Wave spectra measuring from airborne phased-array wave spectrometer
This study proposes a new airborne phased-array wave spectrometer(PAWS),which is a Ku-band,linear polarization two-dimensional phased-array radar.It transmits a wideband linear frequency modulation signal,illuminates the sea surface at a low incidence angle,and receives echo power modulated by quasi-specular reflection from the sea surface.From the echo power,the sea surface backscattering coefficient and the one-dimensional wave spectrum can be retrieved.With conical scanning from 0° to 360°,two-dimensional wave spectrum,and main wave parameters are obtained by PAWS as well,such as significant wave height,wave direction,and wavelength.On one hand,the dynamic beam position chronogram design(DBCD)benefited from the two-dimensional phased array radar is adopted.For the extension of observation time and the suppression of speckle noise of the along-track,it makes non-uniform scanning possible instead of uniform scanning to improve the insufficient along-track signal-to-speckle noise ratio of CFOSAT SWIM.Thus,better efficiency of PAWS is achieved.On the other hand,electrical scanning of the phased-array radar without a rotating mechanism can greatly improve the compactness,adaptability,and reliability of PAWS.Therefore,it can be mounted on various aircraft platforms.The PAWS field campaign was held in the Bohai Sea near Qinhuangdao in 2023,with synchronous buoys moored there.The results show that the accuracy of PWS's dominant wave direction is better than 15°,the accuracy of the dominant wavelength is better than 10%,and the significant wave height is better than 0.3 m.The DBCD is proven to work for the suppression of the speckle noise along the track.The performance of the phased-array conical scanning for receiving sea surface echoes and retrieving wave spectra is also verified.
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