Dual-Band Dual-Polarized Base-Station Antenna Design Using Filtering Dipole Elements

In this communication, a dual-band dual-polarized antenna with very small frequency spacing is proposed for base-station applications. The antenna includes one lower band (LB) and one upper band (UP) dual-polarized filtering dipole elements. The LB antenna is embedded in the UP antenna. Guided by the well-known coupling matrix model, each antenna design yields third-order filter responses with two radiation nulls at the same stopband. The filtering performance is realized by using radiating structures to reduce the insertion loss. In addition to introducing the first radiation null with a parasitic element (PE), a filtering parasitic arm (PA) is adopted to further improve the selectivity and bandwidth of the antennas. As a result, the two adjacent working bands can be very closely placed with high out-of-band suppression. To validate the idea, a dual-band dual-polarized antenna is designed and fabricated, operating at 1.7–2.17 and 2.3–2.7 GHz with isolation of more than 20 dB without any filtering in feeding circuits. The measured results agree well with the simulations, verifying that the proposed antenna is suitable for ever-challenging wireless communication applications.