A compact bandstop filter design for X-band applications

The main objective of this work is to present a compact microstrip bandstop filter for X-band applications. The designed filter covers X-band and has stopband bandwidth with better than 2.5GHz for -20dB. Maximum |S
₁₁
| value in the passband region is below -15dB for the final filter. Optimum distributed bandstop filter design method is used to acquire the design goals. The final filter has a compact size with 12.87mm × 7.04mm. Two-stage design procedure is proposed to realize design objectives. It is proposed in the first stage of the design procedure to have realizable open stubs which is difficult to implement for given dielectric substrate properties. To remedy this difficulty, a wide stopband region is selected. The second stage of the design procedure presents an optimization process to achieve desired filter. In order to examine the frequency responses of all design steps, three commercial electromagnetic simulators are used. Consistent simulation results are obtained before implementation.