A New Transformation of Bandpass Filter to Bandstop Filter Using Multilayer-Technique and U-Defected Ground Structure (DGS)

A novel compact microstrip bandpass/Bandstop filters realized by combining new Multilayer Method with electrically coupled microstrip U-shaped DGS resonators, is proposed. The proposed filters have low insertion loss and are compact in size due to the slow-wave effect. They also have sharp transition regions due to the presence of two- transmission zeros on both sides of their passband. The measured center frequency, bandwidth and insertion loss are 3.4 GHz, 40%, and 0.5 dB respectively. The simulated and measured results show good agreement and validate the proposed approach.