Tolerance Optimization Of Antenna Arrays And Design Of Wireless Terminal Printed Antennas

In modern radar systems, large phased-array radars have been widely used, which have performance advantages such as long working distance, large observation area, large target volume, strong ability to adapt to complex environments, and strong anti-jamming capability, etc. In order to improve the ability of anti-jamming in radar system, the radar antenna requires lower sidelobe. At present, the low sidelobe array antenna has become an important component in high performance radar system, which can improve the performance of anti-jamming for the whole radar system. However, it is very sensitive to various errors for the low sidelobe array antenna, and various errors have greater impacts on the performance of sidelobe. In the terms of wireless terminal antennas, multiband antenna and UWB antenna have attracted more and more attentions, which have been widely used in wireless communication terminal design. Based on the practical requirements, the tolerance optimization for low sidelobe antenna array and the novel design of wireless terminal antennas have been studied intensively in this dissertation. The author’s major contributions and conclusions are as follows:1. A novel self-adaptive hybrid differential evolution (SAHDE) algorithm. First, the simplified quadratic interpolation (SQI) operator is used to tune the control parameters (differential scale factor F and crossover probability CR) self-adaptively, establishing the connection between control parameters and the fitness values. Combing the self-adaptive strategy with hybrid differential evolution algorithm, a novel self-adaptive hybrid differential evolution algorithm is proposed. Then,11 benchmark functions have been used to test and some numerical results show the effectiveness of the proposed algorithm. Finally, the SAHDE algorithm is utilized to synthesize low-sidelobe patterns of sparse linear array, sparse planar array and concentric ring array, respectively. Lots of simulated results illustrate that the SAHDE algorithm can gain lower peak sidelobe levels (PSLLs) than other existing algorithms for the sparse antenna arrays.2. Tolerance optimization for low-sidelobe sparse linear arrays. For sparse arrays, the low-sidelobe levels are directly related to the position of each element, and presence of the position errors will have a great impact on peak sidelobe levels (PSLLs). Therefore, the tolerance optimization problem considering random position errors is worth of research. First, the influence of position errors for sparse linear array has been analyzed. Then, a worst-case tolerance optimization model considering the random position errors is established; sample points are chosen randomly within a fixed position tolerance region, and the random tolerance optimization problem is converted to a deterministic optimization problem. Finally, the errors are assumed to obey the Gaussian distributions, and the SAHDE algorithm is used to minimize the worst-case PSLLs and obtain optimal nominal element positions for the low-sidelobe sparse linear array. Simulated results illustrate that the worst-case peak sidelobe levels for the sparse linear arrays are improved evidently. At the same time, the position coordinates considering errors are obtained.3. Tolerance optimization for low-sidelobe wideband array. It is difficult to desgin a very accurate excitation coefficients for low-sidelobe wideband array. In order to make the array meet design requirements considering errors, it is required that the excitation coefficients can tolerate the errors. First, the influence of position errors for low-sidelobe wideband array has been analyzed. Then, a fixed tolerance optimization model considering the random excitation coefficients errors is established, and the PSLLs of the worst-case is chosen as the optimization goal. The SAHDE algorithm is used to optimize the worst-case PSLLs and obtain optimal nominal excitation coefficients for the low-sidelobe wideband array. Finally, a variable tolerance model for the array is established, and the maximum tolerance excitation coefficients errors are obtained by the SAHDE algorithm and bisection method.4. Design of wireless terminal antennas. Several ultra-wideband and multiband antennas have been designed for the wireless communication terminal.1) T-shaped monopole antenna loading a rectangular ring for multiple bands operation. The rectangular ring is loaded in the terminals of the T-shaped antenna, and triple operating bands can be achieved. 2) T-shaped antenna loading T-shaped slots for multiple band operation. Inspired by the fractal antenna, the proposed method is intended to be used for designing multiple band antennas. Through loading T-shaped slots in the terminals of a T-shaped antenna, dual or triple operating bands can be achieved.3) Microstrip fed UWB antenna with band-notched characteristics. An "umbrella" structure and "bottle-shaped" structure are loaded in the opening elliptic annulus antenna, respectively. The measured impedance bandwidth defined by VSWR< 2 from 3.09 to 11 GHz, with the dual notched bands of 3.4-4 GHz and 5-5.9 GHz, is obtained.4) CPW fed UWB antenna with band-notched characteristics. An "lamp-shaped" structure and "bottle-shaped" structure are loaded in the opening annulus antenna, respectively. The measured impedance bandwidth from 3.0 to 11 GHz, with the dual notched bands of 3.3-3.8GHz and 5.05-6GHz, is obtained.