High speed, low noise, low inductance transmission line cable

Abstract

A transmission line cable that utilizes a plurality of substantially flat insulated conductors, each consisting of two or more solid metallic strands laid side by side in a parallel configuration within an extruded insulator. The plurality of insulated conductors are stacked into groups of two or more and may be utilized as signal conductors or shield conductors. Once the insulated conductors are stacked, the stack is twisted together, and either wrapped in a conductive insulator, placed in an extruded non-conductive insulator, or both, creating a cable that is stable, flexible, and has improved transmission characteristics, including reduced attenuation, noise and signal skew.

Claims

1. A transmission line cable, comprising: two or more solid metallic strands, wherein said strands are each individually disposed in a layer of insulation; a plurality of discrete conductors, wherein each said conductor is comprised of two or more of said strands, arranged in contact side by side on one plane, within a flexible extrusion; and wherein at least two of said conductors are stacked together and twisted together into a spiral formation; wherein at least four strands, defining at least a first conductor comprised of two side by side strands and a second conductor comprised of two side by side strands, are included; said flexible extrusion is defined by a single wire insulator extrusion, said wire insulator extrusion being shaped in a figure 8 configuration defined by opposing wide end sections connected by a narrow middle section; and said first conductor and second conductor are each positioned within one of said end sections of the figure 8 configuration, wherein the two lengthwise planes created by the rows of strands are oriented in parallel with one another.

2. The transmission line cable of claim 1, additionally comprising at least one drain wire.

3. The transmission line cable of claim 1, additionally comprising two drain wires.

4. The transmission line cable of claim 3, wherein said drain wires are positioned outside of and on opposing sides of the middle section such that the drain wires each are equidistant from both the first conductor and second conductor.

5. A transmission line cable, comprising: two or more solid metallic strands, wherein said strands are each individually disposed in a layer of insulation; a plurality of discrete conductors, wherein each said conductor is comprised of two or more of said strands, arranged in contact side by side on one plane, within a flexible extrusion; and wherein at least two of said conductors are stacked together and twisted together into a spiral formation, wherein: said plurality of discrete conductors defining a first outer conductor, a second outer conductor, and an inner conductor; said first outer conductor defining a plurality of strands disposed in a conductive extrusion; said second outer conductor defining a plurality of strands disposed in a conductive extrusion; said inner conductor defining a plurality of side by side strands, wherein said inner conductor is disposed in at least one insulating extrusion; and wherein said inner conductor is stacked with the two outer conductors such that the outer conductors flank the inner conductor, and the stacked conductors are twisted.

6. The transmission line cable of claim 5, wherein the first outer conductor and second outer conductor are disposed in a flat conductive PE extrusion.

7. The transmission line cable of claim 5, wherein the inner conductor is disposed in an oval shaped low-density polyethylene insulator.

8. The transmission line cable of claim 5, wherein the stacked conductors are spiral wrapped with a metalized copper/Mylar foil tape having its copper side of the shield facing inside.

9. The transmission line cable of claim 8, wherein the wrapped stacked conductors are enclosed into a round PVC extrusion.

10. A method of configuring transmission line cables to reduce skew, attenuation, and noise, comprising the steps of: individually covering each of two or more sold metallic strands with a layer of insulation; constructing a plurality of discrete conductors, wherein each said conductor is comprised of two or more of said covered strands, arranged in contact side by side on one plane, within a flexible extrusion; and stacking and twisting together at least two of said conductors into a spiral formation; wherein: at least four strands are covered with a layer of insulation and the step of constructing includes constructing at least a first conductor comprised of two side by side covered strands and a second conductor comprised of two side by side covered strands; said flexible extrusion is defined by a single wire insulator extrusion, said wire insulator extrusion being shaped in a figure 8 configuration defined by opposing wide end sections connected by a narrow middle section; and said first conductor and second conductor each positioned within one of said end sections of the figure 8 configuration, wherein the two lengthwise planes created by the rows of strands are oriented in parallel with one another.

11. The method of claim 10, additionally comprising the step of positioning two drain wires outside of and on opposing sides of the middle section such that the drain wires each are equidistant from both the first conductor and second conductor said wire insulator extrusion.

12. A method of configuring transmission line cables to reduce skew, attenuation, and noise, comprising the steps of: individually covering each of two or more sold metallic strands with a layer of insulation; constructing a plurality of discrete conductors, wherein each said conductor is comprised of two or more of said covered strands, arranged in contact side by side on one plane, within a flexible extrusion; and stacking and twisting together at least two of said conductors into a spiral formation, wherein: the step of constructing includes constructing a first outer conductor defined by a plurality of covered, side by side strands and placing said first outer conductor in a conductive extrusion; the step of constructing includes constructing a second outer conductor defined by a plurality of covered, side by side strands and placing said second outer conductor in a conductive extrusion; the step of constructing includes constructing an inner conductor defined by a plurality of strands arranged as two discrete contiguous rows of side by side strands and placing the inner conductor with an insulating extrusion; and the step of stacking and twisting includes arranging said inner conductor with the two outer conductors such that the outer conductors flank the inner conductor, and twisting the arranged conductors.

13. The method of claim 12, wherein the first outer conductor and second outer conductor are placed in a flat conductive PE extrusion.

14. The method of claim 12, wherein the inner conductor is placed in an oval shaped low-density polyethylene insulator.

15. The method of claim 12, wherein the stacked conductors are spiral wrapped with a metalized copper/Mylar foil tape having its copper side of the shield facing inside.

16. The method of claim 15, wherein the wrapped stacked conductors are enclosed into a round PVC extrusion.

17. The transmission line cable of claim 5, wherein said inner conductor defines a plurality of strands arranged as two discrete contiguous rows of side by side strands and said inner conductor is disposed in an insulating extrusion.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1 is an elevational view of a cross section of an embodiment of the inventive four-conductor shielded audio cable architecture.

(2) FIG. 2 is an elevational view of a cross section of an embodiment of the 75-ohm cable architecture.

(3) FIG. 3 is a perspective view of a cross section of an embodiment of the inventive 23 American Wire Gauge (AWG) 100-ohm balanced pair cable architecture.

(4) FIG. 4 is an elevational view of a cross section of an embodiment of a conventional 24 AWG 100-ohm balanced pair cable architecture.

(5) FIG. 5 is an elevational view of a cross section of an embodiment of the inventive 414 AWG speaker cable architecture.

(6) FIG. 6 is an elevational view of a cross section of an embodiment of a conventional 414 AWG speaker cable architecture.

(7) FIG. 7 is a perspective view of the internal structure of a cable consisting of four (4) flat insulated conductors.

(8) FIG. 8 is a perspective view of a cross section of an embodiment of a 110 ohm balanced pair cable architecture.

(9) FIG. 9 is an elevational view of a cross section of an embodiment of a 75 ohm/110 ohm balanced pair composite cable architecture.

DETAILED DESCRIPTION OF THE INVENTION

(10) Transmission cables, built in accordance with the present invention, will now be described with initial reference to FIGS. 1-9. The conductor strands and wires in each of these descriptions are copper. In other embodiments, however, the conductor strands and wires may also consist of various grades and combinations of copper and silver.

(11) Referring now to FIG. 1, the design of an inventive four (4) conductor transmission cable 10 is defined by four substantially flat conductors each consisting of ten (10) solid metallic strands laid side by side in direct contact in a flat parallel configuration within an extruded insulator. The four conductors are stacked together to form a rectangular profile 11. These conductors include shield conductors embodied by a first outer conductor 12a and a second outer conductor 12b, and signal conductors embodied by a first inner conductor 13a and a second inner conductor 13b. The first outer conductor 12a and the second outer conductor 12b each consist of ten (10) copper strands 14 arranged side by side in a flat parallel configuration within a carbon-loaded conductive polyethylene (PE) extrusion 15. In other embodiments, the extrusion 15 can be of other conductive plastic materials. The first inner conductor 13a and the second inner conductor 13b each consist of ten (10) copper strands 14 arranged side by side in a flat parallel configuration within an extruded polyethylene (PE) insulator 16. In other embodiments, the insulator 16 can be made with other standard, non-conductive materials. The first inner conductor 13a and the second inner conductor 13b may be used as a balanced pair or combined together as a single conductor. To create a uniform and stable structure, the rectangular profile 11 comprising the stacked first outer conductor 12a, first inner conductor 13a, second inner conductor 13b, and second outer conductor 12b is twisted into a 30 millimeter (mm) long spiral configuration.

(12) In all four conductors, each individual copper strand is 0.16 mm in diameter, creating a substantially flat conductor with the dimensions of 0.16 mm by 1.6 mm when arranged in accordance with this embodiment. The four extruded insulators which house the conductors have dimensions of 0.7 mm by 2.3 mm.

(13) The rectangular profile 11 is surrounded by a flexible extrusion 17, which is a tight tubular extrusion of highly conductive Polyvinyl chloride (PVC) with a 0.8 mm wall thickness. This flexible extrusion 17 is surrounded by an outer jacket 18, which is a round PVC extrusion with a 7 mm diameter. In other embodiments, the outer jacket 18 can be other common extruded insulation materials. In this design, the conductor lengths are identical and their relative positions are extremely stable, providing very low skew. Also, the parallel and closely coupled relationship of the conductors provides superior EMI rejection, while minimizing inductive reactance, which reduces signal attenuation. Furthermore, the conductive extrusions reduce triboelectric noise to improve signal quality.

(14) Referring now to FIG. 2, the design of an inventive 75 ohm three (3) conductor transmission cable 20 is defined by three (3) stacked flat conductors, with each conductor consisting of several solid metallic strands laid side by side in direct contact in a flat parallel configuration within an extrusion. With regard to the pair of shield outer conductors 21, each individual consists of twelve (12) 0.18 mm diameter copper strands 22a covered with a flat conductive PE extrusion 22b that measures 0.8 mm by 3.5 mm. The signal inner conductor 23 consists of four (4) 0.18 mm copper strands 24a insulated with a larger oval shaped low-density polyethylene (LDPE) insulator 24b measuring 2 mm by 3.5 mm. Stacked, the three conductors are twisted together to form a rectangular profile 25, with a 35 mm twist length. The rectangular profile 25 is spiral wrapped with a metalized copper/Mylar foil tape 26 having its copper side of the shield facing inside, and then enclosed into a round PVC extrusion 27 with a 7 mm diameter. This configuration has been optimized to produce a characteristic impedance of 75-ohms. The inner conductor 23 provides 20% lower self-inductance than a single conductor of the same effective wire gauge. The two outer conductors 21 also utilize parallel conductor strands to provide substantially lower self-inductance than conventional braided or served shields. The reduced self-inductance afforded by this design has proven to be helpful in reducing signal skew and attenuation, thereby minimizing data errors due to jitter.

(15) Referring now to FIGS. 3 and 4, the designs of an embodiment of inventive 23 American Wire Gauge (AWG) 100 ohm balanced conductor pair transmission cable 30, built in accordance with the present invention, and a conventional 24 AWG 100 ohm balanced conductor pair transmission cable 40 are shown. While the inventive 23 AWG cable 30 and the conventional 24 AWG cable 40 both function as 3-conductor shielded balanced pairs, the inventive 23 AWG cable 30 utilizes a balanced pair of dual strand conductors 31 covered within a figure-of-eight shaped high-density polyethylene (HDPE) foam extrusion 32 and two (2) solid drain wires 33. Each copper strand 31a in the pair of dual strand conductors 31 is 26 AWG, which is 0.4 mm in diameter, and is disposed in a layer of insulation 31b. The individually insulated strands 31a are laid side by side in indirect contact, whereby the insulation 31b of the two strands 31a of each dual strand conductor 31 is in direct contact. The additional insulation 31b isolates the strands 31a, which reduces series inductance. Thus, loss is reduced and transmission speed is increased with only a minimal increase in the overall diameter of the cable 30.

(16) To adequately separate the respective balanced conductor pairs, the figure-of-eight shape of the HDPE extrusion 32 consists of gas injected HDPE foam that is defined in appearance by two (2) stacked ovals, each containing a conductor pair in its center, where each oval has a large diameter of 2.0 mm and a small diameter of 1.4 mm. As a result, the HDPE extrusion 32 is a structure that is 2.8 mm at its point of greatest length by 2.0 mm at its two points of greatest width, with those two points being the large diameter of the ovals with comprise it. The copper drain wires 33, located on either side of the HDPE extrusion 32, each measure 0.4 mm in diameter. The extruded conductors 34 and drain wires 33 are twisted together with a 26 mm twist length and spiral wrapped in a foil shield 35 that is a copper/Mylar foil tape with the copper side on the inside.

(17) In addition, in one embodiment, a braid layer 36 is included outside the foil shield 35 and a jacket 37 is included outside the braid layer 36.

(18) Conversely, the conventional 24 AWG cable 40 utilizes a balanced pair single strand conductors 41 covered within two round extrusions 42 and one (1) solid drain wire 43. Each strand in the balanced pair 41 is 0.51 mm in diameter and the drain wire 43 is also 0.51 mm. The covered conductors 44 and the drain wire 43 are twisted together and spiral wrapped in a foil shield 45 that is an aluminum/Mylar foil tape with the aluminum side on the inside.

(19) In contrast to the conventional 24 AWG cable 40, the inventive 23 AWG cable 30 configuration is especially useful as it provides substantially lower attenuation than the conventional 24 AWG cable 40, while taking up substantially the same amount of space within a cable construction, such as HDMI, where four balanced signal pairs are used. The conventional 24 AWG cable 40, containing a single 0.51 mm diameter strand 41 per conductor and a single 0.51 mm drain wire 43, has a twisted diameter of 2.9 mm and a balanced impedance of 100-ohms. The inventive 23 AWG cable 30, containing dual 0.4 mm conductors 31 and two symmetrically placed 0.4 mm drain wires 33, also has a twisted diameter of 2.9 mm and a balanced impedance of 100-ohms. The use of dual 0.4 mm conductor strands 31 in place of a single 0.51 mm conductor strand 41 provides a 20% reduction in resistance and approximately 30% lower self inductance, thereby providing substantially lower attenuation than the conventional design. Furthermore, the symmetrical pair of drain wires 33 provides improved impedance uniformity, as variations in the centering of the conductor strands will have less effect on the degree of coupling between the signal and shield conductors. The inventive 23 AWG cable 30 also provides greater consistency of the air spaces within the foil shield 35 and it also stabilizes the drain wire 33 positions, providing an additional improvement in impedance uniformity and lower triboelectric noise. Also, the 0.4 mm strands 31 provide higher flexibility and greater flex life than the 0.51 mm strands 41. The compactness of this embodiment is very advantageous in HDMI applications, where high-bandwidth and low attenuation is essential, and the cable diameter is limited by connector dimensions and flexibility requirements.

(20) Referring now to FIGS. 5 and 6, the designs of an inventive 414 AWG speaker cable 50, built in accordance with the present invention, and a conventional 414 AWG speaker cable 60 are shown. The inventive 414 AWG cable 50 utilizes four (4) flat extruded conductors stacked together, with a first outside conductor 51, a first inside conductor 52, a second inside conductor 53, and a second outside conductor 54. The first outside conductor 51, first inside conductor 52, second inside conductor 53, and second outside conductor 54 each have an identical structure, where each one is made up of eighteen (18) strands 55 of 0.4 mm copper arranged sequentially, with six (6) strands side by side in direct contact in a first strand group 56a, with six (6) strands side by side in direct contact in a second strand group 56b, and with six (6) strands side by side in direct contact in a third strand group 56c. In addition, each conductor is covered with a HDPE extrusion 57 measuring 1.25 mm by 10 mm. The extruded conductors are stacked and strands arranged so that each strand group in a conductor is parallel to the corresponding numbered strand group of every other conductor (i.e. the first strand group 56a of the first outside conductor 51 is parallel to the first strand group 56a of the first inside conductor 52, second inside conductor 53, and second outside conductor 54). The four stacked extruded conductors create a rectangular profile 58 that is twisted with a twist length of 60 mm and enclosed within a round PVC extrusion jacket 59 having a 13 mm diameter.

(21) The conventional 414 AWG speaker cable 60 utilizes four (4) round extruded conductors twisted together, with a first conductor 61, a second conductor 62, a third conductor 63, and a fourth conductor 64. The first conductor 61, second conductor 62, third conductor 63, and fourth conductor 64 each have an identical structure, where each one is made up of a plurality of copper strands 65 bundled and twisted together inside an extrusion of HDPE 66. The bundled extruded conductors have a twist length that measure 60 mm and are enclosed within a round PVC extrusion jacket 67 having a 13 mm diameter.

(22) By utilizing flat conductors instead of round conductors, the inventive 414 AWG speaker cable 50 is able to reduce the high inductive reactance and skin effect loss that is inherent to the conventional 414 AWG speaker cable 60. These improvements are accomplished with standard manufacturing techniques and improved efficiency, since the manufacturing process of the inventive design eliminates the strand bundling step required to produce the conventional cable.

(23) Referring now to FIG. 7, the internal structure of a cable built in accordance with the present invention is shown. An inventive cable 70 is shown consisting of four (4) insulated conductors 71 twisted together inside an inner extrusion 72, which is contained within a round extruded outer jacket 73. The outer jacket 73 is surrounded by a nylon braiding 74.

(24) Referring now to FIG. 8, an inventive 110 ohm balanced pair embodiment of the 75 ohm three (3) conductor transmission cable is shown. The inventive 110 ohm four (4) conductor transmission cable is defined by three flat conductors, with each individual conductor consisting of several solid metallic strands in a flat parallel configuration within a flexible extrusion. With regard to the two shield outer conductors 81, each individual conductor consists of twelve (12) 0.18 mm diameter copper strands 82a, each individually disposed in a layer of insulation 82c. The individually insulated strands 82a are laid side by side in indirect contact, whereby the insulation 82c of the strands 82a is in direct contact. The plurality of insulated strands 82a are then covered with a flat conductive PE extrusion 82b that measures 0.8 mm by 3.5 mm. Through the additional insulation 82c on the strands in the extrusion, however, further isolates the strands 82a, reducing series inductance and loss while increasing transmission speed with little to no increase in the overall size of the respective conductor.

(25) The signal inner conductor 83 consists of eight (8) 0.18 mm copper strands 84a positioned in two distinct contiguous rows of side by side strands 84a, with each strand 84a individually disposed in a layer of insulation 84c, and insulated with an oval shaped low-density polyethylene (LDPE) insulator 84b measuring 2 mm by 4 mm. The inner conductor 83 rows of indirectly contacting strands 84a are aligned linearly within a single figure-of-eight shaped extrusion 84b. The inner conductor 83 is then stacked with the two outer conductors 81, so that the outer conductors 81 flank the inner conductor 83, forming a rectangular profile 85 that is twisted with a 35 mm twist length. The rectangular profile 85 is spiral wrapped with a metalized copper/Mylar foil tape 86 having its copper side of the shield facing inside, and then enclosed into a round PVC extrusion 87 with a 7 mm diameter. This configuration, which is optimized to produce a balanced characteristic impedance of 110-ohms, reduces the capacitive coupling between the two conductors, which is considered a parasitic loss unrelated to any necessary electrical characteristics of a balanced signal cable.

(26) Referring now to FIG. 9, an inventive 75 ohm/110 ohm composite transmission cable 90, which allows different impedances to be matched within a single cable, is shown. The composite cable 90 utilizes three (3) flat extruded conductors stacked together, with a signal inner conductor 91 stacked between a pair of shield outside conductors 92. The two outside conductors 92 each have an identical structure, where each one is made up of sixteen (16) strands 92a of 0.22 mm copper arranged sequentially in three distinct sections, with six (6) side by side strands in direct contact in a first outer strand group 93a, four (4) side by side strands in direct contact in a second outer strand group 93b, and six (6) side by side strands in direct contact in a third outer strand group 93c. The strands 92a of the outer conductor 92 are covered in a conductive PE, measuring 0.8 mm by 5 mm. The inner conductor 91 is also made up of sixteen (16) strands 91a of 0.22 mm copper. Moreover, the strands 91a of the inner conductor 91 are similarly arranged sequentially in three distinct sections, with six (6) side by side strands in direct contact in a first inner strand group 94a, four (4) side by side strands in direct contact in a second inner strand group 94b, and six (6) side by side strands in direct contact in a third inner strand group 94c. The strands 91a of the inner conductor 91 are insulated in LDPE by strand group, so that the first inner strand group 94a, second inner strand group 94b, and third inner strand group 94c are enclosed in a first oval shaped insulator partition 95a, a second oval shaped insulator partition 95b, and a third oval shaped insulator partition 95c, respectively. The first oval shaped insulator partition 105a, second oval shaped insulator partition 95b, and third oval shaped insulator partition 95c are aligned linearly, with the second oval shaped insulator partition 95c between the first oval shaped insulator partition 95a and third oval shaped insulator partition 95c, and adjoined about their small diameter. The resulting structure of the inner conductor 91 is a 3 mm by 5.7 mm at its widest and 1.3 mm by 5.7 mm at its most narrow, and has a black stripe on one edge.

(27) The three conductors are stacked and strands arranged so that each strand group in a conductor is parallel to the corresponding numbered strand group of every other conductor (i.e. the first outer strand group 93a parallels the first inner strand group 94a). The three stacked conductors create a rectangular profile 96 that is twisted with a twist length of 45 mm and spiral wrapped in a copper/Mylar foil tape 97, with the copper side facing the conductors. The foil shield is enclosed in an extruded PVC jacket 98 with an 8 mm diameter. The jacket is then covered with a nylon braid 99.

(28) When the inventive composite cable 90 is used as a 75 ohm cable, only the second inner strand group 94b is used. Conversely, when the inventive composite cable 90 is used as a 110 ohm balanced pair cable, the first inner strand group 94a and third inner strand group 94c of the inner conductor 91 are used. In either configuration, the first outer strand group 93a, the second outer strand group 93b, and the third outer strand group 93c are used as shield strands.

(29) The present invention is not limited to the specific embodiments described. Many different embodiments exist without departing significantly from the scope or the spirit of the present invention. The described embodiments thus serve as examples of the present invention and are not restrictive of the scope of the invention.