WIGNER

WIGNER - pseudo wigner distribution

Usage:

WIGNER X NSMT NFIR NFFT

Inputs:

X	input signal, no default (must contain an odd number of samples)
NSMT	smoothing length, default=7 (must be odd, automatic correction)
NFIR	fir filter length, default=7 ( must be odd, automatic correction)
NFFT	fft length, default=2M >= NX, (automatic correction)

Outputs:

Y	smoothed pseudo Wigner distribution (SPWD) in dB

Function:

This atom computes the smoothed pseudo Wigner distribution (SPWD) of the signal X. The time and frequency resolution depends on the parameters NSMT (smoothing length), NFIR (FIR filter length for the computation of the analytical signal) and NFFT (FFT length), and on the length of the input vector NX. The computed SPWD (in dB) consists of NFFT values and is stored in the output vector Y. This implementation of the SPWD is based on the algorithms published by W. Wokurek in his doctor thesis. The picture below shows the content of the frame buffer (input signal) X.

Figure 7: Analysis frame of the Wigner distribution

with:

NX	length of input signal X, frame length
NFIR	length of FIR filter for the computation of the analytical signal
NSMT	length of time smoothing window
NWDW	length of analysis window; the length of the analysis window is a basic parameter of the Wigner distribution. However, in this implementation it cannot be specified directly, rather it is derived from NX, NSMT and NFIR: NWDW = (NX-1)-(NSMT-1)-(NFIR-1)+1