Research On Key Technologies Of Tightly Coupled Arrays

Shannon’s theorem states that channel capacity is proportional to bandwidth,implying the wider the bandwidth,the stronger the wireless system’s information transmission ability.As a critical component in wireless systems,antennas directly determine the performance of the system.Currently,broadbandization has become a development trend in communication,radar,and electromagnetic situation awareness systems.The height of the antenna profile has also been highly required to meet the aerodynamic characteristics in the case of conformal with the special application platforms,such as stealth aircraft and missiles.Tightly coupled arrays(TCAs)have many advantages such as wide operation bandwidth,compact structure size and large scanning angle,which can better meet the current demand of many application systems.Therefore,they have attracted the sustained attention of many domestic and foreign scholars in the past decade.Focused on the TCAs,this thesis conducts in-depth research on improving the performance in terms of the bandwidth,profile,scanning angle,and weight.The main contents and contributions of this thesis are summarized as follows:Firstly,an inductive crossing window(ICW)structure is proposed for the bandwidth expansion of the dual-polarized tightly coupled dipole array with integrated Balun(TCDA-IB).With the ICW loading between the radiation sheet and the reflective ground,the TCDA-IB achieves a bandwidth multiplication of the standing wave bandwidth while maintaining high efficiency.An equivalent circuit model is constructed for this structure,and the analysis shows that loading the ICW structure in between the radiation sheet and the reflective ground of the antenna can suppress the half-wavelength short-circuit effect of the reflector,thereby achieving bandwidth expansion.A dual-polarized tightly coupled dipole array model with the ICW loaded is established and simulated in finite element electromagnetic simulation software,containing a total of 10×10(100)elements with 8×8 elements in the center as the excitation elements and the rest edge elements as dummy elements.Furthermore,prototypes have also been designed,processed,and measured.The theoretical,simulated,and experimental results show that the dual-polarization TCDA-IB achieved a 9.3 octave bandwidth(0.6-5.58 GHz,broadside active VSWR ≤ 3.0),and beam scanning ability of ±60° in E/D plane and ±45° in H plane(active VSWR ≤ 3.5),with an average broadside radiation efficiency of over 92%.Secondly,a planer ultrawideband modular antenna(PUMA)with ultra-thin loading window(UTLW)is proposed for low-profile and wide-angle scanning.The equivalent circuit model of the whole structure and the theoretical analysis model of the local structure are established,both of which show that the UTLW structure has similar impedance matching capability with the conventional wide-angle impedance matching(WAIM)layer.Based on this idea,a low-profile dual-polarized PUMA array model is established for simulation.The array contains 20×20 elements(400 in total)with 16×16 elements in the center excited.The prototypes are designed,processed and measured.The theoretical,simulated,and experimental results show that loading the UTLW structure makes the operation band of the PUMA array range from 6 GHz to 18 GHz.The active VSWR less than 2.6 is maintained when the scanangle increases from 0° to 60° in E/D/H planes.Furthermore,the active VSWR is still less than3.0 when the scan-angle increases up to 70° in E/D/H planes.Meanwhile,the profile height of the whole structure is 3.5 mm,refering to only 0.07 wavelength of the lowest operation frequency.Finally,focusing on reducing the profile height and the weight of the antenna,a slot connected array loaded with quarter split rings(QSR)is proposed.Capacitance is introduced to eliminate the inductance caused by the reflective ground based on the analysis of equivalent complex impedence of WAIM.To solve the resonance appearing in the process of H planescanning,QSR structures are adopted to suppress the resonance.With metal wall loaded between the elements along the E plane,the active impedance matching is improved when scanning in the E plane.A low-profile and lightweight slot connected array of 10×10(100 in total)is designed,fabricated and measured.The theoretical,simulated,and experimental results show that the operation band of the antenna array covers 6-18 GHz with active VSWR ≤ 2.4.Within the frequency band from 7 GHz to 18 GHz,beam scanning ability of ±70° in E/D plane and ±45° in H plane can be achieved(active VSWR ≤ 3.5).The profile height of the whole prototype is 3.25 mm and the weight is less than 75 g.