共查询到19条相似文献,搜索用时 156 毫秒
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为检验电台类装备在高空核爆电磁脉冲(high-altitude electromagnetic pulse, HEMP)环境下的生存能力,降低系统电磁脉冲易损性评估中的不确定度,设计了系统级HEMP辐照试验方案及易损性试验评估流程,建立了基于故障树模型的电台电磁损伤评估算法.以欧讯SG-7200型超短波电台的电磁易损性评估为例,应用电磁损伤评估算法开展威胁级辐照试验.试验结果表明:电台在50 kV/m的辐照试验中发生跳频现象,通信故障;在故障树模型中,根据多次试验数据得到该型电台在50 kV/m的威胁级辐照试验中系统失效概率为78.83%. 相似文献
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针对VHF话音通信无法支持远距离通信的问题,对VOIP技术进行了研究.提出了一种基于会话初始协议(SIP)的VHF话音通信远程接入系统的实现方法,给出了系统体系架构,以及接入控制设备和远程控制软件的参考设计.系统中接入控制设备和远程控制软件实现SIP用户代理功能,从而提供接入SIP系统的能力.仿真结果证明了该方法的有效性,从而为VHF话音通信系统的应用范围扩展提供了新的思路. 相似文献
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本文就如何在现有低速的电台中插入CMX909B芯片,使电台可以实现无线话音信道条件下的高速数据传输这一问题进行了研究。目前,使用的HF、VHF/UHF电台,仍以模拟话音通信为主,通信设备(如电传、传真)传输信息的能力比较低。然而,随着数据传输业务的需求越来越广泛,现有的通信设备在一定程度上已不能较好的满足通信的要求,如何利用无线模拟话音电台实现中高速率的数据传输,已显得尤为重要。本文就如何在现有低速的电台中插入CMX909B芯片,使电台可以实现无线话音信道条件下的高速数据传输这一问题进行了研究。 相似文献
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近年来,民航事业的迅猛发展,飞行流量不断增大,对管制部门的要求越来越高,相应对管制手段的要求也越来越高。主要体现在地空指挥通信上要求通信质量提高,通信覆盖范围扩大和通信系统的稳定性和可靠性提高。空管部门地空指挥通信主要以甚高频(VHF)地空话音通信为主,同时甚高频(VHF)地空数据通信也是主要通信方式。随着通信设备的增多,怎样尽量地避免遭受外界的各种电磁干扰,同时在新增VHF地空通信台站频率时,又不致使新增电台成为其它现有通信设备的干扰源;如何通过对频率资源进行精细的规划,尽可能提高频谱利用率,这是… 相似文献
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民航甚高频作为空中交通的重要管理方式,利用甚高频电台进行地空通信,可以帮助航空业务人员确定飞行状态、下达飞行指令,因此民航甚高频地空通信就显得非常关键和重要。但是,由于甚高频地空通信电台运行中面临着许多的干扰现象,比如同频干扰、互调干扰、邻频干扰、杂散辐射干扰,因此需要采用严格的防御措施,尽可能的避免地空通信电台受到干扰影响飞行,保障人们的生命健康安全和财产安全。 相似文献
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介绍了AD9858在超短波无线电通信领域中的一种应用.基于AD9858设计一种频率合成器,该频率合成器采用"DDS 倍频"的方案,具有相噪低、跳速快等优点,可用于超短波无线电通信系统. 相似文献
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Hsi-Tien Chang 《Antennas and Propagation, IEEE Transactions on》1971,19(6):751-756
Long-distance radio communication at VHF is investigated by the waveguide mode theory taking into account the strong gradient, layered structure of the troposphere. A linear-segmented numerical method for the squared refractive index profile is developed to calculate the wave modes. This method reduces the reflection error from the discontinuities that occur in the conventional step-function approximation. The frequency at which only one mode is reasonably well trapped is used to determine the lowest usable frequency for tropospheric communication. It is found that such communication is possible at almost all VHF frequencies when the refractive index contrast (Delta n ) is greater than40N units. However, ifDelta n is reduced to10N units or less, the troposphere is almost transparent for VHF radio signals. The received field in terms of the field in free space is calculated for antennas located either above or below the layer. It is shown that various long-distance radio observations can be explained by whispering-gallery modes in the troposphere. 相似文献
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A simple digital fading simulator for mobile radio 总被引:1,自引:0,他引:1
An instrument capable of simulating the multipath fading associated with VHF/UHF mobile radio channels is described. The implementation is simple, flexible, economical, and allows the fading waveforms to be repeated exactly. The control section, the quadrature modulator, and the method by which the simulator was tested are described. Level crossing rate and probability distribution function measurements over a wide range of Doppler frequencies indicate good agreement with theoretical results 相似文献
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Design and rapid prototyping of SCA-compliant public safety P25 waveform and P25?CFM3TR?CVoIP bridge
Zhongren Cao Per Johansson Williams Hodgkiss Wenhua Zhao Anthony Nwokafor Jeffrey Cuenco Brian Hobson 《Analog Integrated Circuits and Signal Processing》2011,69(2-3):245-257
Establishing radio communication between military commanders, soldiers and law enforcement officers is an important enabling capability to facilitate interoperability. The Joint Tactical Radio System (JTRS) program is enabling communications within the military by implementing different military radio waveforms on software defined radio (SDR) platforms. It is logical to include a Project 25 (P25) public safety waveform in the JTRS waveform portfolio. This paper describes the rapid development of a P25 waveform on a surrogate JTRS SDR platform. The development process and methodology, which starts from a platform agnostic executable waveform model in Matlab, through an intermediate implementation using open tools on generic platforms, to the final platform-specific implementation, is introduced and discussed. This paper shows that adopting this methodology can speed up waveform development and porting. Furthermore, this paper presents the design and implementation of a three way voice bridge among P25, the future multiband multiwaveform modular tactical radio (FM3TR), and voice over Internet Protocol (VoIP), with software communication architecture (SCA) compliant implementation for both the P25 and FM3TR waveforms. This paper shows that critical issues such as interoperability can be tackled efficiently by leveraging SDR and SCA. 相似文献
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民航VHF地空通信干扰是近年来困扰中国民航的难点问题。首先简要分析了VHF通信干扰的形成机理,结合民航甚高频通信的特点,探讨了造成VHF通信干扰的根源,最后提出了建立无线电监测站、加强与无线电部门的协调沟通等解决干扰的思路。 相似文献