A high-performance bandpass frequency selective structure (FSS) is presented, which consists of a 2-D periodic array of shielded microstrip lines. It exhibits stable elliptical filtering response under large variation of the angle of incidence. Its operating principle and design guidelines are discussed through equivalent circuit models. An efficient full-wave mode-matching method has been developed to analyze the proposed FSS. The proposed structure provides a simple and practically feasible solution to high-performance FSS since it can be fabricated using readily available microstrip line technology.