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The electromagnetic scattering of a plane wave by a penetrable (e.g., dielectric) or impenetrable (e.g., metallic) sphere concentric with a thin metallic disk is considered, in the frequency domain. At low and intermediate frequencies, either separation of variables and mode matching with matrix truncation or a direct numerical approach such as the MoM is adopted, while at high frequencies a combination...
Radar measurements of a radar calibration sphere test target suspended in sea surface multipath propagation conditions are reported. Wideband measurements together with high range resolution (HRR) processing were employed to resolve the direct reflection component and sea surface reflected multipath components of the received signal. The temporal correlation characteristics of the resolved single...
Through-the-wall radar imaging attempts to image complex scenes within enclosed structures. While most of the high-resolution imaging techniques assume point targets, indoor imaging requires dealing with single or multiple walls which are extended targets in nature and violate the point-target assumption. In order to provide high quality imaging, we need to consider point targets and extended targets...
Planar electromagnetic lenses like the Rotman lens are attractive candidates for beambeam forming networks forming networks because of their high bandwidth of operation and their capability to form multiple beams at lower cost as comparable electronic phase shifting networks. The principles of Rotman lenses have been studied for several decades and examples have been successfully built using different...
The capabilities in imaging for forward-looking radar receivers are severely limited so far. This application gap is especially valid for monostatic radars due to their problem producing a significant Doppler shift orthogonal to the direction of illumination. So a two-dimensional resolution of an area of investigation is nearly unattainable. Here bistatic configurations with separated receiver and...
The effects of velocity change, refraction and absorption all must be considered for through-the-wall radar, which can displace the target and defocus in imaging. Based on signal propagation model in presence of the wall and the system concept, the relationship is obtained among the transmit signal, target position and the wall transfer function. In this paper, we will present a method to estimate...
Radar detection of cosmic ray air showers has been discussed for 60 years, but never clearly observed. The topic was reexamined by Gorham in 2001 and some serious simulations were done by Takai, who also initiated the Mariachi project utilizing commercial television transmissions as a signal source. The air showers from ultra-high energy cosmic rays are expected to generate a plasma with plasma frequency...
An algorithm based on the exact maximum likelihood (ML) estimator for retrieving the mean stem volume of mature forest stands on relatively flat ground is presented. A VHF-band forest backscatter model at the individual tree level is used to derive the algorithm. The model interprets the tree trunk volume as a random variable and employs a concept of random forest reflection coefficient to characterize...
Multiple images due to a properly separated CEP plane and a partially reflecting surface are used for the analysis and synthesis of a monopulse array antenna. The interest of such a configuration arises from the very good performances one can achieve by using a reduced number of radiating elements, and the subsequent simplification of the feeding network. Also, the periodical behavior with wavelength...
In recent years, the use of radar technology has been proposed in a wide range of subsurface imaging applications. Traditionally, linear scan trajectories are used to acquire data in most subsurface radar scenarios. However, novel subsurface radar applications, such as breast microwave imaging and wood inspection, require the use of non linear scan trajectories in order to adjust to the geometry of...
Strong interest in radar absorbing materials (RAMs) took place with years due to their extensive sectors of application. RAMs are coatings whose electric and magnetic properties allow the absorption of microwave energy over certain frequencies. In particular, RAMs are very effective means of Radar Cross Section (RCS) reduction in the context of stealth technology. RCS reduction requires absorbers...
In calculating the antenna system noise temperature the question always arises as to how to account for the antenna mismatch. In this paper it is shown that the antenna mismatch introduces another term into the antenna system temperature equation. This term increases the system temperature. It is due to the reflection of the noise coming out of the receiver in the direction of the antenna that is...
MTI radar systems and signal processing algorithms may be made more efficient if a wide range of perfect and background distorted Doppler signatures could be made available to test system hardware and algorithms. This paper addresses emulators of moving vehicle Doppler signatures. Measured Doppler spectra of tracked and wheeled vehicles are used to guide the development of moving target emulators...
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