DGS-SMS Compact Fifth Order Low Pass Filter

Abstract

This paper presents a slow-wave microstrip transmission lines based on a double-layer PCB substrate. The slow wave effect is obtained by inserting metallic via rows within the lower substrate layer. Based on this concept, miniaturized high rejection 5'h order low pass stepped impedance filters with a cut-off frequency of 2.45 GHz are designed, fabricated and measured. Measurement results are in good agreement with simulations. Thanks to the slow-wave transmission lines, the size of the realized filters is reduced by 54% as compared to a classical filter prototype.