Initialization scheme for a hybrid frequency-time domain equalizer
AssigneeKoninklijke Philips Electronics N.V.
InventorDagnachew Birru
Life of this patent
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Abstract
This invention provides a method for initializing the filter coefficients of a hybrid frequency-time domain adaptive equalizer device implementing frequency domain (FD) filter equalization in a forward path and a time domain (TD) filter equalization in a feedback path, with each filter unit having a plurality of adaptable filter taps. Preferably, in initializing the equalizer, the relation 1 + F G = H is obeyed “where (G) is the forward FD equalizer taps, (F) is” the Fast Fourier Transform of the feedback TD equalizer taps, and (H) is the estimated (frequency domain) response of the communications channel.
Claims14
A method for initializing filter coefficients for a hybrid feedback equalizer device for reducing interference of signals transmitted over a communications channel, said hybrid feedback equalizer device implementing frequency domain (FD) filter equalization in a forward path and a time domain (TD) filter equalization in a feedback path, each FD (forward path) and TD (feedback path) filter units having a plurality of adaptable filter taps, said method comprising:
- a) generating an estimated frequency response transfer function (H) of said channel;
- b) performing an inverse Fast Fourier Transform (IFFT) on said channel transfer function (H) to result in a time domain profile of said channel;
- c) limiting energy of each occurrence of post-echoes present said channel to a predetermined value and generating a post-echo profile from said time domain profile;
- d) obtaining a frequency domain representation (A) of the post-echo profile, and
- dividing said frequency-domain representation (A) by “estimated frequency response transfer function (H)” to obtain (A)/(H);
- e) performing an IFFT of (A)/(H) to obtain a time domain representation of the FD equalizer taps and eliminating presence of a predetermined number of taps of said time domain representation of the FD equalizer;
- and,
- f) performing a FFT of the resulting time domain representation of FD equalizer to obtain frequency domain representation of FD equalizer taps (G), whereby said obtained taps are used to initialize the forward FD filter of said hybrid equalizer.
A method for initializing filter coefficients for a hybrid feedback equalizer device for reducing interference of signals transmitted over a communications channel, said hybrid feedback equalizer device implementing frequency domain (FD) filter equalization in a forward path and a time domain (TD) filter equalization in a feedback path, each filter unit having a plurality of adaptable filter taps, said method comprising:
- a) disabling said feedback TD equalizer filter;
- b) generating an estimated frequency response transfer function (H) of said channel;
- c) obtaining time domain representation of equalizer taps in said forward FD equalizer and eliminating taps corresponding to occurrence of post-echoes present in said “estimated frequency response transfer function (H)”;
- d) generating a frequency domain representation (G) of equalizer taps in said forward FD equalizer filter;
- e) generating a frequency-domain representation (F) of the equalizer taps in said feedback TD equalizer filter;
- and,
- f) performing an inverse Fast Fourier Transform (IFFT) on the frequency-domain representation (F) to yield the time-domain feedback equalizer taps, wherein said obtained taps are used to initialize the feedback TD filter coefficients and forward FD filter coefficients of said hybrid equalizer, respectively.
Dependencies are inferred from the claim text.