一种同时传输基带信号的RoF双工系统

分析了用光载波抑制耦合基带信号的RoF系统,给出RoF下行链路传输的改进方案:在中心站将基带信号耦合到被抑制掉的频段处传输到基站,并重复利用边带传输上行链路信号.通过仿真得到的系统光谱图、误码率曲线表明:耦合基带信号传输后,下行链路信号的光纤能量损耗降低,基带信号和上行链路信号也具有较好的抗色散能力.     

基于四波混频同时传输基带信号的ROF系统

文章分析了用四波混频产生边带并传输基带信号的光纤无线通信(ROF)系统.该系统中心站处产生两对载波抑制边带,一对传输下行链路信号,另一对承载基带信号并在基站传输上行链路信号.通过仿真得到的系统光谱图、误码率曲线表明:加入基带信号传输后,下行信号的能量损耗不变,基带信号和上行信号却有较好的抗色散能力.     

WLAN接收AGC调整算法的设计与实现

强信号容易使接收机达到饱和,弱信号因解调器检测不到容易丢失.采用AGC,能把强弱悬殊的信号调整到适合基带解调,基带处理器中AGC算法功能是通过检测接收到的模拟基带信号能量,计算天线馈入的射频信号强度,然后反馈控制射频接收链路增益,得到信噪比最优的模拟基带信号,提高接收机的动态增益控制范围.文中介绍一种AGC算法,并以UW2453射频收发器为例介绍其实现过程.     

一种复用传输射频和基带信号的新方法

介绍了一种在同轴电缆上,射频和基带信号复用传输的新方法。设计了射频信号和基带信号隔离电路,采用C-MBUS标准传输基带信号,在长为1 km、传输射频信号功率为40 d Bm的同轴电缆上,达到了4 800 b/s的数据传送速率,且同时可以为通信从机节点提供10 m A的电流。该方法具有硬件电路简单、成本低廉,容易组网的优点,适用于在射频线路上同时传输低数据速率的附加信息。     

基于FPGA的数字基带传输位同步恢复

提出了一种基于全数字锁相环提取数字基带传输位同步时钟的设计方案,该方案采用环路鉴相器产生误差信号控制本地位同步电路的添加/扣除门在时钟输出的脉冲序列中附加或扣除1个或几个脉冲实现同步。给出了该方案的整体电路,并经VHDL程序设计,在MaxplusⅡ环境下做了时序仿真,从仿真结果分析了设计方法可实现数字基带传输位同步时钟的提取。     

视频基带传输线中双工传输媒体数据的研究

介绍了一种在同轴电缆中进行视频、语音和数据混合信号传输的装置,着重分析了视频基带信号收发器、FM语音信号调制解调器、ASK数据信号调制解调器和滤波器电路4个结构模块的硬件设计.该装置能在传送视频基带信号的同时双工传输FM语音信号和ASK数据信号.实验表明,该装置最大传输距离超过300 m,数据传输率可达20 Kbit/s,可应用于视频监控领域.     

数字匹配滤波器的EDA设计与实现

在无线电台通带内传输直扩信号时解扩是关键技术之一。提出了一种利用数字匹配滤波器进行基带解扩的方案，论述了数字匹配滤波器解扩的基本工作原理和实现方法，给出了基于EDA软件MAX＋plusⅡ设计的数字匹配滤波器芯核顶层电路，其中伪随机码为32位平衡GOLD码。对码片速率为9600chip／s的基带扩频信号解扩的仿真结果表明，该方案正确可行，并最终实现了用于基带解扩的数字匹配滤波器ASIC。     

80kb/s的二线基带调解器研制成功

电子工业部三十所在对时分制和乒乓法的基带信号传输技术进行深入研究的基础上,最近研制成功了一种采用80kb/s速率传输体制的、信号速率为32kb/s的二线基带信号调制解调器,并顺利地联通了32门数字程控交换机。试验表明,传输衰耗为35分贝时误码率不大于10~(-6)。该调解器数字电路的时间配合、相位关系和同步电路的设计都很巧妙,既节省了器件,又满足了技术要求,且有利于大批量生产。另外,设计者还对均衡、再生判决收发转换电路进行了研究和反复试验,选择了较简单易行的方案,实用效果令人满意。该调解器的研制成功在一定范围内较好地解决了目前国内存在的基带信号二线传输问题。这项技术还可以开发其他速率的同类产品,以满足不同用户的要求。     

基带成形滤波器的数字设计与实现

根据基带成型滤波器的工作原理,文中设计出了一种基带成型滤波器的数字实现方案。该方案首先运用MATALB仿真工具得到信号基带成型后的仿真数据,并将仿真数据存储在FPGA中,然后通过查表操作实现了数字基带成型滤波器的功能。文中还给出了通过MODELSIM得到的信号基带成型后的仿真结果,仿真结果表明,由该方案所设计的基带成型滤波器可以很好地完成通信系统中信号的成型特性。     

一种集成无线和有线信号的混合接入系统研究

为了满足不同高带宽业务的需求,提出一种同时传输有线和无线信号的混合接入网系统。在下行链路中,无线信号以相位调制格式在光载波上传输,有线信号以强度调制格式重调制在光载波上,在ONU(光网络单元)采用不同的解调方案进行解调接收;在上行链路中,通过载波重用技术再调制有线基带信号并将其传输至OLT(光线路终端),简化了系统的器件配置。利用光学软件Optisystem验证了系统的可靠性和有效性。仿真结果显示,无线链路信号和有线基带信号经过正交调制传输后,在用户端仍能得到较好效果的眼图,说明它们能被准确地接收。采用载波重用技术的上行基带信号也能被OLT准确地接收。     

THz wireless communication system based on wavelet transform

With a very wide frequency band not allocated at present, THz waves have many optimal characteristics such as high transmission rate, large capacity, and high security. The research of THz communication technology has become a hotspot in wireless communication. For THz wireless communications, it is crucial to study advanced electrical signal processing techniques. In this paper, in view of the shortcomings of traditional orthogonal frequency division multiplexing (OFDM) technology, we propose wavelet transform orthogonal multicarrier modulation method in THz system. In addition, we study THz channel coding technology to ensure that the THz wireless communication baseband system has better bit error rate (BER) performance and low computational complexity. Based on above, a THz wireless communication baseband system is conceived.     

基于蓝牙系统的基带处理仿真教学实验的设计与实现

提出了一种适用于教学的蓝牙基带处理仿真实验，着重研究了基于蓝牙系统的基带包结构和差错控制方法，以及跳频扩频、保密通信等原理及其实现方法。仿真软件界面知识点丰富，有助于理解和掌握无线通信系统对基带信号的处理方法，在教学实践中获得了很好的效果。     

A novel anti-intercepting wireless communication scheme

In this paper, a novel wireless communication scheme is proposed, which has high anti-intercepting ability without the frequency efficiency loss. In this scheme, we use the baseband mixed signal to construct the transmission signal, which is consisted of two independent and useful baseband signals. According to our analysis, we find that the baseband mixed signal transmission scheme can achieve higher anti-intercepting ability than the existing mixed signal schemes, and it can achieve high frequency efficiency since the mixed signals carry useful information simultaneously. We also provide a low-complexity reception algorithm based Gibbs sampling for the proposed scheme. According to simulation results, we demonstrate that the proposed scheme is effective, and validate its anti-intercepting ability.     

球载观测系统的无线图像传输系统设计

为实现系留气球观测系统轻量化无线图像高速稳定传输,文中采用了ZYNQ+AD9361硬件架构和正交频分复用技术实现无线图像传输系统设计。ZYNQ的FPGA部分实现了与AD9361射频前端的数字接口,与ZYNQ的ARM部分的数据通道,以及基于IEEE 802.11a标准的基带处理器物理层。ARM部分运行Linux操作系统,可在该系统上完成对AD9361配置的应用程序的开发、物理层管理以及与上位机和摄像机的数据交互。无线图像传输系统的引入,实现了空中系留气球观测平台与地面控制中心点对点的无线图像传输,增强了系留气球观测系统目标监测的可靠性。该通信系统结合了软件无线电系统灵活性配置、正交频分复用技术频谱利用率高以及抗多径效应等优点,能够随着系留气球观测系统应用于各种复杂环境中。     

Implementation of a MIMO OFDM-based wireless LAN system

The combination of multiple-input multiple-output (MIMO) signal processing with orthogonal frequency division multiplexing (OFDM) is regarded as a promising solution for enhancing the data rates of next-generation wireless communication systems operating in frequency-selective fading environments. To realize this extension of OFDM with MIMO, a number of changes are required in the baseband signal processing. An overview is given of the necessary changes, including time and frequency synchronization, channel estimation, synchronization tracking, and MIMO detection. As a test case, the OFDM-based wireless local area network (WLAN) standard IEEE 802.11a is considered, but the results are applicable more generally. The complete MIMO OFDM processing is implemented in a system with three transmit and three receive antennas, and its performance is evaluated with both simulations and experimental test results. Results from measurements with this MIMO OFDM system in a typical office environment show, on average, a doubling of the system throughput, compared with a single antenna OFDM system. An average expected tripling of the throughput was most likely not achieved due to coupling between the transmitter and receiver branches.     

一种无线宽带收发机I/Q失配校准和补偿技术

本文提出一种基于数字基带的无线宽带收发机中的发射链路I/Q失配的校准和补偿技术。数字基带发射用于I/Q失配校准的信号,经过RF收发机的发射链路、由平方功率检测器、带通滤波器组成的校准通路以及RF接收机的可变增益放大器,数字基带采集此信号并估计I/Q失配的大小,完成I/Q失配的校准和补偿,此技术相比于射频的自校准节省了面积和功耗。本技术已经成功用于IEEE802.11n,可以实现50dB以上的镜像抑制,完全满足了系统要求。     

手机通信干扰设备的设计

在分析常用干扰方法和干扰设计要求的基础上,结合当前手机通信频段频点固定的特点,提出一种最优的干扰设计方法。然后给出其硬件电路设计,并计算干扰效果。详细分析了音调干扰基带信号源模块设计。最后通过测试验证该方案下的音调干扰系统对于手机通信的干扰是有效的。     

Bridging dream and reality: programmable baseband processors for software-defined radio - [integrated circuits for communications]

A programmable radio baseband signal processor is one of the essential enablers of software- defined radio. As wireless standards evolve, the processing power needed for baseband processing increases dramatically and the underlying hardware needs to cope with various standards or even simultaneously maintaining several radio links. Meanwhile, the maximum power consumption allowed by mobile terminals is still strictly limited. These challenges require both system and architecture level innovations. This article introduces a design methodology for radio baseband processors discussing the challenges and solutions of radio baseband signal processing. The LeoCore architecture is presented here as an example of a baseband processor design aimed at reducing power and silicon cost while maintaining sufficient flexibility.     

A Fast-Settling Wideband-IF ASK Baseband Circuit for a Wireless Endoscope Capsule

A novel automatic-gain-control (AGC) architecture utilizing wideband current feedback is proposed for the baseband circuit of a wireless endoscope capsule. The baseband circuit consists of a fast-settling wideband AGC loop and an amplitude-shift-keying demodulator. Additional integrators in the reverse signal path provide negative feedback, bandpass-filtering effect, attenuating low-frequency noises, and dc offset from the radio-frequency front end. The baseband circuit fabricated in a 180-nm complementary metal-oxide-semiconductor process achieves a wide-intermediate-frequency (IF) carrier frequency in the range of 0.5-40 MHz, a measured settling time of 2 mus, and an input sensitivity of -57 dBm. The entire baseband demodulator dissipates only 5 mA, with a 1.8-V supply at a data rate of 1.37 Mb/s and an IF carrier frequency of 10 MHz.     

卫星通信中频谱反转的成因与处理

变频的目的是为了使信号能够在特定的信道内利用合适的频率对信号进行有效传输,是无线通信系统中需要经常涉及到的问题。频谱反转一般是在传输过程中由于变频而造成的接收端所收与发射端所发的信号频谱相反的现象。本文对频谱反转产生的原因以及如何在基带系统中处理的方法进行了分析和介绍。