Abstract:
A multi-band antenna for use, for example, in a wireless communications network, employs multi-resonant microstrip dipoles that resonate at multiple frequencies due to microstrip “islands.” Gaps in the microstrips create an open RF circuit except for desired frequencies. At a desired frequency, RF energy sees a gap as a short circuit between an island and the rest of a dipole antenna, thus, resonating at the desired frequency. In one instance, the multi-band antenna includes a first, second, third, and fourth dipole elements. Gaps between the first and third dipole elements and the second and fourth dipole elements are sufficiently small that the first, second, third, and fourth dipole elements form a second dipole having a corresponding dipole wavelength longer than that of the first dipole.

Description:
RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 11/424,664, filed on Jun. 16, 2006, now U.S. Pat. No. 7,277,062, entitled “MULTI-RESONANT MICROSTRIP DIPOLE ANTENNA”, which is related to U.S. patent application Ser. No. 11/424,614, filed on Jun. 16, 2006, entitled “MULTI-BAND ANTENNA” and U.S. patent application Ser. No. 11/424,639, filed on Jun. 16, 2006, entitled “MULTI-BAND RF COMBINER”. The above-noted applications are incorporated herein by reference. 
    
    
     BACKGROUND 
     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. 
     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. 
     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. 
     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 
     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. 
     The subject matter provides a multi-band antenna for use, for example, in a wireless communications network. The multi-band antenna employs multi-resonant microstrip dipoles that resonate at multiple frequencies due to microstrip “islands.” Gaps in the microstrips create an open RF circuit except for desired frequencies. At the desired frequency, RF energy sees a gap as a short circuit between an island and the rest of a dipole antenna, thus, resonating at the desired frequency. In one instance, the multi-band antenna includes first, second, third, and fourth dipole elements. The first dipole element is on a first side of a dielectric and the second dipole element is on a second side of the dielectric and oriented with respect to the first dipole element so as to form a first dipole. The third dipole element is also on the first side of the dielectric and is linearly displaced from the first dipole element in a direction parallel to the orientation of the first dipole wherein the displacement creates a gap between the first dipole element and the third dipole element. The fourth dipole element is on the second side of the dielectric linearly and is displaced from the second dipole element in a direction parallel to the orientation of the first dipole and opposite of the direction of displacement of the third dipole element from the first dipole element wherein the displacement creates a gap between the second dipole element and the fourth dipole element. The gaps between the first and third dipole elements and the second and fourth dipole elements are sufficiently small that the first, second, third, and fourth dipole elements form a second dipole having a corresponding dipole wavelength longer than that of the first dipole. 
     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 
         FIG. 1  is a block diagram of a multi-band antenna system in accordance with an aspect of an embodiment. 
         FIG. 2  depicts a side view of a multi-band antenna in accordance with an aspect of an embodiment. 
         FIGS. 3A and 3B  depict the two sides of the multi-band antenna in accordance with an aspect of an embodiment. 
         FIG. 4  depicts 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. 
         FIG. 5  depicts a diagram illustrating a multi-band antenna encased in a radome in accordance with an aspect of an embodiment. 
         FIG. 6  depicts radiation patterns of a multi-band antenna with and without a parasitic element in accordance with an aspect of an embodiment. 
         FIG. 7  depicts a system diagram illustrating a communication system in accordance with an aspect of an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     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. 
     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 different wavelengths, λ, from a shorter λ frequency transceiver  104  and from a longer λ frequency transceiver  106 . Dipole elements of the multi-band antenna  102  employ “gaps” in the dipole elements that tune the dipole elements to see more than one desired wavelength (i.e., frequency). Wavelengths, with sufficient length, “jump” the gap and resonate the dipole element at the longer wavelength. In this manner, the dipole element acts like a multi-band dipole element. Thus, 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. 
     Turning to  FIG. 2 , a side view of a multi-band antenna  200  in accordance with an aspect of an embodiment is depicted. The multi-band antenna  200  can be employed as, for example, one of the plurality of towers  730  depicted in  FIG. 7 . The multi-band antenna  200  is a microstrip multi-band collinear array with dipole elements  201 - 204  and  211 - 214  arranged on both sides of serial feedlines  250  and  252  and both sides of a dielectric material  260 . The dielectric material  260  can be any RF dielectric such as, for example, a PTFE (polytetrafluoroethylene)/fiberglass composite. The elements  201 ,  203 ,  211 ,  213 , and  250  on a first side of the multi-band antenna  200  are illustrated with solid lines and the elements  202 ,  204 ,  212 ,  214 , and  252  on the second side of the multi-band antenna separated from the first side by the dielectric material  260  are represented by dashed lines in  FIG. 2 . 
     Serial feedlines (also referred to as microstrips)  250  and  252  and dipole elements  201 - 204  and  211 - 214  are constructed from a metal such as, for example, copper and the like. A pattern is etched and/or otherwise formed into each side of the dielectric material  260  corresponding to the locations of the serial feedlines  250  and  252  and the dipole elements  201 - 204  and  211 - 214  on that side of the dielectric material  260 . Metal is then deposited into the pattern to form the feedlines  250  and  252  and the dipole elements  201 - 204  and  211 - 214 . In the alternative, a metal sheet, such as, for example, copper, is attached and/or deposited on each side of the dielectric. The dipole element and feedline pattern is then formed by printing an acid resistant mask onto the metal and using an acid bath to remove the unpatterned metal. 
     The impedance of the feedlines  250  and  252  should approximately match the impedance of a transmission line carrying RF signals from a transmitter and/or to a receiver. For a coaxial transmission line, this impedance is typically around 50 ohms. The impedance of the dipole elements  201 - 204  and  211 - 214  should be approximately that of free space (i.e., approximately 377 ohms). 
     Dipole element  201  and dipole element  202  on the opposite side of dielectric material  260  form a dipole for a given first wavelength of radiation/reception. Similarly, dipole element  203  and  204  also form a dipole for the same wavelength of radiation/reception since the dipole formed by dipole elements  203  and  204  has an approximately equivalent length to the dipole formed by dipole elements  201  and  202 . A gap  221 - 224  exists between dipole elements  201 - 204  and their corresponding dipole elements  211 - 214 . For shorter wavelengths, the gaps  221 - 224  form an open circuit between dipole elements  201 - 204  and dipole elements  211 - 214 . However, for longer wavelengths, if the gaps  221 - 224  are chosen correctly, the gaps  221 - 224  are effectively short circuited so that a longer dipole equal in length, for example, to the combined lengths of dipole elements  201 - 202 , dipole elements  211 - 212 , and gaps  221  and  223 . Thus, dipole elements  201 - 202  and  211 - 212  form a dipole for a second wavelength of radiation longer than that of the first wavelength dipole. Therefore, the multi-band antenna  200  functions on two bands (i.e., two different wavelengths). The multi-band antenna  200  can also have a cylindrical radome (not shown) placed over the antenna structure for weather proofing. The multi-band antenna  200  is presented as an example of a multi-band antenna and is not meant to imply any architectural limitations. 
     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 the multi-band antenna  200 . In between the two cross-sections shown in  FIG. 3A  and  FIG. 3B  is a layer of dielectric material  260 . The pattern of the microstrips (serial feedlines)  250  and  252 , and the dipole elements  201 - 204  and  211 - 214 , as described above, is etched and/or otherwise formed (for example, by utilizing a reversed mask process) in a dielectric material  260  and an electrically conductive material such as, for example, copper is deposited onto each side of the dielectric material  260  to form the multi-band antenna  200 . 
     Moving on 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 apparent that microstrip (serial feedlines) elements  250  and  252  as well as associated dipole elements connected to microstrip (serial feedlines) elements  250  and  252  are separated from each other by dielectric material  260 . 
     Turning to  FIG. 5 , a diagram illustrating a multi-band antenna  504  encased in a radome  506  is depicted in accordance with an aspect of an embodiment. The multi-band antenna  504  tranceives multiple frequency bands similar to, for example, multi-band antenna  200  in  FIG. 2  and is encased within the radome  506  which has a parasitic element  502  attached to the outside. Without the parasitic element  502 , the radiation pattern of the multi-band antenna  504  is elliptical as illustrated in a radiation pattern  604  shown in  FIG. 6 . However, with the addition of parasitic element  502 , the radiation pattern produced by the multi-band antenna  504  becomes substantially circular and omni directional as depicted by radiation pattern  602  in  FIG. 6 . 
     The antennas depicted in  FIGS. 2-4  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 gaps and additional dipole elements of lengths appropriate to add a longer dipole to the existing dipoles corresponding to the additional bands desired. Additional multi-band dipole elements can be added to improve gain. 
     In order to provide additional context for implementing various aspects of the embodiments,  FIG. 7  and the following discussion are intended to provide a brief, general description of a suitable communication network  700  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. 
     In  FIG. 7 , a system diagram illustrating a communications network  700  in accordance with an aspect of an embodiment is depicted. The communications network  700  is a plurality of interconnected heterogeneous networks in which instances provided herein can be implemented. As illustrated, communications network  700  contains an Internet Protocol (IP) network  702 , a Local Area Network (LAN)/Wide Area Network (WAN)  704 , a Public Switched Telephone Network (PSTN)  709 , cellular wireless networks  712  and  713 , and a satellite communication network  716 . Networks  702 ,  704 ,  709 ,  712 ,  713  and  716  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. 
     IP network  702  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  702  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  702  is a Domain Name Server (DNS)  708  to which queries can be sent, such queries each requesting an IP address based upon a Uniform Resource Locator (URL). IP network  702  can support 32 bit IP addresses as well as 128 bit IP addresses and the like. 
     LAN/WAN  704  couples to IP network  702  via a proxy server  706  (or another connection). LAN/WAN  704  can operate according to various communication protocols, such as the Internet Protocol, Asynchronous Transfer Mode (ATM) protocol, or other packet switched protocols. Proxy server  706  serves to route data between IP network  702  and LAN/WAN  704 . A firewall that precludes unwanted communications from entering LAN/WAN  704  can also be located at the location of proxy server  706 . 
     Computer  720  couples to LAN/WAN  704  and supports communications with LAN/WAN  704 . Computer  720  can employ the LAN/WAN  704  and proxy server  706  to communicate with other devices across IP network  702 . Such communications are generally known in the art and are described further herein. Also shown, phone  722  couples to computer  720  and can be employed to initiate IP telephony communications with another phone and/or voice terminal using IP telephony. An IP phone  754  connected to IP network  702  (and/or other phone, e.g., phone  724 ) can communicate with phone  722  using IP telephony. 
     PSTN  709  is a circuit switched network that is primarily employed for voice communications, such as those enabled by a standard phone  724 . However, PSTN  709  also supports the transmission of data. PSTN  709  can be connected to IP Network  702  via gateway  710 . Data transmissions can be supported to a tone based terminal, such as a FAX machine  725 , to a tone based modem contained in computer  726 , or to another device that couples to PSTN  709  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  728 , can couple to PSTN  709  via computer  726  rather than being supported directly by PSTN  709 , as is the case with phone  724 . Thus, computer  726  can support IP telephony with voice terminal  728 , for example. 
     Cellular networks  712  and  713  support wireless communications with terminals operating in their service area (which can cover a city, county, state, country, etc.). Each of cellular networks  712  and  713  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  712  and  713  can include a plurality of towers, e.g.,  730 , that each provide wireless communications within a respective cell. At least some of the plurality of towers  730  can include a multi-band antenna allowing a single antenna to service both networks&#39;  712  and  713  client devices. Wireless terminals that can operate in conjunction with cellular network  712  or  713  include wireless handsets  732  and  733  and wirelessly enabled laptop computers  734 , for example. Wireless handsets  732  and  733  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  732  can operate via a TDMA/GSM standard and communicate with cellular network  712  while wireless handset  733  can operate via a UMTS standard and communicate with cellular network  713  Cellular networks  712  and  713  couple to IP network  702  via gateways  714  and  715  respectively. 
     Wireless handsets  732  and  733  and wirelessly enabled laptop computers  734  can also communicate with cellular network  712  and/or cellular network  713  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. 
     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. 
     Each of Cellular network  712  and  713  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  712 , cellular network  712  supports voice and data communications with terminal units, e.g.,  732 ,  733 , and  734 . For clarity of explanation, cellular network  712  and  713  have been shown and discussed as completely separate entities. However, in practice, they often share resources. 
     Satellite network  716  includes at least one satellite dish  736  that operates in conjunction with a satellite  738  to provide satellite communications with a plurality of terminals, e.g., laptop computer  742  and satellite handset  740 . Satellite handset  740  could also be a two-way pager. Satellite network  716  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  716  services voice and data communications and couples to IP network  702  via gateway  718 . 
       FIG. 7  is intended as an example and not as an architectural limitation for instances disclosed herein. For example, communication network  700  can include additional servers, clients, and other devices not shown. Other interconnections are also possible. For example, if devices  732 ,  733 , and  734  were GPS-enabled, they could interact with satellite  738  either directly or via cellular networks  712  and  713 . 
     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.