Abstract
An embeddable decoupling structure is proposed for massive multiple-input-multiple-output (M-MIMO) antennas in this paper. The embeddable decoupling structure is made up of an end-folded metal strip and a pair of C-shaped metal strips. By introducing the embeddable decoupling structure near two closely spaced dipole antennas, additional coupling can be generated to counterbalance the original mutual coupling between the dipole antennas. The decoupling structure is firstly designed for a 1×2 MIMO antenna, which can provide a reduction of about 5 dB for the mutual coupling. Then, an evolutional decoupling structure is designed, which is composed of a pair of inverted U-shaped metal strips and two parallel reversed C-shaped metal strips. The evolutional decoupling structure is employed in a 3 × 3 MIMO antenna operating in 5G bands to demonstrate its capability of decoupling. An average reduction of about 10 dB on mutual coupling is obtained over 3.3-4.5 GHz (30.8%). Moreover, it is found that the deteriorated radiation patterns due to the mutual coupling are improved. The decoupling structure can be totally embedded in a M-MIMO antenna, which has no increase in the antenna volume. The proposed decoupling structure exhibits advantages of radiation pattern distortion alleviation, wideband, embeddable, and dual-polarized capabilities for M-MIMO applications.
Highlights
Due to the advantages in high spectral efficiency and large system capacity, the massive multiple-input-multipleoutput (M-MIMO) is a key technology for the fifth generation and beyond (5G & B5G) in mobile communications
As it is well known that the more antennas the transmitters/receivers are equipped with, the more signal channels can be provided, there would probably be tens to hundreds of antenna elements accommodated in a M-MIMO antenna
It has been demonstrated in several previous articles that a M-MIMO system can provide high spectral efficiency and large capacity only with low mutual coupling among antenna elements [1]-[3]
Summary
Due to the advantages in high spectral efficiency and large system capacity, the massive multiple-input-multipleoutput (M-MIMO) is a key technology for the fifth generation and beyond (5G & B5G) in mobile communications. Strong mutual coupling would occur among the antenna elements, which may cause severe harms to the wireless communication systems It has been demonstrated in several previous articles that a M-MIMO system can provide high spectral efficiency and large capacity only with low mutual coupling among antenna elements [1]-[3]. The third category is introducing resonating metal decoupling structures between antenna elements, such as asymmetrical coplanar strip wall [21], H-shaped conducting wall [22], and near-field resonator [23]. It is desirable to develop a decoupling structure for M-MIMO antenna for the purpose of reducing mutual couplings between antenna ports as well as radiation patterns improvement without increasing any extra antenna volume. For dual-polarized dipole-type MIMO antennas, the parasitic decoupling dipoles for side-by-side dipoles and end-to-end dipoles are combined to form embeddable decoupling structures to reduce the mutual coupling.
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