Dual-mode dual-band compact balanced bandpass filter using square patch resonator

A novel dual-mode dual-band compact balanced bandpass filter is designed using four square patch resonators arranged in 2 × 2 configuration. The patches are fed diagonally to suppress the common mode (CM) and transmit the differential mode (DM). Two closely spaced bands are designed at 2.1 GHz and 2.4 GHz, which have good isolation between them. Insertion loss in DM is 1.3 dB and 1.2 dB, and the CM suppression is 10 dB and 16 dB. The bandwidth is 180 MHz and 75 MHz in the two bands.