US 2008/0074178 A1 · MULTIPLE ORDER LOW PASS FILTER FOR AN xDSL SPLITTER IN A TELECOMMUNICATION SYSTEM

Abstract

A single-ended low pass filter and its double-ended or balanced version comprising a first coil (Lp1) coupled between a first input (Vin1) and a first output (Vout1) terminal of the filter, a second coil (Lp2) coupled between a second input (Vin2) and a second output (Vout2) terminal of this filter, and a capacitor (C) coupled between the first and second output terminals. The single-ended or balanced low pass filter further includes filter enhancement means (FEM) comprising a current sense circuit (CS) having first inputs coupled across a first impedance (Rsense1) coupled between the first input terminal and the first coil, second inputs coupled across a second impedance (Rsense2) coupled between the second input terminal and the second coil, and an amplifier (A) having an input coupled to an output of the current sense circuit and having an output connected to a ground terminal (Vgrd) via a third (Ls1) and a fourth (Ls2) coils, preferably mounted in parallel and also forming part of the filter enhancement means. The coils are magnetically coupled by pairs and are located on a same core of a transformer (T1). This filter is used in xDSL splitters. The amplifier may comprise the cascade coupling of a frequency dependent amplifier and a transconductance amplifier. The coil is then enhanced in value and is made frequency dependent, giving a multiple order low pass filter.

Claims11

Dependent claims

A single-ended low pass filter (FIG. 1) comprising a coil (Lp) coupled between an input terminal (Vin) and an output terminal (Vout), and a capacitor (C) coupled between said output terminal and a ground terminal (Vgrd),

characterized in that said low pass filter further includes filter enhancement means (FEM1) comprising an impedance (Rsense) coupled between said input terminal (Vin) and said coil (Lp), and an amplifier (A) having inputs coupled across said impedance and having an output connected to said ground terminal (Vgrd) via a second coil (Ls) also forming part of said filter enhancement means,
and in that the first mentioned coil (Lp) and said second coil (Ls) respectively constitute the primary and secondary winding of a transformer (T).

A balanced low pass filter (FIG. 4) comprising a first coil (Lp1) coupled between a first input (Vin1) and a first output (Vout1) terminal of said filter, a second coil (Lp2) coupled between a second input (Vin2) and a second output (Vout2) terminal of said filter, and a capacitor (C) coupled between said first and said second output terminals,

characterized in that said low pass filter further includes filter enhancement means (FEM) comprising a current sense circuit (CS) having first inputs coupled across a first impedance (Rsense1) coupled between said first input terminal (Vin1) and said first coil (Lp1), second inputs coupled across a second impedance (Rsense2) coupled between said second input terminal (Vin2) and said second coil (Lp2), and an amplifier (A) having an input coupled to an output of said current sense circuit and having an output connected to a ground terminal (Vgrd) via a third (Ls1) and a fourth (Ls2) coils also forming part of said filter enhancement means,
in that said third coil (Ls1) is adapted to be magnetically coupled to said first coil (Lp1),
in that said fourth coil (Ls2) is adapted to be magnetically coupled to said second coil (Lp2),
and in that said first, second, third and fourth coils are located on a same core of a transformer (T1).

1 more element

Dependencies are inferred from the claim text.

MULTIPLE ORDER LOW PASS FILTER FOR AN xDSL SPLITTER IN A TELECOMMUNICATION SYSTEM

Life of this patent

MULTIPLE ORDER LOW PASS FILTER FOR AN xDSL SPLITTER IN A TELECOMMUNICATION SYSTEM

Life of this patent

Abstract

Claims11