Smart, active, and concealable antenna array for portable television reception

This paper describes an array which is concealable with a TV set or set-top box. The array is made of small active antennas which can provide space and polarization diversity by phase switching alone. The array can be manually or automatically controlled to maximize the signal-noise ratio of the desired channel and minimize the interference from undesired channels. The combination of automatically adjustable dual diversity and small physical size makes this device suitable for mobile reception.     

基于SNMP协议的智能小区管理站设计

基于SNMP协议可以实现一个管理工作站远程管理所有支持这种协议的网络设备,包括监视网络状态、修改网络设备配置、接收并处理网络事件警报等.基于SNMPv3,在一台PC上实现智能小区管理站,自动扫描代理端监控数据,定时更新数据库,并对警报信息进行自动及时处理.     

Channel Error Recovery for Transform Image Coding

A method is presented to automatically inspect the block boundaries of a reconstructed two-dimensional transform coded image, to locate blocks which are most likely to contain errors, to approximate the size and type of error in the block, and to eliminate this estimated error from the picture. This method uses redundancy in the source data to provide channel error correction. No additional channel error protection bits or changes to the transmitter are required. It can be used when channel errors are unexpected prior to reception.     

电台音频采集管理系统设计

针对电台接收信号依赖于人工值守还未实现自动化接收的问题,在软件无线电的理论基础上,提出一种电台音频采集管理系统总体技术方案,并设计了一款电台外接的电台音频处理终端,旨在电台工作时终端可以自动采集、记录、识别及回放接收到的音频信号,以提高信号接收效率。该终端由通用软件无线电模块、Morse音频信号处理模块以及语音识别模块构成,模块之间相互独立,具有一定的通用性和实用性。     

互相关干扰下的GNSS弱信号检测算法

GNSS接收机在室内等环境中的应用要求接收机具有接收弱信号的能力.在检测弱信号时,接收机可能由于受到强信号的互相关干扰而错误的捕获或跟踪到强信号的互相关峰.本文采用相干和非相干积分组合的方法来提高灵敏度.同时,通过估计强信号的互相关干扰功率,自动调整检测门限来抑制互相关干扰.仿真结果说明,采用20ms的相干积分和1s的...     

单片机在GPS和CDMA计时系统中的设计

介绍了一种基于MSP430单片机的GPS和CDMA双接收计时系统的设计思路与方法,并给出了系统的硬件电路和软件流程。该系统采用GPS和CDMA时钟信号,其可以自动调整时间,同时还拥有多方位保障时间的精确性、一致性、高可靠性及环境适应性强的优势。     

基于VB实现卫星Keps根数文件自动传输

在气象卫星数据接收系统中,卫星轨道根数的准确性直接影响到气象卫星资料的接收质量。根据对卫星Keps根数文件格式的分析,在VB6．0环境下设计了每天定时获取,编辑整理,并通过串口将Keps根数文件发送至任务调度计算机的方法,不仅可以满足临时增加接收计划的需要,而且实现了Keps根数文件的安全、稳定传输,提高了工作效率。     

An Automatic Control System for Compensating Cross-Polarization Coupling in Frequency-Reuse Communication Systems

In frequency-reuse communication systems using orthogonally polarized waves, depolarization due mainly to rain and Faraday rotation (in satellite systems) reduces channel isolation. The control system described, incorporating a network suggested by T. S. Chu, automatically compensates for cross-polarization coupling without using iterative methods or computations. Control voltages are generated on the receive side by phase-sensitive demodulation of beacons contained in the communication channels. Slightly modified conventional tracking receivers may be used for the demodulation. The system can be used for the reception of dual linear or dual circular polarizations without modification. An analysis of the control system behavior is given and a method for automatic initial balancing of the systemindependent of its initial state-is proposed.     

Transients in wide-angle conical antennas

The response of an antenna to dc pulse excitation, both in reception and in transmission, can be determined by use of Fourier transforms provided the complex impedance and complex effective height of the antenna are known over the frequency range where the excitation has significant components. We have computed the time history of the response of a wide-angle conical antenna to dc pulse excitation and show the results herein for a matched source in transmission and a matched load in reception for several values of cone angle and antenna length. Under matched conditions, the faithful transmission of a pulse shape, requires a long antenna while faithful reception is not possible. Faithful reception can be achieved by a short antenna with a resistive load of high resistance or with a capacitive load, or by a long antenna with a series RC load. Since this work required transfer functions in transmission and reception, we have also presented here graphs of these quantities.     

A High-Dynamic-Range Front End for an Upconversion Car-Radio Receiver

A monolithically integrated high-performance front end for an AM radio receiver is presented. Medium- and long-wave reception without any tuned-circuit alignments or band switches is made possible by using an intermediate frequency of 10.7 MHz, well above the maximum frequency to be received. Image- and oscillator-harmonics-related spurious responses are rejected by a simple low-pass filter. The upconversion concept puts high demands on the front-end circuits. A high intermodulation free dynamic range is realized by applying several unconventional and new circuit techniques. A low-noise low-distortion wide-band input amplifier with capacitive negative feedback realizes the required antenna match. The gain of this amplifier is automatically switched to a lower value in the vicinity of transmitters with high field strengths. A double-balanced mixer, driven by an oscillator employing a novel amplitude stabilization technique, provides the frequency conversion up to 10.7 MHz. Digital toning can be achieved very simply because only the local-oscillator frequency has to be varied. The dynamic range of this front end amounts to 130 dB. Field strengths up to about 20 and 200 mV/m can be handled without noticeable second- and third-order intermodulation, respectively.     

大气无线光通信系统中一种正交空时分组码编译方法

为了降低湍流对大气无线光通信的影响,提高无线光通信系统性能,提出了一种4发射天线、4接收天线的无线光多发射多接收系统模型,针对该模型设计了一种正交空时分组码(OSTBC)编译方法,并对该码的平均误比特性能进行了仿真分析。结果表明,该方案具有很大的分集优势,可获得的最大分集度为16,达到了4发4收系统所能获得的最大空间分集增益,同时该编码方法与传统的Alamouti方案一样能实现最大传输速率。通过对译码算法进行简单修改,OSTBC编译方法也可以应用在接收天线数目为1,2或3个的多光束发射和接收系统中。     

HDTV Mobile Reception in Automobiles

Mobile reception of digital terrestrial broadcasting carrying an 18-Mb/s digital HDTV signals is achieved. The effect of diversity reception in moving automobiles for a 64 quadrature amplitude modulation-orthogonal frequency division multiplexing (QAM-OFDM) signal is investigated by prototype hardware. There are two methods for diversity reception of OFDM signals. The first is the Doppler compensation directivity control system. For this method, high-performance on-glass antennas and new diversity reception systems for OFDM reception have been developed to verify HDTV service availability in mobile reception environments. Novel horizontally polarized on-glass antennas suitable for DTV were developed. The antenna elements were printed on the inside surface of the rear window glass of a passenger van. OFDM signals received by the four antenna elements were weighted and combined using maximal ratio combining (MRC). The experiments were conducted in urban areas and they showed that employing diversity techniques would make HDTV mobile reception possible in many areas. The other method is post-FFT diversity. In the receiver, MRC is performed after an FFT operation on each branch signal. Experimental results show that accurate HDTV mobile reception can be achieved by using a four-branch MRC system. Also, the minimum usable electric field strength could be reduced compared with that of a single dipole antenna.     

长期演进上行分集接收算法研究

为降低3GPP 长期演进（LTE）上行多天线系统分集接收计算复杂度,提高硬件处理效率,改善系统性能,对八天线系统不同干扰强度情况下的干扰抑制合并（IRC）、最大比合并（MRC）、简化的干扰抑制合并（SIRC）和简化的最大比合并（SMRC）算法进行了比较与仿真分析。仿真结果表明在八天线系统中SIRC能够以1dB左右的信噪比损失获得8N倍运算量的降低,并能采用划分天线子阵的方法来提高效率。当存在较强的相关干扰时利用SIRC代替IRC,当干扰较弱或无相关干扰时利用SMRC代替MRC进行分集接收合并,不仅能够明显降低运算量,并能获得较好的效果。     

Multiuser detection and diversity reception for asynchronous CDMA mobile communication

In CDMA mobile communication systems, multiple access interference can be canceled by multiuser detection technique. The Degradation by channel fading can be reduced by diversity reception. This paper investigates a family of multiuser receivers that combined decor-relating detection, antenna diversity and RAKE multipath diversity. The performance of the multiuser receivers is analyzed. The results demonstrate a significant increase in the performance of the receivers by using multiuser detection and diversity reception.     

异步CDMA移动通信系统中采用分集接收的多用户检测器

在CDMA移动通信系统中,多址接入干扰可以通过多用户检测技术来消除,而分集接收可以减小信道衰落的影响。本文给出了一类应用解相关检测、天线分集、RAKE多径分集技术的接收机,并对这一类接收机的性能做了分析。结果表明,在上行链路中,应用多用户检测和分集接收能够极大地提高接收机的性能。     

Superconducting Extremely Low Frequency (ELF) Magnetic Field Sensors for Submarine Communications

The ferromagnetic-core type of solenoid that is used as a trailed antenna for communications reception by submarines has not demonstrated adquate sensitivity to satisfy the performance requirements for deeply submerged submarines receiving extremely low frequency (ELF) transmissions from the planned Sanguine communications system. It is possible, however, that a superconducting quantum interference device (SQUID) can be adapted to this role successfully and can permit all requirements of platform depth, speed, and maneuverability to be met. The present status of SQUID's is described, and some laboratory measurements that prove the potential of these devices for the ELF communications reception capability are presented. The engineering development that must be pursued in the areas of 1) sensor and electronics dynamic range, 2) sensor orthogonality, and 3) refrigeration systems to make SQUID ELF sensors available as operational receiving antennas is also discussed.     

数字电视的条件接收系统原理与应用

数字电视指将传统的模拟信号转化为数字进行处理、传输和接收的系统。数字电视的条件接收系统运用各种数字技术通过对节目的加扰处理，使只有授权用户才能收看被加扰节目，从而保障运营商的利益，保证数字电视发展。 本文主要闻述当前前数字电视使用的条件接收系统的基本原理，以及实际中应用两种条件接收方式的设计和实现，并比较两种方式的优势和不足。最后介绍当前国内数字电视发展的现状。     

Aperture-domain signal processing

An elementary reconsideration of first principles in aperture-domain processing of wave phenomena for reception (and, by reciprocity, for transmission) can yield revealing, and in some cases novel, insights into what can or cannot be achieved. The subjects covered here include direction-selective reception, superdirectivity, direction finding, focused near-field reception, circular arrays and circular modes in such arrays, and the new concepts of arrays composed of `random symmetrical pairs', and of real gain in omnidirectional receiving antennas. The ideas are basic to all wave directional analysis and imagining applications, be they electromagnetic or acoustic, in radar or sonar, communications, navigation, surveillance or medical imaging     

随机谐振在信号接收中的应用研究

在一些非线性系统中,噪声时常有助于信号传输或信号处理的现象称为随机谐振。本文基于信号错误接收概率讨论随机谐振在信号接收中的应用。对于极大阈值网络,当信号在阈下时,适量的噪声能改善信号接收,随机谐振现象存在;随着网络中阈值单元数的增加,错误接收概率的最小值迅速地趋于零,随机谐振功效极大地提高;对于两种典型噪声解析地讨论发生随机谐振现象时的最佳噪声强度,并根据噪声密度函数的变化对随机谐振机理进行了尝试性解释。