Variable gain echo suppressor

Abstract

A variable gain echo suppressor is provided that utilizes two variable attenuators (410) and (412) that are disposed in the receive and transmit paths, respectively, of a communication system. An echo suppressor (414) receives the input from the far end and transmits the output from the near end and controls the two attenuators to set a variable gain therein. The echo suppressor utilizes a normalized power level which is normalized with respect to the background noise at the respective end and then takes the ratio of this normalized power and the normalized power at the opposite end to define an associated power ratio. This power ratio value is utilized to determine the attenuation for the associated end. When the power ratio is high, this indicates that a stronger signal is being received from that end and a small amount of attenuation is associated in the transmit path from that end. When they aye equal, this will result in both systems having approximately the same attenuation, a mid-level attenuation. This is provided through a look up table (450) for the far end and a look up table (452) for the near end. Additionally, the signal power is derived from a peak detection IIR filter (420) and (428) which has the characteristics thereof changed as a function of the power ratio. This is achieved by changing the value of the pole in the IIR filter.

Dependencies are inferred from the claim text.