Abstract:Because of high performance filters’ complicated structure and big dimension, a compact hairpin microstrip bandpass filter centered at 2.45 GHz is designed and developed based on stepped impedance resonator (SIR).The performance of the filter is improved and the dimension is reduced by kinking the half wavelength SIRs coupling structure to ‘U’ shape, which is hairpin.The results of simulation and measurement of the PCB demonstrate that the insert loss is less than 2 dB in the frequency domain from 2.42 to 2.48 GHz, the 3 dB bandwidth is 130 MHz, the return loss in the middle frequency is as high as 30 dB, and the stop band suppression is bigger than 30 dB in the frequency domain from DC to 2 and 2.8 to 11 GHz. It can be seen that this filter not only suppresses the spurious band effectively, but also have simple and small structure with dimension smaller than 26 mm×22 mm.