Design of a Band-pass Filter Using Stepped Impedance Resonators with Floating Con- Ductors

A new type of miniaturized stepped impedance resonator (SIR) for bandpass filter applications is proposed in this paper. The new resonator incorporates a ground plane window with a floating conductor in the backside of the substrate. The ground plane window increase the characteristic impedance of the lines used to implement the inductive region of the quasi-lumped resonator, thus allowing some size reduction. Moreover, the presence of a floating conducting patch printed below the capacitive region of the resonator pushes up the first spurious band of the filter. A meaningful improvement of its out-of-band rejection level is then achieved. The coupling between adjacent resonators is also enhanced thus leading to wider achievable Corresponding author: F. Medina ([email protected]). 32 Velázquez-Ahumada et al. bandwidths. Some filter designs using the new resonator and other standard resonators are included for comparison purposes.