Design of Multi-standard Single/Tri/Quint-Wideband Asymmetric Step Impedance Resonator Filters With Adjustable Transmission Zeros

This paper presents an original Asymmetric Stepped-Impedance Resonator (ASIR) filter combined with meander coupled-line structures and enabling the realisation of finite transmission zeros and the implementation of multi-band bandpass filters. The meander coupled sections tune the transmission zeros and resonant frequencies: with higher order spurious frequencies cancelled by the transmission zeros, a single wide band with wide stopband from 1.18 to 1.84 GHz is possible. Furthermore, by positioning the finite transmission zeros between the high order spurious frequencies and adjusting the coupling strength between resonators, a quint-wideband filter can be realized, with centre frequencies of 1.19, 4.29, 5.43, 6.97, 9.9 GHz and fractional bandwidths of 31.9%, 15.4%, 15.8%, 4.3%, 39.2% respectively. More importantly, two filters with single-/quad-wideband performance can be realized by tuning the parameters of the meander coupled section and therefore they can be designed separately by using only one original structure. The triple-wideband filter is realized with the help of the asymmetric parallel uncoupled microstrip section. These filter structures enjoy the advantage of single-/multi-band versatility, structure reusability and simplicity. The good in-band and out-of-band performance, low loss, and simple structure of the proposed single/tri/quint-wideband filters make them very promising for applications in future multi-standard wireless communication.