A compact high-selective stripline SIR bandpass filter embed in LTCC

A compact high-selective stripeline SIR bandpass filter based on LTCC technology has been proposed in this study. Through the cross-coupling, the filter could provide a single pair of transmission zeros (TZs) near the passband, which greatly enhance the side-band rejection. Due to the optimization of impedance rate of the SIR, we could not only reduce the filter size, but also control the spurious-mode frequencies, as a result the filter have a very wide stopband. Basing on LTCC technology, the filter is embedded in substrate, therefore, it occupies rather little space on the substrate surface in order to leave more space to SMT devices. The filter has a center frequency of 1.5 GHz with a bandwidth from 1.43 to 1.57 GHz, and its stopband rejection is better than 20 dB from 1.60 GHz to 8.18 GHz. The size of the filter is only 12.4 mm x 10.1 mm x 1.13 mm, which has important significance for wireless communication system's miniaturization.