中文摘要：

针对北斗三频长距离参考站间宽巷（含超宽巷）模糊度解算中存在的问题，分析了影响宽巷组合（WLC)法、载波伪距组合的无几何无电离层（GIF)法及分步无几何（TCAR)法的主要因素及各自的局限性.在此基础上，基于参考站间基线已知的特性，提出了一种分步解算的无电离层（SIF)方法.首先采用载波伪距组合求解(0,-1，1)超宽巷模糊度，利用模糊度已固定的（0,-1，1)载波观测值与第2个宽巷/超宽巷观测值组成载波无电离层组合，同时分析了残佘几何项误差对模糊度解算的影响.最后采用了一组长度为265km的实测北斗三频基线数据进行了实验验证.实验结果表明，所提Sff方法能够有效消除长基线情况下电离层延迟的影响，同时受观测值噪声的影响较小.

英文摘要：

Aiming at the triple-frequency wide-lane/extra-wide-lane ambiguity resolution for longrange base stations of Beidou navigation satellite system(BDS),the main factors and limitations were analyzed for wide-lane combination(W LC)method,the carrier and pseudorange combined geometry-free and ionosphere-free(GIF)method,the three-carrier ambiguity resolution(TCAR)method.Then,a new stepwise ionosphere-free(SIF)method was proposed based on the characteristics known by baseline components.First,the(0,-1,1)ambiguity could be solved reliably with single epoch.After that,in order to solve the second wide-lane ambiguity,the ambiguity-fixed(0,-1,1)observation was used to form a ionosphere-free carrier observation together with the second wide-lane combination.The effects on the residual geometry errors were analyzed.BDS triple-frequency baseline data with a real distance of265km were used to test the performance.The results indicate that the proposed SIF method can avoid the influence of ionosphere delay on long-range baselines with smaller observation noises.