Low-pass Filter Design using Two Overlapped Periodic EBG Structures with Low Spurious Responses

This paper presents the design of a low-pass microwave filter based on the EBG (electromagnetic bandgap) concept. The structure is composed of a microstrip line in one of the layers and two different periodic superimposed EBG structures in the ground plane. The first structure defines the characteristics of the filter in the pass-band whereas the second periodic structure is used to reduce the second harmonic spurious response. The filter exhibits a fiat pass-band response and a cut-off rate better than 380 dB/octave.