Load coil and DSL repeater including same
View Patent ↗Systems and methods are disclosed for improving DSL performance, including ADSL and VDSL performance, over a local loop between a telephone company central office and a customer premises. In particular, a DSL repeater is coupled to the local loop and amplifies downstream and upstream DSL signals to at least partially compensate for DSL signal attenuation that occurs as DSL signals pass over the local loop. Pursuant to one embodiment, the DSL repeater includes a POTS load coil to improve the POTS, or voice band, transmission over the local loop. According to this embodiment, the DSL repeater provides both improved POTS band signal transmission and DSL service. One embodiment of the load coil includes a coupled inductor having compensating capacitors coupled thereto for counter-balancing the inter-winding capacitance of the coupled inductor. In another embodiment, the load coil includes a high intra-winding capacitance for counter-balancing the inter-winding capacitance of a coupled inductor. Pursuant to yet another embodiment, the load coil comprises a pair of discrete, uncoupled inductors and a low intra-winding capacitance. Still another embodiment includes a pair of discrete, uncoupled inductors having a pair of compensating capacitors coupled thereto for counter-balancing the intra-winding capacitance of the uncoupled inductors. Reducing, eliminating, or counter-balancing the capacitance of the load coil improves the impedance of the load coil to DSL signals improved, thereby permitting sufficient gain to be developed across the load coil.
1. A DSL repeater for improving transmission of POTS band and DSL band signals over a local loop, the repeater comprising:
an upstream signal amplifier for amplifying upstream DSL signals;
a downstream signal amplifier for amplifying downstream DSL signals; and
a load coil disposed in parallel with the upstream and downstream signal amplifiers for improving the transmission of POTS band signals over the local loop, wherein the load coil comprises:
a first inductor including a first winding and a first core, the first winding having upstream and downstream ends and a first intra-winding capacitance;
a second inductor including a second winding and a second core, the second winding having upstream and downstream ends and having a second intra-winding capacitance;
a first compensating capacitor disposed between the upstream end of the first inductor and the downstream end of the second inductor to offset at least a portion of the first and second intra-winding capacitances for improving the impedance of the load coil to DSL-band signals; and
a second compensating capacitor disposed between the upstream end of the second inductor and the downstream end of the first inductor to offset at least a portion of the first and second intra-winding capacitances for improving the impedance of the load coil to DSL-band signals.
2. The DSL repeater of claim 1 wherein
the first and second compensating capacitors have respective first and second compensating capacitances;
the first and second capacitances approximate the first and second intra-winding capacitances respectively and
the first and second compensating capacitors act to counterbalance the first and second intra-winding capacitances respectively.
3. The DSL repeater of claim 2 wherein
the ratio of the first compensating capacitance to the first intra-winding capacitance is in the range of 0.75 to 1.25.
4. The DSL repeater of claim 2 wherein
the ratio of the first compensating capacitance to the first intra-winding capacitance is in the range of 0.99 to 1.01.
5. The DSL repeater of claim 1 wherein:
the first and second compensating capacitors each have capacitances in the range 770 pF to 1290 pF.