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1.
We present an analysis of the propagation in a uniform tunnel of semicircular cross section that contains two axial conductors. In particular, we show that, even if one of these conductors has high ohmic loss, one of the two propagating modes has relatively low attenuation. This corresponds to the situation where an unloaded dedicated wire is used to improve radio frequency communication in a mine tunnel that contains a heavily loaded trolley wire.  相似文献   

2.
The theory of transmission in a semicircular tunnel containing two axial conductors is simplified for the case of radio frequencies. It is shown that the effect of ohmic losses in the wall can be represented as series impedances per unit length in the equivalent coupled transmission line circuits. This opens the way for a systematic calculation of the mode conversion phenomena that occur when one of the axial conductors has a discrete shunt load to the ground plane. Explicit formulas are obtained for the modal conversion coefficients. These are used to discuss the effect of a shunt load on the trolley wire on the performance of a radio frequency communication system. It is confirmed that the unloaded dedicated communication line provides for a low loss mode that is hardly affected by the shunt load on the adjacent trolley wire in the tunnel.  相似文献   

3.
超短波跳频电台的自适应数据传输   总被引:1,自引:0,他引:1  
介绍了超短波跳频电台点对点数据传输的通信系统模型,在此基础上重点讨论了链路控制层协议,提出并实现了一种高效的自适应变速和自适应变帧长的组合ARQ数据传输方案,线路实验表明,该方案具有很高的数据传输效率.  相似文献   

4.
Graphene has been gradually studied as a high‐frequency transmission line material owing to high carrier mobility with frequency independence up to a few THz. However, the graphene‐based transmission lines have poor conductivity due to their low carrier concentration. Here, it is observed that the radio frequency (RF) transmission performance could be severely hampered by the defect‐induced scattering, even though the carrier concentration is increased. As a possible solution, the deposition of the amorphous carbon on the graphene is studied in the high‐frequency region up to 110 GHz. The DC resistance is reduced by as much as 60%, and the RF transmission property is also enhanced by 3 dB. Also, the amorphous carbon covered graphene shows stable performance under a harsh environment. These results prove that the carrier concentration control is an effective and a facile method to improve the transmission performance of graphene. It opens up the possibilities of using graphene as interconnects in the ultrahigh‐frequency region.  相似文献   

5.
感应无线数据通信中同频干扰抑制   总被引:1,自引:0,他引:1  
陈进 《现代电子技术》2006,29(7):96-98,101
工业现场电气设备产生的与通信载波频率相同或相近的噪声干扰(简称同频干扰),严重地制约了感应无线数据通信的应用发展。提出了采用双传输线与单接收天线同间距交叉的感应无线数据通信同频干扰抑制技术,通过原理阐述和实验分析,表明该技术能够有效地抑制同频干扰噪声,提高信噪比。  相似文献   

6.
7.
Seidel and Wait have investigated the complex propagation constant (phase and attenuation coefficients) of the fundamental mode of propagation for radio waves along a thin wire or cable, located in an elliptical mine tunnel, and found that the attenuation rate for low frequency is insensitive to the shape of the ellipse if the cable-wall distance and cross-sectional area are kept constant. We consider here tunnels of more general cross section, and obtain a characteristic equation for the propagation constant valid for sufficiently low frequency, by means of a variational formulation of an integral equation. The characteristic equation involves only the electrical parameter of the tunnel walls, the radius of the wire, and the capacitance per unit length that the wire would have if the tunnel walls were perfectly conducting. Agreement with exact calculations for several geometries is found to be excellent below about 100 kHz, and acceptable even up to 1 MHz or more, for typical tunnel parameters. Since the wire capacitance can be shown to depend most importantly on its distance from the wall and on the area of the tunnel, the conclusion of Seidel and Wait can be made more precise and extended to tunnels of arbitrary cross section.  相似文献   

8.
主要分析数字储频本身对复制信号绝对相干性的影响 ,讨论了DRFM复制信号的相干性、储频误差与输入信号及系统参数的关系 ,推导出了计算公式。最后根据实际应用对DRFM的相位相干性进行了说明  相似文献   

9.
射频干扰对消技术抗单音干扰性能分析   总被引:1,自引:0,他引:1  
曹星 《电讯技术》2008,48(8):52-54
传统的抗射频阻塞干扰方法会引起有用信号的畸变,同时仅部分抑制了射频阻塞干扰。为了解决这些抗干扰方式存在的不足,提出了一种解决方案射频干扰对消,给出了射频干扰对消抗阻塞干扰的实现方法,并对其抗单音干扰的性能做了计算仿真。结果表明,采用射频干扰对消技术后,在Eb/N0相同的条件下,干信比在10~30dB范围内,对误码率没有影响。  相似文献   

10.
魏辉  朱艳 《现代电子技术》2007,30(17):84-86
在对大直径超长钢管、钢棒的无损检测中,用多通道旋转探头来采集信号,用滑环来传送信号,由于滑环同时又要传送磁化电流,这就给传送的可靠性带来了问题。在分析了基于滑环传送方式中所存在问题的基础上,提出了基于软件无线电的缺陷信号传输方式,将磁化电流和缺陷信号分开传送,经实践验证该方法能有效解决原系统中存在的缺陷,并且传送信号的准确度有了很大的提高。  相似文献   

11.
一种先进结构的数字射频存储器分析   总被引:3,自引:0,他引:3  
介绍了典型数字射频存储器(DRFM)工作原理、作用、主要性能参数及影响其性能参数的因素,讨论了不同结构形式对性能参数的影响,在此基础上重点分析了一种先进结构的DRFM,阐明了该DRFM的基本工作原理、各功能模块的作用和主要特点;探讨了其采用数字正交双通道的原因以及数字双通道的几种实现方法,对DRFM的设计和应用具有一定的参考价值。  相似文献   

12.
毫米波光纤(ROF)传输系统中当采用强度调制器直接调制毫米波信号时,随着传播距离的延长会产生信号强度的周期性衰落问题,限制了毫米波通信技术的发展.光学倍乘法(OFM)将低频或中频调制信号搭载在扫频光信号上,通过在基站生成毫米波的方法,有效缓解信号强度的周期性衰落,具有广阔的发展前景.提出并实验研究了一种基于光学倍乘法产生光毫米波的全双工毫米波光纤传输系统.系统中利用光纤Bragg光栅提取光波作为上行链路光载波,基站中不需配置光源,而且对光功率的损耗小,合理利用了资源.基站中还采用低频本振与毫米波载波混频的方法实现上行链路本振,解决了上行链路本振的生成难题,方法简单,成本低廉,有利于简化基站,降低成本.  相似文献   

13.
提出了一种适合于线性调频体制射频干扰滤除的方法,该方法基于短时傅立叶变换(STFT)的基本原理。针对单一频率的射频干扰在线性调频体制中非平稳性和瞬时性的特点,利用STFT 对含干扰的信号进行分析,并且在时频分布上利用特征值分解的方法得到信号子空间和噪声子空间,利用信号子空间构造投影矩阵滤除射频干扰的影响。经过实测数据的检验,信噪比提高了近10 dB,表明该方法能有效地解决射频干扰的抑制问题。  相似文献   

14.
This paper presents the measured wide-band characteristics of 900 and 1800 MHz band radio propagation channels in a tunnel environment for microcellular and personal communications. The measurements were made using the swept frequency technique. The analysis of the average measured power delay profiles reveals that the rms time delay spread is less than 25 ns when the tunnel is empty and can be as large as 103 ns when the tunnel is blocked by vehicles.  相似文献   

15.
A Cognitive Radio must sense the channel to detect spectrum holes. To this end, it senses the channel for $T_S$ and transmits its data for $N T_S$ , if the channel is not occupied by Primary User. It is expected that the more frequent arrivals of PU, characterized by the arrival rate $\lambda $ , provides CR with less opportunity. The aim of this paper is two-fold: analysis of the interaction between $N$ and $\lambda $ , as well as the access time of CR on the one hand and study of the possible benefits a variable decreasing modulation order might provide for CR on the other. In both cases, data rate of CR and the interference it causes for PU are considered as the performance measures.  相似文献   

16.
中频软件无线电接收机中信号传输和处理技术   总被引:2,自引:0,他引:2  
文章首先构建了基于软件无线电理论的中频接收机实验平台,重点介绍了DMA结合McBSP的数据双向传输技术,DSP/BIOS设置管理应用程序中工作对象McBSP和DMA,并安排工作线程的调度。  相似文献   

17.
简要阐述了射频识别技术的组成原理,分析了其技术特征,主要包括工作频率、工作方式、射频标签存储容量、数据传输速率、读写距离、多标签识别能力和安全性能等,提出了今后进一步研究的方向。  相似文献   

18.
蓝牙射频技术的分析与应用   总被引:2,自引:0,他引:2  
丁龙刚 《现代电子技术》2003,26(24):105-106
从蓝牙技术的基本原理出发。较详细地分析了蓝牙的关犍技术之一——射频技术。同时例举了利用其射频原理实现蓝牙芯片拓展应用的范例。  相似文献   

19.
介绍第三代移动通信系统无线传输技术的研究情况,对当前两种主要的无线传输技术候选方案进行比较和分析,最后对无线传输技术的发展进行预测。  相似文献   

20.
分析了射频识别电路中高频功放的特点,在此基础上提出了一种新型的高频功放电路,并对他的工作原理进行了分析。  相似文献   

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