Multiple-input multiple-output (MIMO) antennas have been a mainstream technology in fifth generation (5G) communications. However, strong mutual coupling between both adjacent and nonadjacent elements is inevitable, especially among highly integrated devices. In this paper, a slit embedded mushroom electromagnetic bandgap structure (EBG) is primarily proposed to suppress the propagation of surface wave between antenna elements. Subsequently, complementary split-ring resonators (CSRRs) are periodically arranged in two sides of the ground to steer the surface wave. By effectively utilizing the unusual electromagnetic property of EBG and CSRR to manipulate the propagation of surface wave, the mutual coupling between antenna elements has immensely alleviated. Finally, an H-shape defected ground structure (DGS) is introduced to reinforce decoupling effect. In order to validate the feasibility of the design principle, a prototype of the proposed antenna has been fabricated and measured. Measured results demonstrate that the decoupling concept in this paper is reasonable and approximately 12 dB reduction of mutual coupling is realized. INDEX TERMS Multiple-input multiple-output (MIMO), mutual coupling, slit embedded electromagnetic bandgap structure (EBG), complementary split-ring resonator (CSRR).
In this paper, a novel PBG planar inverted-F antenna (PIFA) is presented. The PBG structure which is stuck on the back of the Teflon substrate (ε r = 2.65) can suppress the surface waves effectively, the simulated impedance bandwidth of the novel PBG PIFA is 27.5% (1.984 GHz-2.621 GHz), increased 2.1% than that of the regular PIFA, and the resonant frequency is decreased at the same time. It can be proved that the size of the antenna is reduced 10.6%. The measured impedance bandwidth is 40%, and it shows that the novel PBG PIFA is more effective and useful. The simulated radiation patterns at the two principle planes of the novel PBG PIFA are narrower than that of the regular PIFA, so the performance of the antenna is improved. The novel PBG PIFA can be applied in some wireless communication systems such as the WLAN2.4 and Bluetooth wireless technology system etc.
In this article, a broadband beam scanning antenna array is proposed in Q-band attributed to miniaturized size, wideband and high integration. A patch antenna element is utilized with a back cavity, which is formed by metallic via holes and ground plane. A 1 × 4 series fed sub-array is implemented by the patch element using multilayer PCB. Four symmetrical sub-arrays and Butler matrix feeding network are used to form the antenna array with high gain and decrease side lobes. The Butler matrix is implemented by substrate integrated coaxial line, which provides low loss of around 0.09 dB/mm from 40 to 50 GHz. The measured antenna array bandwidth is 9.8 GHz (21.8%) under the condition of voltage standing wave ratio less than 2. The main beam of the antenna array in azimuth direction is tilted to −28.5 , −14.1 , 18.4 and 35.6 and the gains are 13.11, 13.88, 14.02 and 11.78 dBi at 45 GHz, respectively. Both the measured and simulated results agree well.
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