A design of Ka-band bandpass filter based on low temperature co-fired ceramic

This paper presents a stripline low temperature co-fired ceramic (LTCC) bandpass filter at Ka-band, which is embedded into an eleven-layer substrate. A quasi-coaxial structure was utilized to reduce the impedance discontinuity caused by GCPW to stripline transition. The vertical metal vias were utilized to realize grounding and shielding. The measurements of the fabricated filter show an insertion loss of -4.5 dB and a 1.73 GHz passband with the centre frequency at 34.69 GHz, including the two RF coaxial connectors. The measured return loss in the passband is lower than -13.45 dB. The whole bandpass filter occupies an area of 9.8 mm×5 mm×1.056 mm. The compact configuration and measured performance show that the filter is suited for millimeter-wave multi-chip module.