| With the development of wireless technology,the convergence of two forces,technology and application,has propelled research into phased-array antennas.Many applications of phased-array antennas,such as communication distance extension,wireless power transfer,space modulation,and high gain antennas,are trending towards cost reduction,ultra-dense networking,and functional integration.Recently,a new wireless hardware architecture called digital bit array antennas has emerged.It combines traditional phasedarray technology with reconfigurable technology to provide novel capabilities.The antennas are composed of programmable radiating elements,and their electromagnetic(EM)properties can be dynamically modified by applying control signals to the reconfigurable components on the radiating surface.Dissertation focuses on the implementation of digital bit array antennas and their ability to regulate EM waves.The research contents of this dissertation are as follows:1.A novel design of a dual-channel,dual-linear-polarization(LP)2-bit array antenna utilizing the cascaded phase-shifting technique is presented for achieving wide-angle scanning of a dual-LP beam with high isolation.The highly integrated 2-bit antenna is designed based on the symmetry of the E-field distribution and equivalent circuit theory.Additionally,two independent and orthogonal EM control channels are achieved through the orthogonal arrangement of antenna elements,resulting in a channel isolation of 25 d B within the working bandwidth.The simulation and measurement results demonstrate that the array antenna can dynamically modulate the dual-LP beams,giving the sum and difference beam scanning capabilities.2.Two types of dual circularly polarized(CP)2-bit antennas using the spatial phase shifting technique are developed.The first design operates at 3 GHz,utilizing the rotational symmetry of the microstrip square patch to achieve 2-bit phase distribution.A random rotation technique is proposed to mitigate the quantized sidelobe level,and its universality is validated.The second design operates at 10 GHz,using a square ring structure with T-shaped microstrip coupling feeder,which reduces the number of switches by about 25%.The scanning ability of these arrays was verified using two 8-element linear array prototypes.3.A modular subarray with 16 2-bit left-handed circular polarized elements,featuring a hexagonal aperture and non-uniform arrangement,is proposed for global air-toground applications in Earth Station in Motion(ESIM).The occurrence of grating lobes in the subarray factor can be effectively suppressed thanks to the integrated 2-bit phase characteristic within the element.A large-scale planar array with high gain can be obtained by splicing multiple subarrays.The results show that scanning beams can cover about 60? in hemisphere space.Additionally,the splicing method of spherical conformal array is discussed,utilizing pentagon and hexagon subarrays to form a hemispherical array with wider beam scanning range.4.A time-modulated 2-bit array antenna operating in the Ku band is proposed to effectively enhance the complex structure,large size,and low integration of existing timemodulated modules.The periodic coding sequences have been optimized to achieve continuous beam scanning without phase shifters,taking into consideration the 2-bit radiation characteristics of each array element.This breakthrough overcomes the difficulty in designing high-bit arrays.The simulation and experiment results verify the low sidelobe beam scanning and flat-top beam forming capability of the array at +1 harmonic frequency.5.Low in-band RCS phased array antennas without additional EM structure are proposed based on the amplitude/phase coding principle.The polarization and phase states of the elements are controlled by switches to obtain different scattering characteristics.The simulation results demonstrate that the in-band RCS reduction is about 7 d B based on the scattering amplitude coding method and about 15 d B based on scattering phase coding. |
