Abstract:
A multi-antenna garment comprising a first and second antenna incorporated into an electrically nonconductive garment, with tubular composites to improve gain and mitigate radiation hazard. The first antenna includes first and second RF elements attached to a first garment so that a gap exists between them, where the RF elements each form a band when the garment is worn by a wearer. The second antenna includes third, fourth, fifth, and sixth RF elements attached to a second garment worn over the first garment. RF feeds are electrically connected to the first, third, and fifth RF elements. Ground feeds are electrically connected to the second, fourth, and sixth RF elements. Insulating material disposed over gaps between the first and second, the third and fourth, and the fifth and sixth RF elements and in pockets in the regions of the RF feeds limits the wearer&#39;s exposure to electromagnetic field to acceptable levels.

Description:
CROSS REFERENCES TO RELATED APPLICATIONS 
   This application is a continuation-in-part of U.S. patent application Ser. No. 10/263,943, entitled ULTRA-BROADBAND ANTENNA INCORPORATED INTO A GARMENT WITH RADIATION ABSORBER MATERIAL TO MITIGATE RADIATION HAZARD, filed on Oct. 3, 2002 and issued as U.S. Pat. No. 6,788,262 on Sep. 7, 2004, which is a continuation-in-part of U.S. patent application Ser. No. 10/061,639, entitled ULTRA-BROADBAND ANTENNA INCORPORATED INTO A GARMENT, filed on Jan. 31, 2002 and issued as U.S. Pat. No. 6,590,540 on Jul. 8, 2003, and which is herein incorporated by reference. 

   BACKGROUND OF THE INVENTION 
   This invention relates generally to the field of antennas. More specifically, this invention relates to an improved ultra-broadband antenna, comprising of a first and second antenna, which is incorporated into a garment that may be worn around a human torso. 
   The purpose of the first and second antenna incorporated into a garment is to provide ultra-wideband capability—the ability to send or receive a signal at any frequency between 30 and 500 MHz—while hiding the identity of the radio operator from snipers. Because disruption of command, communications, and control is a paramount goal of snipers, reduction of the visual signature of an antenna is highly desirable. Therefore, a need exists for a wideband, man-carried antenna that does not have a readily identifiable visual signature. 
   Although the VSWR of the antenna in U.S. Pat. No. 6,590,540 is less than 3:1 for almost the entire frequency range of 30 to 500 MHz, the gain of the antenna for frequencies greater than 200 MHz was too small. Many antennas for hand-held devices have gains on the order of −10 dBi. The vest antenna had a gain comparable to this in the frequency range of 30 to 90 MHz, which is important for military use. However, the gain for frequencies higher than 200 MHz was often less than −20 dBi, too small for efficient operation. Thus, there is a need for an antenna that provides ultra-broadband capability with improved gain. 
   SUMMARY OF THE INVENTION 
   The invention is directed to an ultra-broadband antenna, comprising of a first and second antenna, which is incorporated into an electrically nonconductive garment and includes tubular composites to improve gain and to mitigate radiation hazards. The ultra-broadband antenna operates over a frequency range of about 30 MHz to about 500 MHz. 
   The antenna garment includes a first antenna integrated into a first garment. First antenna operates very efficiently over a frequency range of about 30 MHz to about 90 MHz. First antenna includes a first radio frequency (RF) element, a second RF element, a shorting strap, left shoulder strap, right shoulder strap, first RF feed, first ground feed, and impedance matching circuit, all of which are attached to first garment. First and second RF elements are attached to first garment so that the RF elements are separated by a gap having a distance D 1 . Generally, D 1 &lt;2.5 cm, although the scope of the invention includes the distance D 1  being greater than 2.5 cm as may be required to suit the requirements of a particular application. When RF energy is input, a voltage difference is generated across the gap. 
   The antenna garment also includes a second antenna integrated into a second garment, which is worn over and attached to first garment by fasteners such as Velcro® or snaps or may also be sewn. Second antenna operates very efficiently over a frequency range of about 150 MHz to about 500 MHz. Second antenna includes third and fourth RF elements, second RF feed, second ground feed, all of which are attached to the front section of second garment. Second antenna also includes fifth and sixth RF elements, third RF feed, third ground feed, all of which are attached to the back region of second garment. By way of example only, third, fourth, fifth and sixth RF elements are rectangular elements separated by a small gap, having a distance D 2 . Other elements that may be used include a triangle (to form a bowtie antenna), a teardrop with a tapered feed, a “home plate,” and others. Generally, D 2 ≦0.7 cm, although the scope of the invention includes the distance D 2  being greater than 0.7 cm as may be required to suit the requirements of a particular application. When RF energy is input, a voltage difference is generated across the gap between the third and fourth RF elements and between the fifth and sixth RF elements. 
   On the inside layer of first and second garments, insulating material is disposed within first and second antennas. Insulating material is disposed in pockets sewn in the regions of the RF feeds. Insulating material is also disposed over the length and width of the gap that separates first and second RF elements, third and fourth RF elements, and fifth and sixth RF elements. By way of example, insulating material may be made of material generally called tubular composites. To fabricate these tubular composites, cylinders of copper and/or ferrite tubules, 25 microns long and 1 micron in diameter, are mixed in controlled amounts with polyurethane or other polymers, which then solidify into a rubber-like sheet. Insulating material reduces the energy that flows into the body and shields the wearer from electromagnetic radiation. Disposed over the length and width of gaps that separate the RF elements, insulating material also reflects energy without shorting first and second antennas. 
   Use of multiple antennas with a diplexer allows optimization of each antenna within a narrower frequency range. A diplexer provides a passive means, i.e., no operator intervention required, to route signals from a radio to the appropriate antenna for efficient operation. A single-pole, two-throw switch is an example of an active means, i.e., requires operator intervention, of directing the signal to the appropriate antenna. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     For a more complete understanding of the improved ultra-broadband antenna incorporated into a garment, reference is now made to the following detailed description of the embodiments as illustrated in the accompanying drawings wherein: 
       FIG. 1A  illustrates an anterior view of a first antenna incorporated into a garment as shown worn by a wearer; 
       FIG. 1B  shows a dorsal view of the antenna garment shown in  FIG. 1 ; 
       FIG. 2A  illustrates an anterior view of a second antenna to be incorporated into a second garment; 
       FIG. 2B  shows a dorsal view of the second garment shown in  FIG. 2A ; 
       FIG. 3A  illustrates an anterior view of first and second antennas incorporated into first and second garments as shown worn by a wearer; 
       FIG. 3B  shows a dorsal view of the antenna garments shown in  FIG. 3A ; 
       FIG. 4A  shows an interior view of the first garment with tubular composites disposed within the inner layer of the garment; 
       FIG. 4B  shows an interior view of the front section of the second garment with tubular composites disposed within the inner layer of the garment; 
       FIG. 4C  shows an interior view of the back region of the second garment with tubular composites disposed within the inner layer of the garment; and 
       FIG. 5  is a block diagram of the circuit that combines a first antenna and a second antenna to form an improved ultra-broadband antenna. 
   

   Throughout the several views, like elements are referenced using like references. 
   DESCRIPTION OF THE PREFERRED EMBODIMENT 
   Referring to  FIGS. 1A and 1B , an antenna garment  20  worn by a human wearer  25  is shown that includes a first antenna  21  integrated into a first garment  22 . First antenna  21  operates very efficiently over a frequency range of about 30 MHz to about 90 MHz. First antenna  21  is integrated into first garment  22  so that first antenna  21  offers no distinctive visual signature that would identify the person wearing antenna garment  20  as a radio operator. First garment  22  is made of an electrically nonconductive material such as a woven fabric selected from the group that includes cotton, wool, polyester, nylon, Kevlar, rayon, and the like. The electrically conductive material of first garment  22  may also include polyurethane for waterproofing. First garment  22  has an outer layer with an anterior or front section  24  and a dorsal or back region  23 . From the perspective of the human wearer  25 , front section  24  of first garment  22  includes a left anterior front section  26  and a right anterior front section  28 . First garment  22  also has a left shoulder section  30  and a right shoulder section  32 . First antenna  21  includes a first radio frequency (RF) element  34 , a second RF element  38 , a shorting strap  42 , left shoulder strap  44 , right shoulder strap  46 , first RF feed  54 , first ground feed  56 , and impedance matching circuit  57 , all of which are attached to first garment  22 . RF elements  34  and  38  are attached to first garment  22  so that the RF elements are separated by a gap  40 , having a distance D 1 . Generally, D 1 ≦2.5 cm, although the scope of the invention includes the distance D 1  being greater than 2.5 cm as may be required to suit the requirements of a particular application. When RF energy is input, a voltage difference is generated across gap  40 . 
   As shown in  FIG. 1B , a flexible, electrically conductive patch  50  is sewn and/or bonded to the bottom center area portion of first RF element  34  on the dorsal side  23  of first garment  22 . Also a flexible, electrically conductive patch  52  is sewn and/or bonded to the top center area of second RF element  38  on the dorsal side  23  of first garment  22 . The patches  50  and  52  are separated by gap  40 , having a distance D 1 . First RF feed  54  is electrically connected to impedance matching circuit  57 , which in turn is electrically connected to patch  50  by soldering or other conventionally known methods for electrically connecting a wire to another electrically conductive structure. Impedance matching circuit  57  is used to finely match the impedance of first antenna  21  with an external load, not shown, and the impedance of the wearer  25 . A first ground feed  56  is electrically coupled to patch  52  by soldering or other means. Patches  50  and  52  provide a generally heat resistive buffer so that impedance matching circuit  57  and first ground feed  56  may be soldered to first antenna  21  without causing heat damage that would otherwise result if first RF feed  54  and first ground feed  56  were directly soldered to RF elements  34  and  38  in applications wherein the latter are made of Flectron®. It is to be understood that first RF feed  54  and first ground feed  56  are RF isolated from each other. By way of example, patches  50  and  52  may be made of electrically conductive copper foil tape such as 3M Scotch Tape, Model No. 1181. 
   Referring now to  FIGS. 2A and 2B , a second antenna  121  is integrated into second garment  122 , which is made of an electrically nonconductive material such as a woven fabric selected from the group that includes cotton, wool, polyester, nylon, Kevlar, rayon, and the like. Second antenna  121  operates very efficiently over a frequency range of about 150 MHz to about 500 MHz. Second garment  122  has an outer layer with an anterior or front section  124  and a dorsal or back region  123 . Second garment  122  also has a left shoulder section  130  and a right shoulder section  132 . 
   As shown in  FIGS. 2A and 2B , the anterior section  124  and dorsal region  123  of second garment  122  are mirror images of each other and include the same elements. Second antenna  121  includes a third RF element  134 , a fourth RF element  138 , second RF feed  154 , second ground feed  156 , all of which are attached to the front section  124  of second garment  122 . Second antenna  121  also includes a fifth RF element  234 , a sixth RF element  238 , third RF feed  254 , third ground feed  256 , all of which are attached to the back region  123  of second garment  122 . By way of example only, RF elements  134 ,  138 ,  234 , and  238  are rectangular elements separated by a small gap. Other elements that may be used include a triangle (to form a bowtie antenna), a teardrop with a tapered feed, a “home plate,” and others. 
   RF elements  134  and  138  are attached to second garment  122  so that the RF elements are separated by a gap  140 , having a distance D 2 . Similarly, RF elements  234  and  238  are attached to second garment  122  so that the RF elements are separated by a gap  240 , having a distance D 2 . Generally, D 2 ≦0.7 cm, although the scope of the invention includes the distance D 2  being greater than 0.7 cm as may be required to suit the requirements of a particular application. When RF energy is input, a voltage difference is generated across gaps  140  and  240 . 
   Second antenna  121  also includes connecting wires  180 ,  182 ,  184 , and  188 , which improve the efficiency of second antenna  121 . Connecting wires  180 ,  182 ,  184 , and  188  electrically connect RF elements  134  and  138  on the front section  124  to RF elements  234  and  238  on the back region  123  of second garment  122 . First and second connecting wires  180  and  182  electrically connect third RF element  134  to fifth RF element  234 . First connecting wire  180  extends from the anterior region  124  to the dorsal region  123  of second garment  122  over left shoulder region  130 . Second connecting wire  182  extends from the anterior region  124  to the dorsal region  123  of second garment  122  over right shoulder region  132 . Third and fourth connecting wires  184  and  188  electrically connect fourth RF element  138  to sixth RF element  238 . Third connecting wire  184  extends from the anterior region  124  to the dorsal region  123  of second garment  122  around the left side region of the wearer&#39;s torso. Fourth connecting wire  188  extends from the anterior region  124  to the dorsal region  123  of second garment  122  around the right side region of the wearer&#39;s torso. 
   Referring again to  FIG. 2A , a flexible, electrically conductive patch  150  is sewn and/or bonded to the bottom center area portion of third RF element  134  on the anterior or front side  124  of second garment  122 . Also a flexible, electrically conductive patch  152  is sewn and/or bonded to the center area of fourth RF element  138  on the anterior or front side  124  of second garment  122 . The patches  150  and  152  are separated by gap  140 , having a distance D 2 . Second RF feed  154  is electrically connected to patch  150  by soldering or other conventionally known methods for electrically connecting a wire to another electrically conductive structure. A second ground feed  156  is electrically coupled to patch  152  by soldering or other means. Patches  150  and  152  provide a generally heat resistive buffer so that second ground feed  156  may be soldered to second antenna  121  without causing heat damage that would otherwise result if second RF feed  154  and second ground feed  156  were directly soldered to RF elements  134  and  138  in applications wherein the latter are made of Flectron®. It is to be understood that second RF feed  154  and second ground feed  156  are RF isolated from each other. By way of example, patches  150  and  152  may be made of electrically conductive copper foil tape such as 3M Scotch Tape, Model No. 1181. 
   Referring now to  FIG. 2B , a flexible, electrically conductive patch  250  is sewn and/or bonded to the bottom center area portion of fifth RF element  234  on the dorsal or back region  123  of second garment  122 . Also a flexible, electrically conductive patch  252  is sewn and/or bonded to the center area of sixth RF element  238  on the dorsal or back region  123  of second garment  122 . The patches  250  and  252  are separated by gap  240 , having a distance D 2 . Third RF feed  254  is electrically connected to patch  250  by soldering or other conventionally known methods for electrically connecting a wire to another electrically conductive structure. A third ground feed  256  is electrically coupled to patch  252  by soldering or other means. Patches  250  and  252  provide a generally heat resistive buffer so that third ground feed  256  may be soldered to second antenna  121  without causing heat damage that would otherwise result if third RF feed  254  and third ground feed  256  were directly soldered to RF elements  234  and  238  in applications wherein the latter are made of Flectron®. It is to be understood that third RF feed  254  and third ground feed  256  are RF isolated from each other. By way of example, patches  250  and  252  may be made of electrically conductive copper foil tape such as 3M Scotch Tape, Model No. 1181. 
   In  FIGS. 3A and 3B , a human wearer  25  is shown wearing antenna garment  20  that includes first antenna  21  integrated into first garment  22  and second antenna  121  integrated into second garment  122 . Second garment  122  is worn over first garment  22  and attached to first garment  22  by fasteners  100  (shown in  FIGS. 1 and 2 ), such as Velcro® or snaps or may also be sewn. In another implementation of antenna garment  20 , first antenna  21  and second antenna  121  may both be integrated into one garment, i.e., first garment  22 . 
   Referring to  FIGS. 1A ,  1 B,  2 A,  2 B,  3 A, and  3 B, collectively, RF elements  34 ,  38 ,  134 ,  138 ,  234 ,  238 , shoulder straps  44  and  46 , and shorting strap  42 , are made of electrically conductive material such as metal selected from the group that includes copper, nickel, and aluminum. In the preferred embodiment, RF elements  34 ,  38 ,  134 ,  138 ,  234 ,  238 , shoulder straps  44  and  46 , and shorting strap  42 , are made of an electrically conductive and very flexible mesh structure that includes woven copper or copper-coated fabric. If formed as a mesh, the mesh spacing should be less than about 0.1 λ, where λ represents the shortest wavelength of the radio frequency signal that is to be detected or transmitted by first antenna  21  and second antenna  121 . One type of suitable, electrically conductive mesh structure from which RF elements  34 ,  38 ,  134 ,  138 ,  234 ,  238 , shoulder straps  44  and  46 , and shorting strap  42  may be made is Flectron®, which is available from Applied Performance Materials, Inc. of St. Louis. The mesh size of Flectron® is much less than 0.1 for a frequency less than 500 MHz. A further characteristic of Flectron® is that it is breathable. Breathability is a very desirable characteristic for RF elements  34 ,  38 ,  134 ,  138 ,  234 ,  238 , shoulder straps  44  and  46 , and shorting strap  42  to facilitate dissipation of heat and moisture generated by wearer  25 . However, the invention may be practiced wherein any or all of RF elements  34 ,  38 ,  134 ,  138 ,  234 ,  238 , shoulder straps  44  and  46 , and shorting strap  42  may be made with electrically conductive structures that are not breathable. 
     FIG. 4A  shows the inside layer  60  of antenna garment  20 . In the preferred embodiment, a pocket  62  has been sewn on the inside layer of antenna garment  20  in the region of first RF feed  54 . Insulating material  300  is disposed in pocket  62  and also disposed over the length and width of gap  40  that separates RF elements  34  and  38 . Insulating material  300  decreases radiation hazard and increases gain. 
     FIG. 4B  shows the inside layer  160  of the front section  124  of second garment  122 .  FIG. 4C  shows the inside layer  260  of the back region  123  of second garment  122 . Referring to  FIGS. 4B and 4C , pockets  162  and  262  have been sewn on the inside layers  160  and  260  in the regions of second RF feed  154  and third RF feed  254 , respectively. Insulating material  300  is disposed in pockets  162  and  262 . Insulating material  300  is also disposed over the length and width of gap  140  that separates RF elements  134  and  138  and over the length and width of gap  240  that separates RF elements  234  and  238 . By way of example, insulating material  300  may be made of material generally called tubular composites. To fabricate these tubular composites, cylinders of copper or ferrite tubules, 25 microns long and 1 micron in diameter, are mixed in controlled amounts with polyurethane or other polymers, which then solidify into a rubber-like sheet. Insulating material  300  reduces the energy that flows into the body and shields the wearer from electromagnetic radiation. Disposed over the length and width of gaps  40 ,  140 , and  240  that separate the RF elements, insulating material  300  also reflects energy without shorting first antenna  21  and second antenna  121 . 
     FIG. 5  is a block diagram of the circuit that combines the first antenna  21 , which is in the VHF band, and the second antenna  121 , which is in the UHF band, to form an ultra-broadband antenna in the range of about 30 MHz to about 500 MHz. Use of multiple antennas, first antenna  21  and second antenna  121 , with diplexer  90  allows optimization of each antenna within a narrower frequency range. The result is increased gain and reduced radiation hazard in a broad frequency range. Diplexer  90  creates a gap in coverage, e.g. 30 MHz–90 MHz, 150 MHz–500 MHz, but requires no operator intervention to route signals from radio  99  to the appropriate antenna for efficient operation. A switch, e.g., a single-pole, two-throw switch, does not have this “dead zone” but requires operator intervention to direct the signal to the appropriate antenna. A switch can also be operated by changing the waveform in radio  99 . 
   Clearly, many modifications and variations of the improved ultra-broadband antenna incorporated into a garment are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described.