Research On The Design Of Antennas Decoupling With Compound Structures

In recent years,multi-antenna systems have become the focus of wireless communication systems and radars.Meanwhile,miniaturization and integration have been the pursuit of multi-antenna systems.However,as for more and more compact design space,since the number of antennas is increasing constantly,researches on antennas decoupling will be desired.Focusing on antennas decoupling of mobile communication base stations and wideband MIMO radars,the research contents include:1.The decoupling theory of polarization diversity and decoupling cancellation circuits is discussed.As for decoupling cancellation circuits,by treating cancellation circuits as microwave networks,cascaded decoupling networks are proposed and decoupling condition is also discussed.By adopting the decoupling cancellation circuits,transfer impedance will be decreased and surface current will be suppressed.Therefore,high isolation will be achieved.2.A simple base station antenna is proposed by using two bow-tie dipoles orthogonally printed on different sides of PCB and fed with straight coaxial cables.High isolation and return loss are enhanced by searching for the best distribution of fragment-type structures in the end part of the bow-tie arms.A simple scheme for joint optimization is applied by introducing a compound design matrix for MOEA/D-GO(MOEA/D combined with genetic operators,MOEA/D-GO),which describes both the fragment-type and the key canonical structures in one design matrix.For demonstration,the design is an antenna for China's 5G band of 3.4-3.6GHz,which achieves a return loss higher than 20dB,isolation higher than 40dB.3.High-isolation design technique for dual-polarization array is proposed by locating fragment-type decoupling circuit above the array.Based on the joint optimization strategy,MOEA/D-GO is used to optimize fragment-type isolation structures,height of fragment-type structures and height of dipoles simultaneously.As a result,isolation improvement of 14dB for co-polarized elements and lOdB for cross-polarized elements is achieved in the frequency band of 3.4-3.6GHz.4.Compact bow-tie MIMO antennas sharing a small common ground plane is proposed for wideband MIMO radars.The four orthogonally deployed bow-tie antennas are optimized by using MOEA/D-DE(MOEA/D combined with genetic operators,MOEA/D-DE)to acquire dual polarization and wideband radiation.Fragment-type structures on the common ground plane are optimized by using MOEA/D-GO to acquire very high isolation.In the design,MOEA/D-DE for optimization of canonical structures and MOEA/D-GO for optimization of fragment structures are combined and iterated.Both simulation and measurement show that the optimized MIMO bow-tie antennas provide isolation higher than 30dB in a relative bandwidth of 40%(from 2.6GHz to 3.9GHz).In summary,with the systematical research on antennas decoupling,a novel and efficient design technique is proposed by using compound structures and two alternative compound multi-objective searching strategies.