Influence of microwave scattering by power transmission lines ondigital radio communications

A method for evaluating power transmission line interference with microwave radio communication circuits due to microwave scattering is presented and used to predict digital radio transmission performance degradation. Numerical results show that the effects of power line screening on highly efficient digital radio systems are more serious than on analog (FM) radio systems since power lines cause quadrature distortion and intersymbol interference as well as average level reduction. An experimental result using a communication satellite beacon shows that conductors within the first Fresnel zone cause the interference     

Software-defined radio technology in the problem concerning with the successive sounding of HF ionospheric communication channels

The problem concerning new software-defined radio technology is investigated as applied to the successive sounding of HF ionospheric communication radio channels. The algorithm for quadrature processing of chirp signals subjected to elementwise compression in the frequency domain is developed. It is established that a channel scattering function and a delay power profile are related to a compressed-signal spectrum and their basic parameters. Data on the key characteristic of HF communications modems are presented. The efficiencies of different modems are estimated using the experimental data on channel parameters. It is demonstrated that the aforementioned technology can be used to estimate not only HF communication channel parameters from the pass band of a radio line but also select the optimal one and, furthermore, makes it possible to combine communications and radio sounding systems in the single device.     

Fading Channel Prediction for Mobile Radio Adaptive Transmission Systems

Adaptive transmission methods can potentially aid the achievement of high data rates required for mobile radio multimedia services. To realize this potential, the transmitter needs accurate channel state information (CSI) for the upcoming transmission frame. In most mobile radio systems, the CSI is estimated at the receiver and fed back to the transmitter. However, unless the mobile speed is very low, the estimated CSI cannot be used directly to select the parameters of adaptive transmission systems, since it quickly becomes outdated due to the rapid channel variation caused by multipath fading. To enable adaptive transmission for mobile radio systems, prediction of future fading channel samples is required. Several fundamental issues arise in the design and testing of fading prediction algorithms for adaptive transmission systems. These include complexity, robustness, choice of an appropriate channel model for algorithm validation, channel estimation and noise reduction required for reliable prediction, and design and analysis of adaptive transmission methods aided by fading prediction algorithms. We use these criteria in the review of recent advances in the area of fading channel prediction. We also demonstrate that reliable fading prediction makes adaptive transmission feasible in diverse wireless communication systems.     

短波宽带信道中噪声与干扰建模

短波通信系统依靠电离层传播,具有通信距离远,灵活性高,抗干扰性强,成本低廉等特点,是一种重要的国防军事通信手段。传统短波通信受电离层特性影响而有效带宽较窄,导致数据传输速率极低。因此,提高信道容量实现高速数据传输的短波宽带通信系统越来越受到重视。短波宽带信道建模是短波宽带通信系统正常发挥性能的关键,对短波宽带通信系统的设计与实际应用具有重要的实际意义。结合现有短波宽带信道的衰落特性模型,介绍了短波宽带信道噪声和干扰模型,并进行了比较和可靠性分析,发现现有模型形式比较单调统一,但和实际测量数据一致,能有效描述短波宽带通信中信道噪声与干扰特性,模型已经比较完善。最后,提出了进一步研究的重点方向。     

军用无线电通信的码间干扰抑制算法仿真研究

军用无线电通信对通信质量和码元的保真性要求较高,军用无线电通信信道受到多径向量的影响产生码间干扰,需要进行码间干扰抑制,降低通信误码率。传统的码间干扰抑制方法采用波特间隔信道均衡算法,当通信信道受到电磁扰动的强度较大时,信道均衡性和码间干扰抑制能力不好。提出一种基于时间反转镜技术的军用无线电通信的码间干扰抑制算法,首先构建了军用无线电通信的信道模型,进行军用无线电通信的信道多径特性测量,采用自适应级联滤波器进行干扰滤波,结合时间反转镜技术实现码间干扰抑制算法改进。仿真结果表明,采用该算法进行军用无线电通信的码间干扰抑制,能有效提高通信传输的保真率,信道均衡性能较好,提高了通信输出的信噪比,降低通信误码率,提高了通信质量。     

通用短波接收机射频前端设计

短波电台可广泛用于军事和民用通信中,具有很高的研究与开发价值。短波通信是目前远距离通信的重要手段。因此介绍了一种通用的短波接收机射频前端的设计方案,主要对其中的关键技术和实现方式进行了论述,重点分析了设计中的非线性失真问题,给出了在工程中实用的设计方法,同时对电路的调试也给出了建议。而且还提供了一种工程实际中噪声系数的近似测试方法,最后列举了此种射频前端的实际应用。     

Millimeter-Wave Thin-Film Downconverter

A 60-GHs hyhrid integrated downconverter intended for use in a mitlimeter-wave radio relay experiment has heen designed and tested. The converter consists of a strip transmission line circuit and two beam-leaded Schottky-barrier diodes which are pumped at a subharmonic of the convectional Iocal oscillator frequency. The conversion loss of the circuit is 6.3 dB and the total single-sideband noise figure, including the noise contribution from the IF amplifier, is 9.1 dB. The circuit looks attractive for millimeter-wave communication systems application up to 100 GHz.     

跳频序列设计理论的研究进展

跳频技术具有抗干扰和多址组网性能，在军事无线电通信、民用移动通信、现代雷达和声纳等电子系统中具有重要的应用。跳频序列用于控制载波频率随机时间的变化规律，其性能对跳频系统的性能有重大影响。本文综述跳频序列设计理论的研究成果，并指出今后的发展方向。     

A Model for Inpulsive Power-Line Radio Disturbance Due to Gap-Type Discharges

Electromagnetic disturbance from power lines is one of the main sources of man-made noise affecting communications in the high-frequency radio band. Most radio disturbances generated by power lines are of two types: gap-type noise caused by electric discharges across line hardware, and corona noise caused by the partial breakdown of the air due to the high electric fields around transmission-line conductors. While the physical mechanisms of these noise types have been investigated in detail, these studies have not yet been used to develop noise models for the evaluation of communication-system performance. This paper presents a mathematical model that allows the fundamental mechanisms of gap-type noise to be simulated. With this model, the effect of gap-type noise processes on various high-frequency communication systems can be determined by direct computation as well as by experimental observation. The mathematical model was used to derive an expression for the demodulated power spectral density (PSD) compared with field observations.     

宽带MFSK/DFH系统抗部分频带噪声干扰性能分析

本文提出一种宽带MFSK/DFH系统模型,与常规差分跳频系统相比,在跳频点数一定条件下,通过增加多进制编码器复杂度,提高编码增益的方法提高系统抗干扰性能。对基于FFT的宽带MFSK/DFH系统接收机抗干扰性能进行了理论分析和计算机仿真验证。结果表明:在相同条件下,提出方法通过增加多进制编码器约束长度提高了系统抗干扰能力,实现方法简单有效,具有一定的实际应用价值。      

低压电力线载波通信结合滤波器设计

低压电力线作为载波通信信道时,其通信特性并不理想,各种负载、用电设备及外界都将引起大量的噪声,给电力线载波通信带来了严重的干扰问题,从而影响电力线通信系统的性能。为了保证载波通信信号和数据的有效传输,通过电路分析并设计一种低压电力线载波通信结合滤波器,经仿真与实验该滤波器能有效过滤低压电力线载波通信信道中的各种干扰信号,从而达到了保证载波通信信号和数据的有效传输的作用。     

Research on Multi-Layer Distributed HF Radio Network Structure

High frequency（HF）transmission is an important communication techniques.However,conven-tional point-to-point transmission can be easily destroyed,which limits its utilization in practice.HF networking communication has the capability against demolishment.The network structure is one of the key factors for HF networking communication.In this paper,a novel analysis method of the network connectedness based on the eigenvalue is derived,and a multi-layer distributed HF radio network structure is proposed.Both the theore-tical analysis and the computer simulation results verify that the application of the proposed network structure in the HF radio communication can improve the anti-demolishment ability of the HF network efficiently.     

短波数据传输流量控制技术研究

短波通信是军事作战指挥的一种重要手段。目前短波数据传输时延大、信道容量小,在不采取任何流量控制机制的情况下,数据信息的时效性和公平性达不到要求。针对此问题,在传输中采用基于时延和公平性约束的流量控制技术,解决了一种服从特殊分布的数据信息的短波传输问题。仿真结果表明,短波数据传输时效性和公平性基本达到预期要求。     

Application of convolutional error correcting codes in ultrawideband M-ary PPM signaling

The interference issues related to ultrawideband (UWB) radio pose tight restrictions on the maximum data rate of UWB radio telecommunication systems. A possible solution is to reduce the required signal to interference ratio (SIR) that gives satisfactory performance to the UWB system. In this letter, we propose coded M-ary UWB radio communication systems. Two classes of convolutional codes, namely, low-rate superorthogonal codes and high-rate punctured codes are considered for this purpose. Simulation results on the bit error rate of the proposed system indicates that the system is capable to work in lower SIR's and therefore supports higher data transmission rates in a real interference environment compared to the previously proposed UWB communication systems.     

Phase Noise Spectral Limits in OFDM Systems

OFDM is recognized to be one of the best transmission techniques for wideband wireless communication systems. However, it exhibits two main drawbacks: its large amplitude fluctuation and its sensitivity to phase noise. Here we consider the phase noise impairments, taking care of the phase noise spectrum, which diverges form the classical Wiener model as the carrier frequency increases. Moreover, we show that the phase noise distortion can be decomposed in two terms, one dependent on the symbol under detection and the other dependent on the symbols of adjacent subcarriers, so that the performance degradation depends on both the constellation used in each subcarrier and the phase noise spectrum. As a consequence of this new results, the penalty due to phase noise expressed in terms of the average signal/noise plus interference ratio is not applicable in the case of modulations with non-constant amplitude constellations, such as 16- or 64-QAM. The method proposed here achieves a good accuracy, while keeping a low computational complexity, and it is confirmed by simulations. Roberto Corvaja was born in Padova (Italy) in 1967. He graduated at the Universisty of Padova in Electronic Enginering on 1990 and got his Ph.D. at the Univeristy of Padova in 1994. Since 1994 he is with the Dipartimento di Elettronica e Informatica of the University of Padova as a researcher and assistant professor on digital communications. Between 1994 and 1995 he spent 8 months at Hewlett-Packard Laboratories, Bristol (UK), working on equalization for a DECT receiver. His research activity in the past has regarded optical fibre communications systems and now is devoted to wireless communication systems. Silvano Pupolin was born in Venice, Italy, on February 17, 1947. He received the Laurea degree in Electronic Engineering from the University of Padova, Padova, Italy, in 1970. Since then he joined the Dipartimento di Elettronica e Informatica of the Universita' di Padova, where he currently is a Full Professor of Electrical Communications. He spent the summer 1985 at AT&T Bell Laboratories on leave from Padova, doing research on digital radio systems. He has been actively engaged in researches on digital communication systems since 1970. The topics covered has been: performance of baseband digital comunication systems, line encoding for spectral shaping, timing extraction, direct detection fiber optic system, spread spectrum communication systems, digital radio communications, with emphasis to the adaptive linearization of the High-Power-Amplifier. Actually, he is actively engaged in researches on digital radio, spread s pectrum systems, packet radio networks, personal communication systems and Cellular access to broadband systems for interactive communications. He is also National Project leader for a research on Personal Communication Systems. Dr. Pupolin is a Senior Member of IEEE and Member of AEI.     

2014年美国海军通信装备与技术发展综述

2014年,美国海军在军事通信与数据链领域围绕战场网络系统、先进战术数据链系统、机载通信系统、卫星通信系统以及新型通信技术等热点领域展开了大量研究和装备部署工作。跟踪外军通信装备的发展动态,研究外军通信装备和技术发展趋势对促进我国海军通信和通信电子战能力建设具有重要借鉴意义。概述了2014年美国海军通信装备与技术的发展情况,并分析了海军信息网络、数据链和软件无线电的未来发展趋势。     

Some practical aspects of digital transmission

There are three worlds of digital transmission?digital transmission as an area of academic research, in which theoretical limitations and complicated schemes of modulation and encoding play the starring role; digital transmission in exotic space and military applications, in which it is, or may seem to be, worthwhile to search through the noise in a huge bandwidth in order to receive a few bits per second; and the digital transmission of everyday bulk communication. This article is concerned with that third area, in which apparatus must be economical and reliable; in which the FCC limits the bandwidth we may use in radio transmission; in which the increase in attenuation with frequency limits the bandwidth it is practical to use in cable transmission; in which error rates should be low enough that error correction is an expedient that need be resorted to only in special situations.     

Optical microwave generation and transmission experiments in the12- and 60-GHz region for wireless communications

Experiments on the optical generation and transmission of millimeter-wave radio signals are reported. The millimeter-wave signals are generated by heterodyning the optical spectral lines of a mode-locked laser (MLL) or of two or more semiconductor lasers at an optic/millimeter-wave converter (OMC). 70-, 140-, and 155-Mb/s data transmission experiments have been carried out successfully in optical single-channel and multichannel systems at radio frequencies of 12 GHz and 58-70 GHz. Bit-error-rate measurements yielded error-free transmission and no error floor was observed. A monolithically integrated tunable optical-signal source was developed and used for generating the millimeter-wave signals. This technology promises a high cost-saving potential for applications in radio-over-fiber systems     

Maritime satellite requirements and utilization

The basic purpose of this paper is to identify the potential requirements for maritime satellite communication and position fixing as it relates to both present and future operational systems (e.g., MARISAT, INMARSAT, etc.). Particular emphasis is given to the need for position fixing and ship terminal equipment utilization in national waters, as well as other major aspects. Present MARISAT operation and industry evaluation activities are briefly discussed, highlighting a few major programs and some of the potential benefit area thus far generally identified by the users of MARISAT. A comparison is made between satellite communication and the existing MF/HF system, including direct-printing radio telegraph (marine radio telex). From various standpoints, it appears that maritime satellite systems are more desirable than conventional (nontelex) marine telegraph/telephone. In addition, the improved performance, capability, and potential of satellites could outweigh the slightly lower annual traffic and equipment cost for HF marine telex.     

Smart Antennas with Two-Dimensional Array Configurations for Performance Enhancement of a Joint Detection CDMA Mobile Radio System

Smart antennas for base stations of cellular mobile radio systems offer the potential of system performance enhancement by taking advantage of the directionally inhomogeneous signal reception at the receiver. In this paper, two-dimensional array configurations employed at the uplink receiver of a joint detection CDMA (JD-CDMA) mobile radio system are investigated. This smart antenna concept can be split up into a novel channel estimator and data detector which incorporate explicitely the information of the direction-of-arrival (DOA) of signals emerging from users assigned to the considered base station. Proceeding from channel models that model the directional inhomogeneity of the mobile radio channel with single DOAs, the link level performance of a JD-CDMA mobile radio system using this smart antenna concept is evaluated for the rural propagation environment. The performance evaluation is based on Monte Carlo simulations of data transmission and average bit error rates versus the average signal to noise ratio per net information bit are presented for different array configurations. Although these results should be considered as upper bounds for the link level performance, they reveal the advantages of implementing two-dimensional array configurations at the uplink receiver of a JD-CDMA mobile radio system.