Modulation Recognition with Frequency Offset and Phase Offset over Multipath Channels

Modulation recognition becomes unreliable at low signal-to-noise ratio(SNR)over fading channel.A novel method is proposed to recognize the digital modulated signals with frequency and phase offsets over multi-path fading channels in this paper.This method can overcome the effects of phase offset,Gaussian noise and multi-path fading.To achieve this,firstly,the characteristic parameters search is constructed based on the cyclostationarity of received signals,to overcome the phase offset,Gaussian white noise,and influence caused by multi-path fading.Then,the carrier frequency of the received signal is estimated,and the maximum characteristic parameter is searched around the integer multiple carriers and their vicinities.Finally,the modulation types of the received signal with frequency and phase offsets are classified using decision thresholds.Simulation results demonstrate that the performance of the proposed method is better than the traditional methods when SNR is over 5dB,and that the proposed method is robust to frequency and phase offsets over multipath channels.

Joint Estimation of Carrier Frequency and Phase Offset Based on Pilot Symbols in Quasi-Constant Envelope OFDM Satellite Systems

Spectral efficiency and energy efficiency are two important performance indicators of satellite systems. The Quasi-Constant Envelope Orthogonal Frequency Division Multiplexing(QCE-OFDM) technique can achieve both high spectral efficiency and low peak-to-average power ratio(PAPR). Therefore, the QCE-OFDM technique is considered as a promising candidate multi-carrier technique for satellite systems. However, the Doppler effect will cause the carrier frequency offset(CFO), and the non-ideal oscillator will cause the carrier phase offset(CPO) in satellite systems. The CFO and CPO will further result in the bit-error-rate(BER) performance degradation. Hence, it is important to estimate and compensate the CFO and CPO. This paper analyzes the effects of both CFO and CPO in QCE-OFDM satellite systems. Furthermore, we propose a joint CFO and CPO estimation method based on the pilot symbols in the frequency domain. In addition, the optimal pilot symbol structure with different pilot overheads is designed according to the minimum Cramer-Rao bound(CRB) criterion. Simulation results show that the estimation accuracy of the proposed method is close to the CRB.

Blind estimation of phase offset in OFDM subcarrier for coherent demodulation

An adaptive algorithm named low complexity phase off- set estimation （LC-POE） is proposed for orthogonal frequency division multiplexing （OFDM） signals. Depending on the requirement, the estimation procedure is divided into several scales to accelerate the adaptive convergence speed and ensure the estimation accuracy. The true phase offset is estimated through shrinking the detection range and raising the resolution scale step by step. Both the convergence performance and complexity are discussed in the paper. Simulation results show the effectiveness of the proposed algorithm. The LC-POE algorithm is promising in the application of OFDM systems.

A Static Phase Offset Reduction Technique for Multiplying Delay-Locked Loop

Static phase offset (SPO) in conventional multiplying delay-locked loops (MDLLs) dramatically degrades the deterministic jitter performance. To overcome the issue, this paper presents a new SPO reduction technique for MDLLs. The technique is based on the observation that the SPO of MDLL is mainly caused by the non-idealities on charge pump (e.g. sink and source current mismatch), and control line (e.g. gate leakage of loop filter and voltage controlled delay line (VCDL) control circuit). With a high gain stage inserting between phase detector/phase frequency detector (PD/PFD) and charge pump, the equivalent SPO has been decreased by a factor equal to the gain of the gain stage. The effectiveness of the proposed technique is validated by a Simulink model of MDLL. The equivalent SPO is measured by the power level of reference spur.

Shaped Offset Quadrature Phase Shift Keying Based Waveform for Fifth Generation Communication

Fifth generation(5G)wireless networks must meet the needs of emerging technologies like the Internet of Things(IoT),Vehicle-to-everything(V2X),Video on Demand(VoD)services,Device to Device communication(D2D)and many other bandwidth-hungry multimedia applications that connect a huge number of devices.5G wireless networks demand better bandwidth efficiency,high data rates,low latency,and reduced spectral leakage.To meet these requirements,a suitable 5G waveform must be designed.In this work,a waveform namely Shaped Offset Quadrature Phase Shift Keying based Orthogonal Frequency Division Multiplexing(SOQPSK-OFDM)is proposed for 5G to provide bandwidth efficiency,reduced spectral leakage,and Bit Error Rate(BER).The proposed work is evaluated using a real-time Software Defined Radio(SDR)testbed-Wireless open Access Research Platform(WARP).Experimental and simulation results show that the proposed 5G waveform exhibits better BER performance and reduced Out of Band(OOB)radia-tion when compared with other waveforms like Offset Quadrature Phase Shift Key-ing(OQPSK)and Quadrature Phase Shift Keying(QPSK)based OFDM and a 5G waveform candidate Generalized Frequency Division Multiplexing(GFDM).BER analysis shows that the proposed SOQPSK-OFDM waveform attains a Signal to Noise Ratio(SNR)gain of 7.2 dB at a BER of 10�3,when compared with GFDM in a real-time indoor environment.An SNR gain of 8 and 6 dB is achieved by the proposed work for a BER of 10�4 when compared with QPSK-OFDM and OQPSK-OFDM signals,respectively.A significant reduction in OOB of nearly 15 dB is achieved by the proposed work SOQPSK-OFDM when compared to 16 Quadrature Amplitude Modulation(QAM)mapped OFDM.

Large Spacing Array with Offset Phase Center Elements for Highly Integrated Applications

A scanning and uniform array architecture with large spacing,low complexity and high scalability is presented for high integration massive array applications.It is constructed by offset phase center elements arranged in a uniform and regular way,but its spacing can be larger than that of traditional arrays.An ideal model of the offset phase center element is established and its far-field distribution is derived.To suppress grating lobes,the phase center of any element is designed to be movable without changing its physical position.Using genetic algorithm(GA),a new constraint condition limiting the number of phase center changes is proposed to solve the objective function of the minimum values of grating lobes(GLs)and side lobes(SLs).It is shown that the optimal results can be achieved by two changes of phase centers.A multimode circular patch is developed and designed,and characteristics of the offset phase center are analyzed and verified.A prototype array of 12×12 offset phase center elements is implemented based on multi-mode circular patches.Full wave simulation results of radiation patterns show that the level of grating lobes is suppressed at least 7dB with 1.12λ spacing,while the scanning angle is 20°.

Tests of relative vertical offsets for several types of GPS receiver antenna phase centers

The correction for antenna phase center is considered in processing Global Positioning System （GPS） data collected from a network of GPS ultra-short baselines. Compared with the leveling measurements, the GPS results show that the relative vertical offsets for the pairs of GPS receiver antenna phase centers still exist, although absolute calibration of the antenna phase center variations （PCVs） has been considered. With respect to the TPS CR.G3 antenna, the relative vertical offset for the LEI AT504 antenna is 8.4 mm, the offset for the ASH701945C_M antenna is 5.5 mm, and those for the ASHY00936E_C and ASH701945B_M antennas are approximately between 2 mm and -3 mm. The relative offsets for the same type of antennas are approximately 1 mm. By correcting the absolute PCVs, the existing relative offset becomes negligible for horizontal positioning.

THE PHASE-OFFSET OVERLAPPED WAVE TECHNIQUE

A new digital communication technology based on the Phase-Offset Overlapped Waves (POOW) has been introduced in this letter. The waves can be considered as a special multicarrier different from traditional ones. The sub-waves in a coded word’s period of the POOW are sine waves and have the same frequencies, but different starting phases. The most important characteristic is that these sub-waves are the piecewise functions and not orthogonal in a code word period. The decoding can be implemented by solving a linear equation group. This code has very high efficiency and thus the data transmission rate is increased greatly.

IRS辅助上行NOMA和速率最大化方案

针对非正交多址接入(non-orthogonal multiple access,NOMA)系统在无线环境下传输速率较低的问题,利用智能反射面(intelligent reflecting surface,IRS)可以改变入射信号相移的特性,提出一种基于IRS辅助上行NOMA和速率最大化算法.首先,在满足每个用户功率、每个用户最小速率、IRS相位偏移的约束条件下,构建一个联合用户功率、IRS相移多变量优化模型;然后,通过问题公式的等效简化将原非凸问题转换为2个容易处理的子问题;最后,通过交替方向乘子法(alternating direction method of multipliers,ADMM)、引入松弛变量等方法对子问题进行求解.仿真结果表明,相较于逐次凸逼近法(successiveconvexapproximation,SCA)所提出的算法平均提升了系统0.4 bit/(s·Hz)的和速率,证明了基于ADMM的算法有效提高系统的和速率.

Improved dichotomous search frequency offset estimator for burst-mode continuous phase modulation

A data-aided technique for cartier frequency offset estimation with continuous phase modulation （CPM） in burst- mode transmission is presented. The proposed technique first exploits a special pilot sequence, or training sequence, to form a sinusoidal waveform. Then, an improved dichotomous search frequency offset estimator is introduced to determine the frequency offset using the sinusoid. Theoretical analysis and simulation results indicate that our estimator is noteworthy in the following aspects. First, the estimator can operate independently of timing recovery. Second, it has relatively low outlier, i.e., the minimum signal-to-noise ratio （SNR） required to guarantee estimation accuracy. Finally, the most important property is that our estimator is complexity-reduced compared to the existing dichotomous search methods： it eliminates the need for fast Fourier transform （FFT） and modulation removal, and exhibits faster convergence rate without accuracy degradation.

页岩凝析气受限空间相态及开发特征研究

涪页10井的钻探获取了东岳庙段典型陆相页岩相关特征参数,其页岩储层介孔和大孔发育,非均质性较强,主要孔隙分布在10nm左右。纳米孔中受限流体的临界参数偏移使得受限空间下凝析气的流体性质与常规室内实验测试结果存在差异。为更合理地开采页岩凝析气,结合室内相态实验、受限流体临界参数偏移计算和数值模拟,开展页岩凝析气相态特征分析和开采特征研究,明确凝析气的相态变化规律和开采特征。考虑临界参数偏移的凝析气相态特征计算表明:随着孔隙半径减小,体系组分的临界温度、临界压力降低,相图向左下收缩,露点压力降低,气相黏度降低,偏差因子增加,反凝析液饱和度逐渐降低。通过机理模型分析了临界参数偏移对衰竭开采效果的影响,结果表明:随着孔隙半径减小,天然气采收率基本不变,凝析油采收率逐渐增加,孔隙半径减小至10nm,凝析油采收率增加9.93%。研究结果对页岩凝析气藏开发具有指导意义。

面向无线传感网络的同步时钟技术研究

考虑到传统的时钟同步技术在信息交互过程中产生的延迟具有不确定性,为了消除其对时钟同步的影响,提出了面向无线传感网络的同步时钟技术研究。通过对任意一个网络节点在真实物理时间的本地时间进行变换处理,构建无线传感网络的线性时钟模型,根据高斯分布所具有的加减特性,计算两个连续同步轮次的动态响应时间差值,在离散形式下,构建无线传感网络观测模型。通过计算无线传感网络时钟差值的均值,得到无线传感网络节点的时间戳,将无线传感网络节点数据交互误差补偿的目标函数转换成向量的形式,补偿无线传感网络节点数据交互误差,实现无线传感网络的时钟同步处理。实验结果表明,在微秒级延迟下,该技术的同步精度仍较高,可以有效消除网络信息延迟的不确定性对同步时钟的影响。

基于DP83640的秒脉冲移相器设计与实现

使用DP83640 IEEE 1588精密时间协议(PTP)收发芯片设计实现了一款秒脉冲精密移相器,它能与外部的标准秒脉冲(1 PPS)进行同步并进行精密相位微调,可应用于高精度相位微跃器。秒脉冲移相器采用DP83640芯片进行级联实现秒脉冲精密移相:利用ARM微处理器控制第二级DP83640实现与外部标准秒脉冲的相位粗调,控制第一级DP83640实现相位微调。相位调整时将外部输入的相位偏移量换算为8 ns整周期倍数的相位粗调值,以及不同时间长度档位的相位微调值,分别写入第二级和第一级DP83640共同实现高精度相位微跃。由于硬件电路特性和器件综合噪声的影响,经测试平均相位微跃准确度可以达到0.1 fs。

用于新型符号的频偏补偿和解调的算法与电路

为提高传统脉冲位置调制(pulse position modulation,PPM)符号的频谱效率,提出了一种新型码片内4-PPM符号调制方法,在实现1 Gbit/s通信速率的同时,又大大减少所需频谱资源。可在解调时,该符号调制的误码率性能受到发射端时钟和接收端本地时钟之间的频率偏移的极大影响。针对此问题,又提出了一种在模拟域对该符号进行频偏补偿,并实现符号同步和高速数据解调的算法与电路。该电路系统通过消除接收数据和本地时钟的初始相差、提取两者的频偏信息、周期性改变本地时钟的瞬时相位3步实现频偏补偿,并同时在第3步利用本地时钟对接收数据进行解调。为提高相位插值器(phase interpolator,PI)的线性度,本文将延迟锁定环与PI相结合。在2π的插值范围内,实现插值区间32个,插值步长992个,分辨率2.016 ps,最大差分非线性(differential nonlinearity,DNL)0.183°,最大积分非线性(integral nonlinearity,INL)0.325°。此外,本文提出的相位控制算法有效避免了由电流毛刺所引起的输出相位突变。电路基于UMC 40 nm CMOS RF LP工艺进行设计与仿真。仿真结果表明:本文所提出的算法与电路,在典型工艺角下,将接收数据和本地时钟间的50×10^(-6)频率偏差度降至1.03×10^(-6),频偏补偿准确度达到97.94%,并实现1 Gbit/s的解调速率。该方法对高速PPM数据同步与解调具有良好的工程应用价值。

带残余频偏的软扩频信号伪码序列盲估计

针对带残余频偏的软扩频信号伪码序列盲估计难的问题,提出一种奇异值分解(singular value decomposition,SVD)结合全数字锁相环(digital phase locked loop,DPLL)的方法。所提方法首先对待处理信号通过不重叠分段生成数据矩阵,每段信号长度为一倍伪码周期;然后利用其自相关矩阵的右上角元素估计失步点进行同步,并且在重新计算自相关矩阵后根据较大特征值个数估计进制数;最后通过多次快速SVD算法结合DPLL最终实现伪码序列的盲估计。仿真结果显示,所提方法在低信噪比条件下可以有效估计出带残余频偏的软扩频信号的伪码序列,并且性能优于其他对比方法。

GNSS天线相位中心模型更新对PPP的影响分析

目前,天线相位中心改正(PCC)模型由igs14.atx更新至igs20.atx,更新后的PCC模型会对精密单点定位的坐标参数估计产生影响。本文对比了更新前后的PCC模型,综合分析了四大全球卫星导航系统(GNSS)的在轨卫星和接收机天线的PCC模型,并选取了31个国际全球卫星导航系统服务组织(IGS)测站的观测数据进行精密单点定位数,通过点位偏差和点位精度来分析模型间差异对测站点位估计的影响。结果表明:在IGS框架和天线产品更新后,全球定位系统(GPS)、格洛纳斯系统和伽利略系统的点位偏差下降0.7、2.4和1 mm,北斗三号全球卫星导航系统(BDS-3)增加了0.3 mm;4个系统的点位精度与更新前相当,变化在1 mm内。多GNSS系统联合处理下定位效果有明显改善,点位偏差平均减少了约1.2 mm,点位精度提高了1.5 mm。除此之外,在IGS20框架下使用igs14.atx中的模型后,4个系统的定位性能受到不同程度的影响。

一种针对TI-ADC的采样时钟相位失配数字校准技术

针对采样时钟偏移失配对多相时间交织采样模数转换器(TI-ADC)性能影响很大的问题,将采样通道输出进行互相关,并利用一阶泰勒展开式进行自适应补偿校准的相位误差提取技术,有效补偿了多通道时序失配。基于65 nm CMOS工艺设计了一种12 bit 1.6 GS/s八相TI-ADC的采样相位失配校准电路。当输入信号频率为626.5625 MHz时,校准后的TIADC有效位数提升了6.29 bit,信噪失真比提升38.1 dB,无杂散动态范围提升44.44 dB。设计结果表明,本技术结构简单,硬件资源消耗少,能够显著提高TI-ADC系统采样性能。

基于脉幅调制的超高速无刷直流电机过零点检测补偿策略

超高速无刷直流电机广泛应用于超高速空压机、晶圆切割、飞轮储能等系统。针对超高速无刷直流电机控制中的三相绕组不完全对称和参考零点不确定偏移导致的失步问题,该文以脉幅调制控制器为基础,通过对非理想电机的研究,建立过零点抗扰动的模型,提出一种综合考虑不平衡过零点和不对称过零点补偿的改进控制策略,建立适用于三种非理想过零点模型的基础延迟时间择优策略的数学模型和换向时间补偿函数。同时,在不平衡不对称过零点扰动存在的前提下,考虑负载变化等因素引起的换相误差并提出相应的变速误差补偿策略。实验结果表明,改进控制策略可以有效减小无刷直流电机的换相误差,显著地提高电机换相的精度进而提高其运行速度上限,为无速度传感器超高速无刷直流电机稳定运行提供了一定的理论基础。

基于Phase-Refining技术的微波宽带频率合成器

为改善宽带频率合成器的相位噪声,提出一种基于Phase-Refining技术的微波宽带频率合成器结构与一种对其相位噪声的准确分析方法。首先,根据线性传递函数与叠加原理得到该频率合成器的相位噪声解析模型,通过对振荡器实测相位噪声谱型进行曲线拟合并带入模型中来准确预测其相位噪声性能。分析表明,在级联偏置锁相环中,整个输出频率范围内都可通过将反馈分频比最小化来改善其环路带宽内的相位噪声。实验结果表明,该频率合成器的输出频率范围为2.1~5.6 GHz,频率步进为1 Hz,当输出为2.1 GHz与5.6 GHz时,在频偏10 kHz处的相位噪声分别为-114.7 dBc/Hz与-108.2 dBc/Hz,其相位噪声测试结果与分析计算结果相吻合。