Abstract:
An antenna assembly having a pair of generally cone-shaped conductive elements directed in divergent directions, with each pair of conductive elements including a conical sheet conductor and a cylindrical sheet conductor, and radiating wire conductors extending away from each cylindrical sheet conductor. A balun feed system is defined between the pair of conical sheet conductors. A radome assembly protects at least the radiating wire conductors from damage from external forces.

Description:
RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application Nos. 61/858,745 filed Jul. 26, 2013, and 61/968,879, filed Mar. 21, 2014, which applications are incorporated by reference. 
    
    
     TECHNICAL FIELD 
     The invention relates generally to antennas for operation over multiple frequency bands and more particularly to electronic systems intended to detect or suppress (e.g., prevent, disrupt, jam, interfere with or otherwise disable) radio frequency transmissions between transmitters and receivers occurring within particular frequency bands. 
     BACKGROUND OF THE INVENTION 
     Radio frequency (“RF”) transmission systems and the various wireless devices that operate within such systems are commercially widely available, and nearly ubiquitous, throughout the world with systems coming on-line daily even in the remotest areas of the world. While commercial RF transmission systems are generally thought to improve the overall well-being of mankind and to advance our society, they have found an unintended use in supporting military or terrorist activity of non-friendly countries, organizations, factions, combatants or other groups. 
     One way by which these non-friendly groups use commercial RF transmission systems is for communication, command, and control. While many commercial RF transmission systems are not secure, their cost and widespread availability, make them an attractive alternative. 
     Non-friendly groups also use commercial RF transmission systems as detonators for improvised explosive devices (“IEDs”). Typically, combatants fashion an IED using an explosive (e.g., C4), a container (e.g., an unexploded shell) and an RF detonator. The detonator may be wired to a short range wireless remote control device such as an electronic car key, garage door opener, remote control, cordless telephone, or other short range RF transmission device; or to a long range wireless remote control device such as a cell phone, PDA, pager, a WiFi receiver or other long range RF transmission device to enable remote detonation. 
     The short range wireless devices, by definition, have a “short” or limited range (e.g., approximately 50 meters, more or less) and typically require line-of-sight operation between the device and the IED. Accordingly, these short range wireless devices pose a significant risk to a combatant (e.g. a terrorist, a foe, a member of a non-friendly group or organization, a neutral party, or other combatant) either in the form of risk of detection or risk of injury from the IED itself. However, exceptions arise more frequently as combatants employ more unique methods of remote detonation via RF transmission, for example, cordless phones. 
     Existing antennae such as conventional dipoles and monopoles suffer from a number of limitations, including narrow frequency coverage, heavy weight, and high visual profile. Dipoles or monopoles with larger cross-sectional area, referred to as “fat” dipoles, provide increased bandwidth, however, are limited to a 3.5:1 frequency bandwidth before the E plane radiation pattern splits into two lobes with a null perpendicular to the antenna major axis. The discone antenna is capable of operation over frequency bandwidths of 10-15:1, however, the beam peak varies considerably from the horizon with frequency, thus affecting useful range. Biconical dipoles that are symmetrical are well known, but provide limited capability, e.g., provide bandwidths comparable to “fat” dipoles. 
     Existing antennae, such as disclosed in Applicant&#39;s U.S. Pat. No. 8,059,050, incorporated by reference herein, include relatively exposed radiating elements constructed of flexible wire or the like. The flexible radiating elements are exposed and can deflect in response to contact with obstacles and then return to position. In some environments and situations the flexible radiating elements may be excessively deformed and fail to return to position. This excessive deformation of the radiating elements may lead to degradation of the antenna&#39;s electrical performance. A need therefore exists for an antenna assembly offering protection against damage to the radiating elements. 
     In light of these and other limitations, dangers and risks associated with RF transmission systems, what is needed is a system and method for detecting or suppressing (e.g., preventing, disrupting, jamming, interfering with or otherwise disabling) RF transmissions between target transmitters and/or target receivers operating in a particular region, thereby disabling the communication, the remote detonation or otherwise suppressing the RF transmissions. 
     SUMMARY OF THE INVENTION 
     To achieve the foregoing objects, and in accordance with the purpose of the invention as embodied and broadly described herein, a multiple element antenna assembly for a radio frequency communication device is provided. 
     Embodiments of the invention include an antenna assembly defining a pair of divergent conical radiating structures each including a sheet conductor and a plurality of radiating wire conductors attached to the sheet conductor and extending in a predetermined form and direction. The sheet conductors each include conical and cylindrical sections. 
     A balun is used to prevent radiation of a coax feedline used to connect the antenna to a transmitter/receiver. A frequency range can be optimized by use of a coiled-coax balun including a ferrite rod placed within the coiled-coax solenoid. 
     A compact, ruggedized, extremely-wide bandwidth antenna is disclosed. The antenna is suitable for operation over a frequency range of at least 80 to 1100 MHZ. 
     Embodiments of the invention include a transceiver that suppresses one or more signals transmitted from a target transmitter in an RF transmission system to a target receiver in a wireless device operating in the RF transmission system to detect, prevent, disrupt, jam, interfere with or otherwise disable an RF transmission between the target transmitter and the target receiver in the wireless device (i.e., target wireless device). 
     A protected antenna assembly including one or more dielectric enclosures or radomes is also provided. The antenna assembly may include a polycarbonate tube consisting of one or more sections. 
     The foregoing has outlined rather broadly the features and technical advantages of the present invention in order that the detailed description of the invention that follows may be better understood. Additional features and advantages of the invention will be described hereinafter which form the subject of the claims of the invention. It should be appreciated by those skilled in the art that the conception and specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present invention. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the invention as set forth in the appended claims. The novel features which are believed to be characteristic of the invention, both as to its organization and method of operation, together with further objects and advantages will be better understood from the following description when considered in connection with the accompanying figures. It is to be expressly understood, however, that each of the figures is provided for the purpose of illustration and description only and is not intended as a definition of the limits of the present invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a more complete understanding of the present invention, reference is now made to the following descriptions taken in conjunction with the accompanying drawing, in which: 
         FIG. 1  is a perspective view of an antenna assembly of the present invention. 
         FIG. 2  is a cross-sectional view of  FIG. 1  taken along lines  2 - 2 . 
         FIG. 3  is a perspective view of a portion of the antenna assembly of  FIG. 1 . 
         FIG. 4  is a detailed perspective view of a portion of the antenna assembly of  FIG. 1 . 
         FIG. 5A  is a bottom view of the antenna assembly of  FIG. 1 . 
         FIG. 5B  is a top view of the antenna assembly of  FIG. 1   
         FIG. 6  is a cross-sectional view of a portion of a protected conducting wire element. 
         FIG. 7  is a side view of an antenna assembly of the present invention. 
         FIG. 8  is a side view of another embodiment of the antenna assembly of the present invention. 
         FIG. 9  illustrates another embodiment of the antenna assembly. 
         FIG. 10  is a perspective illustration of a radome-protected embodiment of an antenna assembly of the present invention. 
         FIG. 11  is a perspective view of a dielectric spacer of  FIG. 10 . 
         FIG. 12  is a partial cross-sectional view of the antenna assembly of  FIG. 10 . 
         FIG. 13  is a perspective view of the antenna assembly embodiment of  FIG. 10 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to  FIG. 1 , antenna  12  includes an upper portion having a first sheet conductor  30  with a plurality of conductively attached radiating wire conductors  32  aligned and held into a conical shape. The lower portion of antenna  12  includes a second sheet conductor  34  with a number of flexible radiating wire conductors  36  conductively attached and formed into a partial conical shape. Radiating wire conductors  36  of the lower portion of antenna  12  are spaced over approximately 180 degrees. Sheet conductors  30 ,  34  are thin sheet metal formed into illustrated shapes. Additional details of radiating wire conductors  32 ,  36  are disclosed in Applicant&#39;s U.S. Pat. No. 8,059,050, incorporated herein by reference. 
     Referring to  FIG. 2 , first sheet conductor  30  includes a generally cylindrical sheet element  50  positioned atop a generally cone-shaped sheet element  52 . Sheet conductor  30  may be formed of thin metal elements which are soldered or welded together. Similarly, second sheet conductor  34  includes a generally cylindrical sheet element  60  positioned beneath a generally conical sheet element  62 . In a preferred embodiment of the invention, the cylindrical sheet element  50  is approximately 1 inch in diameter and 1 inch in length, and the cone-shaped sheet element  52  is approximately ¾ inch in length. 
     Together the first and second sheet conductors  30 ,  34  provide broadband operation for the antenna over a large frequency range in the upper part of the antenna&#39;s frequency range. In comparison, the radiating wire conductors  32 ,  36  provide for operation over the lower frequency range of the antenna. 
     Antenna  12  incorporates multiple radio frequency chokes (C 1 , C 2 , C 3 ) in the radiating wire conductors  32 ,  36 . The RF chokes may be simple conductive coils. Chokes C 1 , C 2 , C 3  facilitate operation over a frequency range of approximately 34:1 by acting as band stops for a higher radio frequency current frequency band, while permitting rf current at a lower frequency band to pass. The number of turns and turn spacing of chokes C 1 , C 2 , C 3  are selected for optimum performance over frequency bands of interest. 
     Antenna  12  is fed at the junction of the two sheet conductors  30 ,  34  by a coax signal line  40  which may be located along the major axis of the antenna. Antenna  12  is fed by a coax signal line  40  passing through the center of second sheet conductor  34 . A feed balun  80  is located beneath the bottom of second sheet conductor  34 . Feed balun  80  can be connected to an RF connector  82 . 
     Referring to  FIG. 3 , an antenna feedpoint  70  is established between the pair of sheet conductors  30 ,  34 . A center conductor  72  of a coax signal line  40  is connected to a lower end of the first sheet element  30  and the shield conductor  74  of the coax signal line  40  is connected to an upper end of second sheet element  34 . 
       FIG. 4  is a detailed illustration of the antenna  12  showing a balun  80  formed by a coiled section  82  of coax signal line  40  surrounding a ferrite rod  84 . 
       FIG. 5  shows views of antenna  12  taken along the antenna&#39;s major axis.  FIG. 5A  is a view taken from beneath the lower portion antenna  12  of  FIG. 2  and  FIG. 5B  is a view taken from above the upper portion of antenna  12  of  FIG. 2 . 
       FIG. 6  illustrates another embodiment of radiating wire conductor  32 , wherein a protective flexible covering  42  encases the conductor. Covering  42  may be a tubing of heat-shrunk material. Other types of coverings  42  would be apparent to those of ordinary skill in the art. Other protective coverings (not shown) may encase sheet conductors  30 ,  34 . 
       FIG. 7  illustrates antenna  12  wherein the plurality of radiating wire conductors  32 ,  36  are protected by coverings  42 .  FIG. 7  also illustrates that the radiating wire conductors  32 ,  36  are preferably substantially deformable in response to external forces. Radiating wire conductors  32 ,  36  are preferably formed of a material having substantial resiliency so that when the external forces are removed, radiating wire conductors  32 ,  36  return to their prior orientation. Radiating wire conductors  32 ,  36  may be of a spring wire, or of a memory wire, such as Nitonol or other types of nickel-titanium shape memory alloys. 
       FIG. 8  is an exemplary illustration of a transceiver and antenna system  1000  adapted for transportation on a vest  1010 . Transmitting unit  1000  includes a transceiver  1002  and antenna  1012  and may include mounting members (not shown), that enable transmitting unit  1000  to be mounted to a standard protective vest. In other embodiments, vest  1010  may be adapted specifically for carrying transmitting unit  1000 . For example, protective vest  1010  may include a pouch, straps, or other adaptations (not shown) for carrying transmitting unit  1000 . 
     Referring to  FIG. 9 , a radiofrequency system including portable antenna  12  and a remote transceiver  14  operates as a base station and relaying an RF signal to a target wireless receiving device  16 , for example an improvised explosive device (“IED”). Portable antenna  12  can be used with a transceiver in a defensive manner to detect or suppress RF transmissions from remote transceiver  14  and/or target receiving device  16 . 
     In some environments, if the target transceiver  14  is unable to initiate or otherwise establish and/or maintain an RF transmission with the target wireless receiving device  16 , the target wireless device may not be used for communication, command and control. In other applications, if the target transceiver  14  is unable to initiate or otherwise establish and/or maintain an RF transmission with the target wireless device  16 , the target wireless device may not be used as, or as part of, a detonator for an IED. Various other embodiments of the invention may thus be used in a defensive manner to detect or suppress RF transmissions to prevent the detonation of IEDs. 
     Transceiver  14  may initiate or establish RF transmission, including an uplink RF transmission portion and a downlink RF transmission portion, with target receiving device  16 . While illustrated as a wireless device, transceiver  14  include fixed, wired, or wireless devices capable of establishing RF transmissions with target receiving device  16  via at least one wireless path that includes an RF transceiver. As illustrated, RF transmissions may be transmitted from a base station or cell tower. In other wireless communication systems (not shown), RF transmissions may be transmitted from satellite or ground-based repeaters or other types of RF transmitters as would be apparent to those of ordinary skill in the art. Radiofrequency transmissions are generally well known and further discussion regarding their operation is not required. 
     In addition to antenna configuration, the volume of influence may be affected by other design considerations. These design considerations may include one or more of an amplifier power output, a size of a heat sink for the power amplifiers, heat dissipation, a desired size of the transceiver, a capacity of a battery, an antenna gain, desired frequency bands, a number of frequency bands used, and other design considerations. 
       FIG. 9  is an exemplary illustration of a transmitting unit adapted for use on a vehicle, such as the US military&#39;s HMMWV. Transmitting unit includes a transceiver  14  and antenna  12  and may include mounting members (not shown) that enable transmitting unit to be mounted to a standard military vehicle. In other embodiments, a transmitting unit may be adapted for air-based platforms, including but not limited to unmanned aerial vehicles. 
     In some embodiments of the invention, the transceiver may operate (selectably or preset) in frequency bands associated with various mobile telephones, such as, 900 MHz, 2.4 GHz, or other wireless telephone frequency bands. Other mobile telephone frequency bands may include “customized” frequency bands that commercial mobile telephone receivers and transmitters may not be to operate at “out of the box.” For example, the “customized” frequency bands may include frequency bands that hostile parties have been able to use in the past (e.g., for remote detonation of IEDs and/or communication) by modifying commercially available wireless telephone components. In some embodiments of the invention, the transceiver may operate (selectably or preset) in frequency bands associated with various short range wireless devices such as an electronic car key, a garage door opener, a remote control, or other short range wireless device. In some embodiments of the invention, the transceiver may operate with various combinations of the wireless frequency bands, the wireless telephone frequency bands, and/or the short range wireless device frequency bands. 
     In some embodiments, the transceiver may transmit in two, three, four, five, or more different frequency bands. For example, in some embodiments of the invention, the transceiver may operate (selectably or preset) in one or more of the same frequency bands as commercially available wireless communication devices, such as, but not limited to, GSM, CDMA, TDMA, SMR, Cellular PCS, AMPS, FSR, DECT, or other wireless frequency bands. 
     In some embodiments of the invention, the transceiver may detect RF transmissions to a wireless device located within a volume of influence of the detecting transceiver. This volume of influence may be based on various factors including a range between the target wireless device and the transceiver, a range between the target wireless device and the target transmitter, a range between the target transmitter and the transceiver, a transceiver power, a target transmitter power, a target receiver sensitivity, a frequency band or bands of the transceiver, propagation effects, topography, structural interferers, characteristics of an antenna at the transceiver including gain, directionality, and type, and other factors. 
     In some embodiments of the invention, the volume of influence may be selected or predetermined to be larger than a volume impacted by the detonation of the IED (i.e., the detonation volume or “kill zone”). In some embodiments of the invention, the volume of influence may be selected or predetermined based on whether the transceiver is stationary (e.g., at or affixed to a building or other position) or mobile (e.g., in or affixed to a vehicle, person, or other mobile platform). 
     In those embodiments where the transceiver is mobile, the volume of influence may be selected or predetermined based on a speed, either actual or expected, of the mobile platform. In some embodiments of the invention, multiple antennas and transmitters may be used to define an aggregate volume of influence. This aggregate volume of influence may be used to detect and/or suppress RF transmissions around a stationary position such as, for example, a base, a building, an encampment or other stationary position, or a mobile position such as a convoy of vehicles, a division of troops or other mobile position. In further embodiments, the multiple antennas and transceivers may also transmit at different frequencies to suppress RF transmissions from a wide variety of wireless devices. 
     In some embodiments, the invention may be sized and/or configured to be mounted in, affixed to, or otherwise carried in a military vehicle or a civilian vehicle (e.g., an armored civilian vehicle) such as HMMWV or other military vehicle, a GMC Tahoe, a Chevrolet Suburban, a Toyota Land Cruiser, or other civilian vehicle. In some embodiments, the invention may be sized and/or configured to be carried by a person in a backpack, case, protective vest, body armor or other personal equipment or clothing. 
     In some of these embodiments, an antenna operating with the transceiver may be affixed to a head apparatus of the person, such as a hat or helmet, or be hand-held. In some embodiments, various components of the antenna may be housed in a ruggedized, sealed, and/or weatherproof container capable of withstanding harsh environments and extreme ambient temperatures. 
       FIG. 10  illustrates a portion of an antenna assembly including a lower polycarbonate radome section  100  and a portion of an upper radome section  102 . The lower spring radiating wire conductors  36  are separated and electrically connect to the bottom half of feed element (sheet conductor  34 ).  FIG. 11  shows lower dielectric spacer  104  which functions to keep radiating wire conductors  36  separated within radome section  100 . Spacer  104  includes a plurality of channels  105  into which portions of radiating wire conductors  36  are received. An upper dielectric spacer  106  similarly functions as a transition between the radome sections  100 ,  102 . Transition spacer  106  may be inserted into an end of lower radome section  100 . Upper radome section  102  may be inserted into transition spacer  106  to mechanically connect the two radome sections  100 ,  102  together, as shown in  FIG. 12 . Lower radome section  100  may be secured to transition spacer  106  with threaded fasteners  108 . The balum RF choke  82 ,  84  described above is included in this antenna assembly embodiment. A lower cap  109  seals off the lower end of radome section  100 . 
       FIG. 13  illustrates a top portion of the antenna assembly of  FIG. 10 . The spring radiating wire conductors  32  are separated and electrically connected to the top half of the feed element (sheet conductor  30 ). Upper radome section  102  is a tubular element and includes a dielectric spacers  110  to maintain separation between radiating wire conductors  32 . An upper cap  114  seals off upper radome section  102 . 
     The radome sections  10 ,  102  are preferably polycarbonate tubular elements, though alternative materials could be utilized. A foam filler (not shown) can be inserted into the radome section  100 ,  102  cavities to further lock the flexible radiating wire conductors  32 ,  36  in place. Additionally, the foam filler provides a moisture/debris barrier and improves the overall structural integrity of the antenna assembly. A variety of setting foam fillers may be utilized during manufacture of the antenna assembly. 
     According to various embodiments of the invention, the antenna and transceiver may be deployed with additional technologies. For example, the antenna and transceiver may be deployed with technologies designed to assess and screen persons, parties, and/or vehicles approaching a designated location, such as, for instance, checkpoints and/or facilities. The screening technologies may be designed to detect bombs being transported by people, within vehicles, or other (e.g., vehicle borne LEDs used in suicide attacks). 
     Although the present invention and its advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims. Moreover, the scope of the present application is not intended to be limited to the particular embodiments of the process, machine, manufacture, composition of matter, means, methods and steps described in the specification. As one of ordinary skill in the art will readily appreciate from the disclosure of the present invention, processes, machines, manufacture, compositions of matter, means, methods, or steps, presently existing or later to be developed that perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein may be utilized according to the present invention. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods, or steps.