一种根据扰码特性来提高多径搜索性能的算法

在CDMA系统中，为了对抗多径衰落，使用Rake接收机对接收信号进行处理。在发射端，通过扰码对信号进行加扰处理。Rake接收机对接收的信号进行解扰，相干积分处理，根据功率时堑函数PDP值来计算多径的相位信息。在信噪比比较差的情况下，搜索出来的多径可能是噪声径，这对Rake接收机解调的性能有一定的影响。介绍一种根据扰码自相关特性，来判断搜索出多径是否为噪声径的方法，提高Rake接收机的性能。     

低噪声接收机模块

随着现代军事系统和民用领域的发展,对低噪声、低功耗接收机模块的需求量越来越大.本文从蜂窝移动、GPS、CDMA和卫星通信四个方面简单阐述了低噪声接收机模块在无线领域的应用.最后,介绍了低噪声接收机模块在军事领域的发展现状.     

CDMA卫星通信系统的一些考虑

本文讨论了在相隔4°轨道空间的两个SCPC通信卫星中,插入一个新的CDMA通信卫星的可能性。给出了每位能量/噪声功率密度与CDMA系统用户数之间的关系。讨论了增加用户数的方法。计算了CDMA系统和SCPC系统相互间的干扰。得到了最大用户数时最佳的干扰功率密度与接收机噪声功率密度比。     

用LMS算法消除开关噪声对射频接收机的影响

针对DC-DC开关电源在为射频接收机供电时,引入过大的电源纹波噪声干扰问题,提出用LMS算法从基带消除纹波噪声干扰的解决方案。从纹波噪声建模出发,根据ZigBee标准利用Simulink仿真工具,搭建了带电源纹波噪声干扰的射频接收机仿真模型,并利用两级LMS算法调整的自适应滤波器,从基带消除纹波噪声干扰。仿真结果显示,在100 mV以下的纹波电压情况下,带LMS算法噪声消除的射频接收机系统仍能正常工作;超过100 mV后,算法能减小纹波噪声对射频接收机的干扰。     

CDMA20001X基站接收机灵敏度与蜂窝呼吸扩张的分析

从理论上分析推导了CDMA20001x系统基站接收机灵敏度的计算公式,并根据协议,分别计算了无分集接收和有分集接收的CDMA2000 1x系统基站接收机的灵敏度。提出了调整链路衰减和加入高斯白噪声实现小区蜂窝呼吸扩张的方法。通过对第一种方法的理论分析和测试结果表明:该方法能够更加便捷地实现小区蜂窝呼吸扩张,优化系统容量。所进行的分析和测试为基站的设计提供了理论依据和实际的参数要求。     

混合噪声环境下的CDMA抗多址干扰接收机研究

本文针对混合噪声环境,提出了一种抗多址干扰的非相干同步CDMA接收机,并对其系统结构、算法及特性进行了分析.本文提出的变革传统CDMA结构及算法的方法,使得系统具有抗多址干扰能力,从而使系统的容量极大化.     

基于VLC的测距算法研究

码分多址(Code Division Multiple Access,CDMA)技术的飞行时间(Time-of-Flight,TOF)测距算法可有效克服光干扰。通过模型和算法,把伪噪声序列加入到测距信号中,并在接收机接收到信号时根据伪噪声序列对信号进行检测,以分辨出所需的测距信号。仿真表明,运用了CDMA技术的飞行时间测距系统相对于不运用CDMA的测距系统在性能上有很大优势。在同一光亮度和误码率的情况下,运用CDMA技术使得测距距离有了显著提高,相邻干扰车辆引起的误码率大大降低。     

开关电源噪声的形成及抑制方法

开关电源产生的噪声比常规线性电源产生的噪声大得多。介绍了开关电源噪声的类型,分析了开关电源噪声的产生原因,讨论了开关电源中噪声的抑制方法,介绍了几种抑制开关电源中噪声的实用电路。     

多径信道下一种线性空时多用户检测方法

给出了用于DS/CDMA系统的线性空时多用户接收机的数学模型,分析了在多用户空时接收机中空域处理和时域匹配滤波的作用,引入SOR算法,并将其改进应用到多径信道下的线性空时多用户检测中。通过迭代避免了直接求逆运算,显著降低了运算复杂度。仿真表明:线性空时多用户接收机能够明显提高接收机性能,并且随着接收机天线数的增加性能明显提高。     

光接收机电源板原理与故障维修

在HFC网络中接地电阻较大或无接地的光接收机,特别是在雷雨季节光接收机供电部分损坏率较高,目前CATV系统的光接收机开关电源大部分采用"UC3842"作场效应型功率晶体管的开关控制电路,只要掌握该种典型电路原理和应用数据,便可以维修由UC3842构成的多种开关电源。根据实物绘出了供电板电源原理图,介绍其工作原理、维修方法。     

Low‐Power‐Adaptive MC‐CDMA Receiver Architecture

This paper proposes a novel concept of adjusting the hardware size in a multi‐carrier code division multiple access (MC‐CDMA) receiver in real time as per the channel parameters such as delay spread, signal‐to‐noise ratio, transmission rate, and Doppler frequency. The fast Fourier transform (FFT) or inverse FFT (IFFT) size in orthogonal frequency division multiplexing (OFDM)/MC‐CDMA transceivers varies from 1024 points to 16 points. Two low‐power reconfigurable radix‐4 256‐point FFT processor architectures are proposed that can also be dynamically configured as 64‐point and 16‐point as per the channel parameters to prove the concept. By tailoring the clock of the higher FFT stages for longer FFTs and switching to shorter FFTs from longer FFTs, significant power saving is achieved. In addition, two 256 sub‐carrier MC‐CDMA receiver architectures are proposed which can also be configured for 64 sub‐carriers in real time to prove the feasibility of the concept over the whole receiver.     

A 1.5-V multi-mode quad-band RF receiver for GSM/EDGE/CDMA2K in 90-nm digital CMOS process

A single chip quad-band multi-mode (GSM900/ DCS1800/PCS1900/CDMA2K) direct-conversion RF receiver with integrated baseband ADCs is presented. The fully integrated RF receiver is implemented in a 90-nm single poly, six level metal, standard digital CMOS process with no additional analog and RF components. The highly digital multi-mode receiver uses minimum analog filtering and AGC stages, digitizing useful signal, dynamic DC offsets and blockers at the mixer output. The direct-conversion GSM front-end utilizes resistive loaded LNAs with only two coupled inductors per LNA. The GSM front-end achieves a 31.5 dB gain and a 2.1 dB integrated noise figure with a 5 dB noise figure under blocking conditions. The CDMA2K front-end utilizes a self-biased common-gate input amplifier followed by passive mixers, achieving wideband input matching from 900 MHz up to 2.1 GHz with an IIP3 of +8 dBm. The GSM receiver consumes 38 mA from a power supply of 1.5 V and CDMA2K receiver consumes 16 mA in the low band and 21 mA in the high band. The multi-mode receiver, including LO buffers and frequency dividers, ADCs, and reference buffers, occupies 2.5 mm/sup 2/.     

无人机合成孔径雷达接收机开关电源研制

无人机合成孔径雷达接收机对电源的纹波和频谱特性要求比较高，一般采用线性电源。该文提出运用开关电源方案解决无人机合成孔径雷达接收机的电源问题，采用推挽和CUK变换器向接收机内的设备供电，可以减小体积、降低重量、提高效率，利用CUK变换器和低噪声低压降稳压器射频噪声低的特点，解决了低噪声放大器和压控振荡器对电源纹波和频谱特性要求高的难题。     

Modeling and experimental verification of substrate noise generation in a 220-Kgates WLAN system-on-chip with multiple supplies

Substrate noise is a major obstacle for mixed-signal integration. While the power consumption scales linearly with the clock frequency, substrate noise does not have this scaling due to the resonances in the transfer function of the supply current to the substrate. This paper addresses a practical technique to estimate the substrate noise frequency spectrum of a large mixed-mode System-on-Chip (SoC) with multiple supplies and embedded memories. The results have been verified with substrate noise measurements on a 60-MHz 220-Kgates telecom SoC implemented in a 0.35 /spl mu/m CMOS process on an EPI-type substrate. We compute a linear chip-level substrate model together with the single-cycle representation of piecewise-linear noise sources of three supply regions used in this ASIC. Based on this model we accurately estimate the four major resonances in the substrate noise spectrum and their relative magnitudes with 2 dB relative error at the major resonance with respect to measurements. We also present substrate noise measurements at different operating modes of the WLAN receiver. These measurements show that output I/O buffers generate significant substrate noise where an increase of 44% is measured for substrate noise peak-to-peak value due to the additional simultaneous switching of six output I/O buffers with already fully switching datapath and two output I/Os.     

Low-Power 2.4-GHz Transceiver With Passive RX Front-End and 400-mV Supply

An ultra low power 2.4-GHz transceiver targeting wireless sensor network applications is presented. The receiver front-end is fully passive, utilizing an integrated resonant matching network to achieve voltage gain and interface directly to a passive mixer. The receiver achieves a 7-dB noise figure and -7.5-dBm IIP3 while consuming 330 muW from a 400-mV supply. The binary FSK transmitter delivers 300 muW to a balanced 50-Omega load with 30% overall efficiency and 45% power amplifier (PA) efficiency. Performance of the receiver topology is analyzed and simple expressions for the gain and noise figure of both the passive mixer and matching network are derived. An analysis of passive mixer input impedance reveals the potential to reject interferers at the mixer input with characteristics similar to an extremely high-Q parallel LC filter centered at the switching frequency     

用于雷达接收机的开关电源的低纹波设计

介绍了某机载雷达接收机电源的实施方案.该方案采用开关电源代替线性电源,通过减少开关电源的输出纹波和干扰,满足接收机对电源的纹波要求.该方案提高了接收机电源的效率,减少了接收机电源的体积和重量,优化了接收机系统的设计.文中主要描述了接收机系统中所采用的开关电源的组成、各部分的作用、关键技术及解决途径.     

差异性QoS条件下CDMA系统在衰落信道中的性能分析

未来B3GCDMA系统采取不同误码率和带宽要求的业务分配不同功率和传输速率的方法。分析了在变速率、多功率级别条件下CDMA系统在衰落信道下的性能，给出了系统接收机信号噪声比的解析表达式和不同业务所需功率之间的关系，并对数值结果进行了讨论。     

High-efficiency power amplifier using dynamic power-supply voltagefor CDMA applications

Efficiency and linearity of the microwave power amplifier are critical elements for mobile communication systems. This paper discusses improvements in system efficiency that are obtainable when a DC-DC converter is used to convert available battery voltage to an optimal supply voltage for the output RF amplifier. A boost DC-DC converter with an operating frequency of 10 MHz is demonstrated using GaAs heterojunction bipolar transistors. Advantages of 10 MHz switching frequency and associated loss mechanisms are described. For modulation formats with a time-varying envelope, such as CDMA, the probability of power usage is described. Gains in power efficiency and battery lifetime are calculated. An envelope detector circuit with a fast feedback loop regulator is discussed. Effects of varying supply voltage with respect to distortion are examined along with methods to increase system linearity     

基于噪声测量技术的开关电源故障诊断方法研究

针对开关电源的核心功率器件MOS 管工作在高功率大电流下易损坏,使得开关电源无法正常工作故障率高的问题, 提出了一种利用噪声测量技术来判断其工作状态的故障诊断新方法,建立了功率MOS 器件的噪声模型,设计了超低噪声前置低频放大器,对伊莱科S-15-12型开关电源测试,结果表明,该方法能够测量到开关电源的低频噪声并准确判断其工作状态,且在准确率上较传统方法提高了65%,为开关电源的典型故障提供了一种可行及有效的评估方法。