公开(公告)号：EP0998787A1

公开(公告)日：2000-05-10

申请号：EP98933120.2

申请日：1998-07-02

申请人： Cirrus Logic, Inc

发明人： CHADHA, Mandeep ,  McCASLIN, Shawn ,  CAMAGNA, John ,  HEMKUMAR, Nariankadu, Datatreya

IPC分类号： H03H21/00 ,  H03H17/02

CPC分类号： H03H17/0238 ,  H03H17/0227 ,  H03H21/0012

摘要： An adaptive filter is provided which has fixed point or floating point data stored in a data RAM (74) and block scale floating point coefficients stored in a coefficient RAM (84). The data and coefficients are utilized in a filter algorithm which utilizes a multiplier and an accumulator to provide a convolution result. Coefficients are uptdated by adding the multiplied result of the data RAM value and the error value to the old value of the coefficient. This is done for all the coefficient values in the coefficient RAM. The error value indicates the difference between the filter output and the sample near-end signal that is the echo. These new coefficients are examined and if any have a value above or all have a value below a predetermined threshold, then the mantissas of all the coefficents are shifted and the exponent adjusted in the next filter cycle.