Combinations Of Multiple Wideband Antennas And Their Decoupling Techniques

Wireless Communications provide most fundamental supports for information and digital society,which also play an important role in people's life,national economy and national defense applications.5G mobile communications are now changing people's life styles and business operations,while evolving forward B5 G and 6G mobile communications systems.Massive MIMO antennas and multi-band aperture-shared antennas are key technologies for future mobile communication systems,which have to deal with the challenges of multi-frequency,multi-mode,multi-function and multi-standard operations.In this dissertation,several combinations of multiple wideband antennas and their decoupling techniques are investigated,which include massive MIMO antennas and aperture-shared dual-band antennas.The novel contributions of this work are summarized as follows:1.Using the theory of field cancellation,an embeddable structure is used to realize the wideband decoupling of massive MIMO antennas.The embeddable structure is composed of a pair of C-shaped metal strip and a pair of U-shaped metal strip.Through the superposition of the C-shaped metal strip and the U-shaped metal strip,a broadband decoupling performance for the embeddable structure is achieved.Besides,the embeddable structure can alleviate the distortion of the radiation pattern caused by the mutual coupling between antenna elements.Experimental results show that the proposed embeddable structure can improve mutual coupling between antenna ports and restore the distortion of radiation pattern without increasing the antenna volume.Consequently,it can achieve practical value for industrial applications,which is suitable for massive MIMO antenna.2.Based on the concept of multiple field cancellation,a new method is proposed to realize wideband decoupling of massive MIMO antennas using a combined structure.The combined structure is composed of metal strip structures and partial reflective surfaces.The superposition of the metal strips and the partial reflective surface on the decoupling performance help realizing the wide-band decoupling performance of the combined structure.In addition,the combined structure can also recover the pattern by improving the pattern distortion caused by the mutual coupling between antenna elements.Experimental results show that the combined structure can better improve the mutual coupling between antenna ports and restore the distortion of radiation patterns in a wideband.Therefore,the proposed combined structure is suitable for decoupling of wideband massive MIMO antennas with compact size.3.An idea of radiation compensation is proposed to realize a fully aperture-shared dual-band antenna using a low-pass partially reflective surface.Without influencing the performance of the low-band antenna,the low-pass partially reflective surface creates a quasi-Fabry-Perot resonant cavity for the high-band antenna,which makes compensation on the radiation performance of the high-band antenna.Then,a method to enhance the bandwidth of the aperture-shared dual-band antenna by using a dual-layer low-pass partially reflective surface is developed.Experimental results show that by introducing dual-layer low-pass partially reflective surface,a fully aperture-shared dual-band antenna is achieved with a bandwidth of 45% for the low-band and 46.1% for the high-band.4.A technique of directional radiation compensation is proposed for an aperture-shared combination of a four-element high-band antenna array and one low-band antenna by introducing a low-pass partially reflective surface into the side of the high-band array.The partial reflection characteristic in the high band of the low-pass partially reflective surface helps in compensation of the directional radiation of high-band array,thus recovers the main beam of the high-band array.Meanwhile,the low-pass partially reflective surface remains the radiation performance of the low-band antenna due to its highly transmissive characteristics in the low band.What's more,the introduction of dual-layer low-pass partially reflective surface can effectively enhance the radiation bandwidth of the high-band antenna without influencing the low-band antenna.Experimental results show that the introduction of the dual-layer low-pass partial surface can effectively realize the aperture-shared dual-band antenna for the four-element high-band antenna array and one low-band antenna with a bandwidth of36% for the low-band antenna and a bandwidth of 46.5 % for the high-band antenna array.5.A principle of multiple compensations is proposed to a wideband aperture-shared combination of a high-band antenna array and a low-band antenna using a low-pass partially reflective surface and ferrite chock rings.A compact wideband antenna is developed for the low-band with a bandwidth of 75%.The low-pass partially reflective surface carries out two functions,including a low profile for the low-band antenna,a directional radiation compensation for the high-band array.Meanwhile,the ferrite chock rings help to suppress the induced common-mode current on the high-band antenna,which restores the radiation pattern distortion of the low-band antenna.Experimental results show that by introducing a single-layer low-pass partially reflective surface and ferrite chock rings,a low-profile aperture-shard combination of a low-band antenna with a bandwidth of 75% and a high-band antenna array with a bandwidth of 45% is achieve,which may find wide applications in the next generation of base-station antennas for mobile communications.