Improving Characteristics of Hairpin Band Pass Filter using SIR concept

This paper presents a novel design of an improved hairpin bandpass filter for Bluetooth application (IEEE802.15.1). Resonant properties of stepped impedance resonators (SIRs) are exploited to improve the characteristics of a hairpin bandpass filter. Due to SIR characteristics spurious response is shifted to more than four times of the fundamental frequency. A third order Chebyshev bandpass filter with central frequency 2.44 GHz is designed, fabricated and measured using the present concept. The proposed filter has wide out-of-band characteristic with rejection of 18 dB. The design and simulation are performed using 3D full wave electromagnetic simulator IE3D. An accurate design procedure is outlined here and numbers of theoretical and experimental results are presented. Good agreement between experimental and simulation results are observed.