A perfectly matched layer (PML) technique is used to limit the computational domain that includes planar structures and which are analyzed with the transmission-line matrix (TLM) method. The approach uses a coupling algorithm between the TLM symmetrical condensed node (SCN) in the computational domain and a finite-difference time-domain (FDTD) algorithm in the PML medium. The proposed procedure is validated by comparison with other methods and/or measurements in the case of a patch antenna fed by a microstrip line.