# A Highly Selective Stripline Lowpass Filter with More Than 100-dB Wide Stopband Attenuation

Belyaev, B. A.; Serzhantov, A. M.; Leksikov, An. A.; Bal'va, Ya. F.; Grushevskii, E. O.; et al. Technical Physics Letters. https://doi.org/10.1134/S1063785020040173

A new miniature design of a highly selective lowpass filter based on a suspended substrate with a two-sided stripline pattern has been developed. The filter frequency response slope (cutoff attenuation rate) and stopband attenuation depth are determined by transmission zeros, the number of which is equal to the filter order. An experimental prototype of a fifth-order lowpass filter on 0.5-mm-thick alumina substrate with dielectric permittivity ε = 9.8 has been synthesized with the aid of numerical electrodynamic analysis of a three-dimensional model. The cutoff frequency of the filter passband at a –1-dB level is *f*_{c} = 1.75 GHz. The stopband width at a –100-dB attenuation level reaches 4.4*f*_{c}.