In order to reduce the complexity of the structure of electrically tuned bandpass filters, an electrically tuned filter based on step impedance resonators is designed in this paper. The varactor diodes are used as tuning elements and the chip inductors are used as input-output coupling elements. The ADS and HFSS software were used to analyze the relationships between the coupling coefficient and the external quality factor with frequency. The simulation results show that the coupling coefficient and external quality factor keep constant from 0.45~1.0 GHz. The proposed filter was manufactured on a Rogers 5880 (tm) dielectric substrate with relative dielectric constant of 2.2 and measured by network analyzer. The measured results are basically consistent with the simulation results.