双场作用下的Λ－型三能级系统是研究电磁诱导透明(EIT)的基本模型，在此基础上，引入强微波驱动场作用于该系统的激发态能级与另一激发态能级间，就构成了三场作用下的级联准Λ－型四能级系统。通过求解系统的密度矩阵方程，分别研究了耦合场和微波驱动场对系统吸收特性的影响。在耦合场和微波驱动场共同作用下，系统的探测吸收谱呈现为Autler－Townes双峰与EIT的叠加，可以用缀饰态理论对此做出合理解释。研究结果表明，Autler－Townes双吸收峰来自于强微波场与系统的相互作用，EIT来源于耦合场与系统的量子相干相互作用。

The Λ-type three-level system coupled by two coherent fields is a basic model to study the electromagnetically induced transparency(EIT). Based on that,the cascade quasi-Λ-four-level configuration is formed when a radio-frequency(RF)field drives the transition between the excited state and an additional excited state level. The absorption property is studied along with the parameters of the coupling field and the RF driving field by numerically solving the relevant equations of motion of the density matrix. It is shown that under the applying of the coupling field and the RF driving field,both the Autler-Townes doublet and the EIT are observed in the absorptive spectra and it can be explained properly by the theory of dressed state. An important conclusion is that the Autler-Townes doublet originates from the atom system interaction with the strong RF field,while the EIT originates from atom system quantum interference interaction with the coupling field.