基于调制域分析的功放线性化测量验证

针对目前功率放大器(Power Amplifier,PA)线性化测量验证方案需要较多的软硬件资源且测试效率低的问题,提出了一种适用于卫星通信领域的PA线性化测量与验证方法.该方法基于信号的调制域分析,首先信源端生成循环I/Q数据,然后经调制域分析仪进行信号采集后,由所提算法进行非线性特性提取,最后进行数字预失真(Dig...     

Frequency-Domain Channel Estimation and Equalization for Continuous-Phase Modulations With Superimposed Pilot Sequences

This paper proposes a new frequency-domain channel-estimation and equalization method for continuous-phase modulation (CPM) block transmissions with superimposed pilot signals. Our method provides spectral and power-efficient broadband CPM wireless communications with less complexity than previous methods. The proposed frequency-domain channel estimation uses the superimposed pilot sequence as a reference signal to reduce the throughput loss caused by traditionally multiplexed pilots. The proposed CPM frequency-domain decision feedback equalizer (DFE) eliminates the complexity overhead of conventional decomposition-based CPM receivers.      

光纤混沌双向保密通信系统研究

本文提出光纤混沌双向保密通信设想,通过耦合光注入半导体激光器激光混沌全光耦合反馈同步系统和光纤传输信道,建立了光纤混沌双向通信系统模型,数值实现了该系统在长距离光纤传输中的同步,详细地分析了系统同步时间随光纤传输长度的关系.证明了光纤的交叉相位调制是限制激光混沌在光纤传输中同步的主要原因,导出了系统传输的非线性相移.数值模拟了具有正弦调制信号的调制频率0.5GHz混沌模拟通信和数字信号调制速率0.4Gbit/s以及20Gbit/s的混沌数字通信以及调制速率0.05Gbit/s 混沌键控通信的应用,计算出光纤混沌数字通信速率和同步误差等关系,还特别分析了系统解码特性和调制带宽,表明系统具有非常好的保密性能和具有高速率通信的能力.光纤混沌双向保密通信是可以实现的.     

OFDM-RoF原理与关键技术

光通信与无线通信的融合是未来通信的发展方向。正交频分复用（OFDM）技术即将成为下一代无线通信的物理层核心技术。OFDM光载无线（0FDM—RoF）接合了无线通信和光通信的优点,具有高速率、高容量、高频谱利用率的优势。OFDM—RoF系统有光纤色散、光纤非线性、调制非线性等问题,可以利用峰值平均功率比（PAPR）降低算法降低光纤非线性、调制非线性;利用循环前缀、信道估计消除色散影响;利用数字相位共轭、偏载波填充、非线性预补偿、降低序列相关性降低光纤非线性。     

一种基于数值模型的4H-SiC MESFET大信号建模方法

提出了一种基于数值模型的4H-SiC MESFET大信号建模方法.该方法基于4H-SiC MESFET的物理参数和结构参数,采用MEDICI的小信号正弦稳态分析法和高频小信号等效电路,模拟得到电流和电容的非线性特性,通过大信号等效电路,分析了建立4H-SiC MESFET大信号模型的途径.模拟与实验测试值的比较表明这种方法是可行的,可用于预先评估器件大信号工作时的非线性特性,指导4H-SiC MESFET的器件设计.     

Training sequence based channel estimation for indoor visible light communication system

Channel estimation is a key technology in indoor wireless visible light communications(VLCs).Using the training sequence(TS),this paper investigates the channel estimation in indoor wireless visible light communications.Based on the propagation and signal modulation characteristics of visible light,a link model for the indoor wireless visible light communications is established.Using the model,three channel estimation methods,i.e.,the correlation method,the least square(LS) method and the minimum mean square error(MMSE) method,are proposed.Moreover,the performances of the proposed three methods are evaluated by computer simulation.The results show that the performance of the correlation method is the worst,the LS method is suitable for higher signal to noise ratio(SNR),and the MMSE method obtains the best performance at the expense of highest complexity.     

Performance analysis of a hybrid CDMA/ISMA protocol for indoorwireless computer communications

A combination of direct sequence code division multiple access (DS-CDMA) and p-persistent inhibit sense multiple access (ISMA) protocols is proposed for indoor wireless communications (IWC). The combination of these two protocols is called the hybrid CDMA/ISMA protocol. The performance of the hybrid CDMA/ISMA protocol is analyzed with a Markov model considering differential phase shift keying (DPSK) modulation. The performance is measured in terms of throughput and delay. The performance is also evaluated using computer simulation of which the results are in close agreement with the Markov model results. The study of indoor wireless communications using a hybrid CDMA/ISMA protocol can be useful for various applications in research and design offices, medical data communication in hospitals, etc     

High Average-Efficiency Multimode RF Transmitter Using a Hybrid Quadrature Polar Modulator

This paper presents a hybrid quadrature polar modulator (HQPM) to drive the power amplifier (PA) highly efficiently in a wireless RF transmitter required for multimode operation. For enhancing the transmit efficiency, a switching-mode PA realized as Class-E design is used in the transmitter. The HQPM consists of a quadrature modulator for processing the RF modulated carrier and a Class-S modulator for processing the supply-voltage signal. The quadrature modulator and the Class-S modulator deliver the output signals with proportional envelope variation before being inserted into the RF-input terminal and the supply-voltage terminal of a Class-E PA, respectively, causing the double envelope modulation to distort the modulated RF signal at the PA output. Therefore, a digital predistorter is embedded in the HQPM for compensation. The proposed HQPM-based transmitter can help reducing the average dc and input RF powers and the output feedthrough levels so as to enhance power added efficiency and adjacent channel power rejection remarkably.     

GaAs MESFET微波非线性电路全频域谐波平衡分析

根据Fourier分析理论推导了全频域分析微波非线性电路的方法,此方法简单明了,适合于分析微波大信号强非线性电路.用此方法对GaAs MESFET微波非线性电路进行分析,给出了实用的分析计算结果.     

基于直接调制的激光无线通信演示实验

利用半导体激光器,通过电流驱动的直接调制方式,低成本地实现了激光无线通信实验系统。系统可以演示传递音频信息和文字信息,其中数字信号是利用单片机的串口或通用IO口收发,同时用软件实现相关编码协议。系统可以通过单片机自行控制,或通过VC++编写的上位机程序操控。本实验系统可用于教学演示,也可以用于仪器设备间的通信、遥控,或是应用于其他特殊的需要无线通信的场合。     

基于混合遗传算法及最低误码率准则的几何特征均衡器

针对高效调制通信系统中带内干扰抑制问题,提出一种基于最低误码率准则的非线性几何特征均衡器,并用径向基函数神经网络来实现.为优化非线性均衡器的参数训练,本文构造了一种新的遗传随机梯度混合算法.仿真表明:对于扩展的二元相移键控信号,在相对强的窄带干扰下,匹配滤波器及线性均衡器已失效,而基于最低误码率准则的几何特征均衡器仍能表现出良好的性能,也大大优于基于最小均方误差准则的非线性均衡器.     

空间调制无线光通信的信号设计

建立了空间调制无线光通信的光强信道模型,并给出了空间信号必须满足的两个基本约束条件。通过定义于二维空间的正交基函数建立了矢量信号空间,并定义了三个衡量空间信号设计方案性能的指标,即误符号率,频带利用效率和功率效率等。参照传统时域信号设计方案,提出了三种空间调制信号具体设计方案,并从带宽效率和功率效率两性能上进行了比较,结果表明正交幅度调制(QAM)具有带宽效率高、功率效率低的特点,而且采用的信号点越多其带宽效率就越高,另外其空间信号图案还具有圆对称性,因此非常适合在空间带宽有限的远距离无线光通信中使用。     

Multiple-subcarrier modulation in optical wireless communications

This article overviews multiple-subcarrier modulation techniques in optical wireless communications. The basic principles and characteristics of MSM techniques in optical wireless communications are presented. MSM optical wireless systems are explained where some block codes that convert information bits to be transmitted to the symbol amplitudes of subcarriers are used to increase the minimum value of the MS electrical waveform. MSM optical communications systems using subcarrier signal point sequences (SSPS) that can improve the power efficiency of MSM systems are also explained. The performance of MSM optical communications systems is presented in the intensity modulation with direct detection (IM/DD) channel without dispersion and in atmospheric optical communications where the effects of scintillation exist.     

基于数/模混合预失真技术的功放线性化北大核心CSCD

随着移动通信信号带宽的增加,传统功率放大器数字预失真线性化技术越来越受到采样率的限制。为了使线性化效果更好,文中提出了一种数字预失真和模拟预失真相结合的混合预失真器,利用模拟预失真宽带宽的特点和数字预失真线性化能力强的优势,把模拟预失真和数字预失真融合在一起,共同补偿功放的非线性。由于受实验设备采样率的限制,文中采用了带宽为60 MHz的5 G NR信号对一个中心频率为3.5 GHz的射频功放进行实验验证。实验结果表明:提出的混合预失真器不仅优于单独的数字预失真器和模拟预失真器的非线性矫正性能,而且还能改善数字预失真因采样率限制无法改善的带外互调失真。     

Predistorter Based on Frequency Domain Estimation for Compensation of Nonlinear Distortion in OFDM Systems

An orthogonal frequency-division-multiplexing signal is very sensitive to the nonlinear distortion of the power amplifier (PA) as a result of its high peak-to-average power ratio. Predistortion, which is an effective countermeasure for balancing off the nonlinearity of a PA, is usually necessary for the sake of mitigating the in-band distortion and the spectrum regrowth. In general, a feedback path is required to estimate the PA characteristic, and a memoryless polynomial is used in modeling the PA characteristic or constructing the predistorter. The polynomial coefficients are solved by least-square (LS) estimation or adaptive identification algorithms in the time domain. In this paper, we examine the estimation problem from the frequency domain and propose five predistortion schemes. The advantage of using frequency-domain estimation is that it is much easier to compensate the delay effect caused by the transmission and receiving filters in the feedback path. Two different criteria are used in the proposed algorithms. The first one is based on the minimization of the square error of the PA input, which is termed as the PA-input-LS criterion. The second one is based on the minimization of the square error between the input of the predistorter and the output of the PA, which is termed as PA-output-LS criterion. We also propose an easy method to cope with the delay effect caused by the transmission and receiving filters in the feedback path. The performances of the proposed schemes are compared in the simulation. The simulation results show that by using the proposed schemes, the power efficiency of the PA can be increased by at least 7 dB in the sense of total degradation for a practical IEEE 802.11a wireless local area network system with a 64-quadrature-amplitude-modulation signal constellation.     

大气无线光通信系统中数字脉冲间隔调制研究

基于光强闪烁的大气无线光通信系统模型,研究了数字脉冲间隔调制(DPIM)方式的差错性能,分析了符号结构、发射功率、带宽需求等问题,并与 OOK(开关键控)和 PPM(脉冲位置调制)调制方式进行比较。理论和仿真研究结果表明,DPIM 调制方式较 PPM 方式有较高的功率效率和较少的带宽需求,特别是在系统实现上相对于 PPM 大大简化。因此 DPIM 应用于无线光通信系统具有一定优势。     

Power-conscious design of wireless circuits and systems

The great importance of power consciousness is well understood in mobile wireless communications. However, with growing experience the fundamental principles underlying power conscious design of RF circuits, systems, and networks are only now becoming known. Using as example ultralow-power wireless devices for messaging such as paging receivers and wireless sensor networks, the first part of this paper presents the relationship between current consumption and dynamic range of low-noise amplifiers, mixers, oscillators, and active filters. The second part of the paper covers issues of modulation, protocols, and networking that would be required in dense networks of wireless sensors, which communicate using very little energy. These ideas are expected to find use in most forms of digital wireless communications     

基于低采样率数模转换器和模数转换器的太赫兹发射机线性化

太赫兹(THz)频率高、带宽大,是6G移动通信中极具优势的潜在无线频谱资源。然而太赫兹器件的非线性失真,限制了功率转换效率与通信传输距离。若采用传统数字预失真(DPD)技术对其进行非线性校正,通常要求数模转换器(DAC)和模数转换器(ADC)的采样速率达到信号带宽的5倍,对于太赫兹频段难以应用。因此,该文提出一种低速率DAC和ADC的DPD算法对太赫兹发射机的非线性进行校正。该方法主要分为3个步骤：首先利用低采样率ADC获取的观测数据进行上采样,恢复出带宽受限的高采样率的观测信号,此时信号采样率为信号带宽的5倍,可以有效表征出5阶非线性失真;然后建立带宽受限的DPD模型,采用最小二乘算法提取DPD校正系数;最后对校正后的信号进行下采样送往DAC以校正发射通道的非线性失真。仿真结果表明,当DAC和ADC工作在1.25倍基带信号速率的采样率条件下,对于64-QAM调制信号,该方法可以把误差矢量幅值(EVM)从8.46%降低到2.27%,从而可以支持更高阶的调制方式。     

Performance of the π/4-DQPSK, GMSK, and QAM modulation schemesin mobile radio with multipath fading and nonlinearities

As mobile communications have become so indispensable, every possible effort should be spent to achieve the optimum operating conditions. In addition to the normal impairments associated with wireless communications, in general, the mobile channel suffers from particular limitations that confine the performance of a mobile radio system. Among those impairments are the bandwidth limitation, interference, and multipath fading. With the strong motivation toward portable radio and personal communication systems, power limitation has manifest itself in the picture, and, consequently, nonlinear operation of the amplifiers involved (hence, the channel) will have to be dealt with. Constant envelope modulation schemes have been used in digital mobile radio systems recently installed. The Gaussian minimum shift keying (GMSK) is employed in the Global System for Mobile (GSM) communications installed in Europe, while in the North American IS-54 system, the modulation scheme used is the π/4-DQPSK. As the quest for higher data rates has kept on increasing, multilevel modulation schemes have been proposed with their performance over nonlinear channels having been overlooked. The paper provides a comparative study, based on simulation, and tests the performance of various modulation schemes operating over a wide variety of mobile radio channel conditions. The effective throughput of all systems is also considered