Design and implementation of a compact LTCC diplexer at SHF-band

This paper presents the design and fabrication of a compact low temperature co-fired ceramic diplexer at SHF-band. The diplexer consists of a T-junction and two bandpass filters with bandwidth of 400MHz at 3.6GHz and 1000MHz at 5.5GHz respectively. The diplexer is constructed by connecting the two filters using a T-junction and they are packaged into a single ceramic substrate to achieve the compact volume, the size is only 4mm × 10mm × 2mm. The measured results show high performance. The return loss is better than -15 dB, the insertion losses of both channels are less than 2 dB, the out-of-band rejections are higher than -30 dB and the isolation between the two channels is better than -35 dB.