Uso de ressoadores de anéis fendidos e ressoadores de anéis fendidos complementares para o melhoramento do desempenho em filtros passa-baixa em microfita

Abstract

This work presents microstrip lowpass filters with improved performance due to the insertion of Split Ring Resonators (SRR) and Complementary Split Ring Resonators (CSRR). The analysis cover three different lowpass filter configurations: steppedimpedance filters, filters using open-circuited stubs and filters using semilumped microstrip sections. The CSRR and SRR resonators have been used to enhance the rolloff and to remodel the rejection band of the filters, achieved by the removal of undesired transmission spurious bands. The improvements in these circuits have been verified by the analysis of performance parameters such as selectivity, transition bandwidth and rejection bandwidth, obtained by electromagnetic simulations and measurements of the designed microstrip lowpass filters. Values of selectivity ranging from 60 to 86 dB/GHz were achieved by the resonator-based lowpass filters. These values are considerably higher than those obtained by the conventional lowpass filters (around 6 to 38 dB/GHz). Results for rejection band from approximately 2 to 10 GHz have been obtained. The insertion of the resonators did not result in major modifications both in passband and in group delay of the analyzed filters. The lowpass filters have low order, with values from 3 to 9. In addition, a low cost dielectric substrate has been used. Though lossy, this substrate meets the intended requirements.