Dr. Nashashibi specializes in millimeter-wave (MMW) radar remote sensing and the development of associated instrumentation sensors with emphasis to target detection applications. He is in the forefront of efforts to characterize both wave propagation through foliage and the radar return from different types of terrain at MMW frequencies. He is a Co-Investigator on several research projects. His responsibilities include management, research, and supervision of both graduate and undergraduate students. He developed a new, ultra-fast, wide-band MMW, polarimetric, instrumentaton radar system for remote sensing applications. This system has become the backbone for many research efforts at the University of Michigan. Under the Federated Laboratories Project, sponsored by ARL, he led a multi-year effort to characterize the MMW backscatter return from clutter at near-grazing incidence. This effort resulted in a first-of-a-kind, web-accessible, database of clutter return at MMW frequencies. The database is currently used by more than 17 researchers from the academy, the government, and the industry to develop clutter models and to test target recognition algorithms. He contributed to the development of theoretical and/or empirical models of bare-soil surfaces, snow and grass-covered surfaces, and tree trunks. He contributed to the development of detection and classification technique of point targets in the presence of clutter based on the frequency correlation function of the radar return measured at grazing incidence. In addition, he developed a technique to retrieve the propagation parameters of millimeter-waves in foliage using a monostatic radar. The observed large, but “finite”, attenuation over short distances inside the foliage encouraged further research on the detectability of targets hidden behind foliage. Under a DARPA sponsored project, Dr. Nashashibi led the research effort to demonstrate the potential application of millimeter-wave, nadir-looking radars for the detection of man-made objects under significant foliage-cover. In addition to data collection and analysis, he developed a robust target detection algorithm for nadir-looking real-aperture MMW radars. He also exploited the temporal de-correlation properties of foliage to develop a target detection technique for MMW polarimetric radars operating at grazing incidence.
Millimeter-wave Monostatic Radar Phenomenology at Near-Grazing Incidence:
Under the Federated Laboratories Consortium program, funded by the Army Research Laboratory, with Prof. F.T. Ulaby as the PI, Dr. Nashashibi led a multi-year outdoor measurement campaign aimed at characterizing the polarimetric MMW radar backscatter of clutter at near-grazing incidence. The outcome of this effort is a comprehensive, first of a kind database that is essential for the validation of automatic target recognition algorithms. Statistics of the radar return at near-grazing were investigated and the dynamic ranges of the radar return from different types of clutter were determined. In addition, theoretical and/or empirical models of clutter radar returns (bare soil, snow-covered, and grass-covered surfaces, and tree trunks) were developed. A journal paper describing a new theoretical model of MMW radar backscatter response of snow during its diurnal cycle is being prepared. In addition, a detection and classification technique of point targets in the presence of clutter, based on the frequency correlation function of the radar return measured at grazing incidence, was developed. A technique to retrieve the propagation parameters of millimeter-waves in foliage using a monostatic radar was also developed.
Dr. Nashashibi has also designed and constructed a novel ultra-fast, wide-band, instrumentation radar system operating at 35-GHz and 95-GHz frequencies. The system has become the backbone of several research efforts at the University of Michigan. He also supervised the design and construction of a 35-GHz correlation receiver intended for measuring the phase-defect due to propagation through foliage, and for the measurement of the height interference pattern used to characterize line-of-sight communication channels at 35-GHz.
Foliage Penetration at Millimeter-wave Frequencies:
Dr. Nashashibi has led the effort in investigating the potential application of millimeter-wave, monostatic, high resolution, polarimetric, nadir-looking radars to the detection of man-made objects under foliage cover. This application was reserved in the past for ultra wide-band, low frequency, radars. In collaboration with the Army Research Lab., several measurement campaigns were conducted during the summer of 2000, on real targets under different types of foliage-cover. In addition, a robust target detection algorithm was developed and basic studies into foliage attenuation and signal coherence were performed. A journal paper on the foliage attenuation and ground the reflectivity observed in these measurements has been submitted for review and another paper on the new detection technique is being prepared. This project was funded by DARPA under a contract with the Army Research Office.
Millimeter-wave Radar Detection of Targets Concealed Behind Foliage:
Dr. Nashashibi exploited the temporal de-correlation properties of foliage to develop a technique for detecting targets positioned behind trees using polarimetric millimeter-wave radars. In addition, he exploited the radar return from foliage to estimate the attenuation through it and retrieve the true RCS of the concealed target. The effort included indoor and outdoor experimental validation. A journal paper is being prepared.
Millimeter-wave Bistatic Radar Phenomenology:
Under the advanced Sensors-Collaborative Technology Alliance program, Dr. Nashashibi has modified an existing indoor bistatic measurement facility so that 35-GHz bistatic measurements can be performed. He is currently supervising the experimental effort to characterize the polarimetric bistatic return from natural surfaces and is investigating the detectability of man-made objects, such as low-flying objects, using bistatic radars.