A stub-loaded stepped-impedance resonator (SLSIR) is proposed. Its input impedance is derived, and its resonant conditions are found. First order and second order triband bandstop filters (BSFs) are designed using this resonator. Simulations on both filters show that they generate three attenuation poles at 0.5, 1.2, and 2.1 GHz. The second order filter is also fabricated and characterized using a microwave vector network analyzer. Simulation and measurement results on the second order filter show good correlation.
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