Two-Port Dual-Band Filtering Network and Its Application on Filtering Antennas

This letter presents a two-port dual-band filtering network, which can be integrated with antennas for dual-band filtering antenna applications in sub-6 GHz systems. The proposed network consists of a slotline resonator and two stub groups, featuring second- and third-order resonant characteristics at the lower and upper frequencies. Analysis by establishing equivalent circuits is carried out to verify the performance of the network. Moreover, the proposed filtering network is integrated with a 2 × 2 antenna array. Notice that the 2 × 2 antenna array serves as the final resonator of the filtering network during the integration. A prototype working at 3.5 and 4.9 GHz is fabricated for verification purposes. The filtering antenna array features sharp roll-off at the edges, with low insertion loss, high polarization purity, and wide fractional bandwidth of 11.7% at 3.5 GHz and 13.5% at 4.9 GHz.