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) & Synthetic aperture radar. 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.

A Compact Dual-Band Dual-Polarized Antenna With Filtering Structures for Sub-6 GHz Base Station Applications

Abstract: This letter presents a novel compact dual-band dual-polarized antenna with filtering structures for Sub-6 GHz base station applications. It is operating at the LTE (2500–2690 MHz) and Sub-6 GHz of 5G (3300–3600 MHz) bands, where the center frequency of upper-band (UB) is 1.32 times of lower-band (LB). Mutual coupling between LB and UB is suppressed by the introduction of the filtering stubs near the feeding lines. A sufficiently high isolation between LB and UB (>25 dB) is also obtained. The size of the proposed antenna is only 0.43 ${{\rm{\lambda }}_1} \times \text{0.43}$ ${{\rm{\lambda }}_1} \times \text{0.26}$ ${{\rm{\lambda }}_{1}}$ ( ${{\rm{\lambda }}_1}$ is the free-wavelength at 2.6 GHz). The half power beam widths are 65° ± 5° over both bands at horizontal planes. A four-element array, which consists of four hybrid antennas (the UB element is nested in the LB element) with a small array width (only 105 mm) is also studied. The proposed antenna and its array are suitable for wireless communication applications.

A monostable piezoelectric energy harvester for broadband low-level excitations

Abstract: This letter presents a monostable piezoelectric energy harvester (PEH) for achieving enhanced energy extraction from low-level excitations. The proposed PEH is realized by introducing symmetric magnetic attraction to a piezoelectric cantilever beam and a pair of stoppers to confine the maximum deflection of the beam. The lumped parameter model of such a system is presented and experimentally validated. Theoretical simulations and experimental measurements demonstrate that the proposed design can bring about a wider operating bandwidth and higher output voltage than the linear PEH. Under a sinusoidal vibration with an amplitude of 3 m/s2, a 54% increase in the operating bandwidth and a 253% increase in the magnitude of output power are achieved compared to its linear counterpart. Moreover, the proposed PEH exhibits rich dynamic features, including the tunable operating bandwidth, adjustable voltage and power levels, and softening hysteresis.

Part-dependent Label Noise: Towards Instance-dependent Label Noise

Abstract: Learning with the \textit{instance-dependent} label noise is challenging, because it is hard to model such real-world noise. Note that there are psychological and physiological evidences showing that we humans perceive instances by decomposing them into parts. Annotators are therefore more likely to annotate instances based on the parts rather than the whole instances. Motivated by this human cognition, in this paper, we approximate the instance-dependent label noise by exploiting \textit{parts-dependent} label noise. Specifically, since instances can be approximately reconstructed by a combination of parts, we approximate the instance-dependent \textit{transition matrix} for an instance by a combination of the transition matrices for the parts of the instance. The transition matrices for parts can be learned by exploiting anchor points (i.e., data points that belong to a specific class almost surely). Empirical evaluations on synthetic and real-world datasets demonstrate our method is superior to the state-of-the-art approaches for learning from the instance-dependent label noise.

Range-Angle-Dependent Beamforming of Pulsed Frequency Diverse Array

Abstract: Different from the conventional phased array, frequency diverse array (FDA) can provide electronic beam scanning without phase shifters and its beam steering is range-angle-dependent. Nevertheless, reported studies on FDA are most in continuous waveforms and the corresponding beampattern is time-variant, which increases difficulty in controlling the mainbeam direction and complexity of signal processing. To alleviate this problem, a pulsed-FDA is proposed with an aim to generate quasi-static beampattern in this communication. The corresponding constraint is derived together with the method to control the mainbeam direction. Moreover, the range-angle-dependent characteristics of the quasi-static transmit/receive beampattern are addressed considering the radar applications. Besides, range-angle-dependent beampattern significantly enhances the flexibility of beam scanning and its signal processing. Simulation results are in good agreement with the theoretical analysis.

Task Offloading in UAV-Aided Edge Computing: Bit Allocation and Trajectory Optimization

Abstract: The deployment of unmanned aerial vehicles (UAVs) in wireless communication systems promises to provide services for devices with limited or without infrastructure coverage. With the emergence of diverse Internet of Things (IoT) applications, there is an ever-increasing demand for computation resources of IoT mobile devices (IMDs) in UAV communication scenarios. Motivated by this, we consider a UAV-aided edge computing scenario and study the task offloading problem between the IMDs and the UAV, aiming to minimize the overall energy consumption for accomplishing the tasks. An alternative optimization algorithm is proposed as our solution, which jointly optimizes task offloading decision-making, bit allocation during transmission, and the UAV trajectory. Numerical results demonstrate the significant energy savings of the proposed scheme.