Microstrip and slotline two-pole microwave filters with additional transmission zeros

The work presents microstrip and slotline two-pole filters, which exhibit two finite symmetrical transmission zeros. To obtain extra transmission zeros, a source-load coupling is used in both cases. The microstrip filter has a center frequency of 3.3 GHz and a fractional bandwidth of 6%. The measured insertion loss is less than 0.35 dB. A bandstop filter is used for improving the rejection performance of the microstrip filter. The simulated performance of the slotline filter is also presented.