An Inline Compact SIW Bandpass Filter With Quasi-Elliptic Response Using Microstrip Extracted-Pole Resonators

Two novel types of microstrip-based extracted-pole resonators are investigated in this brief, which are able to achieve a one-pole response with a transmission zero (TZ) created either below or above the passband. Resonance and transfer characteristics of the resonators are studied and discussed. And a detailed analysis is demonstrated by theoretical derivation and simulation. The application of the proposed extracted-pole resonators to an inline quasi-elliptic substrate integrated waveguide (SIW) filter is then presented, which exhibits a compact size and high selectivity with a TZ located on both sides of the passband. To verify the proposed concept, a filter prototype with a center frequency of 10 GHz is designed and fabricated. And the measured results show good agreement with the simulation, presenting a quasi-elliptic response with high selectivity.