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341 results on '"Long, Yunliang"'

11. A Single-Layer Periodic Leaky-Wave Antenna With Full-Space Scanning Capability

Author

Li, Liangsheng, Li, Yuanxin, Liang, Zhixi, Zheng, Shao Yong, and Long, Yunliang

Abstract

A single-layer periodic leaky-wave antenna with full-space scanning capability is presented. The antenna is made by orthogonally bent coplanar microstrip line, periodically placed coupler and stubs. Couplers are added to allow the two coplanar symmetrical microstrip line to achieve close electromagnetic coupling. As a result, the proposed antenna achieves a high scanning directivity, and higher mode disturbance is avoided. By periodically loading stubs onto the symmetrical rampart structure, the influence of fundamental mode radiation is relieved. A prototype of antenna with aperture 5.8 × 1.5 (${\lambda }_0^2$) is fabricated and tested. The measurement results verify that the main beam of the antenna scans continuously from −90° to 90° with peak realized gain 10.4 dBi within operating frequency band of 5.3–9.3 GHz. Gain variation range is 3.3 dBi and average efficiency reaches 85%. Compared with the traditional periodic leaky-wave antenna, the single-layer structural design of the antenna renders the ground plane and via holes unnecessary, which is very convenient for fabrication.

Published
2024
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19. Trimode Leaky Wave Antenna Based on Hansen–Woodyard Condition Using DSPSL Structure

Author

Mao, Kexin, Li, Yuanxin, Liang, Zhixi, Zheng, Shao Yong, Jiang, Hongyan, and Long, Yunliang

Abstract

A trimode leaky wave antenna (LWA) based on Hansen–Woodyard condition using double-sided parallel stripline (DSPSL) structure is presented in this communication. The minimum permittivity of substrate is found out to exclude the interference from higher order space harmonics. Grooves are added within the unit cells (UCs) to suppress the open stopband (OSB). The full-space scanning mode radiated from ${n}$ = −1 space harmonic is achieved. To improve the radiations and expand the bandwidths in the backfire and endfire direction, the optimum formula of period length and number of UCs is derived based on the Hansen–Woodyard condition. The structure is further modified to maximize the gains in the backfire mode and endfire mode. A prototype of the trimode LWA is simulated, fabricated, and measured. In the backfire mode of 2.85–3.2 GHz, the main beam points to the exact backfire direction. In the full-space scanning mode of 3.2–8 GHz, the antenna scans seamlessly from −90° to +90° with suppressed OSB. In the endfire mode from 8 to 8.8 GHz, the antenna offers stable endfire radiation. The realized maximum gains are 11.34, 15.88, and 15.75 dBi in the three modes, and the size of the antenna is only $4.58\lambda _{0} \times 0.17\lambda _{0}$ .

Published
2023
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40. Higher Order FD-Padé Scheme for 3-D Parabolic Equation in Radio-Wave Propagation

Author

Wu, Xiaoping, Li, Zihao, Liang, Zhixi, and Long, Yunliang

Abstract

This letter presents a higher order finite-difference (FD) and Padé approximations method for the three-dimensional (3-D) parabolic equation (PE) to predict radio-wave propagation. This method uses a fourth-order FD approximation of the differential operator in the transverse direction and a higher order Padé approximation of the operator in the propagation direction. The fourth-order FD and higher order Padé (4FDHP) method is then derived. The Leontovich impedance boundary for the 4FDHP method and boundary for the second-order FD and higher order Padé (2FDHP) method are also derived. The important problem of the propagation angle of the different approximations for the 3D-PE is investigated. Simulated results show that the proposed 4FDHP method achieves a larger propagation angle and higher accuracy than those of the 2FDHP method and the Mitchell-Fairweather alternative-direction-implicit method.

Published
2023
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43. Quasi microstrip leaky-wave antenna with a two-dimensional beam-scanning capability

Author

Li, Yuanxin, Xue, Quan, Yung, Edward Kai-Ning, and Long, Yunliang

Subjects
Antennas (Electronics) -- Analysis, Strip transmission lines -- Analysis, Business, Computers, Electronics, Electronics and electrical industries
Abstract

A quasi microstrip leaky-wave antenna (QMLWA) with a two-dimensional (2-D) beam-scanning capability is presented in this paper. QMLWA consists of two half-width microstrip leaky-wave antennas with a phase-shifter. This new type of microstrip leaky-wave antenna has the advantages of reducing size, 2-D beam-scanning and suppressing back lobes. The main lobe scanning in H-plane (y-z plane) is achieved through varying the operating frequency. When the operating frequency increases from 4.4-6 GHz, the main lobe scans from 84[degrees] to 26[degrees] in H-plane continuously. The main lobe steers in quasi-E-plane with varying the phase difference between two haft-width microstrip leaky-wave antennas. The lobe scans from 78[degrees] to 103[degrees] in quasi-E-plane at 5.4 GHz. The experimental results show this short QMLWA (about 2 wavelengths) leaks power effectively. The back lobe in H-plane of QMLWA is suppressed 13 dB as compared with the conventional whole width MLWA at 5.4 GHz as example. The H-plane radiation characteristics of QMLWA are mainly determined by the width 8 of haft-width MLWA and the distance D between two half-width MLWA together. This size-reduced QMLWA is useful in the automotive radar system and air traffic control. Index Terms--Half-width, microstrip leaky-wave antenna, suppressing back lobe, two-dimensional (2-D) beam-scanning.

Published
2009

48. Dual-beam steering microstrip leaky wave antenna with fixed operating frequency

Author

Li, Yuanxin, Xue, Quan, Yung, Edward Kai-Ning, and Long, Yunliang

Subjects
Microwave antennas -- Design and construction, Microwave wiring -- Equipment and supplies, Finite element method -- Usage, Time-domain analysis -- Methods, Business, Computers, Electronics, Electronics and electrical industries
Abstract

A fixed-frequency dual-beam steering microstrip leaky-wave antenna is presented in this paper. A novel equation with finite-difference time-domain method is proposed to calculate the complex propagation constant of microstrip leaky-wave antenna. The microstrip leaky-wave antenna is excited by multiterminals. By control the novel feeding configuration, the microstrip leaky-wave antenna has the advantage of main lobe's dual-beam and steering at fixed-frequency. The main lobe steers from 41[degrees] to 63[degrees] for right beam and from 117[degrees] to 139[degrees] for left beam symmetrically when operating frequency fixes at 7 GHz. This new microstrip leaky-wave antenna can easily be used as collision avoidance or automobile radar system. Index Terms--Dual-beam, fixed-frequency, microstrip leaky-wave antenna (MLWA).

Published
2008

49. Improved Reference Vector Guided Differential Evolution Algorithm for Many-Objective Optimization

Author

Jie Lin, Long Yunliang, and Shaoyong Zheng

Subjects
Mathematical optimization, education.field_of_study, business.industry, Computer science, Process (engineering), Population, Evolutionary algorithm, Differential (mechanical device), Search engine, Convergence (routing), Mutation (genetic algorithm), Local search (optimization), business, education
Abstract

Most of the existing evolutionary algorithms to deal with many-objective problems are based on the enhancing of selection strategy. Among them, the reference vector-guided evolutionary algorithm (RVEA) achieves excellent performance. In this paper, a new search engine is combined with RVEA to achieve further performance enhancement of the differential evolutionary (DE) algorithm. In the optimization process of differential evolution algorithm on many-objective problems, improving convergence and maintaining diversity are two different optimization directions, and it is usually difficult to maintain a balance between them. To solve this problem, a new search engine based on DE is proposed. The proposed search engine is implemented based on a cooperative scheme of local and global search strategies. In the local search, the population is divided into several sub-populations, each of which evolves independently using the proposed mutation strategy. The distance between the individuals in each sub-population is relatively close. Therefore, it has a strong exploitation capability, and will not make the population lose diversity. Meanwhile, the selection strategy of RVEA enables the population to maintain diversity, and the DE/rand/1 utilized in global search is sufficient to keep a strong exploration capability. Therefore, the proposed approach can achieve a good balance between exploration and exploitation. The experimental results show that the proposed algorithm performs well in many-objective optimizations up to more than 10 objectives.

Published
2020

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