“…Recently, there has been a great interest in balanced bandpass filters (BPFs) on account of high immunity to crosstalk and electromagnetic interference [1,2,3,4,5,6,7,8,9,10,11,12]. Considering the tunability and reconfigurability of RF/microwave system [13,14,15], the microstrip line resonator has been extensively utilized to design tunable balanced BPFs due to its simple manufacture process and easy integration with active devices. Accordingly, great efforts have been paid on tunable microstrip balanced BPFs [16,17,18,19,20,21,22,23,24].…”