Delay spread statistics in vicinity of same-frequency repeater

The statistics of the delay spread in a two-path mobile radio environment where every path is subject to log-normal shadowing are derived. The channel profile thus considered consists of two delta functions whose power levels are in addition, correlated. Analytical expressions for the probability density function, the mean and the standard deviation of the resulting delay spread are obtained and compared with simulation results     

Communication satellite processing repeaters

Two kinds of processing repeaters which may find application on communication satellites in the near future are described. The type I repeater allows access only if the transmitted signal contains a predetermined code structure. This serves three purposes: first, unauthorized users are excluded, second, co-channel interfering signals are not retransmitted on the downlink, so as not to waste a portion of the satellite transmitter power, and, third, removal of the interference signal at the satellite avoids having to do this at the ground receiving terminal. Thus such a repeater would find particular application where there are a large number of ground receiving stations. The type 2 repeater routes signals received at its N input terminals to be transmitted at N output terminals, thus acting as a "switchboard in the sky." Two purposes are served: first, the satellite capacity is more fully utilized in the presence of fluctuating traffic demands, and, second, single-frequency transmission and reception are possible for user ground stations, thus simplifying these stations and still allowing communication to any station in the network. It is established when the type 1 repeater is able to increase the satellite communication capability beyond that of a simple repeater and further that fairly simple filtering is sufficient on the satellite. For the type 2 repeater, a proposed frequency control plan minimizes the filtering required on the satellite where frequency division multiplex is used and reduces the amount of switching required on the satellite to N single-pole N-throw switches where time division multiplex is used without the requirement of any memory on the satellite. A summary of present-day translating repeaters, as used in the Intelsats III and IV and DSCS II satellites, is included.     

Intermodulation distortion in frequency multiplexed satellite repeaters

Expressions have been derived that describe the output spectra (i.e., signal plus distortion) of a saturating amplifier when the input consists of a large number of independent carriers whose amplitudes, bandwidths, and center frequencies may be independently specified. The resulting equations have been programmed on the GE 635 computer using the fast Fourier transform algorithm, permitting rapid computation of the output spectra for very complex input signal formats. Program outputs have been checked against the results of previous authors, e.g., Cahn [1] and against a measured transfer characteristic of a Hughes model 24H traveling wave tube, with good agreement. The program has been found very useful in design optimization studies of channelized communications repeaters with up to 60 channels.     

基于时空处理的阵列扩展及同频干扰抑制

该文推导了基于时空联合处理的 2-D 阵列扩展方法,研究了虚拟阵的结构,构造了虚拟阵的伪数据矩阵;同时提出了抑制同频干扰的算法。当采用m阵元的2-D阵列时,扩展阵列的等效阵列孔径为n=(m+1)2/2-1(m为奇数)或n=m(m+2)/2-1(m为偶数)。这种阵列扩展方法和同频干扰抑制算法能在较低信噪比(0dB)以下工作,并且能实现2-D参数的自动配对。理论和计算机仿真实验均表明这种扩展和算法的有效性。     

直放站的工程设计和调测

0引言 近年来,随着移动通信业务的迅速发展,移动通信直放站以其有效性和经济性得到了运营商的青睐,在网络覆盖中大显身手.与基站相比,直放站有结构简单、投资较少和安装方便等优点,可广泛用于覆盖难度大的盲区和弱区,如山区、宾馆、地下商场、地铁、码头、车站、隧道及电梯等各种场所,有效改善通信质量.目前,直放站已成为优化无线通信网络的重要工具和增强网络延伸覆盖能力的一种优选方案,因此研究直放站的工程设计和调测方法具有重要的现实意义.     

Automatic timing alignment for regenerative repeaters

A novel circuit technique that provides automatic timing alighnment of digital regenerative repeaters is described. The scheme employs correlation feedback to maintain the correct clock and data phase relationship. Theoretical and practical results are presented.     

Regenerative feedback repeaters for programmable interconnections

The use of regenerative feedback repeaters to reduce the delay in programmable interconnections is described. A static, complementary regenerative feedback (CRF) repeater is proposed. This CRF repeater locally regenerates the new level for a fixed time after a transition has been detected. Design issues and limitations are discussed. It is shown that rising transitions can propagate faster than falling transitions through a chain of overdriven nMOS switches with CRF repeaters. Experimental results from a 1.2 μm CMOS implementation show that the loaded delay through 64 switches for static and dynamic repeaters can be reduced by a factor 1.4-2 over conventional repeaters     

无线直放站改光纤直放站方案

无线直放站主要有无线同频宽带直放站、无线选频直放站和无线变频直放站,无线选频直放站和无线变频直放站是在无线同频宽带直放站的基础上,增加了相应的选频模块和变频模块而组成,因此无线直放站中最基本的就是无线同频直放站,无线同频直放站的改造方案也能适用于其它的无线直放站.下面主要以无线同频宽带直放站为例,介绍改造方案.     

Optical technologies for signal processing in satellite repeaters

The evolution of modern communications satellites from the older cable-in-the-sky concept toward more intelligent architectures, exploiting onboard processing (OBP) techniques involving various technologies to improve the system performance and flexibility, is addressed. The key components in advanced communications satellite repeaters compatible with integrated optical device implementation are presented. The relevant device technologies and fabrication techniques are examined, and integrated optical circuit configurations that can be applied to OBP are described with reference to recent experimental data. Particular attention is given to optical beamforming networks. Areas for further research and development are suggested     

Experimental research on the behavior of passive repeaters

The behavior of passive repeaters in microwave radio links has been focused by means of a series of experimental tests. Some of the measurements were concerned with the determination of quantities which characterize the behavior of the repeater alone and in connection with the whole radio link. Some other measurements were planned to investigate closely the behavior of the mirror and the anomalies which have been found. Emphasis has been given to the influence of propagation and the effects of the ground surrounding the mirror. Much of the aim has been to separate these effects. Finally some conclusions are drawn and criteria for the installation of such repeaters are pointed out.     

A wide-band limiting amplifier for optical fiber repeaters

An integrated amplifier having a bandwidth of 470 MHz, and a gain and limiting range of 60 dB has been realized using a cascade of three cells on an uncommitted array. The circuit is capable of operating in optical fiber repeaters in the signal or retiming path at transmission rates up to 650 MBd. Direct expressions for calculating the gain and bandwidth have been derived which allow optimization of the component values, bias conditions, and transistor parameters for a chosen application.     

Supervisory system for cascaded semiconductor laser amplifier repeaters

A technique for locating a transmission path failure in an inline cascade of semiconductor laser amplifier repeaters to within one fibre span is demonstrated. If a fault occurs, the loss of signal is detected in the following repeaters and a locally generated tone modulates the spontaneous emission of the repeater, signalling the fault to the system terminals.<>     

900MHz直放机测量技术探讨

概述在移动通信迅速发展的今天,无论何种无线通信系统的覆盖区域都存在弱信号区和盲区,而对一些偏远地区和用户数不多的盲区,要架设模拟或数字基站成本太高,基础设施也较复杂,为此提供一种成本低、架设简单,却具有小型基站功能的经济有效的设备——直放站是很有必要的。因此,移动通信运营商开始在基站之外的建筑物内部及地下等电波盲区设置直放站,以最大限度地满足用户对于通话服务的要求,提高网络质量。根据统计,中山市已建的移动通信直放站就有277个,其中GSM900MHz/1800MHz直放站有233个,CDMA直放站有44个。移动通信直放站根据传输信…     

高速列车车载直放站方案研究

为了改善高速列车中的通信质量,提出了一种高速铁路移动通信的车载直放站方案。文章简要介绍了车载直放站方案的特点,通过电波传播角度研究了该方案对于克服穿透损耗、缓解快速切换的优点,并从理论和测试结果上说明带有AFC(自动频率控制)功能的车载直放站对于提升信号质量所起的实质性作用。     

On-board regenerative repeaters applied to digital satellite communications

In pulse-code modulation/time-division multiple access (PCM/TDMA) satellite communications, though the number of repeating stage is usually only one, the regenerative repeater will be worthwhile enough to be introduced on board the satellite. This is because the improvement of the communication quality by the increase of the transmission power is difficult in the satellite link and the regenerative repeater is very effective for removing cochannel interferences which will become predominant factor of signal degradation in the future and it will also provide great facility for various kinds of on-board processings. This paper first presents basic configurations of the on-board regenerative repeater, and discusses about simplification of the repeater. Next various kinds of on board processings ate discussed in connection with the regenerative repeating. Then a concrete regenerative repeater applied to satellite switched/TDMA (SS/TDMA) satellite system which augments the communication capacity by frequency reuse is presented and compared with the conventional frequency translating type in terms of link budget, power dissipation, and weight. Lastly the result of the development of an experimental regenerative repeater is described.     

TD-SCDMA直放站下行同步算法性能研究

文章首先介绍了下行同步精度及稳定度在时分同步码分多址(TD-SCDMA)直放站应用中的重要作用,然后结合ADS(Advanced Design System)对特征窗捕获匹配和相关解调两种同步算法的仿真结果,从算法原理上比较了这两种同步算法的抗干扰性能.最后根据仿真统计结果结合直放站实际应用状况分析了两种同步算法的优缺点和适用环境,并根据实际应用中的问题提出了一些改良意见.     

直放站对移动通信网络的干扰分析

在简单介绍直放站的基本原理的基础上，着重就直放站对移动通信系统所造成的各种干扰进行分析，并提出减少干扰的措施，最后简单介绍几个案例的排查。     

140-MHz main IF amplifiers for 2700-channel microwave repeaters

This report presents the circuit configuration and performance of a 140-MHz main IF amplifier satisfying the specifications for 2700- channel microwave repeaters.     

Simple formulas for jitter accumulation in a chain of regenerative repeaters in optical-fibre transmission systems

Simple formulas are derived for evaluating the timing-jitter accumulation in a chain of regenerative repeaters for optical-fibre transmissions. The timing circuit in each repeater is modelled as a phase-locked loop. An example of the use of these formulas is reported with reference to a 140 Mbit/s transmission system.