Ultra-broadband antenna incorporated into a garment

[0001] 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.

[0002] 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.

[0003] 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.

[0004] 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.

[0005] 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.

[0006] 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 D₁. Generally, D₁<2.5 cm, although the scope of the invention includes the distance D₁ 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.

[0007] 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 D₂. 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, D₂≦0.7 cm, although the scope of the invention includes the distance D₂ 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.

[0008] 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.

[0009] 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.

Throughout the several views, like elements are referenced using like references.

[0021] 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 D₁. Generally, D₁≦2.5 cm, although the scope of the invention includes the distance D₁ 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.

[0022] 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 D₁. 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.

[0023] 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.

[0024] 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.

[0025] 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 D₂. 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 D₂. Generally, D₂≦0.7 cm, although the scope of the invention includes the distance D₂ 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.

[0026] 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'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's torso.

[0027] 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 D₂. 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.

[0028] 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 D₂. 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.

[0029] 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.

[0030] Referring to FIGS. 1A, 1B, 2A, 2B, 3A, and 3B, 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.

[0031] 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.

[0032] 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.

[0033] 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.

[0034] 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.