| With the increase of the types of radar observation targets and the rapid development of wireless communication systems in the past decades,the requirements for phased array antennas(PAAs)are getting higher.Thus,the ultra-wideband,wide-angle scanning and shared-aperture PAAs have been developed rapidly under these demands.Ultra-wideband PAAs can meet the requirements of phased array radars and wireless communication systems well in different frequency bands.Moreover,modern phased array radars require360°full airspace surveillance coverage,necessitating a wide-angle scanning range of the PAAs within these systems.Additionally,the shared-aperture PAAs are designed to integrate the antennas of different frequency bands into the same radiation aperture.Besides,different array antennas can work independently.In this way,the whole antenna system can effectively reduce the load weight,volume and radar scattering cross section of the antenna while keeping wideband performance.Therefore,in the studies on PAAs,ultra-wideband,wide-angle scanning and shared-aperture PAAs have important engineering applications.This dissertation aims to conduct in-depth studies on the practical application of ultra-wideband wide-angle scanning PAAs and shared-aperture PAAs.The main contributions and innovations in this proposed dissertation are summarized as follows:1.A planar ultra-wideband PAA using multi-layer printed circuit board(PCB)fabrication technologies is presented in this dissertation,addressing the high integration requirements of modern phased array radars.Initially,the ultra-wideband performance of the tightly coupled PAAs is explained by the equivalent circuit model.Asymmetric dipoles are utilized to improve impedance matching within the operating bandwidth.Subsequently,the operating bandwidth is broadened downward through the integration of a coupling patch beneath the asymmetric dipoles.The dissertation further presents a detailed analysis of common mode resonance based on equivalent rectangular waveguide theory is presented.A metal wall is strategically inserted to mitigate the common-mode resonance.Furthermore,the scanning range is significantly improved by loading a double-layer C-type split ring metasurfaces.Simulation results show that the proposed antenna can achieve a 5.1:1(2.4～12.2GHz)bandwidth with the scanning range of±75°in the E and D planes and±60°in the H plane,and the active Voltage Standing Wave Ratio(VSWR)is lower than 3:1.A 12×12 array prototype is fabricated and measured to demonstrate the proposed idea,with good agreement achieved between measurements and simulations.2.This dissertation presents a full-metal dual-polarized ultra-wideband PAA designed with large element spacing,designed to fulfill the lightweight and cost-effective requirements of space-based phased array radars.Initially,two coupled blocks which can increases the inter-element capacitive coupling are added at the end of the radiating arms to expand the low-frequency bandwidth of the full-metal antenna.Additionally,an equivalent rectangular resonator model is then employed to characterize resonances influencing the high-frequency bandwidth.Subsequently,the high-frequency resonance is shifted from 10.9GHz to 11.6GHz by loading a perturbational metal column block on the ground.This adjustment allows for an increased element spacing of 0.533×0.533λ_h~2.Consequently,the designed antenna has a reduction of at least 6.6%in the number of required expensive transmit/receive(T/R)modules compared to other antennas.Thus,the cost can be noticeably reduced.Simulation results show that the proposed full-metal dual-polarized ultra-wideband PAA demonstrates a 5.33:1(2～12.65GHz)bandwidth with±60°scans in the E and H planes without scan blindness.To validate the design,a prototype of10×9 array is manufactured through precision-machining and measured.Simulations and measurements show good agreement.3.An ultra-wideband dual-polarized PAA with 9:1 bandwidth is proposed in this dissertation,based on the theory of tightly coupled PAAs.Firstly,the short-circuit resonance of the antenna is analyzed and eliminated by loading a split X-shaped resistive frequency selective surface(FSS)according to the equivalent circuit model.Additionally,the active VSWR of the antenna at low-frequency band can be improved at large angle scanning cases by utilizing the split X-shaped resistive FSS.However,the radiation efficiency will decrease due to the loss of the resistive material.To solve this problem,two rectangular patches served as the directors are utilized to increase the forward radiation of the antenna,thereby improving the radiation efficiency in the whole operating band.Simulation results show that the proposed dual-polarized PAA can scan up to±75°/±75°/±60°in the E/D/H planes with the active VSWR lower than 3:1,respectively.Besides,the average radiation efficiency is above 86%throughout the entire operating bandwidth(2～18GHz).Furthermore,a dual-polarized 16×16 array prototype is fabricated to validate the design method of the proposed ultra-wideband dual-polarized PAA.Ultimately,the measured results verify the correctness of it.4.Based on the application requirements of synthetic aperture radar(SAR)system for multi-band antennas,a dual-band shared-aperture PAA operating in L and X band is proposed in this dissertation.Generally,traditional shared-aperture PAAs,characterized by substantial frequency ratios,conventionally position lower-band antenna elements on the uppermost layer,with higher-band counterparts beneath.However,this configuration inevitably degrades the radiation performance of the higher-band antenna.Therefore,to address the limitations,a shared-aperture PAA using a novel topology is proposed in this dissertation.The higher-band antenna is placed above the lower-band one by introducing an FSS layer,which serves as the ground plane of the higher-band antenna.The novel topology suggests using a slot antenna with a coaxial feed for the X-band antenna element,and a metal cavity-backed slot antenna for the L-band antenna element.Simulations indicate that the proposed shared-aperture array antenna can achieve bandwidths of 21%(1.7～2.1GHz)and 46%(7.5～12GHz)in L and X bands,respectively.Furthermore,the X-band antenna can scan±60°and±30°in the E and H planes,respectively.Finally,considering the size and cost,a shared-aperture antenna prototype,which consists of 6×6X-band elements and one L-band element,has been fabricated and measured,considering size and cost factors.The measured results agree well with the simulated ones. |
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