A Folded Bandpass Filter Based on Metal Integrated Suspended Line Technology

The paper proposes a third-order folded bandpass filter based on a metal integrated suspended line (MISL) technology. To achieve the compact design of the filter, the resonators are coupled through a grounded T-shaped structure, which serves as a K-inverter. Therefore, the proposed filter based on parallel resonators has a more compact structure. Based on this, we design a filter with a center frequency of 8 GHz and a fractional bandwidth of 38.6%. The measured insertion losses (ILs) and measured return losses (RLs) are better than 0.88 dB and 15 dB. Good matching levels between the simulated and experimental results have been achieved. The test results indicate that the filter features low loss, miniaturization, and self-packaging.