Article

# A Comparison between Standard and Crossfeed Monopulse Radars in Presence of Rough Sea Scattering and Ship Movements

International Journal of Antennas and Propagation (Impact Factor: 0.68). 01/2010; DOI: 10.1155/2010/126757

Source: DOAJ

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**ABSTRACT:**Radar systems often experience difficulties when tracking low-altitude targets over the ocean because of multipath effects. Whenever the radar cannot resolve the target from its image, it will track a false target position which can move far above or below the actual position. In this paper, mathematical models are utilized to quantitatively determine the degradation in tracking ability of a monopulse radar due to multipath. The model incorporates provisions for the antenna sum and difference patterns, including sidelobes, and for the antenna polarization. Divergence factors are utilized to account for the curvature of the earth's lossy surface. More accurate calculations of the phase length of the direct and reflected rays using the spherical earth model are included. Smooth and rough surface models are used to model the prevailing sea state. The smooth surface model determines both stable and unstable equilibrium directions toward which the target position is indicated. The rough surface model defines a band of maximum error in the indicated position, as a function of the surface waveheight, and it includes both the rough specular and the rough diffuse reflection term.IEEE Journal of Oceanic Engineering 02/1987; · 1.16 Impact Factor - [Show abstract] [Hide abstract]

**ABSTRACT:**Formulations are presented to predict the pattern of interference (multipath) between direct rays and those reflected from the surface of the earth. These formulations can be used to assess the performance of ground-to-air, air-to-ground, ground-to-ground, and air-to-air communication and antenna measuring systems. Methods are also introduced to determine accurately the point of reflection and the path phase difference between the direct and reflected waves. Various divergence factors, used to account for energy spreading from a curved surface, are presented and compared. The formulations introduced can account for any polarization state (linear, circular, elliptical), sense of rotation (right hand, left hand), and tilt angle of the transmitting and receiving elements, and for polarization changes due to reflection.IEEE Transactions on Antennas and Propagation 02/1984; · 2.33 Impact Factor -
##### Conference Paper: Statistics of monopulse measurements of Rayleigh targets in the presence of specular and diffuse multipath

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**ABSTRACT:**In tracking of low-elevation targets with a monopulse radar, the presence of reflections from the sea surface causes severe errors in the direction-of-arrival (DOA) measurements of the target. Since the target echoes that are received directly and via the sea surface are unresolved in time and frequency, tracking targets in the presence of sea-surface induced multipath is a special case of tracking unresolved targets. The sea-surface reflection is modeled by a specular (coherent) component and a diffuse (noncoherent) component. The probability density function (pdf) of the measured amplitude of the sum signal and the amplitude-conditioned pdf of the in-phase and quadrature monopulse ratios are given for low-elevation, Rayleigh targets in the presence of sea-surface induced multipath. The means and variances of the monopulse ratios are used to illustrate the effects of diffuse multipath for a notional S-band radarRadar Conference, 2001. Proceedings of the 2001 IEEE; 02/2001

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