数字电视测试接收机MER和EVM校准方法研究

根据MER和EVM的测量原理,得出MER和EVM与信噪比、IQ幅度不平衡、IQ正交误差之间的关系。此外,提出数字电视测试接收机MER和EVM参数的校准方法,并给出MER和EVM理论值的计算方法。最后,使用R&S公司SFU数字电视测试发射机和ETL数字电视测试接收机对该校准方法进行了验证,验证结果与理论值基本一致,达到了预期效果。     

基于通道误差校准的空域导向矢量多通道SAR-GMTI 杂波抑制方法

针对通道幅相误差和图像配准误差等非理想因素导致地面动目标检测性能下降的问题,该文结合最小方差和空域导向矢量两种杂波抑制算法,提出一种基于通道误差校准的空域导向矢量杂波抑制方法。该方法首先计算最小方差杂波抑制的权向量,通过该权向量构造配准图像,然后利用配准图像计算杂波正交补空间,最后通过正交子空间的方法实现杂波抑制。理论分析及实验结果表明,所提方法在图像配准误差和通道幅相误差较大的情况下仍具有很好的检测性能,能获得较最小方差杂波抑制方法和基于空域导向矢量的杂波抑制方法更高的信杂噪比。      

全数字BPSK/QPSK解调器原理和应用

详细阐述了全数字BPSK/QPSK调制解调器的原理。对实现数字锁相环(DPLL)所面临的各种问题:误差信号提取、相位跟踪及环路滤波等进行了详尽的说明。由于这种技术可以使解调器省去硬件VCO,解调器大部分都是用软件实现的,因此采用该技术实现的解调器不仅设计灵活、可靠性高、性能好,而且还可以降低对接收机本振精度的要求,很适合于小容量数字通信。目前该技术在国外通信系统中广泛应用。     

AD8348正交IQ解调器及其应用

IQ解调是数字调制系统中一种重要的解调方法,AD8348是Analog Devices公司推出的一种IQ正交解调器,广泛应用于QAM/QPSK解调器及各种通信系统中,如W-CDMA/CDMA/GSM等。介绍了AD8348的性能特点、内部结构、具体应用设计,并给出了典型应用电路及结果。     

高速OFDM系统中分时ADC失配误差校准技术

在高速OFDM接收机中利用分时ADC(TIADC)对接收信号进行采样,解决了单片ADC不能满足传输速率高达数Gb/s的通信系统需求的难题。由于TIADC各通道间的不匹配,时钟失配误差和增益失配误差大大影响了系统性能。在传输速率为4 Gb/s的OFDM系统中,利用4通道TIADC对接收信号进行采样,对两种失配误差和信道进行联合估计与均衡,并针对64QAM符号调制,对TIADC进行采样精度仿真。仿真结果证明,校准后的9位TIADC可以使系统误码率接近理想值。     

OFDM-ISAR的稀疏优化成像与运动补偿

正交频分复用(OFDM)技术可用以获得无干扰的高分辨距离雷达成像,该文研究利用OFDM波形实现非合作目标的逆合成孔径雷达(ISAR)成像和运动补偿问题。文中讨论了目标平动对循环前缀(CP)长度的影响,利用了ISAR成像的本质稀疏性同时实现成像重建和相位补偿。实验表明,基于CP的OFDM-ISAR运动补偿算法可有效克服OFDM-ISAR成像的距离干扰和运动误差影响,具有较好的稳健性和精确性。      

OFDM技术及其应用

首先对OFDM的发展以及应用做了简要的介绍,然后讨论了当前OFDM研究过程中的两个关键技术问题,最后展望了OFDM的未来发展。     

视频解调器的误差对图像质量的影响

视频解调器的误差对图像质量的影响南京无线电厂职工大学李耀荣概述彩电接收机生产中有几道工序必须调整色度延时线的相位、幅度及本机振荡的副载波相位等。这些调整的目的是消除ＰＡＬ＿Ｄ彩色解调器的误差，防止两色差信号的串扰，提高图像质量。本文详细分析并归纳了Ｐ...     

有源相控阵雷达多通道幅相校准研究

为实现有源相控阵天线的超低副瓣性能,对通道校准的剩余误差控制,以及通道间的幅相一致性提出了更高的要求.文中介绍了收/发校准的流程,阐述了基于快速傅里叶变换的天线阵面校准原理,对影响天线性能的误差进行了分析,提出了为提高校准精度采用的校准方法.仿真结果表明,在误差控制范围内,雷达的收发天线性能满足设计要求.     

基于激光位移传感器圆径测量的角度安装误差研究

基于激光位移传感器的工件圆径和圆度测量被广泛应用于工业现场的产品质量检测过程中。文中研究了激光位移传感器的角度安装误差对工件圆径测量结果的影响,并提出校准方法。首先,将定量分析位移传感器的角度安装误差与计算得到的圆径结果的误差之间的关系。其次,提出了一种位移传感器角度安装误差校准方法,该方法可在标准圆圆径未知的情况下,根据不同位置下的3个位移传感器的测量值,精确计算出传感器的角度安装误差。详细说明了该校准方法的建模过程,通过仿真确认角度安装误差校准方法的有效性。最后,利用三坐标测量仪对角度安装误差进行校准。实验结果表明,校准后的圆径测量误差从20 μm提高到1.5 μm。     

OFDM WLAN接收机IQ不平衡的时域补偿新方法

针对采用高阶调制的正交频分复用(OFDM)系统在前端模拟处理过程中易遭受到同相相位和正交相位(IQ)不平衡影响的问题,提出了一种新的OFDMWLAN系统接收机IQ不平衡估计和补偿方法。该方法利用较少的时域训练序列进行IQ不平衡参数的估计及补偿。仿真结果表明,该方法在降低了计算复杂度的同时,也获得了较好的估计性能。     

一种可用于DVB-T的OFDM全数字解调器

OFDM是一种高效的数据调制方式，被广泛地应用于宽带数字通信领域。DVB-T就将它作为物理层的传输制式。本文提出了一种可用于DVB-T的OFDM全数字解调器。文章首先分析了各种因素对解调的影响，提出了全数字解调器的结构，然后介绍了符号同步、载波同步、时钟同步和信道补偿等模块在解调器中的全数字实现，最后给出了解调器的误码性能。结果表明，本文提出的全数字解调器具有较好的性能。     

Decoupled compensation of IQ imbalance in MIMO OFDM systems

The direct-conversion architecture is an attractive front-end design for multi-input multi-output (MIMO) orthogonal frequency division multiplexing (OFDM) systems. These systems are typically small in size and provide a good flexibility to support growing number of wireless standards. However, direct-conversion based OFDM systems are generally very sensitive to front-end component imperfections. These imperfections are unavoidable especially when cheaper components are used in the manufacturing process and can lead to radio frequency (RF) impairments such as in-phase/quadrature-phase (IQ) imbalance. These RF impairments can result in a severe performance degradation. In this paper, we propose training based efficient compensation schemes for MIMO OFDM systems impaired with transmitter and receiver frequency selective IQ imbalance. The proposed schemes can decouple the compensation of the transmitter and receiver IQ imbalance from the compensation of the channel distortion. It is shown that the proposed schemes result in an overall lower training overhead and a lower computational requirement as compared to a joint estimation/compensation of IQ imbalance and the channel distortion.     

Joint compensation of IQ imbalance and phase noise in OFDM wireless systems

Physical impairments like IQ imbalance and phase noise can cause significant degradation in the performance of wireless communication systems. In this paper, the joint effects of IQ imbalance and phase noise on OFDM systems are analyzed, and a compensation scheme is proposed to improve the system performance in the presence of IQ imbalance and phase noise. The scheme consists of a joint estimation of channel and impairment parameters and a joint data symbol estimation algorithm. It is shown both by theory and computer simulations that the proposed scheme can effectively improve the signal-to-noise ratio at the receiver. As a result, the sensitivity of OFDM receivers to the physical impairments can be significantly lowered, simplifying the RF and analog circuitry design in terms of implementation cost, power consumption, and silicon fabrication yield.     

Joint Adaptive Compensation of Transmitter and Receiver IQ Imbalance Under Carrier Frequency Offset in OFDM-Based Systems

Zero-intermediate frequency (IF)-based orthogonal frequency division multiplexing (OFDM) transmitters and receivers are gaining a lot of interest because of their potential to enable low-cost terminals. However, such systems suffer from front-end impairments such as in-phase/quadrature-phase (IQ) imbalance which may have a huge impact on the performance. Moreover, since OFDM is very sensitive to a carrier frequency offset, this distortion needs to be taken into account in the derivation and analysis of any IQ imbalance estimation/compensation scheme. In this paper, the effect of both transmitter and receiver IQ imbalance under carrier frequency offset in an OFDM system is studied and an algorithm is developed to compensate for such distortions in the digital domain. The algorithm involved is a very efficient post-FFT adaptive equalization which is shown to lead to near ideal compensation.     

单路反馈射频功放预失真线性化方法

该文基于记忆多项式模型,提出一种采用单路反馈的射频功放预失真线性化新方法,只需用正交解调后的IQ信号中的一路,就可完成对预失真器模型参数的获取。该方法可消除使用正交解调器所带来的增益和相位不平衡问题,且节省了一路反馈采样电路,在降低成本、简化设计的同时还能提高预失真线性化的性能。仿真和物理实验结果表明,该文提出的方法是正确的,能达到比较好的线性化效果。     

Compensation of IQ imbalance and phase noise in OFDM systems

Nowadays, a lot of effort is spent on developing inexpensive orthogonal frequency-division multiplexing (OFDM) receivers. Especially, zero intermediate frequency (zero-IF) receivers are very appealing, because they avoid costly IF filters. However, zero-IF front-ends also introduce significant additional front-end distortion, such as IQ imbalance. Moreover, zero-IF does not solve the phase noise problem. Unfortunately, OFDM is very sensitive to the receiver nonidealities IQ imbalance and phase noise. Therefore, we developed a new estimation/compensation scheme to jointly combat the IQ imbalance and phase noise at baseband. In this letter, we describe the algorithms and present the performance results. Our compensation scheme eliminates the IQ imbalance based on one OFDM symbol and performs well in the presence of phase noise. The compensation scheme has a fast convergence and a small residual degradation: even for large IQ imbalance, the overall system performance for an OFDM-wireless local area network (WLAN) case study is within 0.6 dB of the optimal case. As such, our approach greatly relaxes the mismatch specifications and thus enables low-cost zero-IF receivers.     

Digital predistortion based on single-feedback method and indirect learning structure

This paper proposes a novel digital predistortion method for both memory and memoryless power amplifiers, which only needs one feedback circuit. In comparison with the previous methods, the proposed method has the greatest advantage that it can eliminate the gain and phase imbalance errors of the quadrature demodulator without digital IQ compensator, and the performance of digital predistortion can be improved with lower costs and less computation complexity. Combining with the indirect learning structure, it is easy to design the predistorter. Experimental results show the correctness and effectiveness of the proposed method.     

一种新的IQ不平衡频域估计与补偿算法

针对正交频分复用（OFDM）系统中射频前端失真—同相/正交（IQ）不平衡影响系统性能的问题,提出了一种新型的IQ不平衡频域估计与补偿算法。通过同一个子载波上的两个不同导频信号,抵消信道的影响,以减小算法复杂度,便于实现。仿真结果表明,该算法既极大地降低了计算量,又取得了较好的估计与补偿性能,性能优于传统的算法。     

OFDM中联合IQ不平衡和相位噪声估计补偿新算法

正交频分复用(OFDM)系统中的非理想特性对系统性能影响很大,针对非理想特性中的两个主要部分:同相支路和正交支路(IQ)间的不平衡及相位噪声,提出了一种新的相位噪声和IQ不平衡联合估计算法。该算法首先由一个训练符号利用简单的最小二乘(LS)准则在频域估计出IQ不平衡和相位噪声的复合参数,并从中分离得到IQ不平衡估计值,然后利用估计出的IQ不平衡参数在时域对数据符号做IQ不平衡补偿,最后对IQ不平衡补偿后的数据在频域做相位噪声公共相位误差(CPE)和子载波间干扰(ICI)的估计和补偿。理论分析和仿真结果表明,该算法能简单有效的补偿IQ不平衡和相位噪声带来的性能损失。