in this paper use 4-order resonant strip-line structure and transmission
zeros out of band to increase high stop-band attenuation and achieve good
phase character. The realization of transmission zeros adopts coupling of
non-neighboring and introduced Z-shape-layer or U-shape-layer. The
position of the transmission zeros can be changed by adjusting the shape,
size and position of the Z-shape metal layer. The overall size of the two
filters is 1.63mm 0.63mm 0.83mm.The central frequencies are 52.25 GHz and
61.25GHz respectively, the pass-band widths are 4 GHz and 6.5GHz
respectively. There are two kinds of dielectric material used in the
filters, the relative permittivity are 2.8 and 2 respectively.