结合差分进化(Differential Evolution)和PEXIT(Protograph Exitrinsic Information Transfer)方法,提出了一种具有Tam结构的QC-LDPC码优化设计方法,Diff-PEXIT算法,在优化搜素时,保持了低编码复杂度的QCLDPC码的简单编码结构不变.仿真结果表明,Diff-PEXIT算法优化设计的QC-LDPC码性能优于802.16e中的QC-LDPC码和Tam提出的QC-LDPC码,且优化构造出的QC-LDPC码仍然保持了Tam码的简单递归编码结构及低编码复杂度.
The tunable terahertz(THz) filter has been designed and studied, which is composed of 1D photonic crystal(PC) containing a defect layer of semiconductor Ga As. The analytical solution of 1D defective PC(1DDPC) is deduced based on the transfer matrix method, and the electromagnetic plane wave numerical simulation of this 1DDPC is performed by using the finite element method. The calculated and simulated results have confirmed that the filtering transmittance of this 1DDPC in symmetric structure of air/(Si/SiO_2)~N/GaAs/(SiO_2/Si)~N/air is far higher than in asymmetric structure of air/(Si/SiO_2)~N/GaAs/(Si/SiO_2)~N/air, where the filtering frequency can be tuned by the external pressure. It can provide a feasible route to design the external pressure-controlled THz filter based on 1DPC with a defective semiconductor.
