In this paper, a microstrip combline bandpass filter (BPF) with a broad upper stopband performance is presented. The proposed filter is based on the design of a bandpass filter cascaded with a defected microstrip structure (DMS) bandstop filter. The bandstop characteristic is realized using T-shaped DMS at the external input and output coupling transformers. The measured and simulated electrical performances are in good agreement and demonstrate broad upper stopband bandwidth. The proposed filter is also compared with the characteristic of a conventionally designed filter to highlight the advantages of the proposed approach.
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