A novel differential filtering antenna with high selectivity is proposed. The antenna is mainly composed of three different‐size patches, a slot, a pair of differential feeding lines, and a line resonator. An air gap is adopted to improve the impedance bandwidth and the filtering performance. The line resonator helps to generate high common‐mode (CM) rejection. Owing to the parasitic concave and convex patches, the filtering performance and the bandwidth of the antenna are enhanced. The parasitic concave patch affects the lower band‐edge selectivity while the parasitic convex patch influences the upper band‐edge selectivity. In addition, the frequencies of two radiation nulls can be controlled independently to achieve two high sharp roll‐off rates by adjusting the lengths of the parasitic patches. Considerable impedance matching bandwidth is achieved through an aperture coupling. Finally, a prototype of the differential filtering antenna is fabricated and tested. The measured results are in good agreement with the simulated results, showing an impedance bandwidth of 9.9% and an average realized gain of 7.5 dBi. Besides, two filter zero transmissions located at 3.40 and 3.84 GHz produced two radiation nulls.
A novel tri‐band multiple input multiple output (MIMO) antenna with high‐isolation is proposed in this article. The proposed tri‐band MIMO antenna consists of two tri‐band monopole antennas placed symmetrically. Due to the ground surface wave, a defected ground structure (DGS) is etched to extend the ground surface current and reduce the port‐to‐port coupling. Then two ground branches are loaded on the ground plane as a reflector that inhibit and reflect the coupling between the two parasitic elements. In order to suppress the space surface waves, a novel non‐connected neutralization structure is loaded on the microstrip line of two monopole antenna elements. As a result, the quite good isolation and impedance matching are obtained by generating different resonance at different frequency of the structure. Finally, the proposed tri‐band MIMO antenna with the decoupling structure achieves 5G tri‐band of 2.5–2.7, 3.26–3.83, and 4.73–4.97 GHz (S11&S22 < −10 dB, S12 & S21 < −25 dB). The results show that the proposed tri‐band MIMO antenna can cover the whole 5G bands (sub‐6 GHz) and has good isolation characteristic, which can well meet the 5G applications.
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