Echo canceller with relative feedback control

• US 4,845,746 A
• Filed: 06/23/1987
• Issued: 07/04/1989
• Est. Priority Date: 06/23/1987
• Status: Expired due to Fees

• Current Assignee: Charles Industries Limited (Amphenol Corporation)
• Original Assignee: Rockwell International Corporation
• Inventors: Li, Chan E.
• Primary Examiner(s): Ng, Jin F.
• Assistant Examiner(s): Vaas, Randall S.
• Application Number:
  US07/065,489
• Time in Patent Office: 742 Days
• Field of Search: 379/345, 379/406, 379/410, 379/411, 379/344, 370/32, 370/32.1
• US Class Current: 379/406.06
• CPC Class Codes: H04B 3/234 using double talk detection
• CPC Class Codes: H04B 3/237 using two adaptive filters, e.g. for near end and for end echo cancelling

Abstract

A method for selecting feedback constants for two echo cancellers in an adaptive 2-wire to 2-wire repeater. The repeater is connected to two networks and when signals are received from both networks, the signal having the greater energy level is identified. A feedback constant of the echo canceller associated with the greater signal is set independent of the feedback constant of the other echo canceller. The feedback constant of the other echo canceller is set as a function of a ratio of the signal energy level of a lesser of to larger of the two signals received from the networks.

Claims

1. A method for selecting feedback constants for at least first and second echo cancellers in a 2-wire to 2-wire repeater connected between first and second networks, said repeater processing a first signal received from the first network to produce a RCVb signal and processing a second signal received from the second network to produce a RCVa signal, comprising:

comparing an energy level of said RCVa signal (energy (RVCa)) to an energy level of said RCVb signal (energy (RCVb)) and if said energy level of said RCVa signal is greater than or equal to the energy level of said RCVb signal, then;

setting a feedback constant, Ka, of the first echo canceller to K1×

(1/energy (RCVa)), where K1 is a first predetermined constant; and

setting a feedback constant, Kb, of the second echo canceller to Kb =Ka ×

K2 ×

(energy (RCVb)/energy (RCVa)), where K2 is a second predetermined constant.

2. The method described in claim 1, wherein said method further comprises, if said feedback constant, Kb, is less than a third predetermined constant, K3, and if the feedback constant, Ka, is greater than zero, setting the feedback constant, Kb, equal to the third predetermined constant, K3.

3. The method described in claim 1, wherein if said energy level of said RCVa signal is less than said energy level of said RCVb signal, then said method further comprises;

setting said feedback constant, Kb, of the second echo canceller to K1 ×

(1/energy (RCVb)); and

setting said feedback constant, Ka, of the first echo canceller to Kb ×

K2 ×

(energy (RCVa)/energy (RCVb)).

4. The method described in claim 3, wherein said method further comprises, if said feedback constant, Ka, is less than said third predetermined constant, K3, and if the feedback constant, Kb, is greater than zero, setting the feedback constant, Ka, equal to said third predetermined constant, K3.