In this communication, a novel dual-band dual-polarized filtering antenna with high selectivity is proposed. By etching four slots at each side of a square radiating patch, dual operation bands are observed as well as a natural radiation null between the two bands. Another two radiation nulls are generated by introducing a novel feeding structure, which is composed of a microstrip line with open-circuit stepped-impedance resonators (OCSIR). Thus, a dual-band bandpass filtering response of the realized gain is obtained. Each polarization of the antenna is differentially fed, and the differential port isolation is better than 37 dB. A prototype of the antenna element and a 1×4 array is fabricated and tested to validate our design. Measured results show that the antenna element has dual operation bands of 3.28-3.71 GHz and 4.8-5.18 GHz for VSWR<1.5. Besides, a high out-of-band gain-suppression level which reaches 17.7 dB is also obtained. Good performance of the proposed antenna makes it a promising candidate for 5G sub-6 GHz base station systems.

In this paper, a differentially fed, wideband dual-polarized patch antenna with filtering response is proposed. A novel E-shaped feeding structure with one end shorted to the ground is proposed to excite a square patch antenna, and an extra resonant mode is induced, which leads to a wider operation band. Besides, symmetric open/short-circuited stepped impedance resonators (O/SCSIRs) are proposed to generate the third resonant mode. And the bandwidth is further improved. Moreover, the gain-suppression level outside the operation bands is greatly enhanced as the introduction of O/SCSIRs. A prototype of the proposed antenna is fabricated and tested. Measured results show that the proposed antenna has a wide operation band of 22.2% (3.12-3.9 GHz) for active VSWR < 1.5. Stable in-band gains of 8.1 ± 0.3 dBi and unidirectional radiation patterns are also obtained. Moreover, the out-of-band gain suppression level is better than 18.5 dB. A 1×4 liner array is also developed to validate our design. Good radiating performance of the proposed antenna makes it a promising candidate for 5G Sub-6 GHz base station applications.

A differentially fed dual-polarized planar antenna with a wide bandwidth and high common-mode suppression is presented in this paper. The antenna is composed of four folded dipoles that are connected to each other via the coplanar striplines. Two integrated baluns are utilized to excite the folded dipoles simultaneously to realize ±45° linear polarizations. Owing to the loaded shorting stubs, the impedance matching is improved and the operational bandwidth is broadened. Under differential-mode (DM) excitation, the antenna has a superior unidirectional radiation over a wide bandwidth. Under common-mode (CM) excitation, the antenna achieves a high level of CM suppression performance due to the proposed feeding structure. Measured results exhibit that the antenna gains a wide -15-dB differential impedance bandwidth of 51.1% (1.66-2.80 GHz) and a high port isolation of 38 dB between the differential ports. Moreover, the CM reflection coefficient is larger than -1.32 dB within the DM passband, which indicates that the high CM suppression is attained. To further validate the design concept, a 1×4 antenna array is fabricated and measured to demonstrate the superior performances of wide bandwidth, high port isolation, high CM rejection, and good unidirectional radiation.