参考信号信杂比(SCR)是评估外辐射源雷达积累增益损失的重要参数。利用数字电视地面广播(DTTB)辐射源中的PN序列进行信杂比估计时,将出现接收信号相对于本地帧头的分数阶时延问题,导致信杂比估计出现严重偏差。针对该问题,该文利用信号在时延维的稀疏性,提出基于压缩感知的信杂比估计算法。仿真结果表明,该算法对不同强弱的信号都能得到精确的时延和强度估计,从而保证了信杂比估计的准确性。实测数据处理结果表明,实测数据的参考信号信杂比较高,积累损失较小,约为0.5 d B;信杂比与基线距离有关,基线越长信杂比越低,积累损失越大。
Aim To analyze the transient speciality of nonlinear, anisotropic, AC+DC coupling electric field, and to compare the withstand voltage strength of different insulation structures. Methods The transient process of polarity reversal is analyzed, considering the anisotropic property of oil immersed press board, a new finite element model based on Galerkin method is presented and verified. The model developed is applied to calculate the electric field distribution in four typical winding end structures of the converter transformer. Results\ The whole ring structure possesses the best insulation characteristics. Conclusion\ By introducing reasonable insulation components, insulation strength with the same surrounding sizes can be improved more than 30%.
