Zhaolin Zhang

Study of novel antenna radome for circular polarizer and director

Abstract This study presents the use of contiguous rectangle-patches radome as a method of generating circularly polarized signals from linearly polarized antenna or antenna array that are covered by the structure. Experiment results of the novel structure with 2 × 2 antenna array are demonstrated for L-band operation. It is shown that left hand circular polarization of antenna array can be achieved with appropriate parameters design of radome. In addition, the structure is also built as a director that can greatly improve the gain of the antenna.

One terminal improving method of open-circuit near-field antenna of UHF RFID system

A novel broadband dual-loop antenna is presented for the ultra high frequency (UHF) near-field radio frequency identification (RFID) applications. Owing to the novel structure, the current distribution along the loop is kept in phase, as well as the metal terminals exert less influence on the z-orientation magnetic field. The antenna with novel terminals is described and the principle of operation is explained. A comprehensive parametric study of the new model is carried out and the results are presented and discussed in detail. To prove the novel structure, a prototype is developed and fabricated. The measurement results demonstrate that the antenna could achieve a broad bandwidth and low gain, and produce a strong magnetic field with a relatively small z-orientation magnetic field empty hole in the near field. Hence, the work is very promising for UHF near-field RFID reader applications.

Energy Efficiency TDMA/CSMA Hybrid Protocol with Power Control for WSN

Wireless sensors network (WSN) is widely used in the Internet of Things at present. However, limited energy source is a critical problem in the improvement and practical applications of WSN, so it is necessary to improve the energy efficiency. As another important evaluation criterion of transmission performance, throughput should be improved too. To mitigate both of the problems at the same time, by taking the advantages of Time Division Multiple Access (TDMA) and Carrier Sense Multiple Access (CSMA) at the medium access control (MAC) layer of WSN, we propose a hybrid TDMA/CSMA MAC layer protocol. Meanwhile, we design a novel power control scheme to further reduce the energy consumption and optimize the transmission slots. The simulation results demonstrate that the proposed protocol significantly improves the throughput and energy efficiency.

Cross-layer model design in wireless ad hoc networks for the Internet of Things

Wireless ad hoc networks can experience extreme fluctuations in transmission traffic in the Internet of Things, which is widely used today. Currently, the most crucial issues requiring attention for wireless ad hoc networks are making the best use of low traffic periods, reducing congestion during high traffic periods, and improving transmission performance. To solve these problems, the present paper proposes a novel cross-layer transmission model based on decentralized coded caching in the physical layer and a content division multiplexing scheme in the media access control layer. Simulation results demonstrate that the proposed model effectively addresses these issues by substantially increasing the throughput and successful transmission rate compared to existing protocols without a negative influence on delay, particularly for large scale networks under conditions of highly contrasting high and low traffic periods.

Anti-jamming techniques based on digital multi-beam and robust mode control

The COMPASS Satellite Navigation System has been developing rapidly. Facing the complicated electromagnetic environment, how to effectively improve the anti-jamming capability of navigation receivers becomes more and more important for the future advanced weapon system. In this paper, we study the anti-jamming techniques based on digital multi-beam and robust mode control. The working mode is switched timely and properly according to the environment to achieve flexible beam control. Our proposed scheme improves robustness as well as time-reality and effectively decreases the power consumption while guaranteeing good anti-jamming capability. This scheme has been successfully applied in the practical project and achieved good performance.

Robust SFAP Anti-jamming Algorithm Based on Generalized Sidelobe Cancellation

With the rapid development and the wide application of Global Navigation Satellite System (GNSS), anti-jamming technology has been widely studied and applied for anti-jamming satellite navigation receivers in recent years. The robust space-frequency adaptive processing (SFAP), combining array signal processing theory, adaptive filtering algorithm and Fast Fourier Transform (FFT), based on segmentation of the frequency-domain is proposed in this paper. And the method for calculating the anti-jamming weight of the frequency-domain based on Generalized Sidelobe Cancellers (GSC) is also presented, which reduces the dimension of the matrix during the process of the covariance matrix inversion. Consequently, it makes the system much easier to implement. In addition, the algorithm is improved further, combined with robust beamforming technology. Through notch widen against frequency-domain, the error that exist in the actual system, influencing the performance of algorithm, will be effectively reduced, and the adaptability for high dramatic environment will also be enhanced.

Mutual coupling efficient analysis of rectangle microstrip circular polarization antenna array

Mutual coupling performance of the microstrip circular polarization (CP) antenna array is analyzed in this study. Compared with the single antenna application, in the antenna array, the S11, the radiation pattern, and the axial ratio will all be changed due to the mutual coupling and the axial ratio will be more sensitive. To further prove the concept and performance effect, a model of the microstrip antenna array is developed and analyzed in theory. The simulation and measurement results demonstrate that the relative position of antennas in the array exert different effect on the performances of the antenna. Thus, the study provides some very useful results of the CP antenna array.