New ultra-wideband filters based on tuning forks shape and CSRRs

In this work, the tuning forks (TFs) shape and complementary split ring resonators (CSRRs) are the tools used to present new UWB microwave filters. Two tuning forks are printed on the upper side of the microstrip line covering the host transmission lines. The filter bandwidth containing tuning forks is ultra-wide and equal to 11.8GHz operating at 6.1GHz center frequency. A novel method to upgrade the matching between the host transmission lines and the CSRRs is proposed as well. The bandwidths of the developed filters containing tuning forks with the presence of different CSRRs at different designs are 10, 6.8, 5.5 and 4.7GHz at 5.4, 3.6, 3 and 2.55GHz center frequency, respectively. The negative permittivity metamaterial is made of CSRRs which are etched in the lower side of the microstrip line. These metamaterial filters combine negative characteristics of permeability and permittivity which are created by using TF and CSRRs components respectively to create an UWB response with better performance and size reduction. The simulation results showed that the filters have composite right/left handed (CRLH) behavior with insertion losses less than 1dB and suitable average rejections.