UWB bandpass filter with a multilayer non-uniform periodical structure on LCP substrates

A novel ultra wideband (UWB) bandpass filter (BPF) with a multilayer non-uniform periodical structure including a defected ground is proposed in this paper. The new filtering structure can provide a wide bandpass characteristic with only a few lattices. For the demonstration, UWB BPFs of this type were designed using proposed non-uniform 7-cell and 10-cell defected ground structure (DGS) units. Multilayer liquid crystal polymer (LCP) technology was used to implement the designed prototypes. The fabricated prototypes were measured. Both full-wave simulated and measured results were presented. It is shown that the proposed UWB BPFs have good performances, including ultra wide passband, wide stopband with high rejection level and excellent selectivity at upper pass-band edges. The fabricated filters also have compact sizes, which are 10.8 mm by 9.8 mm (0.39 lambdag by 0.36 lambdag) and 15.6 mm by 9.6 mm (0.57 lambdag by 0.35 lambdag) for 7-cell and 10-cell prototypes, respectively, where lambdag is the guided wavelength of 50 Omega microstrip line at 6.85 GHz. The proposed BPFs are attractive for UWB communications and radar systems.