An S-band low-spurious LTCC BPF using ground-neighbored circular capacitances and length-dispersed connecting lines

An extremely low-spurious band pass filter is presented. The resonators employed in the BPF consist of parallely connected ground-neighbored circular capacitances and short-circuited stubs, and they are connected by connecting lines whose line lengths are dispersed and shorter than quarter wavelength at the pass-band. This configuration is suitable for out-of-band suppression, because frequencies of spurious resonances are high and dispersed. An S-band 8th order BPF with relatively wide 20% fractional bandwidth at S-band is fabricated using LTCC technology. The measured results showed more than 40 dB attenuation up to 40 GHz.