Microstrip bandpass filters using linear tapered-line resonators with tunable transmission zeros

Bandpass filters with tunable transmission zeros and harmonics suppressions are designed using coupled linear tapered-line resonators (LTLR). Tapped lines are used as input and output ports to create and tune two transmission zeros independently, and quarter-wavelength impedance transformers are utilized to ensure the desired quality factors. Measurement results of bandpass filters at 2.4GHz with optimized stopbands are also given to validate the theory.