CAJ | 학술논문

利用无线电全息方法,如正则变换方法或全谱反演方法,可以有效地解决大气多路径条件下GPS掩星信号的反演问题.本文采用正则变换方法反演掩星资料,模拟仿真反演结果显示正则变换方法可以准确地反演包含大气多路径效应的信号.在模拟信号的相位中加入不同程度的高斯相位噪声后,正则变换方法的反演结果会受到不同程度的影响.用正则变换方法对2007年第71天至73天共约4500个COSMIC数据进行处理.将其折射率反演结果和atmPrf资料(利用全谱反演方法计算得到)一起,与对应的ECMWF分析场资料进行统计比较,结果表明:在5 km以下,正则变换方法计算的折射率的相对误差的平均值普遍大于atmPrf资料.其原因可能为:正则变换方法将信号从LEO轨迹后传播至辅助屏,造成孔径缩小,精度下降.同时也讨论了信号截断对低对流层中反演精度和掩星个数的影响.
이용무선전전식방법,여정칙변환방법혹전보반연방법,가이유효지해결대기다로경조건하GPS엄성신호적반연문제.본문채용정칙변환방법반연엄성자료,모의방진반연결과현시정칙변환방법가이준학지반연포함대기다로경효응적신호.재모의신호적상위중가입불동정도적고사상위조성후,정칙변환방법적반연결과회수도불동정도적영향.용정칙변환방법대2007년제71천지73천공약4500개COSMIC수거진행처리.장기절사솔반연결과화atmPrf자료(이용전보반연방법계산득도)일기,여대응적ECMWF분석장자료진행통계비교,결과표명:재5 km이하,정칙변환방법계산적절사솔적상대오차적평균치보편대우atmPrf자료.기원인가능위:정칙변환방법장신호종LEO궤적후전파지보조병,조성공경축소,정도하강.동시야토론료신호절단대저대류층중반연정도화엄성개수적영향.
Under the atmospheric multipath conditions, both canonical transform (CT) and full spectrum inversion (FSI) method can solve the problem of calculating bending angle profiles within the multipath area. The atmospheric propagation of GPS signals under atmospheric multipath conditions is simulated using multiple phase screens (MPS) technique. Bending angle profiles computed by CT method are compared with corresponding solutions to Abel integral (taken as the true value). The results show that CT method is close to the true value in the multipath area. The retrieval accuracy of CT method is degraded to some extent when Gaussian noises are added to the phase of simulated signal. About 4500 COSMIC (Constellation Observing System for Meteorology, Ionosphere and Climate) atmPhs profiles from DOY (day of year) 71 to DOY 73 in 2007 are retrieved by CT method. Statistical comparisons of the retrieved refractivity profiles, together with atmPrf data (retrieved by FSI method), with those from corresponding ECMWF (European Centre for Medium-Range Weather Forecasts) analysis show that CT method contains greater systematic negative bias than atmPrf data below 5 km. A possible reason is that the signal aperture is decreased for back-propagating the signal from LEO position to the back-propagation plane in CT method. The small aperture means low accuracy in the refractivity. The influence of signal truncation on both retrieval accuracy and occultation number is also discussed.