Miniaturized Ultra-Wideband Bandpass Filter Based on Substrate Integrated Quasi-Lumped Resonators

A compact ultra-wideband bandpass filter employing substrate integrated quasi-lumped resonators is presented in this paper. A multi-layer hybrid structure is proposed, combining quasi-lumped resonators and surface mount components. This allows a huge miniaturization degree due to the high capacitive loading. Moreover, strong magnetic and electric couplings can be implemented thus enabling the introduction of transmission zeros for improving response selectivity. A filter example centered at 5.35 GHz with a prescribed channel bandwidth of 2.9 GHz has been designed, manufactured and measured. The filter size is smaller than 7×7 mm². The obtained results show the feasibility of the proposed approach.