Patent ID: 8103711

Claim:
An infinite impulse response filtering system to allow DC using a complex input signal having a real and imaginary part of the complex input signal y r and y i to produce a real part of a dispersion-compensated signal X r comprising: a Hilbert transformer for filtering one of a real and imaginary part of the complex input signal; a first circuit for subtracting the filtered imaginary part of y i from the real part y r and filtering a difference signal Z 1 to produce a filtered real signal w 1 ; a second circuit for summing the filtered imaginary signal y i and the real part of the input signal y r and filtering and time reversing a summation Z 2 to produce a filtered imaginary signal w 2 , the second circuit comprising: a first summing device for summing the input signal y r with the filtered input signal y i from the Hilbert transformer to produce a real signal z 2 ; a first time reversal device connected with an output of the second summing device for time reversing the signal z 2 ; this time-reversal device operates as a first-in-last-out stack where the first stored sample is the last to be fed into the subsequent infinite-impulse-response filter; a first real-coefficients infinite impulse response filter connected with the output of the first time reversal device to filter the signal from the first time-reversal device; and a second time reversal device connected to an output of the real-coefficients infinite impulse response filter to produce the signal w 2 ; and a first output summing device for summing the real and the imaginary filtered signal w 1 and w 2 to produce the real part of a dispersion-compensated signal X r .