Use of Split Ring Resonators and it Complementary for Performance Improvement in Low-Pass Microstrip Filters
lowpass filter, microstrip, microwave, complementary split ring resonators, SRR, CSRR.
This work presents high performance microstrip lowpass filters. Three different filter configurations are modified by the judicious insertion of split-ring resonators (SRR) and complementary split-ring resonators (CSRR). These resonators are used to improve the roll-off and to remodel the rejection band of the filters, achieved by removing undesired transmission spurious bands. The improvements in these circuits are verified using performance parameters such as selectivity, transition bandwidth, rejection bandwidth and insertion loss, obtained by simulation and measurement of the designed microstrip lowpass filter. Values of selectivity ranging from 60 to 86 dB/GHz are achieved, with rejection bandwidths from 2 to 10 GHz. The insertion of the resonators does not result in major modifications in the passband and the group delay of the analyzed filters. The filters used have values of order from 3 to 9. Besides, a low cost dielectric substrate has been implemented. Though lossy, this substrate meets the intended requirements.