软件无线电中的多速率处理

叙述了软件无线电中常用的一种关键信号处理技术———信号的解析表示和多速率信号处理方法 (抽取和内插 ) ,并简要介绍了在抽取和内插中采用的抗混叠滤波器。     

一种分析和设计抗混叠滤波器的方法

信号采集通道中,一般采用高阶抗混叠滤波器来消除频率混叠现象,这同时也增加了滤波器设计难度。为有效降低滤波器设计的难度,在详细分析并讨论了抗混叠滤波器的陡度、阶数与信号抽样频率以及A/D转换器的分辨率之间的内在关系后,提出了抗混叠滤波器、抽样频率和A/D转换器三者之间合理权衡设计的方法。该分析方法为抗混叠滤波器乃至信号采集通道的设计提供了十分有益的参考。     

基于FPGA的某ISAR成像数字中频接收机实现

根据软件无线电理论设计了一种应用于逆合成孔径雷达成像系统的数字化中频接收机,提出了一种可变抽取因子的数字下变频方案,可以大大提高接收机系统的灵活性。该数字化中频接收机最终在Xilinx Virtex-6 FPGA上实现,可保证在不发生频谱混叠的情况下将中心频率为105 MHz,带宽0~20 MHz之间可变的中频信号下变频为低数据率的数字零中频信号。系统提供2~84之间共14种不同的抽取因子,可以根据输入信号带宽进行配置。测试结果表明,该系统设计正确且无虚假动态范围大于90 d B。     

Walsh变换在数字下变频中的应用研究

讨论了软件无线电接收机中数字下变频处理的高效算法和结构,其目的是在DSP中用软件完成数字下变频处理,这样可省去专用数字下变频器硬件集成电路,并增强中频处理的灵活性、适应性。针对软件数字下变频中滤波-抽取的运算量的考虑,文中提出了用W alsh变换替代传统的用FIR滤波器抗混叠滤波的方案,实验结果表明该方案可有效节约数字信号处理器的时间和空间。     

软件无线电中的带通采样分析

近年来,软件无线电技术以其强大的通用性和灵活性得到了广泛发展和应用。研究了软件无线电中广泛采用的带通采样技术。在给出带通采样定理一般结论的基础上,重点分析了实现无混叠带通采样的条件,得到了边界频率点上4种不同取值情况下带通采样频率的取值范围,并利用时域内插进行了带通采样信号的完全重建。最后,采用Matlab进行了仿真验证。     

二次抽样原理及其仿真分析

用Matlab对二次抽样过程进行仿真,可以得到与理论分析相同的结论,充分说明二次抽样可以增大相邻频移项间的距离,避免混叠现象的发生;同时也可以减小信号的频带宽度,有利于节省信道资源,便于进行无线电通讯。     

一种电磁频谱管理盲监测技术

复杂电磁环境下对无线电信号进行监测时,基于时频分析的传统监测方式对频谱混叠信号难以进行识别.针对这一问题,提出了一种电磁频谱管理盲监测技术.在分析研究了盲源分离的理论基础上建立了基于最大信噪比算法的盲监测模型,基于该模型仿真实现了6路频谱混叠无线电信号的分离提取.仿真结果表明:应用所建立的模型能够实现频谱混叠无线电信号的监测分析,判明所监测无线电设备的工作频率、信号形式和带宽等主要特征.     

基于窄带信号抽样的信号高效传输

奈奎斯特抽样定理是对频率宽度有限长的模拟信号进行数字化处理的重要定理之一,而对于这类频宽有限信号中的特殊信号,即窄带信号而言,依据奈奎斯特抽样定理对信号进行抽样时会出现一些新问题。在指出窄带信号存在原因的基础上,以抽样信号的频谱不混叠为根本对窄带信号进行抽样,并使其与按照奈奎斯特定理抽样后的信号进行比较分析。借助通信原理相关知识予以在信道传输中进行分析,得出信号经窄带信号抽样定理处理后的优势所在。     

LTC1569滤波器在信号调理模块中的应用

为实现抗混叠滤波,采用Linear公司的滤波器LTC1569设计输出频率为0—2kHz的信号滤波电路。通过实验验证利用LTC1569搭建的滤波电路对信号具有很好的滤波效果。     

LTC1569滤波器在信号调理模块中的应用

为实现抗混叠滤波,采用linear公司的滤波器LTC1569设计输出频率为0～2 kHz的信号滤波电路.通过实验验证利用LTC1569搭建的滤波电路对信号具有很好的滤波效果.     

软件无线电技术在舰船通信中的应用研究

针对软件无线电技术在舰船通信中应用问题,对软件无线电数字接收理论进行了深入研究,包括了低通采样理论、带通采样理论以及多速率信号处理技术等,同时对软件无线电结构进行了分析。采用软件无线电数字信道化模型,给出了信道化高效实现结构,并通过计算机仿真验证了该软件无线电数字信道化结构的正确性。该软件无线电信道化模型适用于舰船通信系统中应用。     

变频技术在软件无线电中的应用研究

简要介绍了基于变频技术的软件无线电结构的形成,宽带中频采样接收机的变频原理及其过程,并以超外差接收技术和软件无线电理论为基础,从变频技术的视角分析了宽带中频带通采样接收结构的频率变换及频谱搬移过程,并给出了一种基于变频技术的软件无线电宽带中频采样接收机的硬件实现方案。     

基于隐含多项式曲线仿射不变量的目标识别

目标物体的识别和匹配在计算机视觉、图像视频压缩与传输中都有重要应用.由于隐含多项式曲线对物体有良好的描述能力,因而用它识别和匹配目标物体是比较有效的.文章首先证明了隐含多项式曲线封闭有界的充要条件定理,接着基于隐含多项式曲线的二次分解性质,给出了目标物体仿射几何不变量的计算方法.实验证明这种基于首二次因子积的仿射几何不变量准确的描述了物体的特征,从而能较好的设别出复杂的,甚至缺失部分信息的目标物体.     

Reconfigurable radio receiver with fractional sample rate converter and multi-rate ADC based on LO-derived sampling clock

A composite radio receiver back-end and digital front-end, made up of a delta-sigma analogue-to-digital converter (ADC) with a high-speed low-noise sampling clock generator, and a fractional sample rate converter (FSRC), is proposed and designed for a multi-mode reconfigurable radio. The proposed radio receiver architecture contributes to saving the chip area and thus lowering the design cost. To enable inter-radio access technology handover and ultimately software-defined radio reception, a reconfigurable radio receiver consisting of a multi-rate ADC with its sampling clock derived from a local oscillator, followed by a rate-adjustable FSRC for decimation, is designed. Clock phase noise and timing jitter are examined to support the effectiveness of the proposed radio receiver. A FSRC is modelled and simulated with a cubic polynomial interpolator based on Lagrange method, and its spectral-domain view is examined in order to verify its effect on aliasing, nonlinearity and signal-to-noise ratio, giving insight into the design of the decimation chain. The sampling clock path and the radio receiver back-end data path are designed in a 90-nm CMOS process technology with 1.2V supply.     

基于间歇采样的线性调频脉冲压缩雷达干扰技术研究与实现

阐述了间歇采样转发干扰的原理,对基于间歇采样的线性调频脉冲压缩雷达干扰进行了仿真和分析,利用数字射频存储器（DRFM）技术设计了间歇采样转发干扰样式,产生了大量相干假目标。间歇采样转发干扰在工程上易于实现,对线性调频脉冲压缩雷达的干扰有一定的指导作用。     

带通采样在数字多通道中频接收机中的应用

论述了带通信号采样定理,在对带通采样后的频谱结构做了详细分析的基础上,提出中频频率、采样频率的选取方法。将带通欠采样技术运用到软件无线电中频接收机设计中,并给出了带通采样定理在的不同条件下Matlab仿真的结果,验证了带通采样技术在宽带数字多通道、多速率、多模式软件无线电中频接收机设计中的可行性和实用性,在工程应用中具有较大的参考意义。     

Effects of Noise and Jitter in Bandpass Sampling

BandPass Sampling (BPS) is an undersampling technique by intentional aliasing. BPS enables one to have an interface between the IF stage and the ADC in a radio receiver. Conventional uniform BPS at Nyquist rate normally results in a low Signal-to-Noise Ratio (SNR) due to noise spectrum aliasing. The noise (e.g. kT/C noise introduced in a voltage-mode sampler) is combined in each of the Nyquist bands within the bandwidth of the sampling device. Also timing jitter causes a performance degradation in BPS.In this paper, signal spectrum aliasing, noise aliasing and jitter effects in BPS is analyzed. It is verified by simulation that NonUniform Sampling (NUS) has the potential to suppress signal spectrum aliasing and relax the requirement on the anti-aliasing (AA) filter. Jitter effects in BPS are compared to LowPass Sampling (LPS) case. However, a signal cannot be reconstructed from its nonuniform samples by using only ideal lowpass filtering (classic Shannons reconstruction). Finally, signal reconstruction in the presence of noise and jitter are investigated for three Reconstruction Algorithms (RAs) aimed at NUS.Yi-Ran Sun received her bachelor degree in physics in 1998 and master degree in Electronic engineering in 2002 in China and in Sweden, respectively. She is currently pursuing the Ph.D. degree in electronic engineering at Royal Institute of Technology (KTH), Stockholm. Her current research interests are in the area of mixed-signal system design in radio receiver front-ends. Of special focus is bandpass sampling technique and corresponding area of signal processing.Svante Signell (M 95) received the Dr. Sc. degree from the Royal Institute of Technology (KTH) Stockholm, Sweden, in 1987, in the area of periodically time-varying linear systems with applications to filters.From 1987 to 1991, he was with ABB HAFO, working on mixed-signal system-on-chip design, mainly in the area of hearing aids and pacemakers. Between 1991 and 2003, he was with Ericsson Radio working with technology research for base stations and signal processing for future wireless systems. He has been holding various positions such as project leader and as an expert on analog and digital signal processing at the company level.Since 1988, he has been involved as a Consultant to companies such as ABB Hafo, Ericsson Radio, Ericsson Telecom, Siemens Elema, and Standard Radio & Telefon, as well as course developer and lecturer in courses held at companies and universities. Since the beginning of 2000, he is an Adjunct Professor in Mixed Signal System Design at KTH.He has authored around 50 papers published in international conference proceedings and magazines and holds eight patents, with more pending. He has been reviewer for IEEE magazines and conferences, program committee member, expert reviewer for a European Commission project 1997–2001, and reviewer for national research programs on both project and program level. His main research interests include, but are not limited to, systems-on-chip (SoC), software-defined radio (SDR) and critical technologies for the realization of SoC and SDR, in particular, on how to find the best combination of analog and digital signal processing.     

一种非均匀采样下小信号的检测方法

非均匀采样由于其具有不受采样频率限制、频率分辨率高以及抗混叠等优点,使得其应用十分广泛。但非均匀采样会引起信号的频谱噪声,这样使得非均匀采样下小信号的检测不易实现。本文分析了非均匀采样引起频谱噪声的原因,提出一种基于非均匀采样的小信号检测方法。该方法根据非均匀采样检测得到的大幅度信号,应用陷波器将其消除,降低了由大信号引起的频谱噪声,从而检测出小信号。文中详细说明了陷波方法的原理、陷波器宽度和深度的选择、陷波器中心频率的确定以及陷波器在非均匀采样下的应用,最后给出实验结果。理论和实验表明,基于非均匀采样的陷波方法是一种行之有效的信号频率检测方法,使用该方法处理信号可以得到准确的频率估计效果,检测出信号幅度相差100倍以上的多个信号频率。