This paper presents a novel microstrip lowpass filter. The proposed filter consists of two high impedance cells, which are integrated by a stub loaded transmission line. A rectangular stub is utilized to reduce the overall circuit size so that it has a compact size of 0.0135 λg2 where λg is the guided wavelength calculated at 2.5 GHz. In comparison to the previous works, a good figure of merit (FOM) is obtained, which indicates that this filter is designed correctly. An approximated LC circuit is introduced to analyse the configuration of the proposed structure. Based on the transmission line theory, the lumped elements are calculated. Then, the LC model is simulated where the obtained results are approximately similar to the EM simulator results. In order to verify the design methodology, the proposed filter is fabricated and measured. There is a good agreement between the simulation and measurement results.
