Dual-Mode Dual-Band Bandpass Filter Based on a Stub-Loaded Patch Resonator

This letter presents a dual-mode dual-band bandpass filter using a patch resonator with a cross slot and two different groups of stubs loaded. The cross slot with different orthogonal lengths excites orthogonal modes in the passbands and reduces the patch size. Meanwhile, the two sets of stubs can modify the filter's input impedance at different frequencies and control the even and odd modes in the passbands, respectively. Utilizing these two kinds of elements, transmission poles can be realized easily in both passbands. For demonstration, a dual-band patch resonator filter working at 2.4 and 5.2 GHz is designed. The theoretical analysis is given and the simulated and measured results are presented. The good agreement verifies the proposed method.