LTCC Dual-band Bandpass Filter Based on SPPlike Propagation in Substrate Integrated Waveguide

This paper presents a low-temperature co-fired ceramic (LTCC) dual-band bandpass filter based on surface plasmon polariton (SPP) like propagation. The filter consists of a three-layer substrate integrated waveguide (SIW), where the layers represent sub-SIW structures whose effective dielectric constants have opposite signs in different frequency ranges. In that manner, SPP-like propagation occurs at two different frequencies, providing dual-band filtering operation. The SPP-like concept and filter design are explained in detail, together with the numerical analysis, fabrication procedure and measurement results. The filter operates at 4.1/4.9 GHz and it is characterized by excellent in-band performance, high-selectivity, and robust fabrication.