A LTCC cross-coupled bandpass filter for millimeter-wave integrated module

This paper presents design and realization of a Ka-band stripline bandpass filter. A single pair of transmission zeros at lower and upper stopbands are achieved by introducing cross coupling. The whole filter is designed as a three-dimension structure in LTCC multi-layers. EM simulation is employed to estimate the performance of the filter and do optimization. The dimension of the fabricated LTCC filter is 8.3mm × 4.4mm × 1.1mm. The measurement shows a bandwidth of 1.5 GHz with the center frequency of 35.65 GHz. The measured insertion loss is smaller than 6.5 dB and return loss is below -6.4 dB including the RF connectors in the passband. The proposed filter is suitable for the applications in millimeter-wave integrated module.