Developing single-layer ultra-wideband band-pass filter with multiple (triple and quadruple) notches

New ultra-wideband (UWB) band-pass filters (BPFs) with multiple (triple and quadruple) notches are proposed. A systematic approach is demonstrated to establish one to four or more notch-bands within the passband of a UWB BPF on a single-layer substrate using μ-strip technology, while avoiding the use of any via-holes. The proposed filters are based on parallel integration of gap-coupled microstrip resonators (GCMR) and two tri-section stepped-impedance resonators (TSSIR) to generate multiple notches. Two notches are produced by the use of TSSIR fundamental and first spurious resonance frequencies and the third and fourth notches are introduced by developing transmission zeros using additional integrated GCMR. Two samples of triple and quadruple notch-band UWB filters are fabricated and tested. In comparison to the previous triple single-layer notch-band BPFs with via-holes, the proposed single-layer triple notch BPF offers a size reduction of around 52%. The authors have also expanded the concept and designed a new quadruple notch-band UWB BPF. The proposed filter uses only a single layer and can be easily mass-produced with low cost.