| 摘要 |
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 (CS) and having an output connected to a ground terminal (Vgrd) via a third (Ls1) and a fourth (Ls2) coils, mounted in parallel and also forming part of the filter enhancement means. The coils are magnetically coupled 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. |
