Echo cancellation device for full duplex communication systems

• US 7,304,961 B2
• Filed: 06/07/2004
• Issued: 12/04/2007
• Est. Priority Date: 10/23/2003
• Status: Active Grant

• Current Assignee: Realtek Semiconductor Corp.
• Original Assignee: Realtek Semiconductor Corp.
• Inventors: Huang, Chen-Chih, Huang, Chih-Wen
• Primary Examiner(s): SINGH, RAMNANDAN P
• Application Number:
  US10/709,935
• Publication Number:
  US 20050099966A1
• Time in Patent Office: 1,275 Days
• Field of Search: None
• US Class Current: 370/286
• CPC Class Codes: H04B 3/23 using a replica of transmitted signal in the time domain, e.g. echo cancellers

Abstract

An echo cancellation device for a full duplex communications system is provided. The full duplex communication system has a transmitter for transmitting a transmit signal and a receiver for receiving a receive signal. The echo cancellation device has a filter for outputting a filter signal according to the transmit signal, an echo cancellation circuit connected to the filter for outputting an echo cancellation signal according to the filter signal, at least one echo cancellation resistor connected to the transmitter, the receiver, and the echo cancellation circuit, and an echo cancellation detection circuit for outputting a control signal according to an echo residue at the receiver to control the filter.

Claims

1. An echo cancellation device for use in a full duplex communication system, wherein the full duplex communication system comprises a transmitter for transmitting a transmit signal and a receiver for receiving a receive signal, the echo cancellation device comprising:

a filter for outputting a filtering signal according to the transmit signal;

an echo cancellation circuit electrically coupled to the filter for outputting an echo cancellation signal according to the filtering signal; and

at least an echo cancellation resistor electrically coupled to the transmitter, the receiver, and the echo cancellation circuit;

wherein the filter has a transfer function, and the transfer function is corresponding to a parasitic capacitance.

2. The echo cancellation device of claim 1, wherein the echo cancellation signal corresponds to the transmit signal.

3. The echo cancellation device of claim 1 further comprising a digital-to-analog converter.

4. The echo cancellation device of claim 1, wherein the filter further comprises a digital low pass filter.

5. The echo cancellation device of claim 1, wherein the filter further comprises an analog low pass filter.

6. The echo cancellation device of claim 1 further comprising an echo residue detection circuit for outputting a control signal to control at least a characteristic of the filter according to an echo residue received by the receiver.

7. The echo cancellation device of claim 6, wherein the filter is a finite impulse response (FIR) filter and the characteristic is at least a coefficient of the FIR filter.

8. The device of claim 6, wherein the filter is a infinite impulse response (IIR) filter and the characteristic is at least a coefficient of the IIR filter.

9. The echo cancellation device of claim 6, wherein the filter is a resistor-capacitor (RC) network low pass filter and the characteristic is the resistance of the resistor or the capacitance of the capacitor.

10. An echo cancellation device for use in a full duplex communication system, wherein the full duplex communication system comprises a transmitter for transmitting a transmit signal and a receiver for receiving a receive signal, the echo cancellation device comprising:

a filter for outputting a filtering signal according to the transmit signal;

an echo cancellation circuit electrically coupled to the filter for outputting an echo cancellation signal according to the filtering signal;

at least an echo cancellation resistor electrically coupled to the transmitter, the receiver, and the echo cancellation circuit; and

an echo residue detection circuit for outputting a control signal to adjust the filter according to an echo residue received by the receiver;

wherein the filter has a transfer function, and the transfer function is corresponding to a parasitic capacitance.

11. The echo cancellation device of claim 10, wherein the echo cancellation signal corresponds to the transmit signal.

12. The echo cancellation device of claim 10 further comprising a digital-to-analog converter.

13. The echo cancellation device of claim 10, wherein the filter further comprises a digital low pass filter.

14. The echo cancellation device of claim 13, wherein the digital low pass filter is a finite impulse response (FIR) filter and the FIR filter is adjusted through adjusting at least a coefficient of the FIR filter.

15. The echo cancellation device of claim 13, wherein the digital low pass filter is a finite impulse response (IIR) filter and the IIR filter is adjusted through adjusting at least a coefficient of the IIR filter.

16. The echo cancellation device of claim 10, wherein the filter further comprises a RC network filter.

17. The echo cancellation device of claim 16, wherein the RC network filter further comprises a resistor.

18. The echo cancellation device of claim 17, wherein the resistor is implemented by a MOS transistor.

19. The echo cancellation device of claim 18, wherein the RC network filter is adjusted through adjusting a gate voltage applied to the gate electrode of the MOS transistor.

20. The echo cancellation device of claim 16, wherein the RC network filter comprises a capacitor.

21. The echo cancellation device of claim 20, wherein the capacitor comprises a parasitic capacitor.

22. The echo cancellation device of claim 20, wherein the RC network filter is adjusted through adjusting the capacitance of the capacitor.