Browsing by Author "Palmer, Robert D."

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    Three-antenna poststatistic steering using the MU radar
    (American Geophysical Union, 1990-11) Palmer, Robert D.; Woodman Pollitt, Ronald Francisco; Fukao, Shoichiro; Tsuda, Toshitaka; Kato, Susumu
    This paper derives useful expressions for the synthesized beam statistics using poststatistic steenng (PSS), when three antennas are used in a spatial interferometer configuration for two­dimensional steering. These antennas may have arbitrary position and can have nonorthogonal baselines. The use of three (noncollinear) antennas allows altitude dependent two-dimensional steering. This technique is verified using spatial interferometer data obtained in October 1989 using the MU radar, including PSS in directions parallel and perpendicular to the wind direction which is a very convenient advantage of the technique.
    Palabras clave:AntennasInterferometersAntenna array
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    VHF radar interferometry measurements of vertical velocity and the effect of tilted refractivity surfaces on standard doppler measurements
    (American Geophysical Union, 1991-03) Palmer, Robert D.; Larsen, Miguel F.; Woodman Pollitt, Ronald Francisco; Fukao, Shoichiro; Yamamoto, Mamoru; Tsuda, Toshitaka; Kato, Susumu
    At VHF wavelengths, aspect sensitivity may result in an apparent beam direction that is off vertical even for a nominally vertically pointing beam direction if the refractivity surfaces responsible for the scatter are tilted with respect to the horizontal plane. Middle and upper atmosphere radar measurements obtained by using the system in a standard multireceiver configuration typical for radar interferometry (RI) and spaced antenna measurements have been analyzed for evidence of such effects. The analysis is based on the linear variation of the cross-spectral phase as a function of the radial velocity in the frequency doma.Jofor the RI cross spectra. I rue-verucal velocity escimates are obtained by using the fact that the phase difference between two antennas should be equal to zero when the echoes are being received from the vertical direction. The tilt angles of the refractivity surfaces were obtained from the phase of the cross-correlation function at zero lag, and the radial velocity in that direction was determined from the cross spectra. The results indicate that the vertical velocity derived from standard Doppler analyses is actually the velocity perpendicular to the refractivity surfaces and thus can be biased by the projection of the horizontal wind along the effective pointing direction.
    Palabras clave:RadarScatteringAntennas