In the beam of a radio telescope, background radio sources may appear around a target radio source. The polarized radio emission of these background radio sources will influence the polarization measurements of the target source. Through simulation studies on the cases of a single and multiple polarized background radio sources, it is found that if we only measure the polarization parameters at two or three frequencies, the derived rotation measures (RMs) and other polarization parameters of the target radio sources are not reliable. The proper approach is to measure the Stokes parameters Q and U in multiple bands, and then make RM synthesis to get all RMs of the target radio sources.%由于受射电望远镜分辨率的限制,观测视线方向上可能有多源重叠现象.观测目标源的法拉第旋率(rotation measure,RM)及偏振角(polarization angle,PA)的测量值就会受到方向束内其它背景射电源的影响.通过模拟研究发现,背景射电源对目标源偏振参量测量的干扰形式与干扰源的RM值有关.只运用两三个波长的偏振观测数据拟合所得的RM结果并不可靠.正确测量目标源RM需要对多波段Stokes参量Q和U的测量值进行拟合.
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