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排序方式: 共有8528条查询结果,搜索用时 109 毫秒
81.
82.
王晓晶 《计算机工程与科学》2014,36(10):1906-1910
天馈线系统产生的无源互调干扰有其独特性,实践中多采用测试仪表现场排查方法,存在效率低下、准确率低等问题。针对这些问题,提出了利用基站系统作为互调检测硬件平台的天馈线干扰非现场排查法,可以通过干扰频谱数值对比,从复合干扰中分离出由天馈系统引发的互调干扰并对其进行定性,因而提高了检测排查的效率和准确性。 相似文献
83.
To improve the capacity of initial ranging (IR) users simultaneously accessing into network and enhance the performance of the IR, a novel IR algorithm is presented for the orthogonal frequency division multiple access systems with the smart antenna. The beamforming weight vectors provided by the antenna array are introduced for the IR users, and the procedures of the multiuser parameter estimation and the interference cancellation are designed. The proposed method can improve the accuracy of the channel estimation of active paths and efficiently reduce the residual multiple access interference. Simulation results show that the proposed method has a much better performance than the available successive multiuser detection and interference cancellation algorithm and accommodates more active ranging users simultaneously accessing into a cell. 相似文献
84.
Coupled gas chromatography with electroantennographic detection (GC-EAD) using antennae of adult female Manduca sexta was employed to screen for olfactory stimulants present in headspace collections from four species of larval host plants belonging to two families: Solanaceae—Lycopersicon esculentum (tomato), Capiscum annuum (bell pepper), and Datura wrightii; and Martyniaceae—Proboscidea parviflora. Headspace volatiles were collected from undamaged foliage of potted, living plants. GC–EAD revealed 23 EAD-active compounds, of which 15 were identified by GC-mass spectrometry. Identified compounds included aliphatic, aromatic, and terpenoid compounds bearing a range of functional groups. Nine EAD-active compounds were common to all four host plant species: (Z)-3-hexenyl acetate, nonanal, decanal, phenylacetaldehyde, methyl salicylate, benzyl alcohol, geranyl acetone, (E)-nerolidol, and one unidentified compound. Behavioral responses of female moths to an eight-component synthetic blend of selected tomato headspace volatiles were tested in a laboratory wind tunnel. Females were attracted to the blend. A comparison of responses from antennae of males and females to bell pepper headspace volatiles revealed that males responded to the same suite of volatiles as females, except for (Z)-3-hexenyl benzoate. EAD responses of males also were lower for (Z)- and (E)-nerolidol and one unidentified compound. Electroantennogram EAG dose–response curves for the 15 identified EAD-active volatiles were recorded. At the higher test doses (10–100 g), female antennae yielded larger EAG responses to terpenoids and to aliphatic and aromatic esters. Male antennae did respond to the higher doses of (Z)-3-hexenyl benzoate, indicating that they can detect this compound. On the basis of ubiquity of the EAD-active volatiles identified to date in host plant headspace collections, we suggest that M. sexta uses a suite of volatiles to locate and identify appropriate host plants. 相似文献
85.
86.
Xiong‐Min Hu Sai‐Wai Wong Yin Li Jing‐Yu Lin Yang Yang Guang‐Hua Sun Li Zhang 《国际射频与微波计算机辅助工程杂志》2021,31(1)
A broadband high‐gain slot grid array antenna (SGAA) is proposed in this paper. Based on the electromagnetic complementarity principle, the metal elements in the traditional microstrip grid array antenna (GAA) are replaced by a wide slot element. Compared with the GAA, the proposed SGAA achieves broadband and high‐gain performance. In order to demonstrate this concept, a prototype with 9‐element SGAA is designed using wide slot radiation elements and fabricated on Rogers 5880 printed circuit board (PCB) substrates, which is fed by a 50 Ω coaxial probe. The measured and simulated results show a good agreement. The proposed SGAA achieves a measured peak gain of 14.8 dBi at 26.0 GHz, a 10‐dB impedance bandwidth from 22.2 to 28.5 GHz with a fractional bandwidth of 24.9%. These results indicate that the SGAA is with high performance and it is suitable for the fifth‐generation (5G) millimeter wave (mmW) wireless communication system. 相似文献
87.
A low profile circularly polarized (CP) antenna with reconfigurable polarization is designed and presented, which can radiate omnidirectional patterns that can be switched between left‐hand circularly polarized (LHCP) and right‐hand circularly polarized (RHCP). A pair of arc‐shaped complementary dipoles is acted as reconfigurable elements by bridging four pin diodes at the dipole arced arms. A meander phase shift line is employed to connected the arc dipole arms and plate cavity to adjust the phase relationship of two sources. The proposed antenna exhibits the omnidirectional radiation pattern by combining six identical elements placed in a circular array configuration. 24 p‐i‐n diodes are exploited to six elements, by manipulating the dc bias voltage across the diodes, the polarization state of the antenna can be switched. The patterns of the antenna are similar to that of a dipole, but its size is only about Φ0.87 × 0.029λ0 at 5.8 GHz. The overlapped bandwidth of measured 3‐dB axial ratio (AR) and 10‐dB return loss is 5.724‐5.87 and 5.738‐5.91 GHz for two polarization states, which are right on the target of ISM band. It can be well adapted to medical diagnosis systems. 相似文献
88.
In this paper, a broadband dielectric resonator antenna (DRA) with a simple H‐slot feeding structure is proposed. The broad bandwidth (~45%) and uni‐directional radiation enable this DRA suitable to work as a radiation element in the construction of a beam‐scanning array with not only low frequency sensitivity which is important for accurate angle estimation of in‐coming targets, but also a wide scanning range. Moreover, stable coupling coefficients are established around all the above three resonances with respect to its corresponding feeding line, ensuring a low sidelobe level (SLL) across the whole operating frequency range. In order to realize such a DRA, a latticed rectangular structure is utilized to generate the lower two resonances, while the upper resonance is generated by its H‐shaped feeding slot. The shape of the latticed dielectric resonator is also modified according to a 3‐D printed fixing structure for an accurate installation. A 20‐element beam‐scanning prototype is demonstrated and manufactured. The range of scanning angle is from ?36° to +13° within the bandwidth of 10 to 16 GHz, corresponding to a frequency sensitivity of only 122.5 MHz/o. The achieved SLL are smaller than 19 dB for all scanning beams. The above performance indicates that, this array is very suitable for near‐range radar systems requiring an accurate angle estimation. 相似文献
89.
在室内定位设计中,接收信号强度(RSS)容易受到发射功率、信号衰减和多径环境等因素的影响。在锚节点天线高于被测节点天线的应用条件下,提出一种基于RSS的二维到达角(AoA)估计方法。将三个定向天线作为锚节点的波束切换天线且三个波束的方向图重叠,在测向技术中的和差法理论基础上,从多径信号分析和克拉美罗下界推导的角度出发,论证当AoA处于方向图重叠区域时RSS差分处理对于多径和噪声干扰具有一定程度的抑制作用,并研究该抑制效果与波束切换天线参数之间的关系。仿真结果表明,在单个锚节点条件下,该方法在约150 m2的定位区域范围内获得的平均AoA估计误差为4.3°,具有较高的AoA估计和定位精度。 相似文献
90.
数字化相控阵天线远场测试系统设计 总被引:1,自引:0,他引:1
数字化相控阵天线广泛运用于各种相控阵雷达当中,针对数字化相控阵天线测试过程数据量大、耗时长、自动化程度不足的现状,提出了一种数字化相控阵天线远场测试系统设计方案,并进行了测试系统开发验证.系统采用六轴工业机器人、三轴扫描架、冷水机、矢量网络分析仪、功率放大器、电源等设备模块集成并布置于暗室中,测试软件系统采用模块化设计方法,利用多线程技术实现测试设备模块并行调用,实现多频点、多波位、多通道同步测试以及测试过程时序的优化.系统具备良好的维护性和拓展性,集成多样化的测试参数配置和显示界面接口,实际应用表明数字化相控阵天线测试系统能满足相控阵天线方向图测试的各项指标要求,和传统方案相比操作简单、自动化程度高,能较大程度地提高测试效率. 相似文献