Substrate integrated folded-waveguide cross-coupled filter with negative coupling structure

A pseudo-elliptic multilayer substrate integrated cross-coupled filter with two finite transmission zeros based on quasi-ridged resonators was designed using multilayer PCB technology. The filter adjusted for the central frequency of 28 GHz has a bandwidth of 1000 MHz and exhibits good adjacent channel selectivity of 25 dB as well as low insertion and return losses. It has a small size and can be integrated with other filters into diplexers and multiplexers. The approach used in this design can be easily applied for the other multilayer substrates, for example, LTCC.