Method and apparatus for frequency analysis of telephone signals
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United States of America Patent
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Jun 5, 1990
Grant Date -
N/A
app pub date -
May 15, 1989
filing date -
May 15, 1989
priority date (Note) -
Expired
status (Latency Note)
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Abstract
For faster realtime analysis related to Discrete Fourier Transform (DFT), prestored pre-multiplied values of amplitude times cosine and sine functions are used. Method and apparatus for determining the content of a predetermined frequency bin f in the frequency spectrum of a signal and, in particular, a signal which occurs in a telephone network, includes the step of storing on a storage means: C.sub.k (x.sub.k,n)=x.sub.k *cos(2.pi.kn/N) and S.sub.k (x.sub.k,n)=x.sub.k *sin(2.pi.kn/N) for: k=0, . . . , (N-1); n=0, . . . , (n-1); and x.sub.k ranging over all the values of the set of M predetermined digital levels into which the amplitude of the signal is mapped, if the signal is a digital signal, or into which a sample of the amplitude of the signal is mapped, if the signal is an analog signal. N is a predetermined number of amplitudes or samples of the amplitude of the signal which are used in analyzing the frequency spectrum and n is a frequency index.
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