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在2000年世界无线电大会上,第3代移动通信系统(3G)的地面系统被确定可使用5种无线传输技术,它们是CDMA-DS、CDMA-MC、CDMA-TDD、TDMA-SC和TDMA-TDD。其中前3种基于CDMA(码分多址)技术,后两种基于TDMA(时分多址)技术。可见,在3G标准中,CDMA是主流技术。CDMA(Code Division Multiple Access)蜂窝系统由于采用了一种称之为扩频的通信技术,所以与采用TDMA和FDMA(频分多址)的GSM蜂窝系统相比,具有抗干扰性好、系统容量… 相似文献
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软件无线电(Software Radio)的概念是由美国科学家Joe·Mitola于 1992年 5月在美国电信系统会议上首次明确提出的。软件无线电的基本概念是将硬件作为无线通信的基本通用平台,而用软件实现尽可能多的无线及个人通信功能。软件无线电的核心是将宽带A/D和D/A尽可能靠近天线(将A/D和D/A由基带移到中频甚至射频),用实时高速DSP/CPU代替传统的专用数字电路做A/D转换后的一系列处理,将无线通信的各种功能用软件进行定义。 一、软件无线电的特点 随着现代国防和民用设施对通信技术的要求… 相似文献
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简述了机载PD雷达对先进中距离空-空导弹(AMRAAM)的制导过程。介绍了国外机载PD雷达无线电校正通道的研制情况。论述了无线电校正通道的编码及工作过程。 相似文献
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本文简要介绍了CDMA技术 及SCDMA无线接入中的风步CD-MA、软件无线电、智能天线等关键技术。最后介绍SCDMA无线接入设备及 主要技术特性。 相似文献
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一、PDC网的主要优点PDC网是日本于1993年首先实现的,它的主要优点有:(1)节省基站相关资源。PDC采用3个TDMA信道(半速率编码为6个TDMA信道),有效地利用基站(BS)资源和BS与移动业务交换中心(MSC)之间的传输线。(2)无线电频率利用率高。PDC采用移动站辅助越区切换方式,改进了切换技术,因此可以使用更小的蜂窝区。(3)通信质量高。PDC采用数字信号处理技术,有效地改善了通信质量。(4)信令协议先进。PDC采用类似于ISDN用户链路及节点间协议,可以在网络中提供部分多媒体业务… 相似文献
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本文对码分多址(CDMA)进行了一般性的阐述,分析了CDMA中特有的功率控制方案,描述了蜂房环境中宽带波传的一个有趣结果(在蜂房宽带信号上,短期衰落减少,且城市比郊区衰落要少)。本文列出了采用CDMA的一系列优点,充分地讨论了CDMA中的无线电容量。 相似文献
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本文首先回顾第三代移动通信系统的研究动态,并着重对我国提出的S-CDMA系统进行分析比较。得出软件无线电技术是确立我国第三代移动通信系统的关键技术之一。本文还提到S-CDMA采用软件无线电后新开辟的测向定位功能。 相似文献
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Zhisheng Lin Haitau Lin Hangbo Xue Chuhua Pan Yuliang Long 《Journal of Infrared, Millimeter and Terahertz Waves》1998,19(3):551-568
This paper reports an automatical slotted-lin system which has been developed by us. This system is controlled with IBM-PC 80486. Its software is designed with C Language. It can performs a variety of measurements such as high, medium and low SWR measurement, signal source SWR, attenuation, phase shift, scattering coefficient of two port network and dielectric constant measurement etc. rapily, exately and conveniently. In this paper, the hardware composition and software design are described. A series of typical measurement results of SWR at 30MM wave-band are given. This method is adaptable for MM-Wave band and other Micro-wave band. 相似文献
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宽频带低噪声放大器设计 总被引:1,自引:0,他引:1
采用Lange耦合器的宽频带特性设计L/S波段平衡式低噪声放大器电路,并通过仿真设计软件对放大器的工作频带、噪声系数、增益及输入、输出驻波比等几个重要指标进行优化。最后设计的放大器在1.2~2.5GHz频率范围内增益为33~35dB,噪声系数不大于1dB,输入输出驻波比小于1.5,达到了预定的技术指标要求,性能良好。 相似文献
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Efficient sample rate conversion for software radio systems 总被引:1,自引:0,他引:1
An efficient sample rate conversion (SRC) method for software radio (SWR) systems is proposed. The proposed method modifies conventional single- or multistage SRC processes such that the computation of the output of a particular stage is performed in a hierarchical fashion. This SRC method consumes fewer computations than traditional SRC methods over a range of SRC factors and is especially suitable for SWR base station transmitters. The computational requirements of the proposed SRC method and conventional SRC methods are compared and simulation results of the proposed method are discussed. 相似文献
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Adaptive prediction and cancellation digitization method for wideband multistandard software radio base-station receivers 总被引:1,自引:0,他引:1
In this study, a new method for digitizing a combination of different analog signals occupying significantly different bandwidths and having a very high dynamic range is proposed and analyzed. Since it is based upon signal-prediction/cancellation principles, it is referred to as adaptive prediction and cancellation digitization (APCD) method and is applied to various families of signals simultaneously received by a multistandard software radio (SWR) base-station receiver. It is shown theoretically and by means of computer simulations that the APCD method can effectively reduce the high dynamic range of the signals before digitization takes place. Hence, the stringent analog-to-digital-converter (ADC) resolution requirements imposed by the operation of such SWR base-station receivers can be significant relaxed. The signal dynamic-range reduction is achieved by applying appropriate signal processing techniques, e.g., autoregressive (AR) and periodic autoregressive (PAR) prediction. Such techniques allow accurate prediction and subsequent cancellation of high-power narrowband signals present among the composite received analog signal. As these signals usually have cyclostationary statistical characteristics, analysis and performance evaluation of AR and PAR predictors, when used to predict cyclostationary signals, were presented. A new adaptive algorithm for implementing the PAR predictor is also proposed, and its validity is justified by theoretical analysis as well as by various performance evaluation results obtained by means of computer simulations. 相似文献
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M. R. M. Rizk Ehab Abou-Bakr A. A. A. Nasser El-Sayed A. El-Badawy Amr M. Mahros 《Analog Integrated Circuits and Signal Processing》2017,90(3):605-613
For a receiver sub-block , Low Noise Amplifier is the first stage after the receiving antenna and as a key device, its amplification and noise figure (NF) affects the whole performance of the receiving part. In this paper we present a full graphical visualization in terms of gain, standing wave ratio (SWR) and noise for a GaAs HJ-FET transistor in two operating cases; (1) NFmin, (2) Unity \(\hbox {SWR}_{\mathrm{out}}\). The set of curves and contours presented will provide the designer with enough visual information about the transistor operating boundaries and will also visually assist on choosing the appropriate matching points for a wideband operation according to the desired (transducer gain \(\hbox {G}_{\mathrm{T}},\hbox {SWR}\)) for case (1) and (\(\hbox {G}_{\mathrm{T}},\hbox {SWR}_{\mathrm{in}},\hbox {NF}\)) for case (2). Numerical examples are given for each operating case and verified via a microwave circuit design software package to demonstrate the adequacy of the proposed graphical techniques . The results from simulations compare favourably with the visually estimated values. 相似文献
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无线漫游安全(Secure Wireless Roaming,SWR)协议允许隶属于本地服务器的用户漫游到外地时,可以与外地服务器互相验证身份并建立安全的会话密钥.在此基础上,匿名SWR协议能保证即使所有外地服务器串通情况下漫游用户的匿名性和不可追踪性.该文提出了一个匿名的无线漫游安全协议SYM-SWR (SYMmetric key based SWR).而且就目前所知,该协议是第1个完全基于对称密钥的匿名SWR.同其他已知协议相比,SYM-SW的通信复杂度和计算复杂度均最低.因为SYM-SWR只需要4次消息传送,且不需要PKI (Public Key Infrastructure)而采用消息验证码(Message Authentication Code,MAC)和对称密钥加密这两种高效的运算. 相似文献
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Ratajczak P. Brachat P. Guiraud J.-L. 《Antennas and Propagation, IEEE Transactions on》1994,42(8):1077-1088
The paper presents the SR3D software (3D radiating structures), which calculates the electromagnetic characteristics of arbitrarily shaped structures incorporating dielectric material. The rigorous analysis method is based on the integral equation formulation. The authors included a variational approach using the reaction concept of Rumsey. The problem is numerically solved with a surface finite elements method. A guided mode excitation has been introduced in order to compute the reflection coefficient at the transmit port and the transmission coefficient between the different parts fed by guided modes. This software is validated by excellent agreement between simulated and measured radioelectric performances (patterns and SWR) 相似文献