FEP modification using titanium dioxide to reduce skew in data communications cables
A cable is provided with a first twisted pair of insulated conductors having a first lay length and a first insulation resulting in a first signal propagation rate and a second twisted pair of insulated conductors having a second lay length and a second insulation resulting in a second signal propagation rate. The second signal propagation rate is faster than the first signal propagation rate resulting a first amount of signal skew between signals travelling through the first twisted pair and the second twisted pair. A jacket covers the pairs. Titanium dioxide is added to the insulation of the conductors of the second twisted pair so that the dielectric constant of the insulation of the conductors of the second twisted pair is raised, lowering the second signal propagation rate, resulting in a second amount of signal skew which is less than the first amount of signal skew.
1. A cable, comprising:
a first twisted pair of insulated conductors, said first twisted pair having a first lay length and a first insulation made from flame resistant olefin resulting in a first signal propagation rate;
a second twisted pair of insulated conductors, said second twisted pair having a second lay length and a second insulation made from a fluoropolymer resulting in a second signal propagation rate wherein said second signal propagation rate is faster than said first signal propagation rate, wherein titanium dioxide is included in the insulation of the conductors of said second twisted pair so that the dielectric constant of the insulation of the conductors of said second twisted pair is raised;
wherein there is a skew between signals travelling through said first twisted pair and said second twisted pair, and wherein said inclusion of said titanium dioxide in said insulation of the conductors of said second twisted pair results in said skew being lower than a skew that would result between said first twisted pair and a second twisted pair of the same said second lay length and said second insulation that does not have titanium dioxide; and
at least one jacket covering said pairs.
2. The cable as claimed in claim 1 , said cable further comprising third and fourth insulated twisted pairs, each of said third and fourth pairs having an insulation respectively, and each having a lay length between said first and said second lay length of said first and second pairs respectively.
3. The cable as claimed in claim 1 wherein the insulation of said second twisted pair is FEP.
4. The cable as claimed in claim 1 , wherein the insulation of said second twisted pair further includes boron nitride at an amount of substantially 1% or less.
5. The cable as claimed in claim 1 , wherein said titanium dioxide added to said insulation on the conductors of said second twisted pair is added in an amount such that it has no substantial effect on the dissipation factor of said insulation.
6. The cable as claimed in claim 1 , wherein said titanium dioxide is substantially in the range of 1%-30% by weight.
7. The cable as claimed in claim 6 , wherein said titanium dioxide is substantially in the range of 7.5%-15% by weight.