Patent ID: 6954771

Claim:
An adaptive line enhancer comprising an adaptive Gray-Markel lattice notch filter having an adaptive notch frequency, said adaptive Gray-Market lattice notch filter having a transfer function: H lattice = N ⁡ ( z ) D ⁡ ( z ) = ( 1 + α 2 ) ⁢ 1 + 2 ⁢ k 0 ⁢ z - 1 + z - 2 1 + k 0 ⁡ ( 1 + α ) ⁢ z - 1 + α ⁢ ⁢ z - 2 , in which the notch frequency is determined according to a notch frequency variable k, characterized in that said adaptive line enhancer further comprises means for determining a value of k for the n+1 th sample period according to the following equation: k ( n+ 1)= k ( n )−sgn[ y ( n )]sgn[UPDATEFN]×μ in which y(n) is a notch filter output, μ is an adaptation constant, and UPDATEFN has a transfer function in the z-transform domain of: ( α - 1 ) ⁢ ( k ⁡ ( n ) - 1 ) ⁢ z - 1 1 + k ⁡ ( n ) ⁢ ( 1 + α ) ⁢ z - 1 + α ⁢ ⁢ z - 2 where α determines a bandwidth and k(n) is a variable for determining a current notch frequency.