Methods and apparatus for terminating a line and supporting the asymmetric digital subscriber line protocol

• US 6,393,110 B1
• Filed: 09/30/1998
• Issued: 05/21/2002
• Est. Priority Date: 09/30/1998
• Status: Expired due to Fees

• Current Assignee: Hewlett-Packard Development Company, L.P. (HP Inc.)
• Original Assignee: 3Com Corporation (HP Inc.)
• Inventors: Price, Tim Urry
• Primary Examiner(s): Isen, Forester W.
• Assistant Examiner(s): SINGH, RAMNANDAN P
• Application Number:
  US09/163,661
• Time in Patent Office: 1,329 Days
• Field of Search: 379/414, 379/399, 379/394, 379/399.01, 379/406, 370/442-448, 370/916, 370/494, 370/403, 370/467
• US Class Current: 379/93.01
• CPC Class Codes: H04M 1/76 Compensating for differences in line impedance
• CPC Class Codes: H04M 11/062 using different frequency bands for speech and other data

Abstract

A digital access arrangement for (i) isolating downstream components from twisted pair copper wire and (ii) separating upstream and downstream communications channels. The line isolation is performed with relatively small, lightweight components, such as an optical isolation unit for example, and can be operated with signals modulated at relatively high frequencies and having relatively high data rates and amplitudes.

Claims

1. A method for transmitting and receiving data over tip and ring lines, the method comprising:

a) transmitting data by

i) buffering data received from an external source, thereby generating buffered data,

ii) modulating the buffered data in accordance with an ADSL modulation technique, thereby generating modulated data,

iii) converting the modulated data to an analog signal,

iv) amplifying the analog signal while passing it over an optical isolation boundary, thereby generating an amplified analog signal, that is a current;

v) passing the amplified analog signal that is a current through a transresistor amplifier to generate an amplified analog signal that is a voltage;

vi selectively filtering the amplified analog signal, thereby generating an amplified and filtered analog signal, and

vii applying the amplified and filtered analog signal to the tip and ring lines; and

b) receiving data by

i) taking a signal appearing across the tip and ring lines,

ii) blocking a DC component of the signal, to generate a non-biased signal,

iii) amplifying the non-biased signal to generate an amplified signal,

iv) converting the amplified signal to a digital signal, and

v) demodulating the digital signal in accordance with an ADSL demodulation technique.

2. The method of claim 1 wherein the receiving data further comprises filtering out transmitted data from the signal appearing across the tip and ring lines.

3. The method of claim 1 wherein the receiving data further comprises canceling echo from the digital signal.

4. The method of claim 1 wherein the ADSL modulation technique is carrierless amplitude phase modulation.

5. The method of claim 1 wherein the ADSL modulation technique is discrete multitone modulation.

6. A method for transmitting data over tip and ring lines, the method comprising:

a) buffering data received from an external source, thereby generating buffered data;

b) modulating the buffered data in accordance with an ADSL modulation technique, thereby generating modulated data;

c) converting the modulated data to an analog signal;

d) amplifying the analog signal while passing it over an optical isolation boundary, thereby generating an amplified analog signal, that is a current;

e) passing the amplified analog signal that is a current through a transresistor amplifier to generate an amplified analog signal that is a voltage;

f) selectively filtering the amplified analog signal that is a voltage, thereby generating an amplified and filtered analog signal; and

g) applying the amplified and filtered analog signal to the tip and ring lines.

7. The method of claim 6 wherein the selectively filtering comprises filtering out frequencies below 25 KHz.

8. The method of claim 7 wherein the selectively filtering comprises filtering out frequencies above 100 KHz.

9. The method of claim 7 wherein the selectively filtering comprises filtering out frequencies above 138 KHz.

10. The method of claim 6 wherein the amplifying the analog signal while passing it over an optical isolation boundary comprises:

i) applying the analog signal to a light emitting element, and

ii) receiving an amplified signal, as a current, at a light receiving element.

11. The method of claim 10 wherein the amplifying the analog signal while passing it over an optical isolation boundary further comprises:

iii) applying a feedback signal, generated by a second light receiving element, to the analog signal, whereby the amplifying is linear.

12. A device for terminating tip and ring lines, the device comprising:

a) a line interface stage, coupled with the tip and ring lines, for separating, at least to some extent, transmit and receive signals;

b) a transmission stage, arranged between the line interface stage and a data source, the transmission stage comprising

i) an optical isolation unit for electrically isolating the data source from the tip and ring lines and for amplifying a signal received from the data source to provide an amplified analog signal that is a current, and

ii) a transresistor amplifier that receives the amplified analog signal that is a current and generates an amplified analog signal that is a voltage; and

c) a reception stage, arranged between the line interface stage and a data sink, the reception stage comprising

i) capacitors for electrically isolating the data sink from the tip and ring lines.

13. The device of claim 12 wherein the line interface stage comprises a filter for filtering out frequencies below 25 KHz of signals from the transmission stage.

14. The device of claim 12 wherein the line interface stage comprises a filter for filtering out frequencies above 100 KHz of signals from the transmission stage.

15. The device of claim 12 wherein the line interface stage comprises a filter for filtering out frequencies above 138 KHz of signals from the transmission stage.

16. The device of claim 12 wherein the optical isolation unit of the transmission stage operates in a photo conductive mode.

17. A device for transmitting and receiving data in accordance with the asymmetric digital subscriber line protocol, the device comprising:

a) a transmission stage comprising an optical isolation unit for electrically isolating a data source from tip and ring lines and for amplifying a signal received from the data source to provide an amplified analog signal that is a current, wherein the amplified analog signal that is a current is passed through a transresistor amplifier to generate an amplified analog signal that is a voltage; and

b) a reception stage comprising capacitors for electrically isolating a data sink from the tip and ring lines.

18. A terminal adapter for interfacing a terminal to tip and ring lines, the terminal adapter comprising:

a) a splitter, coupled with the tip and ring lines, for separating voice signals and data signals;

b) a digital access arrangement, coupled with the splitter, and comprising

i) a transmission stage comprising an optical isolation unit for electrically isolating the terminal from the tip and ring lines and for amplifying a signal received from the terminal, the optical isolation unit to provide an amplified analog signal that is a current, wherein the amplified analog signal is passed through a transresistor amplifier to generate an amplified analog signal that is a voltage, and a filter filters the amplified analog signal which is applied to the tip and ring lines, and

ii) a reception stage comprising capacitors for electrically isolating the terminal from the tip and ring lines;

c) a digital signal processor coupled with the digital access arrangement and comprising

i) an analog to digital converter for converting analog signals from the reception stage to digital receive signals,

ii) a demodulator for demodulating the digital receive signals in accordance with an ADSL demodulation technique,

iii) a modulator for modulating a digital signal in accordance with an ADSL modulation technique,

iv) a digital to analog converter for converting digital signals from the modulator to analog signals provided to the transmission stage, and

v) an echo cancellation facility for removing a transmitted signal from a received signal; and

d) a controller, arranged between the terminal and the digital signal processor, for controlling the rate of data exchanged between the digital signal processor and the terminal.