摘要: One quick and easy way of estimating scattering coefficient is to assume that the antenna beam is confined in a finite cone with constant gain inside and the range to the antenna is constant for all the cells inside the illuminate... 展开 One quick and easy way of estimating scattering coefficient is to assume that the antenna beam is confined in a finite cone with constant gain inside and the range to the antenna is constant for all the cells inside the illuminated area. Also the variation of the incidence angle is assumed to be small enough inside the illuminated area so one can estimate the incidence angle with only the power return measurements. The above may not be true depending on the antenna gain shapes or the target characteristic. In this report, the so-called narrow-beam approximation is examined using a little more realistic antenna gain functions and range variation and also a specific incidence angle variation function. The numerical integration shows that the narrow beam approximation can give as much as 3.6 dB error for normal incidence to the target with rapidly varying incidence angle when the beamwidths are 9 deg wide. For the incidence angles of 10 deg or larger, the error is in the order of a dB or less depending on the beamwidths and target characteristics. (Author) 收起