RADIO PHYSICS AND RADIO ASTRONOMY

Subject and Purpose. The paper is an effectiveness study of the root-MUSIC technique as applied to elevation angle measurements of low-altitude radar targets over the sea, specifically with account of the radio waves’ phase front sphericity. The purpose is to find out whether and how much can the measurement accuracy be improved through account of the phase front sphericity, as compared with the classical approach assuming a plane phase front.

Methods and Methodology. The work proceeds from computer simulation, considering a variety of sea roughness levels, and covers a range of radio wave reflection conditions from a nearly specular return to strong diffuse reflection from the sea surface. The simulation involves a wide range of target distances within the far-field region with respect to the receive array.

Results. A new approach has been suggested for taking into account the phase-front sphericity of the radio waves arriving from the target. The level of errors of elevation angle measurements has been estimated and compared with such shown by the conventional
root-MUSIC method which assumes a plane phase front for the waves reflected from the target. The comparison concerns a wide range of sea roughness levels and target separations.

Conclusion. It has been established that the proposed version of the root-MUSIC technique which takes wave front sphericity into  account can significantly reduce the errors in elevation angle measurements for low-altitude targets.

Keywords: root-MUSIC, elevation angle, low-altitude target, elevation measuring errors, phase front sphericity, multipath, thermal noise, simulation

Manuscript submitted 29.09.2021

Radio phys. radio astron. 2022, 27(2): 110-120

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