A 35 GHz reduced-size bandpass filter based on SIW in LTCC technology

This paper presents a bandpass filter composed of cavities delimited in a Low Temperature Co-fired Ceramic (LTCC) substrate by a periodic lattice of metallic via-holes. Compared with the conventional two dimensional PCB, LTCC technology achieves higher Q factor, higher density, smaller size, and lower cost[1]. I/O coplanar waveguide (CPW) feeds are printed on the top face of the substrate and are suitable for planar circuit integration. EM simulator HFSS is employed in determining and optimizing the physical dimension of the filter. In this paper, a planar four-pole linear phase filter centered at 35 GHz based on substrate integrated waveguide (SIW) is proposed. The filter´s fractional bandwidth (FBW) is 10% with insertion loss of -0.65 dB and return loss of -20 dB.