SIW-DGS bandpass filter design for C band satellite communications

In this paper, a bandpass filter is designed and fabricated for C-band satellite communication applications. The substrate integrated waveguide and defected ground structures are used in the design process. CST Microwave Studio software is used to analyze and design the proposed filter. It is built over DiClad 880 laminate having a thickness of 0.508 mm, and formed by etching three cascaded DGS cells on the SIW’s top plane. There is a good agreement between the simulated and measured results. The filter is centered at 6.175 GHz with 500 MHz bandwidth (8.1% fractional bandwidth) in line with applicable US Federal Communications Committee Rules. The simulated insertion loss at the center frequency is around 0.80 dB and the return loss in the passband is better than 30 dB. The measured minimum insertion loss is 1.4 dB, and the measured return loss in the passband is better than 14.5 dB. The obtained results are presented, discussed, and compared with other studies. It can be said that the features of the proposed filter such as size, order, return loss, insertion loss, upper band rejection, etc. are better than those of many other filters given in the literature.