HK1150468A - Coaxial cable shielding - Google Patents

Description

Coaxial cable shield

Background

Typical coaxial cables include a Radio Frequency (RF) shield. One common type of shielding is a conductive strip that attenuates interfering electromagnetic fields in the high frequency range.

Referring first to fig. 1A, a prior art coaxial cable 100 is disclosed. As disclosed in fig. 1A, the coaxial cable 100 is terminated at both ends with a connector 150, and referring now to fig. 1B, the prior art coaxial cable 100 generally includes a center conductor 102 surrounded by an insulator 104, a ribbon 106 longitudinally wrapped around the insulator, a braid 108 surrounding the ribbon 106, and a jacket 110 surrounding the braid 108.

Referring now to FIG. 1C, a band 106 surrounds the insulator 104 and generally serves to confine the high frequency electromagnetic field 126 to the center conductor 102 and from the center conductor 102. The tape 106 is a laminated tape that includes a first aluminum layer 112, a polymer layer 114, a second aluminum layer 116, and a polymer adhesive layer 118. The tape 106 also defines a first edge portion 120, the first edge portion 120 overlapping a second edge portion 124 when the tape 106 is longitudinally wrapped around the longitudinal direction of the insulator 104, resulting in an overlapping layer extending parallel to the center conductor 102.

With continuing reference to fig. 1C, and also with reference to fig. 1D, the general problem of the ribbon 106 of the prior art coaxial cable 100 is disclosed. In particular, while the first and second aluminum layers 112 and 116 are generally effective at shielding high frequency electromagnetic fields 126 having frequencies above one skin depth, the layers 114 and 118 are ineffective at shielding the electromagnetic fields 126 because the polymer layer 114 and the polymer binder layer 118 are formed of insulator materials. As a result, some high frequency electromagnetic field 126, e.g., greater than about 50MHz, from the center conductor 102 is transmitted through the overlapping gaps 128 through the polymer adhesive layer 118 to the prior art coaxial cable 100.

Likewise, although the second aluminum layer 116 is generally effective at shielding the high-frequency electromagnetic field 126 at frequencies above one skin depth, a small portion of the high-frequency electromagnetic field 126 from the center conductor 102 can penetrate the second aluminum layer 116. This results in some high frequency electromagnetic field 126 from the center conductor 102, which is transmitted through the overlapping slots 130 through the polymer layer 114 to the prior art coaxial cable 100. The high frequency electromagnetic field 126 of these prior art coaxial cables 100 produces interference that is harmful to surrounding electrical equipment (not shown). Some high frequency electromagnetic fields from surrounding electrical equipment (not shown) can also enter the prior art coaxial cable 100 through the overlapping slots 128 and 130, thereby causing harmful interference with the data signal passing through the center conductor 102.

Referring now to fig. 1E, another prior art coaxial cable 100' is disclosed. Coaxial cable 100 'is identical to coaxial cable 100 except that it includes a helically wound ribbon 106'. As disclosed in fig. 1E, the tape 106 'also defines a first edge portion, and when the tape 106' is helically wound around the insulator 104, the first edge portion 120 overlaps with a second edge portion, resulting in an overlap that surrounds the insulator 104 in a helical configuration. Like tape 106, tape 106 'allows some of the high frequency electromagnetic field to enter/exit coaxial cable 100' by passing through one or more overlapping slots. These high frequency electromagnetic fields generate interference that is harmful to surrounding electrical equipment (not shown) and data signals passing through the center conductor 102.

Disclosure of Invention

Embodiments of the present invention relate generally to coaxial cable shielding. Some embodiments reduce or eliminate overlapping gaps at overlapping layers of the ribbon during the manufacture of the coaxial cable. In coaxial cables, this reduction or removal of overlapping slots leads to an increased homogeneity of the shielding of interfering high-frequency electromagnetic fields.

In one embodiment, a coaxial cable includes a center conductor, an insulator, a ribbon, and a jacket. The band defines first and second edge portions, each edge portion bordering the inner portion. The first edge portion has a thickness less than a thickness of the inner portion. An insulator surrounds the center conductor. The tape is wrapped around the insulator such that the first edge portion overlaps the second edge portion. The sheath surrounds the band.

In another embodiment, a method for manufacturing a coaxial cable includes a plurality of steps. The cable includes a ribbon defining first and second edge portions, each edge portion bordering an inner portion. First, the first edge portion is compressed such that the thickness of the first edge portion is less than the thickness of the inner portion. Next, a tape (which surrounds the center conductor) is wrapped longitudinally around the insulator such that the first edge portion overlaps the second edge portion. Finally, the band is surrounded by a jacket.

In yet another embodiment, a method for manufacturing a coaxial cable includes a plurality of steps. First, an insulator is extruded around the center conductor. Next, a belt defining first and second edge portions, each edge portion bordering an interior portion, is heated and passed through a pair of rollers to compress the first and second edge portions, respectively, such that the thickness of each of the first and second edge portions is less than the thickness of the interior portion. Then, the tape is longitudinally wound around the insulator such that the first edge portion and the second edge portion overlap each other. The band is then surrounded by a braid. Finally, a sheath is extruded around the braid.

This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the detailed description. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter. Furthermore, it is to be understood that both the foregoing general description and the following detailed description of the present invention are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.

Drawings

Aspects of exemplary embodiments of the invention will become apparent from the following detailed description of exemplary embodiments, which is to be read in connection with the accompanying drawings, wherein:

fig. 1A is a perspective view of a prior art example coaxial cable terminated with two typical connectors;

FIG. 1B is a perspective view of a portion of the prior art coaxial cable of FIG. 1A with portions of the various layers of the prior art coaxial cable cut away;

FIG. 1C is a cross-sectional view of the prior art coaxial cable of FIG. 1B;

FIG. 1D is an enlarged view of a portion of the cross-sectional view of FIG. 1C;

FIG. 1E is a perspective view of a portion of another prior art coaxial cable with portions of the various layers of the prior art coaxial cable cut away;

fig. 2A is a perspective view of a portion of a first example coaxial cable with an example layer of a compressive tape, with a portion of the various layers of the example coaxial cable cut away;

fig. 2B is a cross-sectional view of the exemplary coaxial cable of fig. 2A;

FIG. 2C is an enlarged view of a portion of the cross-sectional view of FIG. 2B;

fig. 2D is a partial perspective view of the example compression band of fig. 2A-2C prior to insulation of the example compression band as a layer of the example coaxial cable of fig. 2A-2C;

FIG. 2E is a cross-sectional view of the example compression band of FIG. 2D;

FIG. 3A is a perspective view of a portion of a second example coaxial cable having two example layers of compressive tape, with portions of the layers of the second example coaxial cable cut away;

FIG. 3B is a cross-sectional view of a second exemplary coaxial cable of FIG. 3A;

FIG. 4A is a perspective view of a portion of a third example coaxial cable having two example layers of compressive tape, with portions of the layers of the third example coaxial cable cut away;

fig. 4B is a cross-sectional view of the third exemplary coaxial cable of fig. 4A;

fig. 5A is a perspective view of a portion of an example communication coaxial cable having an example layer of compressive tape, with portions of the layers of the example communication coaxial cable cut away;

fig. 5B is a cross-sectional view of the exemplary communication coaxial cable of fig. 5A; and

fig. 6 is a flow chart of an example method for manufacturing the example coaxial cable of fig. 2A.

Detailed Description

Example embodiments of the present invention relate to coaxial cable shielding. In the following detailed description of some example embodiments, reference will now be made in detail to specific embodiments of the invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention. Other embodiments may be utilized and structural, logical, and electrical changes may be made without departing from the scope of the present invention. Moreover, it is to be understood that the various embodiments of the invention, although different, are not necessarily mutually exclusive. For example: a particular feature, structure, or characteristic described in one embodiment may be included within other embodiments. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present invention is defined only by the appended claims, along with the full scope of equivalents to which such claims are entitled.

I. First example coaxial Cable

Referring now to fig. 2A, a first example coaxial cable 200 is disclosed. Example coaxial cable 200 may be any type of coaxial cable including, but not limited to, 50 ohm and 75 ohm coaxial cables. The coaxial cable 200 generally includes a center conductor 202 surrounded by an insulator 204, a ribbon 206 longitudinally wrapped around the insulator, a braid 208 surrounding the ribbon 206, and a jacket 210 surrounding the braid 208. As used herein, the phrase "surrounded by" means that the inner layer is typically surrounded by the outer layer. However, it should be understood that the inner layer may be "surrounded" by the outer layer, without the inner layer being directly adjacent to the outer layer. The word "enclosed by" thus allows the presence of an intervening layer. Each of these elements of the example coaxial cable 200 will now be discussed in turn.

The center conductor 202 is disposed at the center of the example coaxial cable 200. The center conductor 202 may be configured to carry a range of electrical currents (amps) and RF/electronic digital signals. In certain embodiments, the center conductor 202 is made of solid copper, Copper Clad Aluminum (CCA), Copper Clad Steel (CCS), or silver plated copper clad steel (SCCCS), although other conductive materials are possible. For example, the center conductor 202 may be made of any conductive metal or alloy. Additionally, the center conductor 202 may be, for example, solid, hollow, stranded, corrugated, plated, or clad.

An insulator 204 surrounds the center conductor 202 and generally serves to support and isolate the center conductor 202 and the ribbon 206. Although not shown in the drawings, an adhesive, such as a polymer, may be used to bond the insulator 204 to the center conductor 202. In certain exemplary embodiments, the insulator 204 may be tape-like, solid or foamed polymer or fluoropolymer, but is not so limited. For example, the insulator 204 may be foamed Polyethylene (PE).

The band 206 surrounds the insulator 204 and generally serves to minimize the high frequency electromagnetic field entering and emanating from the center conductor 202. In some applications, the high frequency electromagnetic field is a field greater than or equal to about 50 MHz.

Referring now to fig. 2B and 2C, the tape 206 is a laminated tape that includes a first aluminum layer 212, a polymer layer 214, a second aluminum layer 216, and a polymer adhesive layer 218. However, it should be understood that the discussion herein of ribbon 206 is not limited to a ribbon having any particular combination of layers. For example, the tape 206 may instead include, but is not limited to, the following layers: copper/polymer binder, aluminum/polymer, or aluminum/polymer/aluminum.

Referring now to fig. 2D and 2E, the band 206 defines a first edge portion 220 and a second edge portion 224, each bordering an inner portion 222. As disclosed in fig. 2D and 2E, before the tape 206 is wrapped around the insulator 204, each of the outer edge portions 220 and 224 is compressed such that the thickness of each of the outer edge portions 220 and 224 is less than the thickness of the inner portion 222. More particularly, as disclosed in fig. 2E, the relative thinness of each of the edge portions 220 and 224 as compared to the inner portion 222 may generally be attributed to the compression of the polymer layer 214 and the polymer adhesive layer 218 in the edge portions 220 and 224.

Referring again to fig. 2B and 2C, when the tape 206 is longitudinally wound around the longitudinal direction of the insulator 204, the first edge portion 220 overlaps the second edge portion 224. Since polymer layer 214 and polymer adhesive layer 218 are both insulator layers and thus ineffective at shielding interfering electromagnetic fields, the compression of polymer layer 214 and polymer adhesive layer 218 in edge portions 220 and 224 reduces the size of or completely eliminates typical overlapping gaps in ribbon 206.

For example, the overlapping slits 228 of the polymer adhesive layer 218 in fig. 2C are substantially reduced in size compared to the overlapping slits 128 of fig. 1D. As a result, the example coaxial cable 200 emits less high-frequency electromagnetic field 126 from the center conductor 202 through the overlapping slit 228 than the high-frequency electromagnetic field emitted through the overlapping slit 128 by the prior art coaxial cable 100 (compare fig. 1D and 2C). This reduction in the spilled high-frequency electromagnetic field 126 is caused to occur through the overlapping slit 228 with only a single high-frequency electromagnetic field 126 in FIG. 2C, whereas two high-frequency electromagnetic fields 126 are caused to occur through the overlapping slit 128 in FIG. 1D. This illustration is for illustrative purposes only and is not intended to limit the embodiment to a 50% reduction in the emission of the high-frequency electromagnetic field 126, as the embodiment also encompasses greater or less than 50% reduction.

Similarly, the overlapping apertures 230 of the polymer layer 214 of fig. 2C are substantially reduced in size compared to the overlapping apertures 130 of fig. 1D. As a result, the high-frequency electromagnetic field 126 from the center conductor 202 is emitted from the example coaxial cable 200 through the overlapping slit 230 less than the high-frequency electromagnetic field emitted from the prior art coaxial cable 100 through the overlapping slit 130 (compare FIGS. 1D and 2C).

This reduction in the size of the overlapping slits or the elimination of the overlapping slits increases the shielding effectiveness of the overlapping edge portions 220 and 224 of the tape 206, which increases the uniformity of shielding against interfering high frequency electromagnetic fields in the coaxial cable 200.

It should be understood that the benefits noted herein of reducing the size of the overlapping gap or removing the overlapping gap may also be achieved by alternative configurations of the belt 206. For example, only the thickness of the first edge portion 220 must be less than the thickness of the inner portion 222. Likewise, the thickness of the first edge portion 220 may or may not be equal to about the thickness of the second edge portion 224. In addition, the thickness of edge portions 220 and 224 may each be greater or less than the respective thicknesses disclosed in FIGS. 2A-2E.

Referring again to fig. 2A, braid 208 surrounds band 206 and generally serves to minimize the high frequency electromagnetic fields entering and emanating from center conductor 202. The braid 208 may be formed, for example, from blended, fine gauge aluminum wire or copper wire, such as 34 American Wire Gauge (AWG) wire. Although the braided wires of braid 208 are depicted in fig. 2A as single rectangular wires, each rectangular wire actually represents several circles of 34AWG wire. However, it should be understood that the braid discussed herein is not limited to braids formed from any particular type or size of wire and/or any number of wires.

With continued reference to fig. 2A, a jacket 210 surrounds braid 208 and generally serves to protect the internal components of coaxial cable 200 from, for example, external contaminants such as dust, moisture, and oil, as well as from wear and tear over time. The jacket 210 may be formed, for example, from the following materials: polyethylene (PE), High Density Polyethylene (HDPE), Low Density Polyethylene (LDPE), or Linear Low Density Polyethylene (LLDPE), foamed PE, polyvinyl chloride (PVC), or Polyurethane (PU), or any combination thereof, but is not limited thereto.

Second example coaxial Cable

Referring now to fig. 3A and 3B, a second example coaxial cable 300 is disclosed. The example coaxial cable 300 generally includes a center conductor 302 surrounded by an insulator 304, a first ribbon 306 longitudinally wrapped around the insulator 304, a braid 308 surrounding the ribbon 306, a second ribbon 306 'surrounding the braid 308, and a jacket 310 surrounding the second ribbon 306'. The center conductor 302, insulator 304, braid 308, and jacket 310 are all substantially identical in composition and function to the center conductor 202, insulator 204, braid 208, and jacket 210 of fig. 2A-2C, respectively, although the size and relative position of these layers between the coaxial cables 200 and 300 may vary. In addition, the composition and function of each of the ribbons 306 and 306' is substantially the same as the ribbon 206 of fig. 2A-2E, although the size and relative position of the layers between the coaxial cables 200 and 300 may vary. In addition, the layers 312-318 and 312 '-318' are substantially identical in composition and function to the layers 212-218, respectively. However, the layers of tape 306 'are reversed compared to the layers of tape 306 such that the polymeric binder layer 318' directly abuts the jacket 310. This arrangement of the polymeric adhesive layer 318 'directly adjacent the jacket 310 serves to provide a strong bond between the tape 306' and the jacket 310.

When the tape 306 is longitudinally wound around the longitudinal direction of the insulator 304, the first edge portion 320 overlaps the second edge portion 324. The compression of the polymer layer 314 and the polymer adhesive layer 318 in the edge portions 320 and 324 reduces the size of or completely removes typical overlap gaps in the tape 306.

In particular, the size of overlap gap 328 of polymer adhesive layer 318 and overlap gap 330 of polymer layer 314 are substantially reduced as compared to prior art overlap gaps 128 and 130 of fig. 1D, respectively. As a result, the example coaxial cable 300 emits less of the high frequency electromagnetic field 126 from the center conductor 302 through the overlapping slots 328 and 330 than the high frequency electromagnetic field emitted by the prior art coaxial cable 100 through the overlapping slots 128 and 130. Similarly, the additional layer of shielding provided by second tape 306 ', in combination with the reduction in size of overlapping gap 328 ' of polymer adhesive layer 318 ' and overlapping gap 330 ' of polymer layer 314 ', also results in less high frequency electromagnetic field 126 from center conductor 302 being emitted through overlapping gaps 328 ' and 330 ' of exemplary coaxial cable 300.

This reduction in the size of the overlapping slits or the elimination of the overlapping slits increases the shielding efficiency of the overlapping edge portions 320 and 324 of the tape 306 and the overlapping edge portions 320 ' and 324 ' of the tape 306 ', which increases the uniformity of shielding of interfering high-frequency electromagnetic fields in the coaxial cable 300.

Third example coaxial Cable

Referring now to fig. 4A and 4B, a third example coaxial cable 400 is disclosed. The example coaxial cable 400 generally includes a center conductor 402 surrounded by an insulator 404, a first braid 406 longitudinally wrapped around the insulator 404, a braid 408 surrounding the braid 406, a second braid 406 'surrounding the braid 408, a second braid 408' surrounding the second braid 406 ', and a jacket 410 surrounding the second braid 408'. The center conductor 402, insulator 404, and jacket 410 are each substantially identical in composition and function to the center conductor 202, insulator 204, and jacket 210 of fig. 2A-2C, respectively, although the size and relative position of these layers between the coaxial cables 200 and 400 may vary. In addition, the composition and function of each of the ribbons 406 and 406' is substantially the same as the ribbon 206 of fig. 2A-2E, although the size and relative position of these layers between the coaxial cables 200 and 400 may vary. Similarly, the composition and function of layers 412-418 and 412 '-418' are each substantially the same as layers 212-218, respectively. In addition, the composition and function of each of the braids 408 and 408' is substantially the same as the braid 208 of fig. 2A-2C, although the size and relative position of the layers between the coaxial cables 200 and 400 may vary.

The addition of the ribbon 406 'and braid 408' in the example coaxial cable 400 improves the shielding of interfering high and low frequency electromagnetic fields, respectively, in the example coaxial cable 400.

Example communication coaxial Cable

Referring now to fig. 5A and 5B, an example communication coaxial cable 500 is disclosed. The example communications coaxial cable 500 generally includes a center conductor 502 surrounded by an insulator 504, a ribbon 506 wrapped longitudinally around the insulator 504, a braid 508 surrounding the ribbon 506, a communications wire 550 extending parallel to the center conductor 502, and a jacket 510 surrounding the braid 508 and the communications wire 550. The composition and function of the center conductor 502, insulator 504, ribbon 506, and braid 508 are each the same as the center conductor 202, insulator 204, ribbon 206, and braid 208 bases of fig. 2A-2C, respectively. In addition, the composition and function of the layers 512-418 are substantially the same as the layers 212-218, respectively. Additionally, jacket 510 is substantially identical in composition to jacket 210 of fig. 2A-2C, except that jacket 510 further surrounds braid 508 and communication wires 550, thereby protecting the internal components of communication coaxial cable 500 while securing communication wires 550 to the other internal components of communication coaxial cable 500.

Communication line 550 is typically used to support communication coaxial cable 500 in these cases when communication coaxial cable 500 spans long distances in the air, such as 75 feet or more. The communication wire 550 may be tied off by partially detaching the communication wire 550 from the communication coaxial cable 500, wrapping the communication wire 550 around a hook or other attachment in a configuration, wrapping the communication wire 550 around itself one or more times, and finally wrapping the communication wire 550 around the communication coaxial cable 500 one or more times to further prevent the cable and communication wire from detaching.

V. example method for manufacturing coaxial cable

Referring again to fig. 2A-2E, and now also to fig. 6, an example method 600 for manufacturing the example coaxial cable 200 is disclosed.

At step 602, the center conductor 202 is surrounded by an insulator 204. For example, the center conductor 202 may be conveyed through a first extruder where a pre-coat of a binder, such as a polymer, is applied. The pre-coated center conductor 202 is then conveyed through a second extruder where an insulator 204 is applied to surround the center conductor 202. Optionally, step 602 may be omitted entirely, wherein the center conductor 202 is already surrounded by the insulator 204 prior to performing the example method 600.

In step 604, one or both of the edge portions 220 and 224 of the band 206 are compressed. For example, the belt 206 may be passed through a pair of rollers to compress the insulator polymer layer 214 and the insulator polymer binder layer 218 in the edge portions 220 and 224 such that the thickness of each of the edge portions 220 and 224 is less than the thickness of the inner portion 222. In addition, the tape 206 may be heated in order to soften the insulator polymer layer 214 and the insulator polymer adhesive layer 218 of the tape 206 prior to compressing the edge portions 220 and 224. Such heating of the tape 206 may be accomplished by passing the tape 206 through a heating element to soften the insulator polymer layer 214 and the insulator polymer adhesive layer 218. This heating element may be separate from the drum or integral with the drum, thereby rendering the drum a heated drum. Likewise, heating of the belt 206 may be accomplished by passing the belt 206 through a pair of heated rollers to soften and compress the insulator polymer layer 214 and the insulator polymer binder layer 218. In certain embodiments, the belt 206 is heated to a temperature between about 85 ℃ and about 95 ℃. As discussed above, step 604 optionally includes compression of only one edge portion, such as edge portion 220.

Next, in step 606, the insulator 204 is surrounded with a tape 206. For example, the insulator 204 and the components it surrounds may be fed through a winding operation to wind a layer of tape 206 around the insulator 204. The tape 206 is spirally or longitudinally wound around the insulator 204 such that the first edge portion 220 overlaps the second edge portion 224.

Next, in step 608, the band 206 is surrounded with the braid 208. For example, the band 206 and the elements it surrounds may be conveyed through a braiding operation, thereby braiding, or wrapping the braid 208 around the band 206. It should be understood that: during manufacture of the coaxial cable 200, multiple layers of tape and/or multiple layers of braid barriers may be applied to increase shielding from interfering high and low frequency electromagnetic fields, such as in the exemplary coaxial cables 300 and 400 disclosed in connection with fig. 3A-3B and 4A-4B. Alternatively, step 608 may be omitted entirely when coaxial cable 200 does not include braid 208. It can be understood that: steps 604, 606 and 608 all occur substantially simultaneously during the weaving operation.

Finally, in step 610, braid 208 is surrounded with jacket 210. For example, braid 208 and the elements it surrounds may be conveyed through a third extruder where jacket 210 is applied to surround braid 208. In certain embodiments, the heat used during application of the jacket 210 activates the polymeric binder layer 218 of the band 206, which serves to provide a secure bond between the insulator 204 and the band 206. Similarly, it should be understood that: the heat used during application of jacket 310 to coaxial cable 300 may excite polymeric binder layer 318 of ribbon 306 and polymeric binder layer 318 'of ribbon 306'. This activation of the polymeric binder layers 318 and 318 'serves to provide a strong bond between the insulator 304 and the tape 306 and a strong bond between the tape 306' and the jacket 310. It should be further appreciated that the enclosure 210 may further enclose a communication line during step 610, such as in the example communication coaxial cable 500 disclosed in connection with fig. 5A-5B. After step 610, the coaxial cable 200 may be subjected to electrical and mechanical testing to ensure that once installed, the coaxial cable 200 will operate as desired by the industry.

Thus, the example method 600 may be used to form the example coaxial cable 200. As disclosed elsewhere herein, the relative thinness of the edge portions 220 and 224 reduces the size of or eliminates the overlapping gap on the surface of the first edge portion 220 as compared to the inner portion 222 of the band 206. This reduction in the size of the overlapping slits or the elimination of the overlapping slits increases the shielding efficiency of the portion of the ribbon 206 located on or near the overlap, which results in an increased uniformity of shielding against interfering high frequency electromagnetic fields in the coaxial cable 200.

While the example coaxial cable 200 is configured as a standard coaxial cable, it should be understood that other cable configurations may equally benefit from the ribbon 206 disclosed herein. For example, the spillover coaxial cable may be configured to include a band with compressed overlapping edge portions. Additionally, coaxial cables with helically wound ribbons, such as coaxial cable 100' disclosed in fig. 1E, may likewise be configured with compressed overlapping edge portions similar to edge portions 220 and 224 of ribbon 206. These compressed edge portions may reduce the size of the overlapping seam, or eliminate the overlapping seam altogether, which extends in a helical path along the surface of the tip portion of the helically wound tape, such as the helically wound tape 106' of fig. 1E. Such reduction or removal of the overlapping gap will increase the shielding effectiveness of the helically wound tape 106 'at or adjacent the overlap and will further result in increased uniformity of shielding of interfering high frequency electromagnetic fields in the coaxial cable 100'.

The example embodiment disclosures disclosed herein may be embodied in other specific forms. The exemplary embodiments disclosed herein are to be considered in all respects as illustrative and not restrictive.

Claims (20)

1. A coaxial cable, comprising:

a center conductor surrounded by an insulator;

a band defining a first edge portion and a second edge portion, each edge portion bordering the inner portion, the first edge portion having a thickness less than a thickness of the inner portion, the band being wound around the insulator such that the first edge portion overlaps the second edge portion; and

a sheath surrounding the band.

2. The coaxial cable of claim 1, wherein the second edge portion has a thickness less than a thickness of the inner portion.

3. The coaxial cable of claim 1, wherein the tape comprises:

an aluminum layer; and

a polymer layer adjacent to the aluminum layer.

4. The coaxial cable of claim 3, wherein the tape further comprises a polymer adhesive layer adjacent to the polymer layer.

5. The coaxial cable defined in claim 3, wherein the polymer layer in the first edge portion has a thickness that is less than a thickness of the polymer layer in the inner portion.

6. The coaxial cable of claim 5, wherein the tape further comprises a second aluminum layer adjacent to the polymer layer.

7. The coaxial cable of claim 6, wherein the tape further comprises a layer of polymeric binder adjacent to the second layer of aluminum.

8. The coaxial cable of claim 7, wherein the thickness of the layer of polymeric binder in the first edge portion is less than the thickness of the layer of polymeric binder in the inner portion.

9. The coaxial cable of claim 1, further comprising a braid surrounding the band and surrounded by a jacket.

10. The coaxial cable of claim 1, wherein the tape is wrapped longitudinally around the insulator.

11. A method for manufacturing a coaxial cable, the coaxial cable including a ribbon defining first and second edge portions, each edge portion bordering an inner portion, the method comprising the steps of:

compressing the first edge portion such that the thickness of the first edge portion is less than the thickness of the inner portion;

wrapping a tape longitudinally around the insulator surrounding the center conductor such that the first edge portion overlaps the second edge portion; and

the band is surrounded by a sheath.

12. The method of claim 11, further comprising the step of: the braid is included with a band such that the sheath surrounds the braid.

13. The method of claim 12, further comprising the step of: the braid is surrounded with a second band such that the sheath surrounds the second band.

14. The method of claim 11, further comprising: the second edge portion is compressed such that the thickness of the second edge portion is less than the thickness of the inner portion.

15. The method of claim 14, wherein the tape comprises one or more conductive layers and one or more non-conductive layers, and wherein the step of compressing the first and second edge portions comprises compressing the one or more non-conductive layers of the first and second edge portions.

16. The method of claim 14, wherein the step of compressing the first and second edge portions comprises using a pair of rollers to compress the first and second edge portions.

17. The method of claim 16, wherein the roller is a heated roller.

18. A method for manufacturing a coaxial cable, comprising the steps of:

extruding an insulator around the center conductor;

a heating belt defining first and second edge portions, each edge portion bordering an interior portion;

passing the tape through a pair of rollers to compress the first and second edge portions, respectively, such that the thickness of each of the first and second edge portions is less than the thickness of the inner portion;

wrapping the tape longitudinally around the insulator such that the first edge portion and the second edge portion overlap one another;

surrounding the band with a braid; and

a sheath is extruded around the braid.

19. The method of claim 18, wherein the tape comprises one or more aluminum layers and one or more insulator layers, and wherein the step of compressing the first and second edge portions comprises compressing the one or more insulator layers of the first and second edge portions.

20. The method of claim 19, wherein the step of heating the tape comprises: the tape is passed through a heating element to heat the tape to a temperature between about 85 c and about 95 c to soften the insulator layer of the tape.