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。     

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。     

基于统计特征的 ＩＱ 不平衡高效校正算法

针对零中频接收机的I/Q不平衡问题,提出了一种数字域的基于统计特征的盲估计IQ不平衡校正算法,该算法利用具有循环对称特性的信号的统计特征,直接估计出系统的不平衡参数,进而完成IQ不平衡校正,相比于传统的算法,本算法具有计算复杂度低,校正精度高且不容易受到加性噪声的干扰等优点。仿真结果表明,所提算法不仅可以准确估计零中频接收机的IQ不平衡参数,还能对IQ不平衡进行有效的校正,从而提高系统的镜像抑制比。     

基于信道化架构的宽带I/Q不平衡校准技术

零中频接收机凭借其架构简单、易于集成等特点已被广泛应用于通信系统和雷达系统,为未来雷达通信一体化技术发展奠定了基础。然而,零中频接收机存在I/Q不平衡问题,这不仅会造成通信星座图的偏移,还会引入雷达虚假目标。现有宽带I/Q补偿方法的精度不高,且都集中于后处理,无法做到实时。因此,本文首先建立了宽带I/Q不平衡模型,并提出了一种融合信道化架构和盲估计补偿算法的宽带I/Q失衡校准技术。该技术利用信道化架构将宽带信号划分为窄带信号,并利用盲估计算法对带有镜像信号的子信道进行在线补偿。实验表明,该方法在获得高精度补偿参数的同时,完成了对宽带I/Q失衡的实时补偿。镜像抑制比达到55 dB。     

窄带零中频接收机IQ不平衡校准技术研究

针对窄带零中频接收机存在的IQ不平衡问题,设计实现了一种基于信号统计的IQ不平衡校准方法。首先建模分析了IQ不平衡对接收机性能的影响,在此基础上使用基于信号统计的方法对幅度和相位不平衡参数进行估计,进而实现IQ不平衡的补偿。实验测试表明,本文所设计算法能够有效实现窄带零中频接收机IQ不平衡的校准。     

60GHz通信系统中一种IQ不平衡补偿算法

基于SC-FDE(单载波频域均衡)和OFDM(正交频分复用)的60GHz通信系统,对联合信道估计的IQ不平衡补偿算法进行了研究。通过最小化CRE(信道残余能量),在未知IQ不平衡参数时可得CIR(信道冲击响应)的最优解。一旦得到IQ不平衡参数,CIR的估计可以通过简单的替换计算来获得。因此,该算法可将信道与IQ不平衡分离开来进行灵活的补偿,且对训练序列没有任何限制。仿真结果表明,无论是60GHz LOS(视距)还是NLOS(非视距)信道,使用该方法均可得到很好的性能。     

FDD射频收发机IQ不平衡的片上数字补偿方法

提出一种应用于直接变频结构FDD射频收发机IQ不平衡的片上数字补偿方法。在接收机通道与发射机通道中分别插入一个数字后校正单元与一个数字预失真单元,并结合接收机通路中的数字补偿参数检测电路,针对接收机与发射机的IQ不平衡,先后构建了负反馈环路。在上电初始化时的校准模式下,利用负反馈环路的高通特性,将补偿参数转换为直流成分并精确地提取出来。基于SMIC 0.13 μm RF CMOS工艺,该数字IQ不平衡补偿方法在一种直接变频结构的FDD射频收发芯片中得到了实现。测试结果表明,接收机和发射机的镜像抑制均达到了60 dB。在64QAM调制模式下,相比于没有补偿的情况,接收机的解调EVM从4.67%提升至2.12%,发射机的调制EVM从5.16%提升至2.3%。     

一种用于卫星通信的自适应编码调制信号接收方法

针对常规接收方法接收自适应编码调制信号时存在的接收过程易中断、数据不连续等问题,提出了一种适用于卫星信道的自适应编码调制信号接收方法.该方法通过采用统一的解调结构实现对不同调制信号的连续跟踪;利用接收端保存的帧同步字调制波形副本与接收信号中的帧同步字波形的相关结果,对解调方式切换时载波相位跳变值进行估计和补偿,解决了帧同步的连续跟踪问题.与现有方法相比,该方法不需要导频信号,可节省系统开销.     

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。     

TETRA2自适应调制解调系统性能分析

对TETRA2系统的自适应调制解调技术进行了研究,首先建立了自适应调制解调系统的传输模型,在接收端,对QAM信号采用最大似然估计,然后分析了信噪比估计性能对自适应调制解调系统产生的影响,最后用Matlab对调制解调系统进行了仿真。仿真结果表明：由于信道估计误差的存在,系统选择自适应调制方案的信噪比门限值有了相应的提高。     

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 Compensation of Transmitter and Receiver IQ Imbalance for MIMO-OFDM Over Doubly Selective Channels

Multiple-input multiple-output orthogonal frequency division multiplexing (MIMO-OFDM), as a viable technique, is being widely considered for high data rate and bandwidth efficient wireless communications. However, analog impairments like in-phase/quadrature (IQ) imbalance decrease the performance of this technique. Furthermore, time variations of a doubly selective channel cause intercarrier interference (ICI) which again degrades the performance. In this paper, the digital compensation of both the transmitter and the receiver IQ imbalances in MIMO-OFDM transmission over doubly selective channels is studied. In particular, basis expansion model is employed to develop a novel IQ formulation for a time-varying channel. Using this formulation, two receiver schemes are suggested to jointly mitigate the IQ imbalance and channel time variation effects. In deriving one of these schemes, the general case of an insufficient cyclic prefix (CP) for OFDM modulation is also considered. An insufficient CP results in interblock interference (IBI). The proposed approach for insufficient CP case, unifies several existing methods for IQ imbalance compensation and IBI/ICI cancellation. Simulation results show that this approach considerably improves the achievable bit-error-rate performance.     

调制解调非理想特性联合补偿数字预失真方法

针对调制解调非理想特性影响数字预失真效果,导致邻信道功率比性能较差的问题,提出了一种调制端和解调端联合补偿的数字预失真方法。首先,建立了正交调制器、解调器的基带等效模型;然后,基于多项式预失真,利用正交调制器与解调器的特点,结合递归最小二乘法,推导出了联合补偿数字预失真原理,避免了仅通过调制端补偿,或者调制端、解调端分别补偿只能使数字预失真算法收敛到局部最优解的现象出现;最后,以甚高频航空通信常用的差分八相移键控（Differential 8 Phase Shift Keying,D8PSK）调制方式为例进行了仿真和实现验证,邻信道功率比相对无预失真可以改善28 dBc,相对现有联合补偿数字预失真可以改善16 dBc。     

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.     

Receiver IQ Imbalance Estimation via Pure Noise for 60 GHz Systems

This paper proposes to estimate receiver (RX) IQ imbalance via pure noise for 60 GHz millimeter-wave systems. We study the impact of RX IQ imbalance on noise, and derive the maximum-likelihood algorithm to acquire the imbalance parameters, which is decoupled from transmitter IQ imbalance, channel response, and carrier offset. Also, the proposed method has low computational complexity and meets the low-power and low-cost requirements of 60 GHz systems. Moreover, the jitter performance of the estimation reaches the corresponding Cramer–Rao lower bound under a wide range of imbalance parameters.     

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.     

激光语音检测系统反正切补偿算法

通过理论分析激光语音检测系统,提出一种引入参数估计误差的反正切解调补偿算法,并建立了系统总谐波失真与关键参数及其误差的定量数学关系式。文中用总谐波失真（THD）和无杂散动态范围（SFDR）分别表征系统微振动信号解调效果和可以与大干扰信号（阻塞信号）相区别的最小信号值。实现了非接触、远距离、高灵敏度的微振动信号检测。通过实验和仿真均验证了反正切补偿算法的可行性。实验结果表明:该系统可以检测音频范围内的微弱振动,在现有光学硬件平台基础上,利用文中提出的反正切补偿算法,能在35 m范围内较好地还原语音信号。