The primary purpose of this paper is the improved detection of a nonstationary target signal embedded in a nonstationary background. Accordingly, the first part of the paper is devoted to a detailed exposition of how to deal with the issue of nonstationarity. The material presented here starts with Loève’s probabilistic theory of nonstationary processes. From this principled discussion, three i...

The on-axis image irradiance obtained from a radially symmetric optical system under broadband illumination is analysed in the phase-space domain of the Wigner distribution function associated with a modified one-dimensional pupil aperture. To this end, a coordinate transformation is employed in such a way that the varying on-axis irradiance can be derived from different slices of a two-dimensi...

In this paper, an improved joint time-frequency (TF) analysis method based on a reassigned smoothed pseudo Wigner-Ville distribution (RSPWVD) has been proposed in interference detection for Global Navigation Satellite System (GNSS) receivers. In the RSPWVD, the two-dimensional low-pass filtering smoothing function is introduced to eliminate the cross-terms present in the quadratic TF distributi...

The Wigner-Ville Distribution (WVD) is a promising method for analyzing frequency variations in seismic signals, including those of interest for structural monitoring. Nonlinearities in the force displacement relationship will temporarily decrease the apparent natural frequencies of structures during strong to moderate excitation, and earthquake damage can permanently change building stiffnesse...

We are investigating passive radar imaging of aircraft using reflected TV signals. UHF-band ISAR imaging requires wide-angle data to produce good cross-range resolution. We show that direct Fourier reconstruction (DFR) causes degradation of the reconstructed image due to aspect-dependent scattering. We find that a Smoothed Pseudo Wigner-Ville distribution (SPWVD) applied in the cross-range dire...

It has been shown that detailed information from non-stationary signals such as speech are better represented by an acoustic image, a two dimensional feature representation [10]. Several time frequency representations such as the spectrogram, Wigner-ville and choi-williams distribution have been proposed [6] while the acoustic images based on the two dimensional root cepstrum analysis (TDRC) is...

In case of a strong frequency modulated interference in a spread spectrum communication system, the interference can be effectively suppressed by applying a time-varying notch filter with its zero(s) placed at an instantaneous frequency (IF) estimate of the interference. In this paper, we present the use of a timevarying autoregressive model based IF estimator in such a scenario. We model the r...