5G多频协同技术研究

与4G时代网络能力主要以下行为主不同,5G时代的业务特性正在发生变化.随着直播业务的高清化和无线视频监控类应用等一系列5G基础业务的兴起,对上行能力提出了更高的要求.本文结合5G频率资源现状,简述基于5G R16版本的几种多频协同技术,深入分析多频协同技术的网络性能及组网中面临的问题,并提出在实际组网中多频协同技术的选...     

基于确定性能力的5G垂直行业场景洞察及发展模式探讨

得益于5G革命性的性能提升,下一代信息通信技术对千行百业进行赋能的能力基础也有了大幅提升。2020年,全球已有超过多家运营商提供了5G商用服务,但2C市场带来的收益增长较为有限。因此,各大运营商已重点布局2B行业市场。但该领域目前仍处于发展初期,存在标准制订偏晚,产业链不成熟,场景分类不清晰等问题。本文重点对应用场景进行了探讨归类,并对未来5G垂直行业市场空间和发展方向进行了探讨,为5G垂直行业应用未来发展提供参考。     

超强激光与等离子体相互作用研究的最新进展

本文综述了峰值脉冲功率高达１０＾１２Ｗ的激光与等离子体相互作用研究的进展，这些研究将对原子物理学，等离子体物理的研究和发展以及加速器的应用产生重大影响。     

Temperature Evolution of Energy Gap and Band Structure in the Superconducting and Pseudogap States of Bi_2Sr_2CaCu_2O_(8+δ) Superconductor Revealed by Laser-Based Angle-Resolved Photoemission Spectroscopy

We carry out detailed momentum-dependent and temperature-dependent measurements on Bi_2Sr_2CaCu_2O_(8+δ)(Bi2212) superconductor in the superconducting and pseudogap states by super-high resolution laser-based angleresolved photoemission spectroscopy. The precise determination of the superconducting gap for the nearly optimally doped Bi2212(T_c= 91 K) at low temperature indicates that the momentum-dependence of the superconducting gap deviates from the standard d-wave form(cos(2Φ)). It can be alternatively fitted by including a high-order term(cos(6Φ)) in which the next nearest-neighbor interaction is considered. We find that the band structure near the antinodal region smoothly evolves across the pseudogap temperature without a signature of band reorganization which is distinct from that found in Bi_2Sr_2CuO_(6+δ) superconductors. This indicates that the band reorganization across the pseudogap temperature is not a universal behavior in cuprate superconductors.These results provide new insights in understanding the nature of the superconducting gap and pseudogap in high-temperature cuprate superconductors.     

4.9 GHz异帧干扰问题研究

相对2.6 GHz频段,4.9 GHz频段可以通过灵活的帧结构配置满足上行大带宽的行业应用需求,但异帧结构组网可能导致基站和终端之间存在交叉时隙干扰,因此研究4.9 GHz的异帧干扰问题是非常必要的.基于3D-UMa传播模型,研究了4.9 GHz频段1D:3U:1S和5D:3U:2S帧结构配置下的交叉时隙干扰问题,并结...     

Electric gating of the multichannel conduction in LaAlO_3/SrTiO_3 superlattices

The electric gating on the transport properties of two-dimensional electron gas(2DEG) at the interface of LaAlO₃/SrTiO₃(LAO/STO) heterostructure has attracted great research interest due to its potential application in fieldeffect devices. Most of previous works of gate effect were focused on the LAO/STO heterostructure containing only one conductive interface. Here, we systematically investigated the gate effect on high-quality LAO/STO superlattices(SLs)fabricated on the TiO₂-terminated(001) STO substrates. In addition to the good metallicity of all SLs, we found that there are two types of charge carriers, the majority carriers and the minority carriers, coexisting in the SLs. The sheet resistance of the SLs with a fixed thickness of the LAO layer increases monotonically as the thickness of the STO layer increases. This is derived from the dependence of the minority carrier density on the thickness of STO. Unlike the LAO/STO heterostructure in which minority and majority carriers are simultaneously modulated by the gate effect, the minority carriers in the SLs can be tuned more significantly by the electric gating while the density of majority carriers is almost invariable. Thus, we consider that the minority carriers may mainly exist in the first interface near the STO substrate that is more sensitive to the back-gate voltage, and the majority carriers exist in the post-deposited STO layers. The SL structure provides the space separation for the multichannel conduction in the 2 DEG, which opens an avenue for the design of field-effect devices based on LAO/STO heterostructure.     

超强激光与等离子体相互作用研究的最新进展

本文综述了峰值脉冲功率高达１０１２Ｗ的激光与等离子体相互作用研究的进展．这些研究将对原子物理学、等离子体物理的研究和发展以及加速器的应用产生重大影响．     

Electronic structure of heavy fermion system CePt_2In_7 from angle-resolved photoemission spectroscopy

We have carried out high-resolution angle-resolved photoemission measurements on the Ce-based heavy fermion compound CePt_2In_7 that exhibits stronger two-dimensional character than the prototypical heavy fermion system CeCoIn_5.Multiple Fermi surface sheets and a complex band structure are clearly resolved. We have also performed detailed band structure calculations on CePt_2In_7. The good agreement found between our measurements and the calculations suggests that the band renormalization effect is rather weak in CePt_2In_7. A comparison of the common features of the electronic structure of CePt_2In_7 and CeCoIn_5 indicates that CeCoIn_5 shows a much stronger band renormalization effect than CePt_2In_7. These results provide new information for understanding the heavy fermion behaviors and unconventional superconductivity in Ce-based heavy fermion systems.     

Effect of Cu doping on the secondary electron yield of carbon films on Ag-plated aluminum alloy

Reducing the secondary electron yield (SEY) of Ag-plated aluminum alloy is important for high-power microwave components. In this work, Cu doped carbon films are prepared and the secondary electron emission characteristics are studied systematically. The secondary electron coefficient δ_max of carbon films increases with the Cu contents increasing at first, and then decreases to 1.53 at a high doping ratio of 0.645. From the viewpoint of surface structure, the higher the content of Cu is, the rougher the surface is, since more cluster particles appear on the surface due to the small solid solubility of Cu in the amorphous carbon network. However, from viewpoint of the electronic structure, the reduction of the sp² hybrid bonds will increase the SEY effect as the content of Cu increases, due to the decreasing probability of collision with free electrons. Thus, the two mechanisms would compete and coexist to affect the SEY characteristics in Cu doped carbon films.