快速傅里叶变换载波频偏估计算法

基于最大似然法参数估计,本文提出一种快速傅里叶变换(FFT)的频偏估计算法,它能直接检测得到载波频偏绝对值大小,且精度与输入端信噪比无关.它可应用于中继卫星通信中高速数传且频带有效QPSK的同步解调.     

基于海尔H12011芯片的DVB-S2接收系统

根据新一代数字卫星广播DVB-S2标准的特点,提出一种基于海尔公司H12011CPU的数字卫星信号接收系统;详细说明了电路系统各个主要模块,包括H12011CPU模块、ZL10038和H13102芯片组成的信道解码电路模块以及其它经典外围电路模块等;根据前期设计电路时的分析论证,以及通过对实际制作样本的测试;该系统解调处理后得到的卫星电视信号,图像画面连贯、清晰;立体声质量良好,均达到各项标准;本设计方法简单、可靠,并且成本较低,具有一定的实用价值.     

基于码周期的延时相乘法估计扩频QPSK信号载频

QPSK扩频调制信号的载频在SNR很低的时候基本检测不到或者误差很大,传统的四次方法仅能在信号带宽内SNR大于0dB时检测到载频分量。本文提出一种新的基于码周期的延时相乘方法,在扩频码长1023位,信号带宽内SNR等于-13dB的情况下,仍能够精确估计载频,其精度仅受限于FFT的分辨率。     

基于FPGA的QPSK解调器的设计与实现

根据软件无线电的思想，用可编程器件FPGA实现了QPSK解调．采用带通采样技术对中频为70MHz的调制信号采样．通过对采样后的频谱进行分析，用相干解调方案实现了全数字解调。整个设计基于XILINX公司的ISE开发平台，并用Virtex-Ⅱ系列FPGA实现。用FPGA实现调制解调器具有体积小、功耗低、集成度高、可软件升级、扰干扰能力强的特点．符合未来通信技术发展的方向。     

Evaluation of the feasibility of satellite systems design in the 10–100 GHZ frequency range

We have presented a picture of the total attenuation to be considered in satellite communication and broadcasting systems in the 10–100 GHz frequency range. Although the findings and methodology are of general interest, the numerical results apply to the Italian (mid-latitude) sites of Fucino and Gera Lario and to slant paths of elevation angles 33° and 32° respectively. The rain attenuation probability distribution P(A), of exceeding the value A (dB) at a given carrier frequency in an average year, has been estimated by the synthetic storm technique and an associated formula, presently derived, which links A to frequency for fixed probabilities. The extra fading due to water vapour, clouds, oxygen and scintillations is estimated by applying the ITU-R formulae. After studying how the received carrier power P_R changes as a function of frequency for fixed antenna dimensions and transmitted carrier power P_T, we have carried out an exercise to show what first order values of P_T we need in an ideal QPSK modulation scheme, with a standard uncoded stream of 64 kbit/s, in a complete earth–satellite–earth connection, with regenerative or transparent transponders, for a given maximum bit error rate tolerated by users. After this analysis we have drawn the following conclusions: (a) the results depend very much on the outage probability and on the site; (b) there are two windows at high outage probabilities, e.g. 1%, the first in the 20–50 GHz frequency range and the second beyond 70 GHz; (c) in the frequency range 50–70 GHz any significant service availability level cannot be achieved because of the very large fading due to oxygen; (d) the transmitted power can show sharp minima which depend significantly on the outage probability and on the site; (e) service availability levels better than 99⋅99% of the year cannot be achieved at frequencies of 30 GHz and above, with ground station antennae of 25 cm or less aperture diameter. © 1998 John Wiley & Sons, Ltd.     

PDH数字微波中继站的系统方案设计

本文主要介绍了我省广电PDH数字微波中继站系统方案设计的一些思路,以及系统主要设备动能。     

An assessment of the efficiency performance of linearization schemes in the Australian mobilesat system

The efficiency of class C type amplifiers with digital predistortion linearizers is discussed. It is shown, by simulation with the AUSSAT MOBILESAT modulation schemes as examples, that the maximum efficiency from such a linearizer amplifier combination is significantly reduced for non-constant envelope modulation schemes on that achievable with constant envelope schemes. This aspect is often neglected when linearizer performance with such amplifers is discussed. The results are generally applicable to Cartesian feedback linearization also.     

数字电视的数字调制技术

本主要介绍数字有线电视网上、下行信道频谱的划分，各种数字调制方法、性能特点和优缺点比较。     

浅谈数字卫星电视接收系统的抗噪声性能

从数字卫星电视接收机的R-S解码器、卷积解码器和QPSK解调器等部分电路对系统抗噪声性能方面，对数字卫星电视接收系统的性能进行分析。     

有线电视多路数字微波联网传输技术

本文介绍了有线电视多路数字微波传输技术,分析了各种技术的特点;以及对大连长海县多路电视微波联网工程案例进行介绍。