A compact band elimination filter composed of a mushroom resonator embedded in a microstrip line substrate

This paper proposes a band elimination filter composed of a mushroom resonator embedded in a microstrip line substrate. In the finite-difference time-domain (FDTD) simulation, a small grounded-pad with 0.074λ₀ × 0.074λ₀ creates a deep notch response of -37.7 dB at 7.38 GHz, which prediction is experimentally confirmed by using a low temperature co-fired ceramic (LTCC) prototype model. Mechanism of creating the notch response is fully explained by an equivalent circuit model, and an accurate design procedure is developed. This filter can be used as a compact spectrum synthesizer for improving an original frequency response of microwave components by fabricating this filter onto a same platform with those components.