M. Dawood

Estimation of Power Extinction Factor in Presence of Brillouin Precursor Formation Through Dispersive Media

In this paper, we analyze the advantages of the Brillouin precursor formation through dispersive media for a given modulated monopulse signal. The algebraic power extinction factor associated with the formation of Brillouin precursor appears to be in charge of the optimized propagation distance within the dispersive media. The analysis has been done in UHF band for rectangular and Gaussian pulses for three different dispersive media, namely, triple distilled water, vegetation and soil. It appears that Brillouin precursors will form given a suitable pulse configuration within a proper frequency window that is related to the dielectric model of the underlying media.

Low sidelobe level radar techniques using Golay based coded sequences

A radar system operating at a carrier frequency of 500 MHz and using different coded sequences is built and tested at NMSU. A limited set of experimental results at various ranges for both sequences: pseudorandom binary sequences (PRBS) and Golay were obtained and the comparison between them was done. Our tests indicate, though not conclusively, that Golay sequence seems to offer lower sidelobe level than PRBS sequences. Moreover, Golay sequences may yield higher dynamic range and results in improvement in estimation of the delay spread.

Brillouin precursors through concrete walls for through-the-wall imaging at microwave frequencies

This paper discusses the Brillouin precursor formation in concrete, using the experimentally measured dielectric constant and loss tangent from 10 MHz - 3 GHz. Brillouin precursors are obtained at three carrier frequencies. Experimental data is also compared with the extended Debye model for concrete in the same frequency range.

Design and implementation of a golay-based GPR system for improved subsurface imaging

A bench-top prototype GPR using Golay codes has been designed and implemented. The preliminary experimental results show a reasonable good improvement in terms of SNR. This work is still in progress. Improvements related to some of the other components and subsystems are underway. In particular, we are experimenting with innovative antenna designs having minimum influence on the transmitted waveform, and improved image processing algorithms.

Breast cancer detection utilizing Brillouin precursors at microwave frequencies

For early detection of breast cancer, ultrawideband microwave imaging techniques, among others, are a useful tool. This paper presents some of our numerical results showing the formation of Brillouin precursors from the back-scattered components of the microwave electromagnetic waves propagating through both normal and malignant breast tissues. The advantageous nature of these precursors is also highlighted.

Brillouin precursor waveforms pertaining to UWB noise radar signals propagating through dispersive media

The electromagnetic (EM) waves propagating through causal, linear, and lossy dispersive media (soil, foliage, plasma, water, biological tissue, etc.), experience frequency-dependent attenuation and phase distortion. This has assumed significant importance for systems operating with ultrawideband (UWB) spectrum. This paper analyzes the dynamical evolution of UWB noise radar signals through dispersive media. The effects on the signal propagation due to the evolution of the Brillouin precursor through dispersive media are discussed. The evolving waveforms are then compared with the Brillouin precursor due to rectangular sine-modulated deterministic signals. The advantages of random noise waveforms through dispersive media are also discussed.

Development of 3D human tissues phantoms for analysis of frequency dispersion and human body interaction at 60GHz

Dispersive propagation could result of particular importance in the case of technologies involving human tissues. High-resolution systems as employed in medical imaging require the use of ultra wide band waveforms and for such pulses the medium is inherently dispersive. This will unavoidably lead the Brillouin or Sommerfield precursors to emerge even if they are not explicitly visible. However its analysis is not considered in body-centric radio channel characterization and models. For intra-body communications, the form and shape of the information-bearing transmitted signal is also an important factor to consider (Alejos, et al., JEMWA, 27(17), 2213–2220, 2013). Since the transmitted signal influences the formation and performance of the resulting precursor, we can conclude that a medium-matched signal can lead to optimal performance by combining the benefits of the precursor formation (larger amplitude) with minor impairments (lesser time duration broadening).

Under-sea remote sensing using Brillouin precursors

In this contribution we propose a remote sensing technique for subsurface imaging through the seawater. The technique is based on the detection and processing of the evolving Brillouin precursors due to the ultrawideband(UWB) input electromagnetic waves traveling through the dispersive seawater and sand. The proposed technique is validated using simulation studies for layered media, i.e. Seawater and sand.