A compact microstrip BSF using quasi-lumped elements

A compact microstrip BSF using quasi-lumped elements is proposed in this paper. The filter consists of inductor lines and inter-digital-type gap capacitors as quasi-lumped elements. The resonator using the above elements is represented by a series LC resonator. The design of the resonator was performed by changing the structural parameters so that the reactances of the inductor (positive) and the gap capacitor (negative) have the same absolute values. The measured results of the combination of the resonators for the BSF agreed well with the simulated ones.