Theory And Technologies Of Ultra-Wideband Tightly Coupled Phased Array

In order to meet the needs of modern radar and communication systems for integration and multi-function,ultra-wideband(UWB)antenna array technology came into being.Traditional UWB antenna array design approach focuses on the design of UWB elements,that is,designing a single antenna with UWB characteristics first,and then using single UWB antennas for array design.The performance of the array largely depends on that of the unit.In the design process,mutual coupling between elements is often suppressed as a destructive factor,which usually results in a lager transverse dimension.Ultra-wideband antenna arrays based on tightly coupled effects do the opposite.By introducing strong coupling between the array elements as reactance compensations,the entire array obtains an ultra-wideband characteristic that a single element does not have.This design approach based on the new principle makes the array possess a series of excellent performances such as compact structure,low profile,wide bandwidth,and low cross polarization ratio.In view of the noteworthy advantages of tightly coupled ultra-wideband antenna array,this paper focuses on the research of tightly coupled ultra-wideband antenna array in terms of basic theory and key technologies.The thesis is organized as follows:Firstly,the background and significance of the research work are introduced followed by a review of the research history and current status of the tightly coupled ultra-wideband antenna array.Besides,the Floquet theory involved in periodic arrays is elaborated,and the basic principle of the tightly coupled ultra-wideband antenna array is interpreted in detail based on the equivalent circuit model.Secondly,based on the principle of strong mutual coupling,two ultra-wideband antenna arrays using horizontal dipoles are designed accompanied by the application of key technologies involved.The first array adopts a Marchand balun with perforations for balanced feeding and wideband matching.Through the collaborative optimization of both the balun and the dipole,the array achieves an impedance bandwidth of 5: 1 and wide-angle scanning performance.The second array is dual-polarized,which exploits unbalanced feed and uses a resistive sheet to eliminate the short-circuit resonance.The design provides ultra-wideband impedance matching throughout the 0.2-2.7 GHz band.Thirdly,in order to solve the problem that the second array is complicated to be fabricated,a dual-polarized tightly coupled ultra-wideband antenna array based on vertical dipoles is proposed.A marchand balun with impedance transformation function is employed for broadband matching.A carefully designed frequency selective surface(FSS)is loaded as a reactive component to adjust impedance matching and improve radiation efficiency.A resistive frequency selective surface(RFSS)is integrated with the array to eliminate the short-circuit resonance.The final design also demonstrates an ultra-wide bandwidth of 13.5:1(0.2-2.7 GHz).An 8×8 array prototype is fabricated and tested to validate the design.Measured results demonstrates good agreement with simulations.