Design and Analysis of Dual-Band Planar Band pass Filters using Resonators for Wireless Applications

This paper describes the design and analysis of planar dual-band bandpass filters using stepped impedance resonators. In the proposed filter configurations, dual-band bandpass filters are designed, and realized by using inverted stepped impedance (SIR) resonators. The conventional half wavelength open circuited stub single frequency resonators are replaced with dual band simple two section stepped impedance resonators. Simple equations to design the dual-band SIR's are derived using transmission line analysis. To increase the performance of the filter, and to reduce the size, compact resonators are proposed. This resonator with compact coupling and size reduction are proposed by using split ring stepped impedance resonators with two inner coupling. The performance of the filter structures is investigated using IE3D electromagnetic simulators, where good agreement with the theoretical prediction is observed.