Method and apparatus for time varying spectrum analysis

A signal analyzer, comprising:

• a source of a sequence of digital signals representative of an input signal;
• a first processor, coupled to the source, for computing orthogonal-like discrete Gabor transform coefficients C.sub.m,n in response to the sequence, and a time-varying spectrum of input signal energy in response to the coefficients;
• and
• a second processor, coupled to the first processor, which processes the spectrum.

A method for computing a time-varying spectrum of an input signal, comprising:

• acquiring a sequence of digital signals representative of the input signal;
• sampling the sequence of digital signals to define a plurality of windows of length L, each window in the plurality including a plurality of digital signals and each window shifted by length .DELTA.M digital signals relative to an adjacent window;
• computing orthogonal-like discrete Gabor transform coefficients C.sub.m,n in sampling intervals .DELTA.N and .DELTA.M, for n=0 through N-1 for each window m, and for the plurality of windows m=0 through M-1, such that .DELTA.N .DELTA.M is less than L;
• computing the time-varying spectrum of energy of the input signal in response to the coefficients C.sub.m,n, and
• analyzing the input signal in response to the time-varying spectrum.

A signal analyzer, comprising:

• a converter, having an input, which generates a sequence of digital signals representative of an input signal supplied to the input;
• input memory means, connected to receive the sequence generated by the converter, for supplying the sequence in a set of overlapping frames;
• first means, coupled to the input memory means, for computing orthogonal-like discrete Gabor transform coefficients C.sub.m,n in response to the set of overlapping frames, by performing a discrete Gabor transform with a localized, gaussian discrete window function h, and a discrete auxiliary function .gamma. similar to h;
• second means, coupled with the first means, for generating a time-varying spectrum of input signal energy in response to the coefficients by computing a cross-terms deleted Wigner-Ville distribution;
• and
• analysis means, coupled to the second means, for processing the spectrum.

A signal analyzer, comprising:

• a source of a sequence of digital signals representative of an input signal;
• a first processor, coupled to the source, wherein said first processor comprises:
• a first means including a computation engine for computing an orthogonal-like discrete Gabor transform resulting in coefficients C.sub.m,n based upon a non-periodic, localized discrete window function h, and a discrete auxiliary function .gamma. similar to h;
• and
• a second means comprising:
• a computation engine for computing an energy distribution function for each of the coefficients C.sub.m,n, the energy distribution function including a first factor based upon the magnitude of the Gabor coefficient, and a second factor varying according to the localized discrete window function of the Gabor transform;
• and
• storage means for storing a precomputed table of values used for the second factor of the energy distribution function for a particular coefficient C.sub.m,n computed by the first means, accessible in response to coordinates i, k of factors of the localized discrete window function near coordinates m, n of the particular coefficient;
• and
• a second processor, coupled to the first processor, which processes the energy distribution function.

A signal analyzer, comprising:

• a source of a sequence of digital signals representative of an input signal;
• a first processor, coupled to the source, wherein said first processor comprises:
• a first means including a computation engine for computing an orthogonal-like discrete Gabor transform resulting in coefficients C.sub.m,n based upon a non-periodic, localized discrete window function h, and a discrete auxiliary function .gamma. similar to h;
• and
• a second means comprising:
• a computation engine for computing an energy distribution function for each of the coefficients C.sub.m,n, the energy distribution function including a first factor based upon the magnitude of the Gabor coefficient, and a second factor varying according to the localized discrete window function of the Gabor transform;
• and
• means for determining an update region for each coefficient C.sub.m,n in response to the first factor, wherein the distribution for each coefficient is computed within the determined update region;
• and
• a second processor, coupled to the first processor, which processes the energy distribution function.

A signal analyzer, comprising:

• a source of a sequence of digital signals representative of an input signal;
• an input buffer system connected to receive the sequence supplied by the source;
• a first processor, coupled to the input buffer which receives the sequence from the input buffer, wherein the input buffer supplies the sequence to the first processor in a set of overlapping frames, wherein the first processor computes orthogonal-like discrete Gabor transform coefficients C.sub.m,n in response to the sequence, and a time-varying spectrum of input signal energy in response to the coefficients;
• and
• a second processor, coupled to the first processor, which processes the spectrum.