Xidian University

About: Xidian University is a education organization based out in Xi'an, China. It is known for research contribution in the topics: Antenna (radio) & Computer science. The organization has 32099 authors who have published 38961 publications receiving 431820 citations. The organization is also known as: University of Electronic Science and Technology at Xi'an & Xīān Diànzǐ Kējì Dàxué.

Sparse hashing for fast multimedia search

Abstract: Hash-based methods achieve fast similarity search by representing high-dimensional data with compact binary codes. However, both generating binary codes and encoding unseen data effectively and efficiently remain very challenging tasks. In this article, we focus on these tasks to implement approximate similarity search by proposing a novel hash based method named sparse hashing (SH for short). To generate interpretable (or semantically meaningful) binary codes, the proposed SH first converts original data into low-dimensional data through a novel nonnegative sparse coding method. SH then converts the low-dimensional data into Hamming space (i.e., binary encoding low-dimensional data) by a new binarization rule. After this, training data are represented by generated binary codes. To efficiently and effectively encode unseen data, SH learns hash functions by taking a-priori knowledge into account, such as implicit group effect of the features in training data, and the correlations between original space and the learned Hamming space. SH is able to perform fast approximate similarity search by efficient bit XOR operations in the memory of a modern PC with short binary code representations. Experimental results show that the proposed SH significantly outperforms state-of-the-art techniques.

Design of Tri-Band Filter Based on Stub Loaded Resonator and DGS Resonator

Abstract: A tri-band bandpass filter using stub loaded resonator (SLR) and defected ground structure (DGS) resonator is proposed in this letter. The DGS resonator on the lower plane constructs the first pass-band, and the SLR on the upper plane forms the second and third pass-bands, in which a DGS loop is properly used to provide the coupling between the SLRs. The three pass-bands are combined together with a common T-shaped feed line, and a reasonable tuning method is adopted to tune the three pass-bands with smooth responses. A compact tri-band filter with three pass-bands centered at 2.45, 3.5, and 5.25 GHz is designed and fabricated. The measurement results agree well with the full-wave electromagnetic designed responses.

High-Isolation Eight-Element MIMO Array for 5G Smartphone Applications

Abstract: In this paper, an eight-element MIMO array for 5G smartphone applications in the 3.45-GHz band (3.3–3.6 GHz) is presented. The array consists of two types of four-antenna arrays (U-shaped and L-shaped coupled-fed loop elements), which are symmetrically distributed in the inner of the smartphone frame. The dimension of the system circuit board is $124\,\,\text {mm}\times 74$ mm and the size of two elements is $4.8\,\,\text {mm}\times 9.8$ mm ( $0.055\lambda \times 0.11\lambda $ , $\lambda $ represents the free-space wavelength at 3.45 GHz) and 4.9 $\text {mm}\times 12.5$ mm ( $0.056\lambda \times 0.14\lambda$ ), respectively. The proposed MIMO array is simulated, and a prototype is fabricated and tested. The results show that all the elements can cover the desired band of 3.3–3.6 GHz under the condition of −6-dB impendence bandwidth. The isolations are enhanced to 15 dB by combining the inverted-I ground slots with neutralization line (NL) structure. In addition, the envelope correlation coefficient (ECC) via any two elements is below 0.15 that shows good independence in far-field radiation characteristic. The measured efficiencies of the elements in the operating band are higher than 40%. Moreover, the array ergodic channel capacity is also calculated based on the correlation matrix method to be about 35 bps/Hz with a 20-dB signal-to-noise ratio. In addition, the effects of the user’s hand and the head has been analyzed as well. Based on the above, the proposed eight-element MIMO array is a prospective candidate for future 5G smartphone applications.

Adaptive backstepping dynamic surface control for systems with periodic disturbances using neural networks

Abstract: This paper addresses the adaptive neural network tracking control problem for a class of strict-feedback systems with unknown non-linearly parameterised and time-varying disturbed function of known periods. Radial basis function neural network and Fourier series expansion are combined into a new function approximator to model each suitable disturbed function in systems. Dynamic surface control approach is used to solve the problem of ‘explosion of complexity’ in backstepping design procedure. The uniform boundedness of all closed-loop signals is guaranteed. The tracking error is proved to converge to a small residual set around the origin. A simulation example is provided to illustrate the effectiveness of the control scheme designed.

Efficient Wireless Power Transfer System Integrating With Metasurface for Biological Applications

Abstract: Wireless power transfer (WPT) is a key technique for many existing and emerging applications in biomedical devices. This paper presents a novel implantable magnetic coupling resonate WPT system by integrating with metasurface for biological applications. The receiver element is implanted under the skin surface 3 mm and has the dual-band property for transferring power and data telemetry simultaneously. A conformal strongly coupled magnetic resonator coil is used as the transmitting coil to construct the wireless power link. In addition, we integrate the proposed WPT system with negative permeability (MNG) metasurface over the human skin surface as a miniaturized wearable device to improve the WPT efficiency. The property of the MNG and its effect on the WPT efficiency are analyzed. Considering the special implantable environment, various misalignment tolerances between the metasurface and the receiver are discussed to evaluate the coupling response of the proposed WPT system. Finally, the efficient WPT system integrating with MNG has been verified by the experimental measurements, and the measured result shows that 15.7 dB coupling enhancement can be obtained by integrating with the MNG metasurface.