Abstract: A novel method to suppress the spurious response of microstrip bandpass filter is proposed in this paper.By cascading lowpass filter using stepped impedance hairpin resonator,the stopband rejection of a bandpass filter can be significantly improved.Equation for stopband transmission zeros of such lowpass filter is derived from a new equivalent circuit model.All the theoretical analysis and design procedures have been successfully verified by the design of an L-band broad stopband bandpass filter.