frequency division standard (e.g. the Global System for Mobile Communications (GSM)), or any other appropriate wireless communication method. Independent of the standard(s) supported by cellular network  912 , cellular network  912  supports voice and data communications with terminal units, e.g.,  932 ,  933 , and  934 . For clarity of explanation, cellular network  912  and  913  have been shown and discussed as completely separate entities. However, in practice, they often share resources. 
         [0042]    Satellite network  916  includes at least one satellite dish  936  that operates in conjunction with a satellite  938  to provide satellite communications with a plurality of terminals, e.g., laptop computer  942  and satellite handset  940 . Satellite handset  940  could also be a two-way pager. Satellite network  916  can be serviced by one or more geosynchronous orbiting satellites, a plurality of medium earth orbit satellites, or a plurality of low earth orbit satellites. Satellite network  916  services voice and data communications and couples to IP network  902  via gateway  918 . 
         [0043]      FIG. 9  is intended as an example and not as an architectural limitation for instances disclosed herein. For example, communication network  900  can include additional servers, clients, and other devices not shown. Other interconnections are also possible. For example, if devices  932 ,  933 , and  934  were GPS-enabled, they could interact with satellite  938  either directly or via cellular networks  912  and  913 . 
         [0044]    What has been described above includes examples of the embodiments. It is, of course, not possible to describe every conceivable combination of components or methodologies for purposes of describing the embodiments, but one of ordinary skill in the art may recognize that many further combinations and permutations of the embodiments are possible. Accordingly, the subject matter is intended to embrace all such alterations, modifications and variations that fall within the spirit and scope of the appended claims. Furthermore, to the extent that the term “includes” is used in either the detailed description or the claims, such term is intended to be inclusive in a manner similar to the term “comprising” as “comprising” is interpreted when employed as a transitional word in a claim.