AbstractIn this article, stepped impedance resonator with dual‐band admittance inverter is proposed to design the dual‐band microstrip filter to operate at (2.4, 5.2) GHz and at (0.9, 2.3) GHz, respectively. The proposed dual‐band microstrip filter consists of stepped‐impedance resonators (SIRs) in shunt cascaded by dual‐band inverter. The half‐wavelength SIR is constructed to simultaneously excite the dual resonances at those specified frequencies. The dual‐band admittance inverter used is composed of two open stubs and one transmission line to make the contribution of the performance of the J‐admittance. The transmission zeros of the admittance inverter can also enhance that of SIRs. The enhanced transmission zeros can be designed on the basis of the required J value and characteristic impedances of the inverter. The study has indicated that the proposed structure and method can achieve the design goals of dual‐band filter. Experimental filters are fabricated and measured to confirm the design. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:140–143, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25626