Measurement of Atmospheric Aspect Sensitivity Using Coherent Radar Imaging after Mitigation of Radar Beam Weighting Effect

Jenn-Shyong Chen Department of Computer and Communication Engineering, Chienkuo Technology University, Changhua City, Taiwan

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Jun-ichi Furumoto Research Institute for Sustainable Humanosphere, Kyoto University, Kyoto, Japan

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Abstract

The aspect angle, a measurement of the aspect sensitivity of atmospheric refractivity irregularities, was estimated with multiple-receiver coherent radar imaging (CRI) of very high frequency (VHF) atmospheric radar. Two CRI parameters retrieved by Capon’s method were utilized to derive the aspect angle: brightness width from the vertical radar beam and the direction of arrival (DOA) of the echo center from the oblique radar beam. Differing from previous studies with CRI, the radar beam weighting effect on the CRI brightness distribution was considered, and moreover, the radar beamwidth used in study was adaptive to the signal-to-noise ratio (SNR) of data as well as the off-beam direction angle. The study is based on statistical results. It is shown that the brightness width, a representative of the aspect angle, obtained from the modified CRI brightness distribution of the vertical radar beam was generally larger than that without correction, and it was very close to the values derived from the DOA of the 1° oblique radar beam and the power distribution of multiple beam directions. Moreover, the aspect angle derived from the DOA varied with the radar beam direction, which was similar to that obtained from the comparison of echo powers of a radar beam pair; however, the DOA approach yielded a much larger aspect angle in the low-SNR condition. This study recommended a feasibility of improving the measurements of atmospheric parameters with CRI after removing the radar beam weighting effect suitably from the CRI brightness distribution.

Corresponding author address: Jenn-Shyong Chen, Department of Computer and Communication Engineering, Chienkuo Technology University, No. 1, Jieshou N. Rd., Changhua City 500, Taiwan. E-mail: jschen@ctu.edu.tw

Abstract

The aspect angle, a measurement of the aspect sensitivity of atmospheric refractivity irregularities, was estimated with multiple-receiver coherent radar imaging (CRI) of very high frequency (VHF) atmospheric radar. Two CRI parameters retrieved by Capon’s method were utilized to derive the aspect angle: brightness width from the vertical radar beam and the direction of arrival (DOA) of the echo center from the oblique radar beam. Differing from previous studies with CRI, the radar beam weighting effect on the CRI brightness distribution was considered, and moreover, the radar beamwidth used in study was adaptive to the signal-to-noise ratio (SNR) of data as well as the off-beam direction angle. The study is based on statistical results. It is shown that the brightness width, a representative of the aspect angle, obtained from the modified CRI brightness distribution of the vertical radar beam was generally larger than that without correction, and it was very close to the values derived from the DOA of the 1° oblique radar beam and the power distribution of multiple beam directions. Moreover, the aspect angle derived from the DOA varied with the radar beam direction, which was similar to that obtained from the comparison of echo powers of a radar beam pair; however, the DOA approach yielded a much larger aspect angle in the low-SNR condition. This study recommended a feasibility of improving the measurements of atmospheric parameters with CRI after removing the radar beam weighting effect suitably from the CRI brightness distribution.

Corresponding author address: Jenn-Shyong Chen, Department of Computer and Communication Engineering, Chienkuo Technology University, No. 1, Jieshou N. Rd., Changhua City 500, Taiwan. E-mail: jschen@ctu.edu.tw
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