Research On Ultra-wideband Low-profile Low-scattering Tightly-coupled Antenna Technology

Modern radar and communication systems require increasingly more integration and multifunctionality.Ultra-wideband antenna technology can solve the problem of insufficient installation space and frequency interference caused by traditional multiple antennas.Unlike traditional ultra-wideband phased array antennas,tightly coupled array antennas fully utilize electromagnetic coupling to achieve ultra-wideband performance,with the advantages of low profile and low scattering.Based on the achievements of tightly coupled phased antennas,this thesis focuses on the research of ultra-wideband,low profile and low scattering tightly coupled antennas based on the basic theory and key technologies of tightly coupled antennas.The main work and research results of this thesis are as follows:First of all,at the beginning of the thesis,the background and significance of the research work and the development status of tightly coupled UWB antennas are discussed in detail,and the infinite periodic array design theory involved in UWB tightly coupled antennas is analyzed.based on the equivalent circuit model,the structure of tightly coupled UWB antennas is described.Then,the tightly coupled antenna is designed from three aspects:ultra-wideband,low profile and low scattering performance,and the key technologies applied in the design process are analyzed in detail.In the study of the radiation performance of single-polarized antennas,a single-polarized close-coupled antenna containing a new resistive surface,a wide-angle matching layer and a tapered gradation-coupled balun were designed,and the impedance bandwidth of 51:1(0.33-17 GHz)was obtained,which can be scanned at a wide angle and maintain 1/20λ_L low profile characteristics.In the study of the scattering performance of single-polarized antennas,two closely coupled antenna arrays of different antenna forms are designed,and RCS reduction is realized in the 2:1(7.5-15 GHz)operating frequency band by checkerboard arrangement.Finally,a dual-polarization tightly coupled UWB array antenna is designed.considering the complex processing problem of the horizontal dipole as a radiation unit,its structure arrangement is adjusted and tapered gradual coupling Balun feed is adopted.To improve impedance matching and radiation efficiency,a well-designed frequency selection surface,a resistive layer to eliminate short-circuit resonance,and the loading of an upper wide-angle matching layer to improve antenna impedance matching also achieve ultra-wideband impedance matching at 50:1(0.33-16.5 GHz)while maintaining1/20λ_L low profile characteristics,where the antenna active standing wave is optimized for 45°and 60°scans on the E/H plane.In order to determine the effectiveness of the designed dual polarization tightly coupled antenna,a set of 10×10antenna array was machined and tested.