US 4,231,103 A · Fast Fourier transform spectral analysis system employing adaptive window

Abstract

A spectral analysis system includes a Fast Fourier Transform (FFT) processor which receives a time domain signal and provides a specified number of initial signal strength estimates, each of the initial estimates being equal to one of the frequency domain coefficients of the Fast Fourier Transform of the time domain signal which is generated when the time domain signal is sampled at a number of intervals equal to the number of initial estimates, over a time period of specified duration. The system further includes an adjustable window element receiving a selected number of the initial estimates for sensing or detecting the presence of a leakage component in a given one of the initial estimates, and for providing an adjusted signal strength estime, the adjusted signal strength estimate comprising the difference between the given initial estimate and the leakage component. A spectral recorder receiving a number of adjusted estimates is provided to record the spectral lines, or frequency components, of the time domain signal, and the relative strengths thereof.

Claims16

Dependent claims

Spectral analysis apparatus comprising:

a Fast Fourier Transform processor receiving a time domain signal for providing the frequency domain coefficients of the Fast Fourier Transform of said time domain signal which is generated when said processor is operated to sample said time domain signal at a specified number of intervals over a time period of specified duration, each of said coefficients comprising an initial estimate;
a selected number of adjustable window means, a given one of said adjustable window means receiving a selected number of said initial estimates for sensing the presence of a leakage component in a given one of said received initial estimates, and for providing an adjusted signal strength estimate, said adjusted signal strength estimate comprising the difference between said given received initial estimate and said sensed leakage component;
and
means for monitoring the adjusted signal strength estimate of said given adjustable window means, and also for monitoring other adjusted signal strength estimates provided by the remaining adjustable window means.

1 more element

Spectral analysis apparatus comprising:

means for sampling a signal received by said apparatus at a selected sampling rate;
filter means receiving a specified number of samples of said received signals during a specified time period for providing initial estimates of the strength of said signal at selected discrete frequencies in a range of frequencies;
a number of adjustable window means, each of said initial estimates uniquely corresponding to a different one of said adjustable window means, each of said window means receiving its corresponding initial estimate and also receiving a selected number of non-corresponding initial estimates, a given one of said window means for selectively weighting each of its received non-corresponding initial estimates to minimize a given window means output, said given window means output comprising the sum of the corresponding initial estimate and the weighted non-corresponding initial estimates of said given window means;
and
spectral recording means receiving a window means output from each of said window means for recording the strength of said received signal at each of said discrete frequencies.

2 more elements

A method for spectral analysis comprising the steps of:

sampling a received signal at a selected sampling rate;
carrying out a Fast Fourier Transformation upon a specified number of samples of said received signal during a specified time period to provide a number of initial estimates of the strength of said received signal at selected discrete frequencies in a range of frequencies;
weighting each of the initial estimates which is included in a set of selected initial estimates by variable weighting values, at least one of the initial estimates provided by the Fast Fourier Transform being excluded from said set;
adjusting said weighting values to minimize the variance of said weighted initial estimates and said excluded initial estimate, said variance comprising one of the adjusted signal strength estimates in a set of adjusted signal strength estimates;
repetitively performing said weighting and adjusting steps to determine each of the remaining adjusted signal strength estimates in said adjusted estimate set;
and recording each of said adjusted signal strength estimates in said adjusted estimate set.

3 more elements

Dependencies are inferred from the claim text.

Fast Fourier transform spectral analysis system employing adaptive window

Life of this patent

Fast Fourier transform spectral analysis system employing adaptive window

Life of this patent

Abstract

Claims16