Odd-order low-pass pots device microfilter

• US 6,285,754 B1
• Filed: 04/06/2000
• Issued: 09/04/2001
• Est. Priority Date: 04/06/2000
• Status: Expired due to Term

• Current Assignee: ARRIS Solutions, Inc. (CommScope Holding Company, Inc.)
• Original Assignee: 2Wire, Inc. (CommScope Holding Company, Inc.)
• Inventors: Sun, Ting, Hinman, Brian L.
• Primary Examiner(s): Isen, Forester W.
• Assistant Examiner(s): SINGH, RAMNANDAN P
• Application Number:
  US09/544,731
• Time in Patent Office: 516 Days
• Field of Search: 379/399, 379/419, 379/389, 379/397, 379/93.07, 379/93.1, 370/494, 370/493, 370/495, 375/220, 375/259, 375/219
• US Class Current: 379/399.02
• CPC Class Codes: H04L 25/085 Arrangements for reducing interference in line transmission systems, e.g. by differential transmission
• CPC Class Codes: H04M 1/738 Interface circuits for coupling substations to external telephone lines H04M1/78 takes precedence
• CPC Class Codes: H04M 11/062 using different frequency bands for speech and other data

Abstract

An odd-order low-pass microfilter is disclosed for being interposed between a home telephone wiring network and a POTS, or voice-band, device to separate voice-band signals from higher frequency signals, such as ADSL signals and home networking signals. The filter topology is substantially symmetric so that the filter is reversible in that either end of the filter may be directly coupled to the home telephone wiring network without impairing high frequency signal performance or the filter characteristic of the filter. In one embodiment, the filter is a three-pole filter with a single capacitor disposed between a pair of coupled inductors. Each of the coupled inductors advantageously has an interwinding capacitance over about 100 pF to improve the filter frequency response without increasing the cost of the filter. In another embodiment, the filter is a reversible three-pole filter with a single capacitor disposed between first and second pairs of uncoupled, or discrete, inductors.

Claims

1. A reversible odd-order low-pass filter for insertion between a POTS device and a home telephone wiring network to separate certain high frequency signals on the home telephone wiring network from the POTS device, comprising:

a first pair of inductors, each inductor having an inductance in the range of 5-15 mH, the first pair of inductors having an interwinding capacitance greater than 100 pF in the frequency range of 10 kHz-100 kHz;

a second pair of inductors, each inductor having an inductance in the range of 5-15 mH, the second pair of inductors having an interwinding capacitance greater than 100 pF in the frequency range of 10 kHz-100 kHz;

a capacitor disposed between the first and the second pairs inductors and separated from the home telephone wiring network by either the first or the second pair of inductors to prevent high frequency signals from being shorted across the capacitor regardless of whether the home telephone wiring network is coupled to the filter adjacent to the first or the second pair of inductors.

2. The reversible odd-order filter according to claim 1, wherein the capacitor has a capacitance in the range of 0.022-0.068 microfarads.

3. A reversible three-pole filter for separating a voice-band device from certain high frequency signals on a home telephone wiring network, comprising:

a first coupled inductor having an interwinding capacitance greater than 100 pF in the frequency range of about 10 kHz-100 kHz;

a second coupled inductor having an interwinding capacitance greater than about 100 pF in the frequency range of 10 kHz-100 kHz;

a capacitor disposed between the first and second coupled inductors so that when the filter is interposed between the home telephone wiring network and the voice-band device, either the first coupled inductor or the second coupled inductor separates the single capacitor from the home telephone wiring network to prevent certain high frequency signals on the home telephone wiring network from shorting across the single capacitor regardless of whether the first coupled inductor or the second coupled inductor is disposed closest to the home telephone wiring network.

4. The reversible filter according to claim 3, wherein the interwinding capacitance of the first coupled inductor is in the range of about 1,000-2,000 pF in the frequency range of 10 kHz-10 kHz.

5. The reversible filter according to claim 3, wherein the capacitor has a capacitance in the range of 0.022-0.068 microfarads.

6. The reversible filter according to claim 3, wherein each winding has an inductance in the range of 2.7 mH-8.3 mH.

7. The reversible filter according to claim 3, further comprising at least one ferrite bead for reducing common mode noise through the filter.

8. The reversible filter according to claim 3, further comprising a transient voltage suppressor for protecting the POTS device from hazardous transient voltages.

9. A low-pass filter for separating a voice-band device from DSL signals on a home telephone wiring network, comprising:

a first coupled inductor having a pair of windings wrapped about a core, the first coupled inductor having an interwinding capacitance greater than 100 pF and each winding having an inductance in the range of about 2.7 mH-8.3 mH;

a second coupled inductor having a pair of windings wrapped about a core, the second coupled inductor having an interwinding capacitance greater than 100 pF and each winding having an inductance in the range of about 2.7 mH-8.3 mH; and

a capacitor having a capacitance in the range of 0.022-0.068 microfarads disposed between the first and the second coupled inductors to provide over 30 dB of signal attenuation to signals in the DSL band.

10. The filter according to claim 9, wherein the interwinding capacitance of the first coupled inductor is between 1,000-2,000 pF.