Weiwen Li

Design of printed notched-monopole UWB antenna

To meet the requirement of ultra band wide (UWB) communications, a printed monopole antenna of tapered and notched radiator is designed. The simulated and measured results show that the proposed antenna achieves a broad operating bandwidth of 3.07–10.92 GHz for the 10-dB return loss. This antenna features omni-directional radiation patterns and high radiation efficiency. The parametric studies indicate that to maintain the UWB impedance performance the width of the residual lower-side metal patch must be larger than one eighth of the higher resonant wavelength. To miniaturize the antenna size, for the rectangular ground plane the width can be a bit smaller than half of the lower resonant wavelength and the height a bit larger than a quarter of this wavelength.

Synthesis of Unequally Spaced Linear Antenna Arrays With Minimum Element Spacing Constraint by Alternating Convex Optimization

A novel method called alternating convex optimization is presented to synthesize unequally spaced linear arrays with minimum element spacing constraint. In this method, the problem of synthesizing an unequally spaced array is formulated as a sequence of alternating convex optimization problems, and the excitation vector and auxiliary weighting vector are alternately chosen as the optimization variables. The minimum spacing constraint for considering the physical element antenna size can be easily imposed in this alternating optimization process. Two examples for synthesizing unequally spaced linear arrays with focused and shaped patterns are provided to validate the effectiveness and advantages of the proposed method.

A novel phase shifting surface-integrated horn antenna

We present the design of a phase shifting surface-integrated horn antenna (PSSIHA) which consists of the horn antenna and planar array lens. Planar array lens just needs one type of antenna-filter-antenna element and is applied to obtain a relatively uniform phase distribution on the aperture of the horn antenna. The PSSIHA prototype has been fabricated. Measured results match with simulated ones well. The PSSIHA achieves a higher gain and a better directivity than the horn without the lens.

Design of a metasurface Luneburg lens antenna with flared structure

This article demonstrates the design of a meta-surface Luneburg lens antenna with flared structure. The lens antenna is composed of two flared metallic cones, a metasurface Luneburg lens and a reflection plate. The refraction index of Luneburg lens can be obtained by gradually changing the radius of patch arraying on the substrate. Such an antenna structure is easy to implement with low fabrication error. Some modified methods are applied to improve the radiation performance of this antenna. Simulation results show that the designed metasurface Luneburg lens antenna has a focused beam pattern with relatively low sidelobe level.

A dual-polarized cavity-backed annular slot antenna of high isolation

In this paper, we propose a uni-directional, dual-polarized MIMO antenna for indoor 2.4-GHz WLAN systems. This antenna consists of a cavity-backed annular slot and two inverted microstrip feed lines which are mutually orthogonal. To further suppress the cross-polarized levels and enhance the ports isolation two grounded strips are symmetrically mounted in the opposite direction of the feed lines and have the same size with them. By using this way the electrical field distributions in slot are more symmetrical. The experimental results show that the prototype antenna has more than 26-dB ports isolation and the cross-polarized levels are 27dB less than the co-polarization over the working band. This designed antenna has compact size and can be easily applied in indoor MIMO WLAN base stations.

Construction of a refined practical course: Experiments of electromagnetic field and microwave technology

As a quality curriculum, the construction of our refined practical course is focused mainly on growing experiment scale and updating experiment items, in particular increasing the ratio of design experiments to meet the training requirement for high-volume engineering students. The successful construction of the course is the result of tireless efforts made by our curriculum group over the years in teaching methods, information technology application, experimental formation and team building. In this paper, the work of these years will be recalled to make a communication for the further development of the refined course.

Ultra-wideband implementation of printed rectangular monopole antenna

To meet the ultra-wideband (UWB) radio applications, a microstrip-fed printed monopole antenna is designed with a rectangular radiation patch of the golden section ratio. To maximize the impedance bandwidth and miniaturize the antenna size, a concave ground plane and a feed gap are introduced into the printed antenna. The simulation results show that the impedance bandwidth defined by the reflection coefficient S11 less than −10 dB is from 2.9 GHz to 13.3 GHz with a ration of about 1∶4.59. These results are confirmed by the experimental measure. And a nearly omnidirectional radiation pattern is exhibited

Pattern bandwidth improving of printed notched-monopole antenna

A printed monopole antenna of the tapered and notched radiator with the microstrip feed-line is designed. The simulated and measured results show that the printed antenna achieves a broad impedance bandwidth of 3.1–11.1 GHz for the 10-dB return loss. This antenna features the stable omni-directional radiation patterns over the impedance bandwidth. Using the current distribution modes the influence of the radiator cut on the radiation performance is analyzed. It is indicated that the notched radiator can improve the pattern bandwidth due to the enhanced standing-wave current by the cut at the high frequency. Compared with the cut depth, the cut width performs more important functions on the radiation characteristics. To maintain the similar radiating performance, the width of the residual lower-side patch of the notched radiator must be larger than one eighth of the high-frequency resonant wavelength.

Endless Polarization Control Based on Simulated Annealing Algorithm

A novel endless polarization control algorithm based on simulated annealing (SA) algorithm is proposed. The application of the SA algorithm in a fast feedback polarization controller (PC) constructed by four electro-optic ceramic variable waveplates for the continuous conversion of the state of polarization (SOP) is presented. The experiment results show that the fluctuation of the light intensity in the desired output SOP is less than 2 % for a random input SOP. It is demonstrated that, this SA-based PC can run reset-freely and the response time is less than 400mus.