Claims
- 1. An apparatus for increasing the dynamic range of a receiver in a communications system, comprising:a transmit path and a receive path for communicating data; an analog to digital (A/D) converter disposed in communication with the receive path, wherein the AID converter operates at a first sampling rate; a first echo canceller in communication with the receive path that operates at the first sampling rate for estimating a portion of an echo signal leaking from the transmit path to the receive path; a decimator disposed in communication with the receive path, whereby the decimator filters an incoming signal having the first sampling rate on the receive path and emits a signal output at a reduced sampling rate; and a second echo canceller in communication with the output from the decimator for generating an echo replica estimation of an echo signal leaking from the transmit path to the receive path, wherein the second echo canceller operates at the reduced sampling rate and operates to estimate the remaining echo signal leaking from the transmit path to the receive path.
- 2. The apparatus of claim 1, further comprising:an adder disposed in communication with the receive path and configured to subtract the output of the first echo canceller from the output of the A/D converter; and an adder disposed in communication with the receive path and configured to subtract the output of the second echo canceller from the output of the decimator.
- 3. The apparatus of claim 2, further comprising:a digital gain disposed in communication with the receive path and configured to amplify the signal amplitude output from the first adder.
- 4. The apparatus of claim 3, wherein the signal amplitude is increased by the digital gain such that the signal communicated on the receive path is unclipped.
- 5. The apparatus of claim 2, further comprising:a digital gain disposed in communication with the receive path and configured to amplify the signal amplitude output from the second adder.
- 6. The apparatus of claim 1, wherein the resolution of the decimator is less than the resolution of the A/D converter.
- 7. The apparatus of claim 1, wherein the first echo canceller operates to reduce the signal amplitude input to the decimator.
- 8. The apparatus of claim 1, wherein the first and second portions of the echo signal comprise the complete echo signal present on the receive path.
- 9. The apparatus of claim 1, further comprising:a computer in communication with the receiver and coupled to a network.
- 10. An method for increasing the dynamic range in a receiver in a communications system, comprising the steps of:receiving an analog signal on a receive path for communicating data; converting the received analog signal to a digital signal at a first sampling rate; estimating a first portion of an echo signal leaking from a transmit path in the receiver to the receive path, wherein the first portion of the echo signal is subtracted from the converted digital signal; reducing the first sampling rate of the converted digital signal to a reduced sampling rate; and estimating a second portion of an echo signal leaking from the transmit path in the receiver to the receive path, wherein the second portion of the echo signal is subtracted from the converted digital signal at the reduced sampling rate.
- 11. The method of claim 10, further comprising the step of:increasing the signal amplitude of the converted digital signal after the first portion of the echo signal is subtracted from the converted digital signal.
- 12. The method of claim 1, wherein the amplitude of the converted digital signal is increased by an amount whereby the converted digital signal is unclipped.
- 13. The method of claim 12, wherein the amplitude of the converted digital signal is increased by up to 12 dB.
- 14. The method of claim 10, further comprising the step of:increasing the signal amplitude of the converted digital signal after the second portion of the echo signal is subtracted from the converted digital signal at the reduced sampling rate.
- 15. The method of claim 10, wherein the first echo portion subtracted from the converted digital signal reduces the amplitude converted digital signal by up to 12 dB.
- 16. The method of claim 10, wherein the sampling rate is reduced at a rate of three to one.
- 17. The method of claim 10, wherein the first and second portions of the echo signal comprise the complete echo signal present on the receive path.
- 18. An system for increasing the dynamic range in a receiver in a communications system, comprising:a transmit path and a receive path for communicating data; means for converting the received analog signal to a digital signal at a first sampling rate; means for estimating a first portion of an echo signal leaking from a transmit path in the receiver to the receive path, wherein the first portion of the echo signal is subtracted from the converted digital signal; means for reducing the first sampling rate of the converted digital signal to a reduced sampling rate; and means for estimating a second portion of an echo signal leaking from the transmit path in the receiver to the receive path, wherein the second portion of the echo signal is subtracted from the converted digital signal at the reduced sampling rate.
- 19. The system of claim 18, further comprising the step of:means for increasing the signal amplitude of the converted digital signal after the first portion of the echo signal is subtracted from the converted digital signal.
- 20. The system of claim 18, wherein the first and second portions of the echo signal comprise the complete echo signal present on the receive path.
CROSS-REFERENCE TO RELATED APPLICATIONS
This application claims the benefit of U.S. Provisional Application Serial No. 60/255,602, filed Dec. 14, 2000, and entitled “Dual Echo Canceller Increases Dynamic Range of a Receiver,” which is hereby incorporated by reference.
US Referenced Citations (3)
Number |
Name |
Date |
Kind |
5917809 |
Ribner et al. |
Jun 1999 |
A |
6421377 |
Langberg et al. |
Jul 2002 |
B1 |
6625279 |
Eom |
Sep 2003 |
B1 |
Provisional Applications (1)
|
Number |
Date |
Country |
|
60/255602 |
Dec 2000 |
US |