基于TIADC的高速、高带宽信号采集系统

对基于国产现场可编程门阵列（FPGA）和时间交织模数转换器（TIADC）的信号采集系统进行了研究,分析了TIADC应用过程中的硬件设计问题,考虑了噪声、抖动、频谱泄露等因素对信号采集系统性能的影响,并基于最小二乘法完成了TIADC通道失配误差的标定和校准。对设计的信号采集系统进行了动态性能测试,测试结果表明,设计的信号采集系统采样率达到10 GSa/s,实时采样带宽达到4 GHz。     

基于线下估计和线上补偿的时间交错采样ADC失配误差补偿方法

该文提出一种改进的时间交错采样模数转换器(TIADC)失配误差补偿方法。系统通过误差参数和简化的拉格朗日插值算法分别实现了对偏置、增益的失配误差补偿和采样时间的失配误差补偿。该补偿方法在FPGA中采用低复杂度的定点运算实现,在TIADC硬件平台中实现了对多通道ADC采样数据的线上校正。实验结果表明:所提改进方法在仿真环境下使无杂散动态范围提升了51 dB,并且在硬件实现过程中使SFDR优化达45 dB。在保持失配误差估计精度和补偿效果优良的前提下,该方法不仅降低了算法的计算复杂度,而且该补偿结构不受TIADC通道数目的限制。     

基于频域稀疏性的时间交替模数转换器时间相位失配盲测量算法

该文研究时间交替模数转换器(TIADC)的通道间时间相位失配参数的盲测量问题。基于TIADC系统架构、输入模拟信号的频域稀疏性和非混叠频率点,以采样定理和欠采样理论为基础,探索TIADC系统输入信号、输出信号以及与子ADC输出信号之间的频谱关系,推导出了一种新的基于非混叠频率点的相对频谱的离散傅里叶逆变换序列的相位信息的TIADC通道间时间相位失配参数的盲测量算法。仿真实验表明该文所提出的盲测量算法具有可以与正弦拟合算法相比拟的参数测量精度,并且具有对噪声不敏感,对输入信号频率无限制,对TIADC系统通道数无限制,不需要对输入信号过采样等突出优点。TIADC系统真实捕获数据测试进一步验证了该算法的准确性和有效性。     

基于参考信号注入的TIADC时间失配校准算法

提出了一种基于参考信号注入的TIADC时间失配后台校准算法。该校准算法统计通道间的参考信号过零点个数,比较相邻2个峰值的大小,计算得出误差系数,并将该误差系数反馈回时钟采样控制单元进行校正。采用Simulink软件建立12位5通道TIADC模型,仿真结果表明,当fin/fs≈0.040 3时,有效位数从8.1位提升到11.8位,验证了算法的可行性。算法中的时间失配误差提取与TIADC分开,并行处理,保证了输入信号在整个奈奎斯特频率范围内不受影响。该校准算法消耗资源少,易于硬件实现。     

基于沃尔什函数的TIADC全数字校准算法

提出了一种校准时间交织模数转换器(TIADC)通道失配误差的全数字自适应后台算法。该算法利用沃尔什函数仅从TIADC的输出中调制产生伪杂散信号,可以重构出失配误差,并自适应地从TIADC输出中减去三个失配误差。所提出的技术的优势在于它只需要知道测量的输出信号和TIADC通道数,而无需任何其它信息,包括参考通道。同时针对算法(大多数调制算法)存在特殊频率点无法校准的问题,设计了一个频率判断模块,并通过一组低通滤波器和带通滤波器对特殊频率点进行额外杂散消除,克服了算法的局限性。仿真结果表明,所提技术能够有效消除通道失配误差,从而显著提高了TIADC系统性能。     

基于记忆多项式的时间交织模数转换器自适应非线性失配校正方法

为了提高时间交织模数转换器(TIADC)的有效分辨率,需要对其通道之间的线性/非线性失配误差进行估计和补偿。该文针对M通道TIADC的带有记忆效应的非线性失配误差提出了一种自适应盲校正算法。通过子通道重构结构(SCR)重构非线性误差信号,并通过滤波降采样最小均方(FDLMS)算法估计非线性失配误差系数。实验仿真结果表明,该方法可以有效校正带有记忆效应的非线性失配误差,并且可以大大降低实现难度和硬件资源消耗。     

时间交替ADC系统的实现

时间交替ADC系统通过几片低速的ADC芯片进行并行交替采样,可以成倍地提高系统的采样频率,同时保持较高的分辨率[1]。但是由于芯片及具体实现过程中一些实际因素的影响,不可避免地会引入通道失配误差[2]。本文利用两片ADC芯片及外围电路来实现时间交替ADC系统,并通过Matlab软件对采样数据进行通道失配误差的估计和校正。Matlab仿真结果表明,该系统的采样率基本上达到了单片ADC的两倍,同时其通道失配误差通过算法校正后得到了有效地消除。     

通道间差值统计的TIADC时序误差校准方法

利用某相邻采样通道的绝对差值与全部相邻通道的平均绝对差值应保持一致的原理,对TIADC的采样时序误差进行估计,再利用泰勒展开的方法实现误差补偿。在校准过程中,将误差估计模块和误差补偿模块组成一个自适应的环路,实现了采样时序误差的实时校准。全部校准过程在纯数字域中完成。这种纯数字后处理式的误差估计方法简单有效,3阶泰勒误差补偿方法的补偿效果良好。基于MATLAB建立了4通道TIADC的时序失配误差校准模型,验证了该校准方法的正确性和有效性。结果表明,通道间的时序误差为1%~2%,在输入归一化频率fin/fs为0.397时,校准后系统的SNR由原来的18.85 dB提高到73.31 dB。     

基于时间交替采样技术的高速高精度ADC系统

介绍了一种基于时间交替采样结构的高速ADC系统,整个系统采用全数字方式实现时间交替采样技术,结构灵活多变。使用2片ADC芯片及外围电路、FPGA作为逻辑控制和数据接收缓存,来搭建时间交替ADC系统的硬件电路。其最高采样率可达400MSPS,采样精度为12位。通过分析时间交替ADC系统的原理及其通道误差特性,利用Matlab软件分析通道失配误差来源,对采集到的数据进行误差估计和校正     

针对时间交织采样的后台自适应频域校准技术

针对高速双通道时间交织采样(Time-interleaved Analog-to-Digital Converter, TIADC)系统通道失配的问题,提出了一种后台自适应频域校准技术。该技术采用数字混频+低通滤波技术,将失配镜像点搬移至零频,并形成I/Q复数信号;然后基于信号统计学进行校准系数计算,并利用该系数完成共轭对消校准;最后将校准后信号通过数字混频搬移回原始频率,完成整个校准过程。进一步提出了基于FPGA/ASIC的算法实现电路。经实物测试验证,在6 Gsample/s双通道TIADC系统中,该技术能够优化失配比达33.3 dBc以上,失配优化程度高,同时具有全流水实时后台处理特性,且不需要增加额外系统资源。     

Corona Based Optimal Node Deployment Distribution in Wireless Sensor Networks

This paper shows the trade off between different modulation techniques such as multi level quadrature amplitude modulation, multi level phase shift keying, and multi level differential phase shift keying for upgrading direct detection optical orthogonal frequency division multiplexing systems with possible transmission distance up to 15,000 km and total bit rate of 2.56 Tb/s. The 2.56 Tb/s signal is generated by multiplexing 64 OFDM signals with 40 Gb/s for each OFDM. Variations of optical signal to noise ratio (OSNR), signal to noise ratio (SNR), and bit error rate (BER) are studied with the variations of transmission distance. Maximum radio frequency power spectrum, and output electrical power after decoder are measured for different multi level modulation techniques with carrier frequency. It is observed that multi level QAM has presented better performance than multi level PSK and finally multi level DPSK in optical OFDM systems. Maximum output power after decoder is enhanced with both 32-PSK, and 64-QAM. Quadrature signal amplitude level at encoder is upgraded with 64-QAM. It is noticed that OSNR, SNR, and BER are improved using 4-QAM OFDM system than either QPSK or 4-DPSK.     

9.6Gsps 10bit 宽带雷达接收机设计与实现

交叉采样是提升雷达接收机采样率的有效方法,但该方法会引入通道失配,通道失配将严重降低系统的性能。本文首先介绍基于OpenVPX平台的四通道交叉采样宽带雷达接收机的硬件设计;其次对采集系统通道失配误差及其估计方法进行分析;最后针对传统的通道失配校正方法耗费大量时间的问题,提出一种在线校正系统通道失配的方法,该方法提高了通道失配校正的效率。测试结果表明,该设计可实现以采样率9.6Gsps、精度10bit对频带为1GHz~4GHz的中频信号直接采集,能够满足宽带雷达接收机脉冲压缩处理的要求,已成功应用于某宽带雷达。      

卷积码在光正交频分复用系统中的应用

将卷积码成功地应用到直接检测的光正交频分复用(OFDM)光纤传输实验系统。实验中,产生了2 Gb/s的QPSK OFDM编码光信号,并成功地在标准单模光纤中传输了200 km,和没有采用卷积码的相比,系统的误码性能获得明显提高。在误码率10-3时,可节省1 dBm左右的光功率。实验结果表明,卷积码可应用到OFDM系统。     

Joint adaptive code rate technique and bit interleaver for direct-detection optical OFDM system

In this paper, we have theoretically analyzed that the existence of inter-subcarrier mixing interferences (ISMI) and frequency selective fading (FF) in the directed-detection optical orthogonal-frequency-division-multiplexing (DDO-OFDM) system will cause an unbalanced error distribution and degrade the system performance. Then we propose to employ the adaptive code rate technique (ACT) and bit interleaver in the DDO-OFDM system to combat ISMI and FF. The experimental results show that the receiver sensitivity of 5.9-Gb/s 64-ary quadrature-amplitude-modulation (64QAM) OFDM signal employing ACT(9.43 Gb/s after encoding) is improved more than 2 dB compared with the 5.9-Gb/s OFDM signal with 0.66 turbo coding rate (8.85 Gb/s after encoding) at the bit-error ratio (BER) of 1e-4. When the coding rate is all 0.625, the OFDM signal employing ACT has more than 1-dB gain improvement compared with the OFDM signal encoded with fixed-rate turbo coding. And additional ∼1-dB receiver sensitivity improvement is enabled when the OFDM signal employ ACT and bit-interleaver simultaneously.     

70-GHz-Band OFDM Transceivers Based on Self-Heterodyne Scheme for Millimeter-Wave Wireless Personal Area Network

70-GHz-band orthogonal frequency-division multiplexing (OFDM) transceivers were developed by combining self-heterodyne transmission with two-element diversity reception. The transceivers were used to study and demonstrate a millimeter-wave wireless personal network that enables cost-effective broadband data transmissions in a multipath channel environment. A 100-MHz sampling OFDM modulator/demodulator was developed for the baseband part. It has a payload data rate of 100 Mb/s using quadrature phase-shift keying (QPSK) modulation and a coding rate of 3/4 (many other modulations and coding rate are available). The bit error rate was experimentally evaluated when a pair of devices was placed on a wooden table under line-of-sight path conditions. The results showed that the combined use of the self-heterodyne technique and two-element diversity receiver successfully avoids serious signal fading at unpredictable transmission distances. The transceiver with QPSK modulation and coding rate of 1/2 for forward error correction achieves error-free data transmission over a distance of up to 3.4 m. In addition, a successful transmission in 64 quadrature amplitude modulation mode was demonstrated, although the communication range was quite short.     

一种时间交织ADC采样时间误差校正方法

提出了一种用于时间交织模数转换器(TIADC)通道间采样时间误差的校正算法。该算法是基于参考通道的后台校正算法。通过比较参考通道与带校准通道的输出差异提取出采样误差信息,并通过负反馈逻辑进行校准。该算法的校正模块硬件消耗低,可支持包括完全随机输入信号的多种类型输入信号。将该校正算法应用于一个4 GHz、8 bit四通道TIADC,后仿真结果表明,当输入信号接近奈奎斯特频率、存在其他非理想因素的条件下,该算法能将通道间采样时间误差相关的频谱尖峰抑制到35 dB。     

基于10 Gb/s传输链路的40 Gb/s光传输实验研究

基于中国自然科学基金网(NSFCNet)的400 km×10 Gb/s光传输链路实现了40 Gb/s光传输,没有出现误码率(BER)平台,说明在常规的中短距离10 Gb/s系统可以直接升级至40 Gb/s系统,而不需要升级传输链路。但是,由于相对10 Gb/s系统而言40 Gb/s系统的色散容限非常小,在升级时必须精确补偿原有链路的色散,在接收机前一般需要加可调色散补偿单元。同时,还分析了光纤注入功率对系统性能的影响,结果表明在设计这种由10 Gb/s向40 Gb/s升级的系统时,不仅要考虑信号带宽增加带来信噪比要求的提高,而且必须充分考虑光纤非线性的影响。     

Experiments on real-time 1-Gb/s packet transmission using MLD-based signal detection in MIMO-OFDM broadband radio access

This paper presents experimental results on real-time packet transmission of greater than 1 Gb/s using 4-by-4 multiple-input-multiple-output (MIMO) multiplexing and maximum-likelihood detection (MLD)-based signal detection with a decreased level of computational complexity in orthogonal frequency-division multiplexing (OFDM) radio access. We apply our previous algorithm called adaptive selection of surviving symbol replica candidates (ASESS) based on the maximum reliability in MLD employing QR decomposition and the M-algorithm (QRM-MLD) to reduce the extremely high level of computational complexity in the conventional MLD. The experimental results using multipath fading simulators are in good agreement with the computer simulation results. The loss in the required received signal energy per bit-to-background noise power spectrum density ratio (E/sub b//N/sub 0/) is suppressed to within approximately 1-2 dB. Therefore, through experiments, we demonstrate that the QRM-MLD employing ASESS is very beneficial in reducing the influence of hardware implementation loss, as well as in decreasing the required received E/sub b//N/sub 0/. We further show that the extremely high-speed real-time packet transmission of greater than 1 Gb/s in a 100-MHz channel bandwidth (i.e., 10 bit/s/Hz) is achieved at the average received E/sub b//N/sub 0/ per receiver antenna of approximately 12 dB using 16QAM modulation and turbo coding with the coding rate of 8/9 in 4-by-4 MIMO multiplexing.     

W波段正交频分复用信号传输系统的实验研究

实验研究了工作在W波段的正交频分复用毫米波传输系统的传输特性。系统中应用了优化信道估计的符号内频域平均技术和减少信号峰均比的基于离散傅里叶变换的扩频技术(DFT-Spread)来提高传输性能。实验成功地将21.2 Gb/s 84.5 GHz载频的16QAM OFDM信号传输2 m的无线距离,误码率控制在7%冗余度的软判决纠错码门限内(比特误码率为3.8×10-3）。