The present invention relates generally to communication cables and more specifically, to communication cables utilizing a separator between wires forming a twisted pair that maintains a specific distance between wires.
Traditional category cabling such as Cat 6a is manufactured using common processes of insulating individual conductors, twinning (twisting) two insulated conductors together to form a twisted pair, and stranding four twisted pairs together to form a cable. The four pairs may be stranded together with a dividing member, or cross web, to create distance between the pairs. In addition, the four pairs may be enclosed circumferentially by barrier layers such as Matrix Tape to achieve a desired electrical characteristic. Ultimately, the entire cable is enclosed inside an outer jacket. An example of a modern Cat 6a cable such as the cable is shown in
There is a constant desire to reduce the cost and size of category cabling to gain market share and competitive advantages over the competition. Recent advancements in the twinning process have allowed the removal of the dividing member resulting in an optimized cable shown in
SUMMARY
A communications cable has coated conductor wires separated by a wire separator having at least one hole in the cross section to form a twisted pair configured to maintain a distance of approximately 0.375 mm between the conductors and a characteristic impedance of approximately 100 ohms. The coating on the conductors may be an enamel or other appropriately thin insulating material.
Fig shows a cross-sectional view of a prior art cable.
Traditional twisted pairs found in Cat 6a cabling are made from two individually insulated conductors. The insulation around the conductor serves two primary electrical purposes. Electrically, it prevents the conductor from shorting to nearby conductors and ensures the cables ability to withstand high DC voltages. The thickness of the insulation also serves the purpose of providing a specific amount of separation between two twisted conductors. This separation is critical to achieve a specific characteristic impedance of the twisted pair when used as a differential transmission line. Typically, this characteristic impedance is targeted to be 100 ohms +/- 10 ohms.
Because the insulation is extruded around the entire circumference of the conductors, the total diameter of the twisted pair orbit (2.1 mm) is determined by the diameter of the insulation surrounding each conductor as shown in
The novel twisted pair orbit diameter (1.55 mm) is now determined by the diameter of the coated conductors and the critical dimension of the wire separator shown in
In addition to the reduction in size, the amount of dielectric insulating material is substantially reduced by implementing the novel twisted pair construction. The profile of the pair separator shown in
The dielectric constant (Dk) of the material between the two conductors of a pair will largely dictate the capacitance between the conductors. This capacitance in turn directly relates to the differential characteristic impedance of the pair which is designed to nominally be maintained at 100 ohms. During differential mode transmission over a twisted pair, an electric field is present between the two conductors. The vast majority of this field exists within the volume of the dielectric pair separator which is why its Dk along with its size, largely defines the capacitance and the characteristic impedance of the pair. The Dk of HDPE shown in
As described above, a pair separator as shown in
The dielectric constant of a material also has a direct impact on the propagation speed of a high frequency signal traveling through the material. In a vacuum, high frequency signals travel at approximately 3×108 meters per second. When traveling through a dielectric material, the velocity of propagation is inversely proportional to the Dk of the material.
The impact on propagation velocity can be leveraged in a cable design by manipulating the size of the hole within the pair separators. Tightly twisted pairs have slower propagation times compared to loosely twisted pairs making delay skew (time delta between fastest pair and slowest pair propagation times) difficult to meet. Using a large hole in a tightly twisted pair relative to a loosely twisted pair, will favorably decrease the skew between these pairs by enabling a faster propagation velocity in the tightly twisted pair relative to the propagation velocity in the loosely twisted pair. With the ability to manipulate the propagation velocity in each individual pair and improve the delay skew between pairs, the window of possible pair lays is expanded. Either tighter twists, looser twists, or both can now be considered while still achieving the required delay skew. These new pair lay options could provide improved near end crosstalk performance when properly designed.
Other embodiments of the pair separator could be explored to further leverage the benefit of air within the pair separator.
While exemplary embodiments are described above, it is not intended that these embodiments describe all possible forms of the invention. Rather, the words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the invention. Additionally, the features of various implementing embodiments may be combined to form further embodiments of the invention.
This application is a continuation-in-part of U.S. patent application Ser. No. 17/411,749, filed Aug. 25, 2021, the entirety of which is hereby incorporated by reference herein.
Number | Date | Country | |
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Parent | 17411749 | Aug 2021 | US |
Child | 18378175 | US |