Nyquist filter for use in a joint VSB/QAM demodulator

Details Nyquist filter for use in a joint VSB/QAM demodulator Nyquist filter for use in a joint VSB/QAM demodulator

1995-03-02

1997-07-15

Malzahn, David H.

Boots, shoes, and leggings

36472413, G06F 1710

Patent

active

056489234

ABSTRACT:
A Nyquist filter implemented as a FIR filter comprising a series of N filter cells, where N is an integer is disclosed. The Nyquist filter is especially well suited for use in demodulators capable of demodulating both VSB and QAM signals. During VSB mode operation, each filter cell acts as a single tap of an N tap Nyquist filter. During QAM mode operation, an additional unit delay element, not used during VSB mode operation, is inserted into the signal path of each cell of the Nyquist filter. The introduction of this second unit delay element into the signal path of each filter cell effectively serves to convert each filter cell into two filter taps with the coefficient of the second filter tap being zero. Thus, during QAM mode operation, the Nyquist filter of the present invention operates as a 2N-tap FIR filter which has coefficients of zero for half of the 2N taps.

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