Design of Compact Bandpass Filter Using a Ring Resonator Loaded Dual-Mode Triangular Ring Resonator

This paper proposes a compact microstrip filter. The filter is developed from a microstrip loop resonator loaded with a approximate triangular loop resonator. The center frequency of the proposed filter is 3.86 GHz and the a 3-dB fractional bandwidth is 17.61%. The minimum insertion loss is 0.91dB. Two transmission zeros are distributed in near the two sides of the pass band at 2.98GHz and 4.73GHz, both with attentional over 50dB. The filter has the advantages of compact size, low insertion loss, high selectivity, especially good out-band suppression characteristics. The effects of adjusting the filter parameters have also been researched. The test results presented in the paper are in resonable agreement with the simulation results.