A novel and compact UWB filter with improved upper stop band

Abstract

A novel, compact band pass, UWB (Ultra Wide Band) filter has been designed. Equi-ripple stepped impedance resonator (SIR) for low pass filter (LPF) response is implemented to improve upper stop band characteristics. Three shorted unsymmetrical rectangular ring resonator (SURRR) is implemented to improve the high pass response that in turn improve the lower stop band characteristics of the proposed UWB filter. SIR (LPF) and SURRR (HPF) together produce good out of band characteristics for the UWB filter with low insertion loss. In addition transmission zero (TZ) is placed to improve the sharp skirt (roll-off) at upper stop band. The TZ are implemented by two quarter wavelength stubs. Finally, proposed filter is fabricated (dielectric constant ε <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">r</inf> =2.2 and thickness=0.787 mm) and measured to validate the predicted results. The group delay of the filter is relatively constant and less than 0.25 ns over the operating pass band.